The master’s thesis, Graduate Institute of Speech and Hearing Disorders and Science, National Taipei University of Nursing and Health Sciences
Advisor: Sheng Hwa Chen, Ph. D., CCC-SLP
The Comparison of Vocal Functions and Voice-related Life Quality between Students with Cochlear Implants and with Normal Hearing on Multidimensional Evaluation
Name: Hung-Wei Hsu July, 2012
NATIONAL TAIPEI UNIVERISTY OF NURSING AND HEALTH SCIENCES
GRADUATE INSTITUTE OF SPEECH AND HEARING DISORDERS AND SCIENCES
THE COMPARISON OF VOCAL FUNCTIONS AND VOICE-RELATED LIFE QUALITY BETWEEN STUDENTS
WITH COCHLEAR IMPLANTS AND WITH NORMAL HEARING ON MULTIDIMENSIONAL EVALUATION
A Thesis
SUBMITTED TO THE GRADUATE FACULTY
In partial fulfillment of the requirements for the Degree of Master of Science
BY
HUNG-WEI HSU TAIPEI, TAIWAN
JULY, 2012
MAJOR ADVISOR: Sheng Hwa Chen, Ph. D., CCC-SLP
誌謝 誌謝 誌謝 誌謝
這可能不是一本最棒的論文，但我相信是最有「愛」的一本著作。
感謝我的指導教授—盛華教授，盛老師是一盞明燈，協助我釐清許多觀念，
教導我寫作的要點，此本論文才得以完成。老師有時也像媽媽一樣，用愛提供我 做研究的所需、關心我的生活，讓我心中感到一股暖流。謝謝長庚耳科主任吳哲 民醫師熱心地轉介個案名單，並請助理提供一切的幫助。感謝師大特教系張蓓莉 教授分享其研究聽力障礙專長，給予本研究實用的建議。
謝謝所有參與此研究的電子耳小朋友和家長們，謝謝你們的信任、愛心及熱 心招待，讓我這位陌生人進到你們的家中為孩子們做評估，你們的付出、生命的 故事感動了我及好多人。上帝必將更多的恩典加給你們。
謝謝何嘉仁蘆洲分校的主管Erin、同事Justin, Wen, Yvonne、參與學生及家 長，謝謝你們的熱心回應，放心把孩子交給我收集對照組的資料。何嘉仁蘆洲分 校對我的意義，早已超過公司，而是一個互相扶持的大家庭。
特別要謝謝新光醫院復健科語言治療曾鳳菊老師，曾老師是我生命的啟蒙 者，謝謝老師在實習期間不斷地開發我的潛力、翻轉我的性格，讓我享受語言治 療的成就感，而且開始懂得體驗生命的美好，並幫忙招募適合的受試者。也謝謝 物理治療師陳文珊老師、職能治療徐梅芳老師，謝謝兩位老師伸出援手，你們的 愛心及幫助是我最好的治療師榜樣。感謝三軍總醫院耳鼻喉科語言治療蕭麗君老 師擔任聽知覺評分者，老師慷慨的協助及溫柔問候讓我心中感到平安。
謝謝北護聽語所的楊義良所長、童寶娟老師、詹妍玲老師，謝謝你們栽培我 成為一名專業的語言治療師，並掛念我的狀況，常常提供工讀機會給我。
謝謝新生命小組教會的牧長同工們，謝謝你們在我大學生命最低潮時期，用 愛接納我進到教會，用你們自己的生命示範、教導我要成為眾人的祝福。
最後我要謝謝家人，謝謝父親、大姐、二姐、二姐夫、翔翔，成為我心中最 大的支柱、永不動搖的力量。最大的感謝要獻給在天堂的母親。Love!
ABSTRACT
Children with cochlear implants (CI) have been proved to have voice problems.
However, the previous studies adopted only one or two objective assessment tools. CI children’s vocal functions and voice-related life quality remained unknown. Therefore, the purpose of the study was to investigate the vocal functions and voice-related life quality of CI children by comparing the data between CI children and the
normal-hearing children from aerodynamic, acoustic, auditory perceptual, and self-reported assessments.
The study comprised two groups. The experimental group consisted of 35 Mandarin-speaking 8-to-12-year-old elementary school students with CI, and the control group consisted of 35 normal-hearing and sex-and-age matched counterparts.
The speech samples of sustained vowel and reading were analyzed aerodynamically, acoustically and auditory perceptually. Pediatric Voice-related Quality of Life
Survey-Chinese Version was filled by the subjects’ parents. The Independent t-test or Mann-Whitney U test was used to find the significance of all parameters between the two groups, and the standard deviations of the parameters were examined by the Levene test. Pearson correlation coefficient was used to explore the relation between aural rehabilitation duration and the severity of each voice parameter.
The results showed CI children had significantly lower mean airflow rate and
higher phonation threshold pressure than the normal-hearing, which indicated CI children had hyperadducted vocal folds and high laryngeal resistance. CI children had higher fundamental frequency variation, peak amplitude variation and
noise-to-harmonics ratio than the normal-hearing. They implied CI children’s irregular vocal folds vibration. During reading, CI children had larger speaking intensity range than the normal-hearing. It reflected CI children’s speaking intensity control was less stable. In auditory perceptual evaluation, CI children had
significantly more deviant loudness, speaking rate, strain and monotone, hard attack, and resonance than the normal-hearing, and their overall severity was larger. The results displayed CI children had worse voice quality. In Pediatric Voice-related Quality of Life Survey-Chinese Version, CI children had significantly higher severity scores than the normal-hearing. It meant CI children had less satisfactory
voice-related life quality. No significant difference between the two groups was found in all other parameters. Factors such as implantation age and aural rehabilitation duration were also discussed.
The multidimensional assessment protocols are identified to be useful for
evaluating CI children’s voice characteristics. For improvement of CI children’s voice, speech pathologists are suggested to diminish CI children’s laryngeal tension.
Key words: cochlear implants, voice disorders, voice evaluation, aerodynamics, acoustics, auditory perceptual evaluation, caregivers-reported assessment
中文摘要
研究證實使用人工電子耳的兒童也有嗓音異常。但先前研究僅使用一、兩項
客觀評估方法，無法了解電子耳兒童的喉部功能及嗓音相關生活品質。因此，本
研究目的為透過多面向氣動學、聲學、聽知覺、及自覺評估方法，探討電子耳兒
童的喉部功能及嗓音相關生活品質。
本研究受試者共分兩組。實驗組為35位使用電子耳的8到12歲國小學童（電
子耳學童），控制組為35位和電子耳學童性別、年齡配對的聽力正常學童（聽常
學童）。受試者持續發母音及朗讀短文的語料以氣動學、聲學、聽知覺方式測量。
兒童嗓音相關生活品質問卷由受試者主要照顧者填寫。
研究結果顯示，電子耳學童的平均氣流速率顯著低於聽常學童，而發聲門檻
壓力顯著高於聽常學童。這顯示電子耳學童發聲時，喉部容易用力，使得喉部阻
力提高。電子耳學童的頻率變動率、振幅變動率及噪諧比均顯著高於聽常學童。
此結果表示電子耳學童的聲帶震動較不規律。在朗讀短文時，使用電子耳學童的
說話音量範圍較大，顯示其控制說話音量的能力較不穩。聽知覺評估顯示，電子
耳學童的音量、說話速度、拉緊音、單調音、硬起聲、共鳴、及整體音質皆顯著
異於聽常學童。在兒童嗓音相關生活品質問卷中，電子耳學童於各面向的嚴重度
皆顯著大於聽常者。這顯示電子耳學童的嗓音相關生活品質較聽常學童差。
本研究證實多面向嗓音評估工具能評估反應電子耳兒童的嗓音特質。為改善
電子耳兒童的嗓音品質，語言治療師應減少其說話喉部緊張。
TABLE OF CONTENTS
Page Table of contents………I List of Figures………..IV List of Tables……….VIII Chapter
1. Introduction………1
Research Motive……….3
Research Purpose……….13
Research Questions………..15
2. Review of Literature……….16
Auditory Feedback Mechanism………16
The Definition of Hearing Loss and Its Impacts on Language/Speech/Voice………...22
The Impacts of Voice Disorders: Patients/Caregivers-reported assessment………36
Introduction to Cochlear Implants………39
Voice of CI recipients……….………..40
Multidimensional Protocol in Voice Evaluation………...47
3. Methodology………52
Research scheme………..52
Subjects………54
Materials………...56
Instruments and the Assessment Items……….58
Calibrations………..62
Test-retest Reliability on the Aerodynamic and Acoustic Measurements…64 Intra-rater Reliability on the Perceptual Assessments………..65
Procedure..………66
Data Analysis………74
4. Results………..75
Background Information………..75
Aerodynamics………...80
Acoustics………..85
Auditory Perceptual Evaluation……….100
Caregivers-reported Assessments………...109
The Influence of Implantation Age on Voice Parameters………...116
The Relation between Aural Rehabilitation Duration and the Severity of Each Voice Parameter……….117
5. Discussion………...118
Aerodynamics……….118
Acoustics………124
Auditory Perceptual Evaluation……….136
Caregivers-reported Assessments………...143
The Influence of Implantation Age on Voice Parameters………...145
The Relation between Aural Rehabilitation Duration and the Severity of Each Voice Parameter………146
6. Clinical Implications, Research Limitations, Suggestions for Future Studies………...147
Clinical Implications………..147
Research Limitations………..149
Suggestions for Future Studies………...150
7. Conclusion………..152
References………..154
Appendixes……….166
I.A Background information form………..166
I.B Background information form………..168
II. Instructions on recording………...169
III. A 6-point, equal-appearing interval scale……….171
IV. Pediatric Voice-Related Quality of Life Survey-Chinese version………172
LIST OF FIGURES
Figure Page
1.1 The speech chain………...2
3.1 Research scheme………52
3.2 Recording calibration………...62
3.3 Procedure of aerodynamic measurements………..68
3.4 Procedure of MDVP analysis………...71
3.5 Procedure of CSL Main Program analysis………...72
4.1 Boxplot comparing the maximum phonation time between CI males and control males………..81
4.2 Boxplot comparing the maximum phonation time between CI females and control females………...82
4.3 Boxplot comparing mean airflow rate between CI group and control group…… 83
4.4 Boxplot comparing the phonation threshold pressure between CI group and control group………..83
4.5 Boxplot comparing jitter between CI group and control group……….86
4.6 Boxplot comparing fundamental frequency variation (vF0) between CI group and control group……….87
4.7 Boxplot comparing shimmer between CI group and control group………...87
4.8 Boxplot comparing amplitude-peak variation (vAM) between CI group and control group………..88 4.9 Boxplot comparing noise-to-harmonics ratio (NHR) between CI group and
control group………88 4.10 Boxplot comparing the amplitude difference between the 1st and 2nd
harmonics (H1-H2) between CI group and control group………...89 4.11 Boxplot comparing the mean speaking fundamental frequency between
CI males and control males………..92 4.12 Boxplot comparing the highest speaking fundamental frequency between
CI males and control males………..93 4.13 Boxplot comparing the lowest speaking fundamental frequency between
CI males and control males………..93 4.14 Boxplot comparing the speaking fundamental frequency range between
CI males and control males………..94 4.15 Boxplot comparing the mean speaking fundamental frequency between
CI females and control females………95 4.16 Boxplot comparing the highest speaking fundamental frequency between
CI females and control females………95 4.17 Boxplot comparing the lowest speaking fundamental frequency between
CI females and control females………96 4.18 Boxplot comparing the speaking fundamental frequency range between
CI females and control females………96 4.19 Boxplot comparing the mean speaking intensity between CI group and
control group………97 4.20 Boxplot comparing the highest speaking intensity between CI group and
control group………98 4.21 Boxplot comparing the lowest speaking intensity between CI group and
control group………98
4.22 Boxplot comparing the speaking intensity range between CI group and
control group………99 4.23 Boxplot comparing the overall severity between CI group and control
group………...102 4.24 Boxplot comparing pitch severity between CI group and control group……...103 4.25 Boxplot comparing loudness severity between CI group and control group….103 4.26 Boxplot comparing rate severity between CI group and control group……….104 4.27 Boxplot comparing breathiness severity between CI group and control
group………...104 4.28 Boxplot comparing roughness severity between CI group and control
group………...105 4.29 Boxplot comparing diplophonia severity between CI group and control
group………...105 4.30 Boxplot comparing strain severity between CI group and control group……..106 4.31 Boxplot comparing monotone severity between CI group and control
group………...106 4.32 Boxplot comparing resonance severity between CI group and control
group………...107 4.33 Boxplot comparing hard attack severity between CI group and control
group………...107 4.34 Boxplot comparing falsetto severity between CI group and control group…...108 4.35 Boxplot comparing glottal fry severity between CI group and control
group...108 4.36 Boxplot comparing Question 1 between CI group and control group………....113
4.37 Boxplot comparing Question 2 between CI group and control group…………113 4.38 Boxplot comparing Question 3 between CI group and control group…………113 4.39 Boxplot comparing Question 4 between CI group and control group…………113 4.40 Boxplot comparing Question 5 between CI group and control group…………114 4.41 Boxplot comparing Question 6 between CI group and control group…………114 4.42 Boxplot comparing Question 7 between CI group and control group…………114 4.43 Boxplot comparing Question 8 between CI group and control group…………114 4.44 Boxplot comparing Question 9 between CI group and control group…………115 4.45 Boxplot comparing Question 10 between CI group and control group………..115 4.46 Boxplot comparing the sum scores between CI group and control group…….115
LIST OF TABLES
Table Page 4.1 Background information of CI subjects ………76 4.2 Sex and age matched subjects between CI group and the control group………...78 4.3 The comparison of maximum phonation time between CI males and
control males by Mann-Whitney U Test………81 4.4 The comparison of maximum phonation time between CI females and
control females by Mann-Whitney U Test……….82 4.5 The comparison of mean airflow rate and phonation threshold pressure
between CI group and control group by Independent t-test………...83
4.6 The comparison of standard deviations of mean airflow rate and phonation threshold pressure between CI group and control group
by Levene test………...84 4.7 The comparison of perturbations and amplitude difference of
the 1st and the 2nd harmonic of the sustained phonation /a/ between
CI group and control group by Independent t-test……….86 4.8 The comparison of standard deviations of perturbations and
amplitude difference of the 1st and the 2nd harmonic of the sustained
phonation /a/ between CI group and control group by Levene test………89 4.9 The comparison of frequency data in the passage reading acoustic
analysis between CI males and control males by
Mann-Whitney U Test...92 4.10 The comparison of frequency data in the passage reading acoustic
analysis between CI females and control females by
Mann-Whitney U Test………..94 4.11 The comparison of intensity data in the passage reading acoustic
analysis between CI group and control group by Independent t-test…………...97 4.12 The comparison of standard deviations of intensity data in the passage
reading acoustic analysis between CI group and control group
by Levene test……...99 4.13 The comparison of the auditory perception scores between CI group
and control group by Independent t-test……….101 4.14 The comparison of standard deviations of auditory perception
scores between CI group and control group by Levene test………...102 4.15 The comparison of scores on Pediatric Voice-Related Quality of
Life Survey-Chinese version between CI group and control group
by Independent t-test………..110 4.16 The comparison of standard deviations of scores on Pediatric
Voice-Related Quality of Life Survey-Chinese version between CI
group and control group by Levene test……….112 4.17 The comparison of scores on Pediatric Voice-Related Quality of
Life Survey-Chinese version between the subjects with CI implanted
before and after 3 years old by Mann-Whitney U test………...116
CHAPTER 1
Introduction
The typical communication mode is the interaction between production and reception of spoken language, as proposed in “The Speech Chain” (Denes & Pinson, 1993) (Figure 1.1). In this mode, a subtle mechanism loop, the auditory feedback mechanism, plays an important role in a speaker’s monitoring, regulating and
adjusting his/her own speech. Speech is produced from the coordination of respiratory, phonation, articulatory and resonance systems. Reasonably inferred, individuals with hearing loss are more likely to suffer from voice disorders than those with normal hearing due to their less robust auditory feedback. When they speak, they often display too high or low pitch and too high volume. They lack pitch and intensity variations with hypernasality. They tend to be effortful in initiating speaking, which is harmful to their vocal folds, and they often present unpleasant resonance. They are vulnerable to voice disorders (Pruszewicz, Demenko, & Wika, 1993; Wilson, 1987).
Such voice deviances hinder their communication effectiveness, because the deviances lower their speech intelligibility, which in turn makes them spare great efforts to be understood (Perkell, et al., 2000). In addition, their too high volume sometime makes listeners uncomfortable and then reluctant to communicate with them. The frustration as well as isolation feelings withdraw the hearing-impaired from
interactions with others, reducing the frequencies of their social activities and thus lowering their life qualities (Madeira & Tomita, 2010). Speech pathologists are ones who help those with communication disorders improve their communication functions and further life qualities. In this way, the voice problems of the hearing-impaired deserve speech pathologists’ attention.
Fig 1.1 The Speech Chain (Denes & Pinson, 1993)
Research Motive
Spoken language is the primary communication mode for human beings. The language symbols are conveyed through speech sounds, which are the products of the interaction among respiration, phonation, articulation, and resonance. Lung supplies air to make vocal folds into vibration to produce sound. Sound is further shaped by resonant characteristic of the vocal tract to produce voice, so voice determines the quantity and quality of the energy source for speech sounds. In other words, voice is a powerful communication medium. Voice reflects a speaker’s emotions and attitudes, and it varies as a speaker’s circumstances changes to meet the pragmatic purposes. In addition, a speaker’s voice quality, pitch, and loudness impact his/her speech
intelligibility so significantly that it plays an important role in communication effectiveness and thus further interpersonal relationships (Stemple, Glaze, & Klaben, 2010).
Wilson (1987) pointed out pleasant and clear perceptual quality, appropriate oral/
nasal resonance and loudness, age-and-sex-matched pitch, and moderate pitch and loudness variations make up good voice quality. These elements are also the parameters often used to ascertain if a speaker has voice problems.
In terms of hearing-loss individuals’ voice characteristics, hyper -cul-de-sac or -nasal resonance, high pitch and loudness, poor pitch and loudness control, deviant
problems of the hearing-loss population (Bolfan-Stosic & Simunjak, 2007;
Bolfan-Stosic & Tatjana, 1998; Lu, 2010; Nickerson, 1975; Plant & Hammarberg, 1983; Wilson, 1987; Chang, 2000). During their phonation, hard attack onset, glottal fry, too high or low pitch, monotone, monoloudness, and hoarseness are common.
These parameters worsen their speech intelligibility, making their speech difficult to be understood. Besides, they tend to speak with too much effort and intensity to compensate for the diminished feedback of their own phonation (Plant &
Hammarberg; Stemple et al., 2010). This compensation strategy would not only make their voice quality unpleasant and but also injure their vocal folds due to misused laryngeal muscle tension (Thomas-Kersting & Casteel, 1989). The increase muscle tension throughout the larynx and paralarynx leads to laryngeal isometric disorder or lateral hyperadduction, putting speakers at risk of muscle tension dysphonia or organic damage such nodules or polyps (Morrison & Rammage, 1993). Laryngeal isometric disorder is characterized with extrinsic and intrinsic laryngeal muscle hypertonicity, especially the abducting muscles-posterior cricoarytenoid muscles, resulting in posterior glottal chink. It may lead to breathiness. Or the shearing stress of lateral hyperadduction can cause easy fatigue or worse bring damage to mucosa and superficial lamina propria (Morrison & Rammage). In other words, the
hearing-impaired are more vulnerable to laryngeal pathologies than the
hearing-normal. Besides, their hypernasality muffles their speech sounds, making listeners hard to identify what they say (Fletcher, Mahfuzh, & Hendarmin, 1999).
These problems have been attributed to their deficient auditory feedback loops which make them hard to modify their own voice. The more severe the hearing loss is, the more deviant the voice problems are (Coelho, Bevilacqua, Oliverira, & Behlau, 2009;
Lee, in press). People with severe or profound hearing loss have more aberrant voice characteristics than people with mild or moderate hearing loss. What’s more, the earlier hearing loss happens, the more severe speech/voice problems will be (Waldstein, 1990).
Even mildly deviant voice quality impedes speakers’ speech intelligibility (Hazen & Markham, 2004) and lowers communicative effectiveness (Rogerson &
Dodd, 2005). Rogerson and Owing pointed out students’ spoken language processing was better in listening to a teacher with normal voice than listening to teachers presenting mild or severe dysphonia, but the students’ performance wasn’t
significantly different between the two different severities of dysphonia. The authors concluded voice with impaired auditory quality would put extra loading on listeners’
working memory. Listeners would spare more effort to deal with perceptual
processing in speech identification, finding it less available for comprehension. Due to the aforementioned voice quality, listeners may find it more difficult to understand
the speech of the hearing-impaired than that of the hearing-normal, which worsens communication effectiveness of the hearing-impaired. The difficulty impacts their life functions/emotions (Madeira & Tomita, 2010). Due to the inferior voice quality, their participation in social activities is limited, and it further impacts their socio-psycho statuses. For instance, they may avoid talking to friends, neighbors and relatives because of feeling embarrassed about their voice (Madeira & Tomita). These researchers consented to the finding that deviant voice quality causes lower speech intelligibility and further intensifies the reduction of communicative effectiveness.
This implies, with lower communicative effectiveness indirectly caused by voice problems, hearing-impaired children may less participate in group discussion because of both their hearing and voice problems.
To the group’s relief, cochlear implants (CI) are electronic prosthetic device embedded in the inner ear that restores partial hearing to the individuals with severe to profound sensorineural hearing loss, which has developed since 1990s. CI may not only help them retrieve their hearing but also indirectly improve their voice
production through the refired or more robust auditory feedback mechanism (Hocevar-Boltexar et al., 2006; Hocevar-Boltexar, Vatovec, Gros, & Zargi, 2005;
Seifert et al., 2002).
However, CI recipients still have deficits with various degrees on some voice
parameters, so exploring the voice of the CI recipients will be facilitative for programs of aural rehabilitation and voice diagnosis and treatments for them
(Baudonck, D’haeseleer, Dhooge, & Lierde, 2011; Garcia, Rovira, & Sanvicens, 2010;
Hassan et al., 2011; Thomas, 1996; Ubrig et al., 2011). Understanding their voice characteristics and the deviance degree from the normal-hearing will help speech pathologists set up the treatment goals and plan specific interventions. For instance, lessening strained vocal behavior, hypernasality, and monotone of the CI recipients will dampen their vocal fatigue, eliminate unpleasant voice quality, elevate their speech intelligibility, and further improve their communicative effectiveness
(Baudonck et al.; Ubrig et al.). With better communicative effectiveness, life functions are indirectly meliorated, since they may feel engaged in more social activities and relieve their socio-psycho statuses.
Some European and American researchers have explored the voice
characteristics of CI users and suggested treatment indications. They pointed out high pitch and loudness, hypernasality, and strained and unstable voice quality are the most common features (Baudonck et al., 2011; Garcia, Rovira, & Sanvicens, 2010). For example, CI children showed a slight grade of hoarseness, roughness, and strain on the GRBAS perceptual scale, and higher pitch and intensity levels than the
normal-hearing, leading to their less pleasant vocal quality (Baudonck et al.). Garcia
et al. compared the F0, jitter, and shimmer of the speech samples /a/ from four groups, the prelingually hearing-impaired with analogue hearing aids, with digital hearing aids, and with CI, and the hearing-normal. The hearing-impaired as a whole showed poorer voice quality than the control group. CI users showed significantly higher F0, jitter, and shimmer the normal hearing peers.
Recently, speech pathologists have been encouraged to adopt evidence-based practice in speech therapy (Jeng, 2010). A problem may occur when speech
pathologists search for the references to deal with the voice of the hearing-impaired.
Does the voice (e.g., fundamental frequency) of hearing-impaired Americans represent that of the Taiwanese hearing-impaired individuals? Vocal performance varies by different races and languages (Chen, 2005; Krogman, 1972; Wheat &
Hudson, 1988; Whittaker, Suttion & Beardsmore, 2005); African American children grow faster than Causasian children, so the size of African American children’s larynxes was larger than that of the age-equivalent Causasians (Krogman). The speaking fundamental frequency of African American children are lower than that of Causasians (Wheat & Hudson). Languages impact vocal behaviors, too. Chen found greater fundamental frequency range, speaking intensity, and speaking intensity range in tone-language-speaking people than in intonation-language-speaking ones. Chen concluded that larynx continuously adjust to produce tonal variations, which further
strengthen laryngeal control ability so that people speaking tone languages have larger fundamental frequency range, speaking intensity, and speaking intensity range than those speaking intonation languages. In this way, the research outcomes from the Western hearing-impaired group aren’t appropriate to examine Taiwanese group.
Secondly, although there have been some published studies on the CI recipients’
voice, no studies embed a more holistic approach to analyze their voice. The so-called holistic approach of voice evaluation should include visual examination, aerodynamic, acoustic, auditory perception and patients/caregivers-reported life quality (Dejonckere, et al, 2001; Stemple et al., 2010). A multidimensional assessment leads to a better description of present voice symptoms, a stronger tool for patient education and motivation, and a more individualized management plan. It can pave the way for higher success rate of voice treatments so that the inconvenience caused by voice problems will decrease to improve communication quality (Stemple et al.). Therefore, the voice characteristics of the CI users, its functional/physiologic/emotional impact, and appropriate interventions will be shown if a multidimensional protocol is adopted.
For instance, Thomas (1996) reported a female patient with severe hearing loss underwent speech and voice assessment before she decided to be fitted with a bone anchored hearing aid (BAHA). The assessment results recommended her the BAHA surgery. After the surgery, she received speech and voice therapy in which she learned
to use proper pitch. Following training, lowered pitch and increased pitch range improved her intonation performance. Getting rid of depression and low-esteem, she became positive and confident because of the multidisciplinary intervention. Recently, Hassan et al. (2011) examined the effect of cochlear implants and post-operative rehabilitation on voice qualities in postlingual hearing-impaired adults by acoustics.
Those who received auditory rehabilitation in which speech pathologists paid
attention to their voice quality showed more improvements on F0, jitter, shimmer than those who didn’t. The authors concluded cochlear implants augmented with auditory rehabilitation bring better control ability in pitch and loudness. The only three studies on Taiwan hearing-impaired individuals or CI users’ voice (Chang, 2000; Lee & Lin, 2009; Lu, 2010) merely used acoustic or acoustic/auditory perceptual evaluation respectively, instead of a multidimensional evaluation. CI recipients’ vocal functions and voice-related life quality remained unknown.
Last, recruiting elementary school students, especially those at 8-to-12 years old, as subjects is for the experimental validity, contribution, and practicability. Su et al.
(1997) reported that Taiwanese boys start mutation voice with the range from the age of 11 to 14, with the average age of 12 years and 8 months old. Girls undergo the period a little earlier than boys (Hocevar-Boltezar, Burger, & Žargi, 1997). Therefore, the voice of grade-three and grade-four elementary school students can exclude
factors affecting internal validity; that is, the perturbations of mutational voice.
Considering its clinical contribution, children have higher phonatory neuromuscular plasticity in learning new vocal behaviors than adults who have already had fixed vocal behaviors hard to be changed (Hocevar-Boltezar et al., 2006). The research outcome may offer indications to the practice of pediatric aural rehabilitation and speech therapy in which children have higher success rate in acquiring new vocal skills. As to the experimental practicability, elementary school students can follow the instructions more easily than preschool-aged kids, so it is more practical for
researchers to investigate elementary school students. In sum, the aforementioned three reasons make up the rationale of recruiting elementary school students as the subjects.
With the three research motives, it is necessary to adopt a multidimensional assessment to gain a more comprehensive picture of the voice of the Taiwanese elementary school students with CI, which may further become the indications for speech therapy for the group. As to the clinical contribution of the present study, it is hoped that through the present research, speech pathologists will comprehend the voice characteristics of Taiwanese elementary school students with CI and the impacts of their voice. The information may provide indications for speech pathologists to manage interventions for the voice problems of the group. For example, by comparing
their voice with that of the normal-hearing, speech pathologists will select the focused points, select the proper treatments, and predict the prognosis. Once their voice
problems get lessened or resolved, their speech intelligibility may be improved. With better communication effectiveness, they may be more willing to participate in class and extracurricular activities. Their life functions are thus elevated.
Research Purpose
Individuals with severe to profound hearing loss are a risky group of voice disorders due to their less robust auditory feedback in manipulating their voice. High pitch and intensity, hypernasality, and strained vocal quality are the main
characteristics. Even CI recipients present different severities on some voice parameters. The deviant voice lowers their speech intelligibility, worsening their communication effectiveness and further limits their activities participation.
Although there have been some European and American researches on the voice of the CI recipients, which also offered treatment indications, it is doubtful to directly apply the research outcomes to Taiwanese CI group. Vocal performance varies by different races and languages (Chen, 2005). Besides, it has been strongly urged to use the multidimensional assessment in voice evaluation recently, since the approach can help detect specific problems and further lead to proper treatments (Dejonckere, et al, 2001). The major limitation of previous European and American researches on the CI group’s voice is the lack of a multidimensional method. Considering experimental validity, contribution, and practicability, elementary school students with CI are the subjects in the current study. Through the present research, speech pathologists will understand the voice characteristics of elementary school students with CI more deeply so that they can know how improve voice quality of the group. With better
for them, which may bring them better life functions and emotion (Madeira & Tomita, 2010).
In this way, the purpose of the study was to investigate the vocal functions and voice-related life quality of CI children by comparing the data between CI children and the normal-hearing children from aerodynamic, acoustic, auditory perception, and caregivers-reported assessments. Due to the financial and technical problems, visual examination was excluded.
The outcomes may facilitate clinical workers understand the voice characteristics and voice-related life quality of the elementary school students with CI, and
appreciate the individual differences. Therefore, in addition to the traditional cores in aural rehabilitation-articulation therapy and language richness, they will know one aspect of the vocal approach with the hearing-impaired must be focused on the
protocol for improvement of the deviant voice quality and the use of appropriate pitch and intensity (Baudonck, D’haeseleer, Dhooge, & Lierde, 2011; Hassan et al., 2011;
Thomas, 1996; Ubrig et al., 2011).
Research Questions
The purpose of the present study is to compare vocal functions and voice-related life quality between the elementary school students and their normal-hearing
counterparts CI from a multidimensional view. The following two research questions are proposed to fetch a broader picture about the voice of the hearing-impaired.
1. Does the voice of the elementary school students with CI differ aerodynamically, acoustically, and auditory-perceptually from the students with normal hearing?
2. Does the caregivers-reported voice-related life quality of the elementary school students with CI differ from the students with normal hearing?
CHAPTER 2
Review of Literature
In this chapter, the published studies on auditory feedback mechanism, the definition of hearing loss and its impacts on language/speech/voice, the impact of voice disorders: patients’ caregivers-reported assessments, the introduction to cochlear implants, and cochlear implant recipients’ voice, and multidimensional protocol in voice evaluation were reviewed.
Auditory Feedback Mechanism
Auditory feedback has been theoretically defined as an internal communication loop which helps speakers self-monitor, control, and adjust their voices when they phonate or speak for using their voices appropriately like expressing their emotions and social status (Burnett, Senner, & Larson, 1997; Donath, Natke, & Kalveram, 2002;
Waldstein, 1990).
Almost all speech production models such as Target Model and Feedback and Feedforward Model regard auditory feedback as the most primary internal feedback loop regulating and maintaining voice and supra-segmental speech elements among all vocal feedback mechanisms, including kinesthetic, tactile, visual, and other
proprioceptive feedback information (Ferrand, 2007, chap. 14; Ludlow, 2005; Mallard, Ringel, & Horii, 1987; Monsen, Engebreston, & Vemula, 1979; Perkell et al., 2000).
Target Model proposes speakers code a chain of speech targets in the brain in advance, with acoustic and other feedback information sent back to their brains to achieve expected movements and revise any deviances (Borden, Harris, & Raphael, 1994). As to Feedback and Feedforward Model, feedback signals (primary through auditory system) help detect and correct any errors in speech output while feedforward information makes on-line speech adjustments at the peripheral system (Guenther, 1995). It is hard for the hearing-impaired to not only utilize auditory feedback but also develop feedforward pattern of which the prerequisite is the feedback signals.
Perkell et al. (2000) proposed a modeling framework on how auditory feedback information affects speech and voice production by comparing three subjects’ speech and voice. They were one subject with normal-hearing, one with cochlear implants, and one with a neurofibromatosis-2. The researchers recorded the three subjects’
reading of Rainbow Passage and did the acoustic analysis. The researchers found more deviant speech and voice productions in one with cochlear implants and one with a neurofibromatosis-2. The researchers concluded that speakers use auditory feedback as an inverse kinematics controller to resend acoustic signals into speech and voice production centers in the cerebrum to re-organize and adjust motor planning signals. Speakers can activate the target speech and voice muscles for achieving expected acoustic outcomes. The results were consistent with the research findings of
Monsen, Engebretson, and Vemula (1979) and of Waldstein (1990). Monsen et al.
collected the glottal volume-velocity waveform of 20 severe to profound
hearing-impaired adolescents, who produced a three-syllable word with the first stress on the middle syllable. Diplophonia, hard attack onset, greater jitter and shimmer values (i.e., period-to-period fundamental frequency and amplitude variability respectively) and irregular glottal pulse changes were observed. The finding implied deafness straitened the hearing-impaired in acquiring the maintenance and alteration of time-varying phonatory muscular gestures and subglottal pressure. In addition, Waldstein compared the fundamental frequency (F0), F0 standard deviations and jitter value of seven postlingually deafened adults and of seven gender-and-age matched normal-hearing individuals in a sentence-reading task. The postlingually deafened speakers showed slightly but no significantly higher F0, comparable F0 standard deviations, and significantly lower jitter. Less jitter in the postlingually deafened speakers could be attributed to auditory feedback deprivation. Such deprivation caused their less ability to monitor their own acoustic signals which in turn resulted in monotonous speech. The research of Economou, Tartter, Chute, and Hellman (1992) also reflected the existence of such a feedback loop. They found increased F0 in a 10-year-old girl after her first single-channel cochlear implant failed but a decrease to normality with a multi-channel reimplantation.
The auditory feedback mechanism was also observed in empirically-controlled experiments. Kirk and Edgerton (1983) reported F0 and relative intensity were the parameters that changed the most largely in perceptual and acoustic domains in cochlear implants use. Four speakers with cochlear implants produced F0 and intensity in the direction of the parameters produced by the normal-hearing speakers in the ON condition instead of the OFF condition. Kirk and Edgerton regarded the reduced need for kinesthetic feedback as the rationale of more appropriate pitch and loudness in the auditory feedback ON condition. Similar result was found in Svirsky, Jones, Osberger, and Miyamoto’s research (1998); pediatric CI users had normal-like nasalance in ON instead of OFF condition.
Burnett, Senner and Larson (1997) did a randomized-controlled experiment in which 67 normal-hearing young adults emitted an American English vowel /a/ at their habitual speaking pitch and loudness as long as they could or sang musical scales under the circumstance that the pitch of their voice was modulated and fed back through earphones. Masking noise was incorporated into the earphones to prevent the subjects from hearing their actual voice; besides, they were told to neglect any
intermittent shifts in pitch feedback in the earphones. It showed the fact that 96%
subjects increased their F0 while the feedback pitch was decreasing and 78%
decreased their F0 while the pitch feedback was being altered upward. The findings
strengthened the evidence that auditory feedback loop exists and indeed works and were consistent with the hypothesis of the model framework mentioned (Perkell et al., 2000) that speakers depend on auditory feedback to control voice. Donath, Natke and Kalveram (2002) supported the effect of auditory feedback carrying over
supra-segmental aspects of voice rather than confined to only one segment. They measured the F0 for the first two syllables of the nonsense word [΄ta:tatas] produced by 22 normal-hearing German adults. These subjects wore headphones through which the pitch feedback adjusted from their own actual voice productions were transmitted back. They underwent some masking procedures as well to minimize the interference from hearing their real F0. The subjects not only increased their pitch for the stressed syllable but also maintained such level upon the unstressed syllable while they were receiving the after-modification lowered F0 feedback emerging only in the stressed syllable.
Similarly, Ferrand (2006) found normal-hearing female speakers significantly increased their intensity of the vowel production /a/ from normal auditory feedback to an 80-dB masking level condition. Auditory feedback plays an important role in regulating voice; however, it is not the sole contributor. Ferrand reported the increased intensity of the sustained phonation /a/ under an 80-dB masking; however, F0, jitter, and harmonics-to-noise ratio didn’t differ significantly between 0-dB masking level
and 80-dB level conditions. The author pointed that the increased intensity justifies the Lombard effect. The stability of F0, jitter, and harmonics-to-noise ratio may be the product of kinesthetic feedback compensation for the auditory feedback disruption.
That is, under masking noise disruption, as intensity increases, the vocalis and cricothyroid muscles as well as the sensory mechanoreceptors of mucosal layers of the larynx engage kinesthetic feedback more fully to employ a more balanced force of vocal folds. It further stabilizes the fluctuations in the vocal folds length and tension.
Hence, F0, jitter, and harmonics-to-noise ratio didn’t change significantly under different masking situations. The author also pointed out there were great
inter-individual differences, which might be attributed to the varying degree to which they used the compensatory strategies.
In summary, these reviewed studies bring out a fact that internal auditory feedback mechanism is an important regulator for vocal behaviors, that is, the audio-vocal reflex.
The Definition of Hearing Loss and Its Impacts on Language/Speech/Voice Hearing loss refers to any extent of impaired ability to apprehend sound (Tye-Murray, 2009). Its cause can be organic deficits or functional breakdown, and congenital or acquired. Hearing loss can be further classified according to its onset, form, and severity.
As to the onset of hearing loss, a hearing loss can be marked as prelingual, perilingual or postlingual. There is still no an absolute cut-off age to determine the three labels. However, it is generally accepted that a hearing loss occurring before the age of two years is labeled as prelingual, one occurring after acquiring some but not complete spoken language is perilingual, and one happening after the acquisition of language and speech (around at the age of five years) is postlingual (Tye-Murray, 2009).
In terms of the forms, hearing loss is divided to conductive, sensorineural, mixed types. Conductive hearing loss is a problem conducting sound waves along the outer ear, the tympanic membrane, and the middle ear cavity. Sensorineural hearing loss happens when deficits occur in vestibulocochlear nerve, the inner ear, or the central auditory processing path to the cortex. Mixed-type hearing loss is a situation
conductive hearing loss occur in conjunction with sensorineural hearing loss (Tye-Murray, 2009).
average (PTA). PTA refers to the average hearing thresholds at 500, 1000, and 2000 Hz, which covers the frequency band of most speech sounds. PTA within 0 to 25 dB HL is normal hearing, 26 to 40 dB HL means mild hearing loss, 41 to 55 dB HL is moderate, 56 to 70 dB HL is moderate-to-severe, 71 to 90 dB HL means severe, and above 91 dB HL refers to profound hearing loss (Goodman, 1965).
Hearing is an important factor for determining language and speech development (Guenther, 1995). Speaking of its influence on language development, slow language acquisition, limited lexicon, immature syntax such as telegraphic speech without functional words, difficulty in comprehending abstract words and in initiating a conversation and using repair strategies, and a plateau effect on reading and writing ability are often found in students with hearing loss (Hegde & Maul, 2006; Moeller, Osberger & Eccarius, 1986). As to speech development, articulation/phonological disorders are common in people with hearing loss, because they are less capable of acquiring place and manner of articulation and decoding the phonological systems of their native languages. It is harder for them to detect their own articulatory errors and make revisions (Tye-Murray, 1992). Forner and Hixon (1977) found the profoundly hearing-impaired individuals had less efficient use of lung volume on speaking, too much airflow per syllable, waste of airflow during pauses, and inhalation/exhalation at inappropriate syntactic units. They attributed the bizarre speaking respiratory
behavior to the abnormal auditory sensation and inappropriate early speech skills instruction.
In terms of the hearing onset effect on speech, it is known that there existed a negative relationship between hearing onset and speech severity (Tye-Murray, 2009;
Waldstein, 1990). The construction of speech development requires auditory feedback;
for example, the activities of place/manner of articulation and vocal manipulation are gradually pruned by hearing others and self-hearing (Tye-Murray, 1992). Plant and Hammarberg (1983) reported a 59-year-old speaker whose deafness happened at age 49 preserved the ability to raise F0 to signal emphatic stress while two 18-year-old speakers who were deafened at age 8 and 9 failed to do so. There seems to be a critical period of speech development (Hocevar-Boltezar et al., 2006). The earlier the intervention gets into the hearing-impaired, the higher possibility their speech can develop normally will be. Seifert et al. (2002) reported the different degrees of deviant voice in 20 German prelingually deaf children with cochlear implanted at different ages. The analyses showed a general pattern where the F0 values of children implanted before their fourth birthday didn’t significantly deviate from those of normal-hearing peers; nonetheless, the F0 values of cochlear implants children undergoing their implantations at older ages were significantly higher than their matched pairs’ values. Prelingually deaf children who received their implantation
before they were four years old might attain to a sturdier laryngeal control that further carried over to better acoustic qualities than those who received after their fourth birthday. Hocevar-Boltezar et al. assessed the influence of acquired or re-acquired auditory control on voice in 29 prelingually deafened children and adults before and after cochlear implantation. The prelingually deafened children showed significant improvement in jitter, shimmer, F0 variation, and peak-amplitude variation after 6 to 12 months’ cochlear implants use; on the contrary, postlingually deafened adults showed no significant improvements in any of the voice parameters. It was indicated that children have the plasticity of phonatory neuromuscular control and of adapting themselves to a new situation.
The relationship between hearing loss severity and speech severity is positive (Tye-Murray, 2009). Elfenbein, Hardin-Jones, and Davis (1994) reported more misarticulations of fricatives and affricates and higher hoarseness and resonant deviances in those with severe hearing loss than those with mild-moderate hearing loss. Coelho, Bevilacqua, Oliverira, and Behlau (2009) found the higher consonants recognition accuracy was, the richer prosody in sequential speech, the lower standard deviation of fundamental frequency, and the lesser the strain, pitch and resonance problem was in 25 children with cochlear implants. Lee (in press) used power spectral analysis to detect F0 variability of sustained vowels in speaker with sensorineural
hearing loss. The author found the low-frequency modulation (<3 Hz) were greater in subjects with sensorineural hearing loss than in normal-hearing speaker. The greater hearing loss was, the larger low-frequency modulation would be.
Hearing loss deviates voice production as well. Voice disorder refers to the condition in which a person’s voice quality, pitch, and loudness perceptually differ from those of similar age, gender, cultural background and geographic location. It also means the time when either the structure, the function or both of the laryngeal
mechanism no longer meet the voicing requirements by the speaker, who may report his/her vocal symptoms which others don’t recognize (Stemple, Glaze, & Klaben, 2010). Vocal abuse/misuse, medically-related causes, primary disorder etiologies, and personally related factors are the etiologies. The voice disorder rooted from hearing loss belongs to primary disorder etiology (Stemple et al., 2010).
Due to the less robust auditory feedback mechanism, the hearing-impaired cannot monitor and manipulate their own voice as the normal-hearing individuals can.
Hence, the hearing-impaired is a vulnerable population to voice problems (Madeira &
Tomita, 2010; Pruszewicz, Demenko, & Wika, 1993; Wilson, 1987).
Limited exposure to auditory stimuli deviates infants’ vocal motor as well as speech sounds development (Maskarinec, Cairins, Butterfiled, & Weamer, 1981).
Maskarinec et al. compared three normal-hearing and two hearing-impaired infants’
vocalizations in their first 8.5 months, finding that hearing-impaired infants produced significantly different vocal activity patterns from the normal-hearing group.
Although both groups produced vocalizations, the former manifested lower emersion rate of speech-like vocalizations and more variable declination of non-speech ones than the later did. This finding implied the fact that hearing-impaired infants don’t get ready for founding the steady vocal and phonatory basis for normal voice and speech production as normal-hearing individuals with sufficient voice and speech input usually do in the first year of their life due to their auditory perceptual dysfunction.
Older individuals’ voice characteristics were also influenced by insufficient auditory feedback, which distinguishes their voice from that of the hearing-normal.
Voice is the product from the coordination of respiratory, phonation, and resonance systems. Hearing-impaired individuals are vulnerable to bizarre speech breathing due to insufficient acoustic feedback (Cavallo, Baken, Metz, & Whitehead, 1991; Forner
& Hixon, 1977). Forner and Hixon found the prelingually deaf subjects had rib cage predominance in the in rib cage-abdomen contribution to speech breathing as the normal-hearing did. However, the deaf started their expiratory limbs lower than the normal-hearing did and they had low resistive mechanical loads to the larynx and upper airway, leading to less efficient speech breathing usage. Cavallo et al.
ascertained the normalcy of congenitally profoundly hear-impaired persons’
prephonatory chest wall posturing (i.e., rib cage expansion and abdominal contraction) but the anomaly of higher air loss during the prephonatory posturing adjusting time.
In short, the speech breathing disorder of the hearing-impaired results from the incoordination between their laryngeal and respiratory systems instead of their ventilatory function.
The hearing-impaired also had difficulty in controlling intrinsic muscles to maintain periodic vocal folds oscillation and in manipulating appropriate laryngeal structures during phonation, which further resulted in hyperadduction or
hypoadduction of their vocal folds (Formby & Monsen, 1982; Mahshie & Conture, 1983; Mahshie & Öster, 1991; Metz, Whitehead, & Whitehead, 1984; Monsen, 1979).
Inadequate F0, over-aspiration, spectral noise were often noted in hearing-children (Bolfan-Stosic & Tatjana, 1998). Monsen recorded monosyllabic productions from twenty-four hearing-impaired children between three to six years old and analyzed them both perceptually and acoustically. Unlike the smoothly-falling F0 contour produced by the hearing-normal, the hearing-impaired children produced several deviant F0 contours, including, changing, flat, falling-flat, and short-falling contours, which served as the most important voice characteristic distinguished the
hearing-impaired from the hearing-normal. Diplophonia and breathiness were described in the utterances of the hearing-impaired. Besides, the subjects’ hearing
thresholds significantly negatively related to the perceived voice quality. Monsen attributed the observations to their poor control over the air supply and vocal-fold tension which led to their undesirable vocal production. Formby and Monsen (1982) reported more irregular and poorly defined harmonic structure and steeper spectral slopes in deaf adolescents’ speech spectrum, indicating deaf talkers’ less delicate laryngeal control. Mashie and Conture (1983) found hard-of-hearing speakers used different laryngeal behaviors for different tokens of a particular phoneme production (e.g., both adducted laryngeal gesture and abductory-adductory gesture for /p/), attributed to their inadequate laryngeal motor control. Metz et al. (1984) used high-speed laryngeal image to examine how deaf speakers’ laryngeal valve acted in producing the syllables /əhə/. Deaf speakers’ /h/ duration (288-600 ms) was
significantly longer than that of the normal-hearing (174-272 ms). During phonation, the glottis width of some deaf speakers was as twice as that of the latter. The results may explain the deaf speakers’ less ability in controlling laryngeal muscles to keep periodic oscillation and the excessive airflow expenditures during their speech.
Mahshie and Öster (1991) recorded less glottal efficiency in eight deaf speakers, which was reflected in their higher Minimum Flow rate, Open Quotient, Abduction Ratio, and lower Speed Quotient (ratio of glottis opening phase duration divided by closing phase) than their normal-hearing counterparts by the measurements of glottal
volume velocity and electroglottography.
As techniques progressed, Higgins, Carney, and Schulte (1994) used
electroglottography, a respiratory plastic facemask, a nasal mask and a polyethylene tube to investigate the impact of the hearing loss on phonatory, velopharyngeal, and articulatory functioning of 11 moderate-to-profound hearing loss adults with good to excellent oral communication abilities. Among the three speech subsystems, in spite of notable between-subject variability, abnormal behaviors were more evident in phonation than in velopharyngeal function and articulation. Compared with the normal-hearing, higher subglottal pressure, higher F0 and vocal folds
hyperconstriction/hypoconstriction were noted in the hearing-loss group. The F0 of the hearing-loss males and of the hearing-normal males were 158.5 Hz and 118.6 Hz respectively while 223.8 Hz and 186.8 Hz for females. The subglottal pressure of the hearing-loss group was 13.5 cm H2O for males and 8.9 cm H2O for females. In the hearing-normal group, the figure was 6.6 cm H2O for males while 6.0 cm H2O for females. To facilitate auditory self-monitoring, the hearing-impaired speakers may have greater tactile sensation from increased vocal folds contact and the tension of extrinsic laryngeal muscles which in turn causes higher subglottal pressure and thus greater loudness. As to higher F0, it may be the product of their increased subglottal pressure, as Titze (1989) pointed out 1 cm H2O increase in subglottal pressure brings
two to 6 Hz in F0. Higgins, McCleary, Ide-Helvie, and Carney (2005) collected the physiology of ten five-to-fifteen year-old hard-of-hearing children’s voice, tokens of
“pop,” “puppy,” “baby,” “bye-bye baby” and the consecution of the syllables [ma], [pa], and [pi], by electroglottograph (EGG) and Nasometer II. Voice onset time (VOT), F0, phonatory airflow, and nasal airflow were examined. Compared to the authors’
previous data consisting of fifty-six normal-hearing children and seven cochlear implants children, it exhibited abnormally similar voice onset times (VOTs) for both voiced and voiceless stops, higher than normal F0 and other deviant or
borderline-deviant voice behaviors despite individual differences of phonatory and nasal airflow in these children’s voice. Higgins et al. attributed these poor voice productions related to vocal fold tension and vocal fold articulation to these children’s diminished audition.
Bolfan-Stosic and Simunjak (2007) reported the voice of ten school-age boys with congenital sensorineural hearing loss to be higher in F0 variability (12.15 Hz vs 2.73 Hz) and in voice perturbation indices such as jitter (2.56 % vs 0.88 %), shimmer (1.37 dB vs 0.78 dB), while lower in harmonics-to-noise ratio (2.48 dB vs 4.22 dB) in their sustained Croatian vowel /a/ production than those of the age-match
normal-hearing peers. These may be explained by excessive air escape and irregular vocal folds vibration of the hearing-impaired. Absence of normal long-term F0
variability in the hearing-impaired may be ascribed to their impotent respiratory support and vocal folds tension. Besides, broader nasal antiformants at around 1000 Hz were present in the hearing-impaired. The presence may due to hearing-impaired individuals’ mislearning velopharyngeal insufficiency which produced immoderate nasal resonance. They further pointed out that the overall impression of
hearing-impaired people’s voice is over-aspiration and made of higher spectral noise.
Over-aspiration is a compensatory behavior for the hearing-impaired, especially for harmonics above 500 Hz, because it may increase their tactile feedback while they phonate or speak. The hypertonicity of posterior cricoarytenoid muscle led to the posterior glottal chink shape, causing a breathy quality and changing the temporal features. Higher F0 for the hearing-impaired was usually seen in various relevant studies. In all, Bolfan-Stosic and Simunjak verified the hypothesis that less auditory feedback led to the hearing-impaired subjects’ deviant respiratory, phonatory, and resonant functions. The acoustic research on the voice of Iranian boys with profound hearing-loss obtained the near-same results (Dehqan & Scherer, 2011).
Lee and Lin (2009) studied the changes of rhythm of vocal F0 of the Mandarin vowel /a/ in sensorineural hearing loss adults. The vocal intensity of the sensorineural hearing loss (84.5 dB) was significantly higher than the normal-hearing (79.0 dB). As to the F0, it (168.4 Hz) wasn’t significantly different from than the normal-hearing
(158.2 Hz); however, its fluctuation was in significantly slower but larger amplitude.
The authors pointed out that it was due to the insensitive response reaction of audio-vocal reflex underlying the clients.
The hearing-impaired usually present a functional disorder of the velopharyngeal sphincter physiology, resulting in their resonance problems-hypernasality or
hyponasality. Ysunza and Vazquez (1993) examined the valving mechanism of velopharyngeal port of 53 adolescents with prelingual profound bilateral hearing loss and with intact velopharyngeal structure. They found abnormal rhythm and weak strength of the velopharyngeal sphincter in more than three-quarter of the subjects despite normal electromyographic muscle activity. This corresponded to the subjects’
severe hypernasality speech. Fletcher, Mahfuzh, and Hendarmin (1999) used a Kay Elemetrics 6200 Nasometer to investigate nasalance in thirty profoundly deaf children and in thirty children with normal hearing. The experimental group had significantly higher nasalance when nasal consonants were absent and significantly lower
nasalance when the targeted speech was loaded with lots of nasal consonants. These evidences may be interpreted as the hearing-impaired individuals’ limitation in manipulating nasal versus oral sound emission. The authors of both studies concluded absence of auditory regulation during phonation might be the cause. If the auditory feedback is restored, the deviant resonance of the hearing-impaired may be lessened.
As to auditory perceptual evaluation on the voice of the hearing-impaired, Plant and Hammarberg (1983) reported four speech pathologists’ perceptual evaluation of speech of two deaf individuals whose deafness occurred at eight or nine years old and one whose deafness acquired at forty-nine. The common characteristics included pressed voice and monotone. The researchers pointed out individuals with impaired hearing were easily in the habit of increasing pressure and laryngeal tension to maximize non-auditory feedback to phonation. Thomas-Kersting and Casteel (1989) pointed out 18 severe-to-profound hearing-impaired children’s sustained /a/ and /u/
sounded as tense, strained, and metallic. Finding a positive correlation between the perceived vocal effort and the inharmonic components in these children’s speech, they also observed the children’s tense shoulder and thoracic postures, breath-holding prior to phonation, exaggerated breathing patterns, facial grimaces, exaggerated mouth opening and closing, and tightening neck muscles during phonation. Chang (2000) investigated the perceptual and acoustic qualities of 100 Taiwanese moderate to profound hearing-impaired elementary and junior high school students’ voice (speech data: one short sentence and Mandarin Chinese vowel /a/). Among the fourteen perceptual items, the author found most students’ voice were characterized by too high or low pitch, too high loudness, slow rate, breathiness, roughness, strain, and hard attack, which conformed to the acoustic results: high shimmer (5.86%), low
harmonics-to-noise ratio (16.04 dB), and less harmonic numbers (7.15). However, aerodynamic and patients/caregivers-reported assessments weren’t included in Chang’s study so that the Taiwanese hearing-impaired individuals’ glottal valving function and how their voice problems impacted their life still remained unknown.
The Impacts of Voice Disorders: Patients/Caregivers-reported Assessments
Voice is a powerful communication tool because it conveys speech sounds. It can also decide an individual’s self-impression (Stemple, Glaze, & Klaben, 2010). Once it gets disordered, speakers’ communication functions will be negatively impacted.
Voice problems may not only lower speakers’ speech intelligibility but also result in worse life functions and emotion. The definition of the impacts of voice disorders in the present study refers to voice-related function impairment, activity limitation, and participation restrictions (World Health Organization, 2000). Function impairment means an individual’s physical function or structure gets damaged. Activity limitation refers to the difficulty an individual encounters in doing activities. Participation restriction denotes the situation in which an individual’s voice problem influences his/her social activity, environment, economics, and emotion.
Smith et al. (1996) used a questionnaire to investigate the impact of voice
disorder of 174 patients from two voice clinics. Physically, about 60% to 70% of these patients reported they found it hard or effortful to initiate speaking, especially when they spoke in a noisy environment. Functionally, talking on the telephones was also a trouble for many of them (58%), and they were often asked to repeat themselves to be understood (58%). Their voice disorders brought difficulties to their jobs (55%).
Three-fourth of them reported their voice problems limited social activities.
Additionally, the more severe the voice was, the more negative impacts and feelings they had.
Like those with laryngeal pathology, the individuals with hearing loss also experienced the disruptions of voice-related function impairment, activity limitation, and participation restrictions because of the voice problems caused by their
insufficient audition. Using Voice Handicap Index (VHI), a self-assessment tool to know the voice-related function impairment, activity limitation, and participation restrictions of an individual, Madeira and Tomita (2010) found higher index in seventy-eight bilateral sensorineural hearing loss clients than the normal-hearing individuals. In the VHI functional aspect, the experimental group showed a median score of 9.5 while it was 1 for the experimental group. In the VHI physical domain, it was 7.5 for the former and 0 for the latter. The VHI emotional subitem had 9.9 for the former while 0 for the latter. The total score was 23.5 for the hearing-impaired and 4.0 for the hearing-normal. Due to the difficulties in hearing their own voice, they were distressed in their functional, physical, and emotional life. They felt struggled to produce their voice, felt breathless when talking, and so on, so they usually felt themselves difficult to be understood. Gradually, they restricted themselves from personal and social lives (such as telephone talking and group of people) because of their voice. They were more likely to feel ashamed of their voice problems and
embarrassed when listeners ask them to repeat themselves than those without hearing and laryngeal problems. There was a trend toward a greater social or economical disadvantage from the disability or physical impairment associated with the vocal deviances caused by hearing loss.
However, Madeira and Tomita (2010) didn’t involve objective measurements such as aerodynamics and acoustics. Whether the higher VHI scores were reflected in the objective performances remained unclear. The next section would illustrate the value of multidimensional protocol in voice evaluation and its ingredients.
