The anatomy of the auditory system can be divided into three main parts: the outer ear, the middle ear and the inner ear (Martin & Clark, 2015). The outer ear consists of the auricle, the visible part of the ear and the ear canal. This mechanical energy is transferred to the fluid-filled organ of the inner ear, the cochlea.
Frequency is the rate at which sound pressure fluctuates over a period of time (CDC, 2016). Moldable earplugs can be made from materials such as polymer foam or silicone putty and are molded to the shape and size of the ear canal after insertion (Alam et al., 2013). The first test of the hearing system to determine an individual's hearing health is otoscopy.
The eardrum allows for inferences about the condition of the rest of the middle ear system. Based on the flexibility of the eardrum, a graph called a tympanogram is drawn and the status of the middle ear system can be deduced (Martin & Clark, 2015).
LITERATURE REVIEW LITERATURE REVIEW
A study of young adults in Flanders, Belgium showed that 7% of young adults already have NIHL. Additionally, identifying the severity of the NIHL risk will depend on the environment in which the hearing protective device will be used. HPDs have higher attenuation values than subject-matched HPDs due to accurate and consistent fit of the protector by a single trained experimenter (Murphy et. al 1998).
NBN was used as one of the stimuli in sound field testing, as it was used in previous related studies (Salmani Nodushan et al., 2014). The outer hair cells of the cochlea relay stimuli to high-frequency sounds, so when they are damaged, the ability to hear higher frequencies is lost. A Swedish study covered in Lie et al.'s (2016) systematic review found that only 8-28% of the "workers" in their study, workers in the automotive industry, shipyards and quarries, had normal hearing in compared to 70% with normal hearing among office workers.
A study of Egyptian metallurgists from the same review showed that their NIHL occurs at higher frequencies (Lie et al., 2016). Impact noise has been found to be more harmful than long-term exposure to loud noise (Lie et al., 2016). The high energy levels of sound mean that the length and frequency of exposure required to cause damage is much shorter than continuous exposure.
The review by Lie et al. (2016) contained a study of artillery recruits exposed to percussion noise such as gunshots and explosions, showing that 17% of recruits had a hearing loss greater than 15 dB in at least one frequency. An additional study in the review compared Canadian foundry workers from different departments of the same factory (Lie et al showed that the prevalence of hearing loss was highest in pulse noise areas and lowest in continuous noise areas. Additionally, the study investigates whether the attenuation of foam earplugs will be similarly affected by using narrowband noise or distorted tone as test stimuli.
Research question #2: Foam earplugs News frequency attenuation of the two selected stimuli, narrowband noise and warble tones, will be different.
METHODS METHODS
Participants responded to an email (see Appendix A) stating the overall purpose of the study and an incentive to enter a sweepstakes for one of three $15 Starbucks gift cards or additional credit in a predetermined class. When describing the purpose of the study in the email, deception was used so as not to influence the participants' response. This principle is known as the Hawthorne effect (Chiesa & Hobbs, 2008). Knowledge of the purpose of this study may have led participants to insert the earplugs in a different way than they would in practice.
Participants were aware that multiple hearing evaluations regarding earplugs would occur, but not that their performance would be measured against an experimenter. Otoscopy consisted of checking the ear canal using an otoscope (Welch Allyn Otoscope, Welch Allyn Inc., Skaneateles Falls, New York) to ensure a clear ear canal and an absence of abnormalities in the outer ear (CDC, 2016) ). Pure-tone audiometric testing was performed using a two-channel clinical audiometer (GSI Audiostar Pro, Grasen-Stadler Inc, Eden Prairie, Minnesota).
During otoscopy, the proper bracing procedure, as described in the American Speech-Language-Hearing Association guidelines for audiological screening (ASHA, 1997), was used to ensure that the tip of the otoscope did not extend too far into the subject's ear canal. Audiometry was performed following ASHA standard operating procedure to ensure subject safety during testing (ASHA, 2005). At the top of the data collection sheet, record the otoscopic and tympanic membrane results as well as the results of the hearing screening.
These measures were recorded under three conditions: baseline threshold without hearing protection, threshold for self-fitting earplugs, and threshold for experimenter-fitted earplugs. After the audiometric test was completed, participants completed a 13-question questionnaire (see Appendix C) regarding their experience in the study, as well as their history of hearing protection in the past. In addition, a copy of the IRB-approved consent form was provided to each participant at the time of consent (see Appendix E).
Upon completion of the study, participants were debriefed and signed a reconsent form (Appendix F), agreeing to the use of their data following the disclosure of deception.
RESULTS
At the end of this step, the participants removed the earplugs and the researcher placed a new pair in their ears using the ASHA approved procedure. The first hypothesis considered was: The foam earplugs' lower frequency attenuations will be affected differently by user error than the higher frequency attenuations. For the purpose of this research, user error was defined as the threshold obtained by the experimenter-fitting earbuds minus the threshold obtained by the self-fitting earbuds.
User error was calculated at each frequency, then averaged together by high or low level to arrive at an average user error for both low and high frequencies. As a result, the data supported Research Question #1, which indicated that there would be a difference in how user error affected low and high frequencies. The user error found in the NBN testing was compared to the user error found in the WT testing.
The results showed that the difference in user error between narrowband noise and ringing was not clinically or statistically significant. Consequently, the data did not support research question no. 2, which showed that there would be a difference in how the two sound stimuli affected user error. A two-way repeated-measures ANOVA was performed to compare user error scores across frequency (high vs. low) and stimuli (NBN vs. WT).
Follow-up paired sample t-test revealed a statistically significant difference in user errors between NBN and WT in low frequencies, t p = 0.003, but not in high frequencies, p = 0.46. Strong positive correlations included, but were not limited to: user error on low frequency NBN and high frequency NBN, user error on low frequency WT and high frequency WT, between low frequency WT and low frequency NBN, and high frequency NBN and high frequency WT. There was a weak positive association between the last instance of HPD use and user error in all conditions.
There was a slight negative correlation between the frequency of HPD use and user error in all conditions.
DISCUSSION
For the purpose of this study, user error was calculated and then averaged over low frequencies (250Hz, 500Hz, 1000Hz) and high frequencies (2000Hz, 4000Hz, 8000Hz) for comparison in both the narrowband noise test and the warble tone test. Similarly to when user errors were compared at high and low frequencies, the difference between user errors between NBN and warble tone was greater at the lower frequencies than the high frequencies. The first research question considered was: The bottom of the foam earplugs. frequency attenuations will be affected by user error differently than the higher frequency attenuations.
For the first research question, user error was greater at lower frequencies compared to higher frequencies across all participants. Regarding the second research question, there was no significant difference between the user error found in the NBN trial compared to the ringer trial. According to the results of this current study, user error was present in all participants, regardless of reported training, with greater values at lower frequencies than at higher frequencies.
This user error highlights the lack of adequate training for young adult students. An examination of the collected results shows that the difference in user error between the narrowband noise tests and the tone tests is less than 5 dB and therefore clinically insignificant. As noted in Section IV, there was a slight positive correlation between the last HPD use case and user error in all conditions, as well as a slight negative correlation.
The small correlations for frequency of HPD use show that the more often the participant reported using HPDs, there was a small decrease in user errors in all conditions. As indicated in Chapter IV, paired sample t-tests revealed a statistically significant difference in user errors between high and low frequencies for both NBN and WT. Furthermore, paired sample t-tests showed a statistically significant difference in user error between NBN and WT in low frequencies.
Specifically, more research is needed to better understand the effect of user error at different frequencies. Study Title: Frequency Attenuations of Foam Earplugs Affected by College Student User Error. After summarizing, I approve that the information collected by me in the study The Frequency Attenuations of Foam Ear Plugs Influenced by College Student User Error may be used by Alyse Lemoine.
