YOP Sound Lecture.ppt 2551KB Jun 23 2011 10:24:32 AM

Please

be

The physics of sound:

What makes musical

tones different?

Special Lecture for the 2005 Year of Physics in coordination with the

French National Center for Scientific Research and the

Special Guests:

Michẻla Castellengo, Research Director,

Musical Acoustics Lab, University of Paris Hugues Genevoire, Research Engineer,

Musical Acoustics Lab, University of Paris Charles Besnainous, Research Engineer,

Musical Acoustics Lab, University of Paris Joseph Curtin, stringed instrument maker

Benoît Rolland, bow maker

Standard electronic wave forms

• Sine wave

• Sawtooth wave

• Pulse train

Fourier’s Theorem:

Any complex wave can be

“synthesized” by adding its

harmonics together with the

proper amplitudes and phases.

Fourier Synthesis

Fourier Synthesis

Fourier Synthesis

Fourier Synthesis

Fourier Analysis

or

Analysis

of

Factors in Tone Quality

1. Amplitudes of harmonics

2. Attack and decay transients

3. Inharmonicities

4. Formants

5. Vibrato

Origin of Vocal Formants

(~17.5 cm closed tube)

Frequency:

f1 = 500 Hz

f₃ = 1500 Hz f₅ = 2500 Hz

Vocal range:

150-850 Hz 500-2500 Hz 1500-3500 Hz

Simple formant model

Vowel formant production

Vowel Formant Frequencies

The

Singers

Formant

Averaged spectral energy distribution:

Light: ordinary speech

Dark: orchestral accompaniment Brown: Good singer with orchestra

Sound

Vocal Formant spectra

“OO”

“AH”

Matching vocal spectrograms

Helium Voice

Singing frequency remains the same

(vibration of vocal folds)

Formant frequencies rise because

S

_he

>>

S

_air

Vowel formant production

Speed of Sound

in

Helium and Sulfur Hexafluoride

He

SF

₆

M/M

_air

1/7

4.6

The End

Thank you for your attention

We are on the web at

http://www.physics.umd.edu/lecdem/