(Vowels Alone): The three
vowels are presented one after the other.You should be able to identify the three vowels.
(see AUDIO FILES for information on the *.wav files)
In this demonstration three vowels are generated with a periodic pulse source for the fundamental frequency of each vowel. The three vowels are then added together. Under this condition, it is difficult to hear the three individual vowels. Each vowel is then sinusoidally amplitude modulated at 50 Hz and with 100% depth of modulation. The individual modulated vowels segregate out from the mixture.
The three vowels, their Fundamental Frequencies (Fo), and
their first three formants (F1, F2, F3) are:
Vowel as in the word Fo F1 F2 F3 /a/ half 135 Hz 730 Hz 1090 Hz 2440 Hz /i/ free 135 Hz 270 Hz 2290 Hz 3010 Hz /u/ ooz 135 Hz 300 Hz 870 Hz 2240 Hz
Amplitude Modulated Vowels in isolation (Vowels Alone): The three
vowels are presented one after the other.
You should be able to identify the three vowels.
Mixture of the Three Vowels (Vowels Mixed):
The mixture of the three vowels is presented for one second, followed by each of the three vowels in the mixture being amplitude modulated in succession each for one second, while the remaining two vowels are not modulated. The first one second of the waveform should not sound like any particular vowel or speech sound. You should then be able to hear out the three vowels in succession as each is amplitude modulated while the other two are not amplitude modulated. This demonstrates that amplitude modulation is a potential physical variable that could be used by the auditory system to help segregate sound sources in a complex sound field.
Sample references:
Yost, William A., Auditory Image Perception and Analysis, Hearing Research 56, 8-19, 1992
Slaney, M. and Lyon, R., Apple Hearing Demo Reel, Apple Technical Report #25, Apple Computer Company, 1991
McAdams, S., Spectral Fusion, Spectral Parsing, and the Formation of Auditory Images, Technical Report STAN-M-22, CCRMA, Department of Music, Stanford University, CA, 1984
Moore, B.C. J., Alcantra J.I. Vowel Identificationl based on Amplitude Modulation, Journal of the Acoustical Society of America 99, 2332-2344, 1996.