The relative importance of spectral cues for vowel recognition in severe noise

The importance of formants and spectral shape was investigated for vowel perception in severe noise. Twelve vowels were synthesized using two different synthesis methods, one where the original spectral detail was preserved, and one where the vowel was represented by the spectral peaks of the first three formants. In addition, formants F1 and F2 were suppressed individually to investigate the importance of each in severe noise. Vowels were presented to listeners in quiet and in speech-shaped noise at signal to noise ratios (SNRs) of 0, -5, and -10 dB, and vowel confusions were determined in a number of conditions. Results suggest that the auditory system relies on formant information for vowel perception irrespective of the SNR, but that, as noise increases, it relies increasingly on more complete spectral information to perform formant extraction. A second finding was that, while F2 is more important in quiet or low noise conditions, F1 and F2 are of similar importance in severe noise.