Perceptual segregation of concurrent vowels
Peter F. Assmann, Quentin A. Summerfield · The Journal of the Acoustical Society of America · 1987
The ability to group together the acoustic components of a voice and segregate them from competing voices is an important skill in speech communication. To study the auditory processes involved, pairs of vowels were presented simultaneously to listeners with normal hearing. Identification performance improved as the fundamental-frequency difference between the members of the pair increased. Two auditory models were compared to predict this result. The composite waveform was passed through an array of bandpass filters simulating the cat's limited frequency resolution. The “place” model estimated the two fundamentals from peaks in the profile of the rms outputs of the filters. It then sampled the profile at integer multiples of each fundamental to reconstruct the spectra of the constituent vowels. The “place-time” model estimated the fundamentals from dominant periodicities in the waveforms emerging from the filters. The amount of synchronization to each fundamental was plotted as a function of filter center frequency to reconstruct the spectra. The place-time model estimated the two fundamentals more accurately than the place model, and predicted identification responses more precisely. This outcome is compatible with the idea that a temporal analysis is involved in the segregation of concurrent sounds.