RECOGNITION OF SPECTRALLY AND AUDIBLY VARIED STIMULI IN THE PRESENCE OF COMPETING STIMULI
Moriah Garcia, Edward Bartlett, Aravindakshan Parthasarathy.
Purdue University, West Lafayette, IN.
Listening is a complex process in which one must discriminate specific sounds from competing stimuli in conditions where ambient noise is often louder than the target sound. In these conditions, temporal processing deficits due to age make it difficult for the listener to distinguish the target sound. The purpose of this study was to determine how changing the spectral content and signal to noise ratio (SNR) of a target sound in the presence of a masker would influence the recognition of this sound. Five subjects sought to recognize a target sound in the presence of a competing sinusoidally amplitude-modulated tone. SNRs of 60, 50, 40, 30, 20, 10, 5, 0, -5, and -10 were used to vary the sound levels of the tones, while carrier frequencies of 2,000 Hz, 2,500 Hz, and 3,143 Hz were used to vary the spectral content. Recognition of the target decreased with an increase in SNR, showing a sharper decrease when the tones had similar carrier frequencies. This indicates that as ambient noise increases, the ability of a listener to recognize their sound of interest decreases, especially for noises that are spectrally similar to their target. This suggests that for a listener, both increasing the sound level and differing the carrier frequency of the sound of interest are key to gaining recognition of that sound in the presence of competing stimuli. This knowledge is of great importance when designing hearing aids, showing that they should acknowledge the frequencies that the user struggles to distinguish in addition to increasing sound levels.