Normative variation of auditory stream segregation in adults

Human beings receive a variety of sounds in their everyday lives. These sounds are generated by different sources, and are heard simultaneously or with a small time sequence. A characteristic of the auditory system is its ability to analyze complex sounds, and to make decisions about the source of each constituent part of these sounds. The present study intends to assess normative variation of auditory stream segregation in adults.
This study has a cross-sectional design and was conducted on 40 normal adults with the age range of 18 to 35. Stimuli were presented in the form of pure tones A and B as ABA-ABA triplet pattern at the intensity level of 40 dBSL. The A tone frequency was selected as the basis at 500, 1000, and 2000 Hz. The B tone was presented with a difference of half to twelve and half semitones above the basis tone frequency in each phase.
The fission boundary (FB) threshold was obtained in 500-2000 Hz. FB threshold was better in low frequencies than high frequencies. FB thresholds were independent of frequency when expressed as equivalent rectangular bandwidth (ERB).
Fission boundary threshold increased with the increase of frequency. When we used ERB, FB threshold was independent of frequency.