Differences in loudness of tone complexes with positive and negative Schroeder phase

Abstract

Tone complexes with positive (m+) and negative Schroeder phase (m−) have an identical long-term spectrum, the same temporal envelope but are inverted in time. They show large differences in masking efficiency most probably being related to a different cochlear representation. The current study investigates to which extent loudness perception is affected similarly by the different phase characteristic of m+/m− stimuli. Therefore, the loudness of m+/m− stimuli (1.6 octave bandwidth) was matched in seven normal hearing and three hearing impaired subjects. In the first experiment the fundamental frequency f0 of the tone complexes was varied from 2–1536 Hz for different center frequencies at a soft level of the reference signal (m−). In normal hearing subjects the m+ stimuli need a 6 dB higher level to be perceived as equally loud as the respective m− stimuli (for f0 in the range of 24–96 Hz). In the second experiment the difference in loudness of m+/m− was investigated as function of the of the reference-stimulus level (5–80 dB SL) at a center frequency of 2660 Hz and f0 at 48 Hz. The largest differences in loudness were found for levels between 40–60 dB, clearly reduced for higher and lower levels of the reference stimulus.