Intensity discrimination of Gaussian-windowed tones: Indications for the shape of the auditory frequency-time window

Abstract

The just-noticeable difference in intensity jnd(I) was measured for 1-kHz tones with a Gaussian-shaped envelope as a function of their spectro-temporal shape. The stimuli, with constant energy and a constant product of bandwidth and duration, ranged from a long-duration narrow-band "tone" to a short-duration broadband "click." The jnd(I) was measured in three normal-hearing listeners at sensation levels of 0, 10, 20, and 30 dB in 35 dB(A) SPL pink noise. At intermediate sensation levels, jnd(I) depends on the spectro-temporal shape: at the extreme shapes (tones and clicks), intensity discrimination performance is best, whereas at intermediate shapes the jnd(I) is larger. Similar results are observed at a higher overall sound level, and at a higher carrier frequency. The maximum jnd(I) is observed for stimuli with an effective bandwidth of about 1/3 octave and an effective duration of 4 ms at 1 kHz (1 ms at 4 kHz). A generalized multiple-window model is proposed that assumes that the spectro-temporal domain is partitioned into "internal" auditory frequency-time windows. The model predicts that intensity discrimination thresholds depend upon the number of windows excited by a signal: jnd(I) is largest for stimuli covering one window.

Auditory Time-Frequency Masking for Spectrally and Temporally Maximally-Compact Stimuli

“…The value of α was chosen according to the study by van Schijndel et al . [50], who used similar Gaussian stimuli to measure spectro-temporal integration. They made the assumption that the auditory system performs a TF analysis through its own TF windows.…”

“…Gabor atoms have Gaussian shapes in both time and frequency and minimize the TF uncertainty principle [1, 2]. Additionally, it has been suggested that Gaussian-shaped stimuli with an appropriate support in the TF domain excite a limited number of hypothesized TF observation windows of the auditory system compared to broadband and/or long stimuli [50]. Using stimuli with a compact support in the time domain also has the potential advantage to avoid the influence of auditory efferents like the MOCR.…”

Additivity of nonsimultaneous masking for short Gaussian-shaped sinusoids

“…The equivalent rectangular bandwidth of the Gaussian is given by C. The equivalent rectangular duration of the Gaussian equals C À1 . The value of C was chosen based on the study by van Schijndel et al (1999) on intensity discrimination, in which the parameter a of the Gaussian defined above was varied. The goal of the authors was to derive the shape of the "internal" time-frequency observation window of the auditory system.…”

“…This elementary signal has a Gaussian shape in both domains. Gaussians have been used in a study attempting to measure the shape of the auditory time-frequency window (van Schijndel et al, 1999) and in studies on the effects of spectral and temporal integration in auditory masking (e.g., van den Brink and Houtgast, 1990).…”

Relations between intelligibility of narrow-band speech and auditory functions, both in the 1-kHz frequency region

“…This shape factor was chosen because it defines a signal with the spectral width of a critical band ͑equivalent rectangular bandwidth: 1 4 octave͒ combined with a short duration ͑equivalent rectangular duration: 2.8 ms͒. For low-level stimuli with this particular spectro-temporal shape, listeners are not able to combine stimulus information across multiple frequency channels or across ''multiple looks'' in time ͑van Schijndel et al, 1999͒. The energy of the Gaussian pulse only depends on the amplitude factor A. In its generation, the Gaussian pulse was cut off at 60 dB below the top.…”