Lateralization of low-frequency tones and narrow bands of noise

Abstract

It is well known and universally accepted that people's ability to use ongoing interaural temporal disparities conveyed via pure tones is limited to frequencies below 1600 Hz. We wish to determine if this limitation is the result of the constant amplitude and periodic axis-crossings which characterize pure tones. To this end, an acoustic pointing task was employed in which listeners varied the interaural intensitive difference of a 500-Hz narrow-band noise (the pointer) so that the position of its intracranial image matched that of a second, experimenter-controlled stimulus (the target). Targets were either pure tones or narrow bands of noise (50 or 100 Hz wide). The narrow bands of noise were delayed interaurally in two distinct manners: Either the entire waveform or only the carrier was delayed. In the latter case, the envelopes and phase-functions of the bands of noise were identical interaurally. This resulted in noises which resemble the pure tone case in that the interaural delay is manifested as a constant phase-shift and resemble ordinary noises in that the envelope and phase are random functions of time. Surprisingly, it appears that all three targets were lateralized virtually identically regardless of frequency or bandwidth. Apparently, the dynamically changing envelopes and phases did not affect the listeners' use of interaural temporal disparities in any discernible fashion.

Responses of Auditory Nerve and Anteroventral Cochlear Nucleus Fibers to Broadband and Narrowband Noise: Implications for the Sensitivity to Interaural Delays

“…Several psychophysical studies have addressed ITD-induced lateralization of bands of noise of varying center frequency and bandwidth. To the extent that ITD-induced lateralization reflects sensitivity to ITDs, these psychophysical data show exactly the same bandwidth effects as our neural thresholds: at low frequencies (<1,600 Hz), the effect of bandwidth on lateralization is marginal (Schiano et al 1986); at high frequencies (4 and 8 kHz), the amount of lateralization increases markedly with bandwidth (Bernstein and Trahiotis 2003). …”

Envelope and spectral frequency-following responses to vowel sounds

“…A 1300 Hz limit for following temporal signals is also found in studies of sound localization wherein the timing of signals is compared between the ears (Zwislocki and Feldman, 1956). Interestingly, such localization is dependent on the carrier timing and independent of envelope timing (Schiano et al, 1986).…”

The effects of lateralized adaptors on lateral position judgements of tones within and across frequency channels

“…They were merely to report the apparent intracranial azimuth of each tone. This task does not have the history of use as pointing tasks used by other authors (e.g., Yost, 1981;Schiano et al, 1986), and it is an empirical question as to whether the present task provides measures of perceived intracranial location with the reliability of the earlier methods. The data obtained in present study were, however, quite orderly and systematic, and showed no obvious biases in control (pre-adaptation) conditions.…”