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 wished to determine if this limitation is the result of the constant amplitude and periodic axis crossings which characterize pure tones. To this end, we employed an acoustic pointing task in which listeners varied the interaural intensitive difference of a 500-Hz narrow-band noise (the pointer) so that it matched the intracranial position 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. We delayed either the entire waveform or only the carrier. In the latter case, the envelopes and phase functions were identical. This resulted in a noise which resembles the pure tone case in that the interaural delay is manifested as a constant phase shift and resembles the ordinary noise 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 effect the listeners' use of interaural temporal disparities in any discernable fashion.

Aging in Binaural Hearing Begins in Mid-Life: Evidence from Cortical Auditory-Evoked Responses to Changes in Interaural Phase

“…The upper limits for binaural hearing based on IPD in young subjects was ϳ1300 Hz, consistent with results of several previous studies (Garner and Wertheimer, 1951;Zwislocki and Feldman, 1956;Schiano et al, 1986;Macpherson and Middlebrooks, 2002) At frequencies above 1500 Hz, the IPD in tones becomes ambiguous in humans because ITD (determined by the head size) becomes larger than one period of the sound. Thus, the frequency limit could be thought as a meaningful outcome of evolutional specialization in humans.…”

Additive versus multiplicative combination of differences of interaural time and intensity.

“…We found that the shape of p (~,,,~fc~) plays a primary role in determining the lateral position of high-frequency tones in Schiano et al (1986). In the Domnitz and Colburn experiment, the lateral position of each liD-curve follows a sinusoidal trend over ITD, and the cue-reversal points migrate with liD.…”

“…Section 2.1 describes the major stages used by the model to produce an estimate of lateralization. In Section 2.2 we review the model's predictions for the lateralization of tones experiments performed by Domnitz and Colburn (1977), and by Schiano et al (1986) …”

“…In 1987 Shear modified the position-variable model to operate stimuli with a broader range of frequencies. He did this by constraining one function in the position-variable model by using the data from Schiano et aL (1986), which showed how the lateral position depended the frequency of a tonal stimulus. Stern, Zeiberg, and Trahiotis (1988a) observed lateralization results from a 500-Hz bandpass noise presented with no liD and various combinations of ITD, IPD, and bandwidth.…”

“…All experiments involved the subjective lateralization of either tones or bandpass noise. A list of each experiment and its stimulus is listed below: Domnitz and Colburn (1977) -500-Hz tone with combinations of ITD and liD Schiano, Trahiotis, and Bernstein (1986) -pure tones from 200 Hz to 2000 Hz with a small ITD but zero liD Buell and Trahiotis (1991) -noise with a 500-Hz center frequency and various combinations of ITD, IPD, and bandwidth Buell and Trahiotis (1991) -noise with a 500-Hz center frequency and various combinations of ITD, IPD, liD, and bandwidth A broad description of the relevant results of these experiments is presented in the following paragraphs. The original position-variable model (Stern and Colburn, 1978) predicted results of stimuli from 500-Hz tones.…”