Model for auditory localization

Self Cite

In the usual one-dimensional resolution (discrimination or identification) experiment, the stimuli vary along one dimension, the target dimension, and the observer is required to respond differentially on the basis of the stimulus value along that dimension. In this note, we focus on experiments in which the observer's task remains the same, but in which the other parameters that define the stimuli, the background parameters, are varied randomly over specified ranges of these parameters. Thus, for example, the stimulus set might consist of tone pulses of fixed duration, the target parameter T might be the carrier frequency of the tone pulse, and the background parameter B that is randomly varied might be the amplitude of the tone pulse. The terms FIXED or CERTAIN are used for situations of the first type, whereas ROVED or UNCERTAIN are used for situations of the second type. Obviously, paradigms of the second type converge to those of the first type as the range of variation for the background parameters goes to zero. In this sense, FIXED paradigms can be regarded as a special case of ROVED paradigms.

Section: Extension Of Model To One-dimensional Resolution Experimentsmentioning

confidence: 99%

Notes and Comment Resolution in one dimension with random variations in background dimensions

Durlach

Tan

Macmillan

et al. 1989

Self Cite

“…The actual direction of motion of the probe tones presented over headphones might result in a poor representation of the auditory system's response to real environmental sounds in motion. Not only is the spectral content of tones quite restricted compared to that of natural stimuli, but presenting the stimuli through headphones automatically eliminates many cues that are known to be important in human auditory spatial processing (e.g., Searle, Braida, Davis, & Colburn, 1976).…”

Section: Methodsmentioning

confidence: 99%

Motion aftereffects with horizontally moving sound sources in the free field

Grantham¹

1989

A horizontally moving BOund was presented to an observer seated in the center of an anechoic chamber. The BOund, either a 500-Hz low-pass noise or a 6300-Hz high-pass noise, repeatedly traversed a semicircular arc in the observer's front hemifield at ear level (distance: 1.5 m), At lO-sec intervals this adaptor was interrupted, and a 750-msec moving probe (a 500-Hz low-pass noise) was presented from a horizontal arc 1.6 m in front of the observer. During a run, the adaptor was presented at a constant velocity (-200°to +200 0/sec), while probes with velocities varying from -10°to +10 0/sec were presented in a random order. Observers judged the direction of motion (left or right) of each probe. As in the case of stimuli presented over headphones (Grantham & Wightman, 1979),an auditory motion aftereffect (MAE) occurred: subjects responded "left" to probes more often when the adaptor moved right than when it moved left. When the adaptor and probe were spectrally the same, the MAE was greater than when they were from different spectral regions; the magnitude of this difference depended on adaptor speed and was subjectdependent. It is proposed that there are two components underlying the auditory MAE: (1) a generalized bias to respond that probes move in the direction opposite to that of the adaptor, independent of their spectra; and (2) a loss ofsensitivity to the velocity of moving BOunds after prolonged exposure to moving BOunds having the same spectral content.We have reported the existence of an auditory motion aftereffect (MAE), analogous to the well-known waterfall effect in vision (Grantham & Wightman, 1979). In the previous study, we exposed subjects to sounds that moved repeatedly through the head in one direction (created by dynamically varying the interaural time differences and interaural level differences of pure tones presented over headphones). Following such exposure, subjects tended to respond that subsequently presented probes moved in the opposite direction. This tendency indicates that an auditory MAE exists, although whether the effect is a sensory one or simply a response bias is not yet clear.The visual MAE is almost certainly a sensory effect. A generally accepted theory to account for this effect postulates the existence of directionally sensitive analyzers in the visual system (Sekuler & Pantle, 1967). These analyzers become fatigued from prolonged stimulation by a pattern moving in their preferred direction; subsequently, upon presentation of a neutral (stationary) pattern, activity in the analyzers tuned to the opposite direction dominates, resulting in the perception of movement when none is present. The fact that single units that respond selectively to the direction of a moving target have been found in the eat's cortex (Hubel & Wiesel, 1962)

“…A related point has been noted before; Searle, Braida, Davis, and Colburn (1976) modeled the effect ofchanges in the area spanned by arrays of loudspeakers (hence, the response choices available) on the localization error to be expected. One outcome that underscores this point and raises further questions is the differential effect of the two different orientations on cross-plane errors.…”

Section: Actual Elevation In Degreesmentioning

confidence: 99%

Available response choices affect localization of sound

Perrett

Noble

1995

Successful replication of an experiment by Butler and Humanski (1992) showed that listeners are able to proficiently localize sources on a lateral vertical plane on the basis of interaural differences alone, When a lateral horizontal array was included in the test setup, that finding was replicated only for a broadband signal interacting with the pinna, not for ones (lowpass and pure tone) providing only interaural differences. Cross-plane errors conforming to "cones of confusion" were observed for those latter sounds. In a second experiment, response options were made more unconstrained, which clarified the nature of the cross-plane confusions. Lowpass signals from lateral vertical plane sources tend to be heard at or close to the horizon. Measurement of cue values needs to take account of the response options available to listeners, as well as signal properties.Classical theory of sound localization in space has stressed the role of the binaural system. Early research (Stevens & Newman, 1936) showed that the auditory system is sensitive to interaural time differences for lowfrequency sounds and interaural level differences for sounds of high frequency. The low-frequency cue is considered to be largely an effect of time and phase difference detection; the high-frequency cue is the result ofincreasingly sharp acoustic shadowing by the head. In classical theory, the head is assumed to be a perfect sphere, with the ears as holes located at the extremes of a diameter through the sphere (Mills, 1972). Using this model, interaural differences specify the horizontal angle of the sound source to' the left or right of the median vertical plane (MVP). Absence of difference specifies that the source is somewhere on the MVP. Such differences cannot unambiguously specify the vertical angle of the sound source relative to the horizontal plane nor, relatedly, whether it lies forward or rearward of, or above or below, the interaural axis. In normal listening conditions, and with a broadband noise signal, those aspects of spatial whereabouts seemingly not revealed by "classical" interaural differences can nonetheless be distinguished.In a recent report, Butler and Humanski (1992) presented results showing that listeners could accurately discriminate the whereabouts of sound sources displaced at 15 0 intervals in a quadrant above the interaural axisin the lateral vertical plane (LVP). Proficient performance was observed for bursts of 3-kHz highpass filtered noise. Such short wavelength signals interact withThe authors thank Bruce Stevenson for valuable advice about the design of Experiment 2.