Perceiving the range of a sound source when the direction is known

Abstract

A modification is proposed in Hirsch's equation for determining the range of a sound source of unknown strength [H. R. Hirsch, J. Acoust. Soc. Am. 43, 373–374 (1968)]. The modified formula applies to the case where the direction of the sound source is known. Greene's comments on Hirsch's letter are investigated for their ability to predict the limitations on the resolution obtainable in human auditory ranging [D. C. Greene, J. Acoust. Soc. Am. 44, 634 (1968)]. In a brief experiment, two subjects were unable to make distance judgments for sustained pure-tone sources over ranges of 3 to 48 ft.

Auditory Reachability: An Affordance Approach to the Perception of Sound Source Distance

“…However, oul methodology is probably closesr ro rhose of studies resring absolute distance judgments (e.g', which ask listeners to estimate source distance in feet or inches). When compared ro these studies, our listener accutacy is impressive relative to Performance under conditions using anechoic environments (Mershon & King, 1975;Mershon' Ballenger, Little, McMurty, & Buchanan, 1989); recorded rather than live sounds (Butlei, Levy, &Neff, 1980); and impoverished stimuli (Molino, 1973) ' The currenr srudy provides another finding which is not obviously predicrable from the auditory disrance tirerature. our listeners successfully judged distance relacive to their own body dimensions.…”

“…In direcr evidence that binaural structure might be helpfui comes from research of Holt & Thurlow (1969) as well as Gardner (1969), who found that distance judgments improved as sound source locations deviated ftom the equato' rial plane. However, rhere is evidence rhat binaural information does not facilitate accuracy when listeners are asked to judge which of five speakers is emicting a simple tone source (Molino, 1973) . Ir could be, however, that binaural sffucture will prove useful when rested with a more natural sound and an affordance based task which is direcrly linked ro listener action.…”

Head-Related Transfer Functions in the Near Field

“…Note that this model is similar in concept to one suggested by Hirsch (1968), further explored by Greene (1968) and expanded by Molino (1970). This model demonstrated the possibility of determining the distance of a sound source based on the relationship between the IID and ITD.…”

Tori of confusion: Binaural localization cues for sources within reach of a listener

“…see Makous and Middlebrooks, 1990;Wenzel et al, 1993;Wightman and Kistler, 1999͒. One cue for resolving this confusion is the spectrum of the signal reaching the eardrum, which varies with source position due to the acoustic effects of the head, pinnae, and torso ͑e.g., see Shaw, 1997͒. However, despite the fact that the spectrum of the signal at the eardrum also depends on the spectrum of the source signal itself, a number of experiments support the idea that a major cue for resolving cone-ofconfusion ambiguities is the spectral content of the signals reaching the eardrums ͑e.g., see Roffler and Butler, 1968;Butler and Planert, 1976;Butler and Humanski, 1992;Wenzel et al, 1993;Gilkey and Anderson, 1995;Wightman and Kistler, 1997b;Hofman et al, 1998;Kulkarni and Colburn, 1998͒. ITD and IID cues are not perfectly constant for sources on the same cone of confusion because the ears are not diametrically opposed to one another, the head is not a perfect sphere, and the head and ears are not perfectly symmetric about the interaural axis ͑e.g., see Molino, 1973;Searle et al, 1976;Searle et al, 1976a;Middlebrooks et al, 1989;Duda and Martens, 1998͒. Such asymmetries probably aid in localizing sound sources ͑e.g., see Searle et al, 1976b͒.…”

“…For distances more than a meter from the head, these hyperbolic surfaces approximate cones centered on the interaural axis ͑i.e., the well-known ''cones of confusion''͒. A better approximation takes into account the effects of a spherical head on the path lengths to the ears ͑e.g., see Mills, 1972;Molino, 1973͒; however, even these iso-ITD contours depend only on the angle from source to interaural axis for distant sources. Empirical measurements of ITD as a function of source direction show that these approximations are quite accurate ͑e.g., see Mills, 1972͒. For relatively distant sources, IIDs arise primarily because of acoustic interference of the head ͑e.g., see Mills, 1972͒. In particular, for frequencies whose wavelengths are small relative to the dimensions of the head, the ear farther from the source generally receives less energy than the nearer ear.…”