Utility of Monaural Spectral Cues Is Enhanced in the Presence of Cues to Sound-Source Lateral Angle

Abstract

The contention that normally binaural listeners can localize sound under monaural conditions has been challenged by Wightman and Kistler (J. Acoust. Soc. Am. 101:1050Am. 101: -1063Am. 101: , 1997, who found that listeners are almost completely unable to localize virtual sources of sound when sound is presented to only one ear. Wightman and Kistler's results raise the question of whether monaural spectral cues are used by listeners to localize sound under binaural conditions. We have examined the possibility that monaural spectral cues provide useful information regarding sound-source elevation and front-back hemifield when interaural time differences are available to specify sound-source lateral angle. The accuracy with which elevation and front-back hemifield could be determined was compared between a monaural condition and a binaural condition in which a wide-band signal was presented to the near ear and a version of the signal that had been lowpass-filtered at 2.5 kHz was presented to the far ear. It was found that accuracy was substantially greater in the latter condition, suggesting that information regarding soundsource lateral angle is required for monaural spectral cues to elevation and front-back hemifield to be correctly interpreted.

Effects of Head Movements on Sound-Source Localization in Single-Sided Deaf Patients With Their Cochlear Implant On Versus Off

“…The results presented here suggest that these benefits do indeed carry over into localization when listeners move, as listeners often do in everyday life. Martin et al (2004) and also Wightman and Kistler (1997) have shown that, in order for high-frequency spectral cues to be useful for front-back discrimination, binaural cues for the lateral displacement of the sound source are probably necessary. Also, Janko et al (1997) implemented a neural net model and found that monaural spectral cues only contained enough information to produce localization results on a par with human listeners if the ITD that would specify lateral sound source location was also provided.…”

“…Notwithstanding the work of Martin et al (2004), Wightman and Kistler (1997), and others, the degree to which spectral shape cues can be used monaurally, without binaural difference cues to provide an estimate of laterality, is still the subject of considerable debate and research (e.g., Hofman and van Opstal, 2003;Jin et al, 2004;Searle et al, 1975).…”

“…During a four-day period during which subjects wore their earplugs at all times (even when sleeping), and which included approximately hour-long training sessions where listeners were given feedback, monaural localization improved, suggesting that SSD listeners could learn to use the spectral shape information related to their pinnae in horizonal localization. It should be noted, however, that Wightman and Kistler (2002) showed that even the small amount of low-frequency energy that passes through an ear plug is sufficient to provide an ITD that facilitates the use of monaural spectral cues (see also Martin et al, 2004), whereas when all low-frequency information is removed monaural localization was essentially impossible. It is, in practice, very difficult to achieve full attenuation of low-frequency energy with earplugs, and even as much as 30 dB of attenuation does not remove a usable ITD cue (Wightman and Kistler, 2002).…”

Sound localization with head movement: implications for 3-d audio displays

“…The overall mean elevation error was around 14 for the 2° azimuth window which confirms that spectral cues to elevation were reduced. [The mean elevation error is normally around 8° for a brief white noise stimulus (Martin et al, 2004 )]. A One-Way repeated-measures ANOVA revealed a significant effect of azimuth window, F (3.0, 21.1) = 10.8, p < 0.001, partial η 2 = 0.61.…”

Synchronizing Automatic Gain Control in Bilateral Cochlear Implants Mitigates Dynamic Localization Deficits Introduced by Independent Bilateral Compression

“…For signals with high-frequency information of sufficient bandwidth, NH listeners can often reliably distinguish front from back sound source location by exploiting differences in the pattern of high-frequency spectral shape cues that may be extracted from the head-related transfer function (created by the interference of the head, pinnae, and torso, see Hebrank & Wright 1974; Zahorik et al 2006). However, Janko et al (1997, with a neural net model), Wightman & Kistler (1997, for human behavioral data), and Martin et al (2004), found that high-frequency spectral shape cues were only useful for front-back discrimination when the correct interaural difference cues were also available (see Pastore et al 2020a for an in-depth discussion).…”