Interaural Intensity Difference Limen

Rowland, Roy C.; Tobias, Jerry V.

doi:10.1044/jshr.1004.745

Cited by 20 publications

(7 citation statements)

References 1 publication

(1 reference statement)

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“…First, listeners reported using a change in the lateral position of the sound image to perform both the ILD-and ITD-discrimination tasks. Second, mean thresholds for ILD discrimination are higher than those for monaural intensity discrimination at 0.25 and 2 kHz (but not at 6 kHz), even when the overall stimulus level in the ILD tests is not randomized (40). Thus, listeners appear to use the ILD cue when it is present, even though their performance could be better if they used the available monaural-intensity cue.…”

Section: Relationship Between Pretest Thresholds and The Amount Of Lementioning

confidence: 90%

Different patterns of human discrimination learning for two interaural cues to sound-source location

Wright

Fitzgerald²

2001

Proc. Natl. Acad. Sci. U.S.A.

145

144

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Two of the primary cues used to localize the sources of sounds are interaural level differences (ILDs) and interaural time differences (ITDs). We conducted two experiments to explore how practice affects the human discrimination of values of ILDs and ongoing ITDs presented over headphones. We measured discrimination thresholds of 13 to 32 naive listeners in a variety of conditions during a pretest and again, 2 weeks later, during a posttest. Between those two tests, we trained a subset of listeners 1 h per day for 9 days on a single ILD or ITD condition. Listeners improved on both ILD and ITD discrimination. Improvement was initially rapid for both cue types and appeared to generalize broadly across conditions, indicating conceptual or procedural learning. A subsequent slower-improvement stage, which occurred solely for the ILD cue, only affected conditions with the trained stimulus frequency, suggesting that stimulus processing had fundamentally changed. These different learning patterns indicate that practice affects the attention to, or low-level encoding of, ILDs and ITDs at sites at which the two cue types are processed separately. Thus, these data reveal differences in the effect of practice on ILD and ITD discrimination, and provide insight into the encoding of these two cues to sound-source location in humans.A listener who determines the position of a singing bird concealed among tree leaves, a jet passing overhead hidden by clouds, or a car approaching from behind, does so by using several auditory cues to the location of sound sources. Here we report the results of two investigations into how practice influences the ability of human listeners to discriminate small differences in each of two of these cues, interaural level differences (ILDs) and interaural time differences (ITDs).In humans, the horizontal location, or azimuth, of sound sources is computed from differences in the information that arrives at the two ears. At frequencies above about 1.5 kHz, listeners determine sound azimuth primarily from sensitivity to differences in sound level at the two ears. These interaural level differences occur because the head forms a sound barrier between the two ears, so sounds are attenuated at the ear farthest from the source relative to the ear nearest to the source (1, 2). At frequencies below about 1.5 kHz, listeners determine sound azimuth primarily from sensitivity to differences in the arrival time of the sound at the two ears. These interaural time differences arise because there is distance between the two ears, so sounds reach the ear nearest to the sound source first and the other ear later (1, 2). For sound durations greater than about 150 ms, listeners are far more sensitive to differences at the two ears in the ongoing fine time structure of the sound than in the onset time of the sound (3, 4). These ongoing time differences are equivalent to interaural phase differences (IPDs) for tonal stimuli, but will be referred to as ITDs in this paper.There have been many investigations into whether huma...

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Section: Relationship Between Pretest Thresholds and The Amount Of Lementioning

confidence: 90%

Different patterns of human discrimination learning for two interaural cues to sound-source location

Wright

Fitzgerald²

2001

Proc. Natl. Acad. Sci. U.S.A.

145

144

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“…The linear mapping maximum was set to 60% of the total DR at 90°, that is, 1° azimuth change corresponded to 0.67% ILD (DR) change. While naturally occurring ILDs are highly frequency-dependent, the motivation for choosing a frequency-independent map is twofold: First, the human ILD discrimination ability is mostly frequency-independent (e.g., Rowland & Tobias, 1967 ). Secondly, the loudness growth and average DR of CI users is on average independent of the tonotopic place of stimulation ( Busby, Whitford, Blamey, Richardson, & Clark, 1994 ).…”

Section: Methodsmentioning

confidence: 99%

Coherent Coding of Enhanced Interaural Cues Improves Sound Localization in Noise With Bilateral Cochlear Implants

Williges

Jürgens

et al. 2018

Trends in Hearing

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Bilateral cochlear implant (BCI) users only have very limited spatial hearing abilities. Speech coding strategies transmit interaural level differences (ILDs) but in a distorted manner. Interaural time difference (ITD) information transmission is even more limited. With these cues, most BCI users can coarsely localize a single source in quiet, but performance quickly declines in the presence of other sound. This proof-of-concept study presents a novel signal processing algorithm specific for BCIs, with the aim to improve sound localization in noise. The core part of the BCI algorithm duplicates a monophonic electrode pulse pattern and applies quasistationary natural or artificial ITDs or ILDs based on the estimated direction of the dominant source. Three experiments were conducted to evaluate different algorithm variants: Experiment 1 tested if ITD transmission alone enables BCI subjects to lateralize speech. Results showed that six out of nine BCI subjects were able to lateralize intelligible speech in quiet solely based on ITDs. Experiments 2 and 3 assessed azimuthal angle discrimination in noise with natural or modified ILDs and ITDs. Angle discrimination for frontal locations was possible with all variants, including the pure ITD case, but for lateral reference angles, it was only possible with a linearized ILD mapping. Speech intelligibility in noise, limitations, and challenges of this interaural cue transmission approach are discussed alongside suggestions for modifying and further improving the BCI algorithm.

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“…This is not in line with threshold measurements of ITDs and ILDs. While ILD thresholds are constant over frequency (Yost 1988;Grantham 1984;Rowland and Tobias 1967), ITD thresholds have been shown to be lowest at 800 Hz (Klumpp and Eady 1956;Brughera et al 2013).…”

Section: Discussionmentioning

confidence: 99%

“…This leads to a reduction in sound intensity at the contralateral ear relative to the ipsilateral ear and leads to ILD cues (Blauert 1984). ILD detection thresholds have been shown to be approximately constant over a broad range of frequencies (Yost 1988;Grantham 1984;Rowland and Tobias 1967).…”

Section: Introductionmentioning

confidence: 99%

Perceptual weighting of binaural lateralization cues across frequency bands

Ahrens

Joshi

Epp

2019

Preprint

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The auditory system uses interaural time-and level differences (ITD and ILD) as cues to localize and lateralize sounds. The availability of ITDs and ILDs in the auditory system is limited by neural phase-locking and by the head size, respectively. Although the frequency-specific limitations are well known, the relative contribution of ITDs and ILDs in individual frequency bands in broadband stimuli are unknown. To determine these relative contributions, or spectral weights, listeners were asked to judge the lateralization of stimuli consisting of eleven simultaneously presented 1-ERB-wide noise bands centered between 442 Hz and 5544 Hz and separated by 1-ERB-wide gaps. Interaural disparities were applied to each noise band and were roved independently on every trial. The weights were obtained using a multiple linear regression analysis. In a second experiment the effect of temporal context on the spectral weights was investigated. Ten of the noise bands were used as pre-and postcursors and listeners were asked to lateralize the stimuli. Results show that only the lowest-or highest frequency band received highest weight for ITD and ILD, respectively. Temporal context led to significantly enhanced weights given to the band without the pre-and postcursor. The weight enhancement could only be observed at low frequencies, when determined with ITD cues and for low and high frequencies for ILDs. Hence, the auditory system seems to be able to change the spectral weighting of binaural information depending on the information content.

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Interaural Intensity Difference Limen

Cited by 20 publications

References 1 publication

Different patterns of human discrimination learning for two interaural cues to sound-source location

Different patterns of human discrimination learning for two interaural cues to sound-source location

Coherent Coding of Enhanced Interaural Cues Improves Sound Localization in Noise With Bilateral Cochlear Implants

Perceptual weighting of binaural lateralization cues across frequency bands

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