scholarly journals Crocodiles use both interaural level differences and interaural time differences to locate a sound source

2020 ◽  
Vol 148 (4) ◽  
pp. EL307-EL313
Author(s):  
L. Papet ◽  
M. Raymond ◽  
N. Boyer ◽  
N. Mathevon ◽  
N. Grimault
Keyword(s):  
Sound Source ◽  
Interaural Time Differences ◽  
Interaural Level Differences

scholarly journals Information conveyed by inferior colliculus neurons about stimuli with aligned and misaligned sound localization cues

2011 ◽  
Vol 106 (2) ◽  
pp. 974-985 ◽  
Author(s):  
Sean J. Slee ◽  
Eric D. Young
Keyword(s):  
Inferior Colliculus ◽  
Sound Localization ◽  
Virtual Space ◽  
Central Nucleus ◽  
Single Neurons ◽  
Interaural Time Differences ◽  
Marmoset Monkey ◽  
Interaural Level Differences ◽  
Broadband Sound ◽  
Response Area

Previous studies have demonstrated that single neurons in the central nucleus of the inferior colliculus (ICC) are sensitive to multiple sound localization cues. We investigated the hypothesis that ICC neurons are specialized to encode multiple sound localization cues that are aligned in space (as would naturally occur from a single broadband sound source). Sound localization cues including interaural time differences (ITDs), interaural level differences (ILDs), and spectral shapes (SSs) were measured in a marmoset monkey. Virtual space methods were used to generate stimuli with aligned and misaligned combinations of cues while recording in the ICC of the same monkey. Mutual information (MI) between spike rates and stimuli for aligned versus misaligned cues were compared. Neurons with best frequencies (BFs) less than ∼11 kHz mostly encoded information about a single sound localization cue, ITD or ILD depending on frequency, consistent with the dominance of ear acoustics by either ITD or ILD at those frequencies. Most neurons with BFs >11 kHz encoded information about multiple sound localization cues, usually ILD and SS, and were sensitive to their alignment. In some neurons MI between stimuli and spike responses was greater for aligned cues, while in others it was greater for misaligned cues. If SS cues were shifted to lower frequencies in the virtual space stimuli, a similar result was found for neurons with BFs <11 kHz, showing that the cue interaction reflects the spectra of the stimuli and not a specialization for representing SS cues. In general the results show that ICC neurons are sensitive to multiple localization cues if they are simultaneously present in the frequency response area of the neuron. However, the representation is diffuse in that there is not a specialization in the ICC for encoding aligned sound localization cues.

scholarly journals Cues for Directional Hearing in the Fly Ormia ochracea

2021 ◽  
Vol 9 ◽  
Author(s):  
Andrew C. Mason
Keyword(s):  
Arrival Time ◽  
High Accuracy ◽  
Sound Stimulus ◽  
Directional Hearing ◽  
Neural Responses ◽  
Ormia Ochracea ◽  
Parasitoid Species ◽  
Interaural Time Differences ◽  
Internal Parasites ◽  
Interaural Level Differences

Insects are often small relative to the wavelengths of sounds they need to localize, which presents a fundamental biophysical problem. Understanding novel solutions to this limitation can provide insights for biomimetic technologies. Such an approach has been successful using the fly Ormia ochracea (Diptera: Tachinidae) as a model. O. ochracea is a parasitoid species whose larvae develop as internal parasites within crickets (Gryllidae). In nature, female flies find singing male crickets by phonotaxis, despite severe constraints on directional hearing due to their small size. A physical coupling between the two tympanal membranes allows the flies to obtain information about sound source direction with high accuracy because it generates interaural time-differences (ITD) and interaural level differences (ILD) in tympanal vibrations that are exaggerated relative to the small arrival-time difference at the two ears, that is the only cue available in the sound stimulus. In this study, I demonstrate that pure time-differences in the neural responses to sound stimuli are sufficient for auditory directionality in O. ochracea.

Spatial Stimulus Cue Information Supplying Auditory Saltation

Perception ◽  
10.1068/p3293 ◽  
2002 ◽  
Vol 31 (7) ◽  
pp. 875-885 ◽  
Author(s):  
Dennis P Phillips ◽  
Susan E Hall ◽  
Susan E Boehnke ◽  
Leanna E D Rutherford
Keyword(s):  
Spatial Perception ◽  
Interaural Time Difference ◽  
Free Field ◽  
Spatial Location ◽  
Interaural Level Difference ◽  
Sound Sources ◽  
Interaural Time Differences ◽  
Spatial Stimulus ◽  
Click Train ◽  
Interaural Level Differences

Auditory saltation is a misperception of the spatial location of repetitive, transient stimuli. It arises when clicks at one location are followed in perfect temporal cadence by identical clicks at a second location. This report describes two psychophysical experiments designed to examine the sensitivity of auditory saltation to different stimulus cues for auditory spatial perception. Experiment 1 was a dichotic study in which six different six-click train stimuli were used to generate the saltation effect. Clicks lateralised by using interaural time differences and clicks lateralised by using interaural level differences produced equivalent saltation effects, confirming an earlier finding. Switching the stimulus cue from an interaural time difference to an interaural level difference (or the reverse) in mid train was inconsequential to the saltation illusion. Experiment 2 was a free-field study in which subjects rated the illusory motion generated by clicks emitted from two sound sources symmetrically disposed around the interaural axis, ie on the same cone of confusion in the auditory hemifield opposite one ear. Stimuli in such positions produce spatial location judgments that are based more heavily on monaural spectral information than on binaural computations. The free-field stimuli produced robust saltation. The data from both experiments are consistent with the view that auditory saltation can emerge from spatial processing, irrespective of the stimulus cue information used to determine click laterality or location.

scholarly journals Influence of head morphology and natural postures on sound localization cues in crocodilians

2019 ◽  
Vol 6 (7) ◽  
pp. 190423 ◽  
Author(s):  
L. Papet ◽  
N. Grimault ◽  
N. Boyer ◽  
N. Mathevon
Keyword(s):  
Sound Localization ◽  
Sound Source ◽  
Social Life ◽  
Transfer Functions ◽  
Azimuthal Angle ◽  
Sound Sources ◽  
Low Frequencies ◽  
Top Predators ◽  
Head Morphology ◽  
Interaural Level Differences

As top predators, crocodilians have an acute sense of hearing that is useful for their social life and for probing their environment in hunting situations. Although previous studies suggest that crocodilians are able to localize the position of a sound source, how they do this remains largely unknown. In this study, we measured the potential monaural sound localization cues (head-related transfer functions; HRTFs) on alive animals and skulls in two situations, both mimicking natural positions: basking on the land and cruising at the interface between air and water. Binaural cues were also estimated by measuring the interaural level differences (ILDs) and the interaural time differences (ITDs). In both conditions, HRTF measurements show large spectral variations (greater than 10 dB) for high frequencies, depending on the azimuthal angle. These localization cues are influenced by head size and by the internal coupling of the ears. ITDs give reliable information regarding sound-source position for low frequencies, while ILDs are more suitable for frequencies higher than 1.5 kHz. Our results support the hypothesis that crocodilian head morphology is adapted to acquire reliable localization cues from sound sources when outside the water, but also when only a small part of their head is above the air–water interface.

scholarly journals Wearable Hearing Assist System to Provide Hearing-Dog Functionality

Robotics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 49
Author(s):  
Shimoyama
Keyword(s):  
Sound Source ◽  
Sound Pressure ◽  
Male Subject ◽  
Front Side ◽  
Short Term ◽  
Sound Sources ◽  
Interaural Time Differences ◽  
The Subject ◽  
Impaired Person ◽  
Tracking Period

This study developed a wearable hearing-assist system that can identify the direction of a sound source while using short-term interaural time differences (ITDs) of sound pressure and convey the sound source direction to a hearing-impaired person via vibrators that are attached to his or her shoulders. This system, which is equipped with two microphones, could dynamically detect and convey the direction of front, side, and even rear sound sources. A male subject was able to turn his head toward continuous or intermittent sound sources within approximately 2.8 s when wearing the developed system. The sound source direction is probably overestimated when the interval between the two ears is smaller. When the subject can utilize vision, this may help in tracking the location of the target sound source, especially if the target comes into view, and it may shorten the tracking period.

scholarly journals Interaural Level Differences and Sound Source Localization for Bilateral Cochlear Implant Patients

2014 ◽  
Vol 35 (6) ◽  
pp. 633-640 ◽  
Author(s):  
Michael F. Dorman ◽  
Louise Loiselle ◽  
Josh Stohl ◽  
William A. Yost ◽  
Anthony Spahr ◽  
...  
Keyword(s):  
Cochlear Implant ◽  
Source Localization ◽  
Sound Source ◽  
Sound Source Localization ◽  
Bilateral Cochlear Implant ◽  
Interaural Level Differences

scholarly journals Effects of Bilateral Automatic Gain Control Synchronization in Cochlear Implants With and Without Head Movements: Sound Source Localization in the Frontal Hemifield

2021 ◽  
pp. 1-14
Author(s):  
M. Torben Pastore ◽  
Kathryn R. Pulling ◽  
Chen Chen ◽  
William A. Yost ◽  
Michael F. Dorman
Keyword(s):  
Source Localization ◽  
Sound Source ◽  
Automatic Gain Control ◽  
Gain Control ◽  
Broadband Noise ◽  
Head Movements ◽  
Sound Source Localization ◽  
Sound Source Identification ◽  
Interaural Difference ◽  
Interaural Level Differences

Purpose For bilaterally implanted patients, the automatic gain control (AGC) in both left and right cochlear implant (CI) processors is usually neither linked nor synchronized. At high AGC compression ratios, this lack of coordination between the two processors can distort interaural level differences, the only useful interaural difference cue available to CI patients. This study assessed the improvement, if any, in the utility of interaural level differences for sound source localization in the frontal hemifield when AGCs were synchronized versus independent and when listeners were stationary versus allowed to move their heads. Method Sound source identification of broadband noise stimuli was tested for seven bilateral CI patients using 13 loudspeakers in the frontal hemifield, under conditions where AGCs were linked and unlinked. For half the conditions, patients remained stationary; in the other half, they were encouraged to rotate or reorient their heads within a range of approximately ± 30° during sound presentation. Results In general, those listeners who already localized reasonably well with independent AGCs gained the least from AGC synchronization, perhaps because there was less room for improvement. Those listeners who performed worst with independent AGCs gained the most from synchronization. All listeners performed as well or better with synchronization than without; however, intersubject variability was high. Head movements had little impact on the effectiveness of synchronization of AGCs. Conclusion Synchronization of AGCs offers one promising strategy for improving localization performance in the frontal hemifield for bilaterally implanted CI patients. Supplemental Material https://doi.org/10.23641/asha.14681412

Role of pinnae and head movements in localizing pure tones 1The authors would like to thank Mr. Remi Humbert for implementing the experiment in Turbo Pascal and for his further assistance.

1999 ◽  
Vol 58 (3) ◽  
pp. 170-179 ◽  
Author(s):  
Barbara S. Muller ◽  
Pierre Bovet
Keyword(s):  
Sound Source ◽  
Head Movement ◽  
Movement Analysis ◽  
Head Movements ◽  
Sound Sources ◽  
Localization Accuracy ◽  
Sound Effects ◽  
Posterior Quadrant ◽  
Localization Performance ◽  
Pure Tones

Twelve blindfolded subjects localized two different pure tones, randomly played by eight sound sources in the horizontal plane. Either subjects could get information supplied by their pinnae (external ear) and their head movements or not. We found that pinnae, as well as head movements, had a marked influence on auditory localization performance with this type of sound. Effects of pinnae and head movements seemed to be additive; the absence of one or the other factor provoked the same loss of localization accuracy and even much the same error pattern. Head movement analysis showed that subjects turn their face towards the emitting sound source, except for sources exactly in the front or exactly in the rear, which are identified by turning the head to both sides. The head movement amplitude increased smoothly as the sound source moved from the anterior to the posterior quadrant.

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