Binaural and spatial hearing
Stanley A. Gelfand in Hearing, 2017
Another aspect of directional hearing involves determining the smallest difference in location between two sound sources that results in a different perceived location. Since the two sound sources are viewed relative to the head, this is the same as asking what is the smallest angle (or difference in azimuth) that a listener can discriminate. Mills (1958, 1963, 1972) studied this phenomenon in depth, and called it the minimal audible angle (MAA). Specifically, he tested the MAA as a function of frequency when the sound sources were located in front of the subject (0°), and when they were 30°, 45°, 60°, and 75° off to the side. The logistics of the basic task are illustrated in Figure 13.12, where we see that the listener must distinguish the difference between two points in space. Notice that the figure actually shows two different conditions, one in which the MAA is being determined when both sound sources are directly in front of the listener (at 0° azimuth) and another one in which the two sound sources are off to one side (at 45° azimuth).
Perception of Sounds at the Auditory Cortex
John C Watkinson, Raymond W Clarke, Christopher P Aldren, Doris-Eva Bamiou, Raymond W Clarke, Richard M Irving, Haytham Kubba, Shakeel R Saeed in Paediatrics, The Ear, Skull Base, 2018
Research studies in humans have shown that unilateral lesions interfered with the localization of sound in the contralateral hemisphere of space, suggesting that each cortex preferentially processes acoustic signals on the contralateral side.40 However, there appear to be some differences between the right and left ACs in their responses to sounds. For example, Spierer et al. found that lesions in the right hemisphere typically affected the localization of sound sources originating from both the ipsilateral and contralateral hemifields, whereas left hemisphere lesions were limited to contralateral sound sources.40,41 They also found that the deficits noted among their subjects tended to be more severe following right hemisphere compromise than left hemisphere damage, and that greater deficits were noted for the processing of ITD than ILD cues. Based upon their findings, these researchers have proposed that the right hemisphere plays a dominant (but not an exclusive) role in the processing of spatial location, and it has an integrative role in representing sound localization.41
ENTRIES A–Z
Philip Winn in Dictionary of Biological Psychology, 2003
The central auditory system preserves the place code in the form of a TONOTOPIC REPRESENTATION in each nucleus from the brainstem to the CEREBRAL CORTEX; there is, however, little evidence of phase-locked spike responses for frequencies above 100 Hz, except in the most caudal nuclei. The central auditory pathway has an architecture that shows both PARALLEL PROCESSING and SERIAL PROCESSING. Some brainstem circuits are involved in SOUND LOCALIZATION; others may be involved on processing of a sound's spectral fine structure. The fact that all such nuclei and circuits are tonotopically organized means that these analyses are performed on a frequency-by-frequency basis. Information from these circuits ultimately reaches the AUDITORY CORTEX. The PRIMARY SENSORY CORTEX, and some adjacent fields, have their own tonotopic representation in the form of strip-like assemblies of neurons tuned to the same preferred frequencies. Overlaying this representation is a patchy mosaic of territories dedicated to elaboration of the processing of other stimulus dimensions initiated in the auditory brainstem. The fidelity of this information sets limits on that available to higher, non-auditory processors (such as ATTENTION and LANGUAGE). In this regard, the auditory cortex on each side of the brain processes spatial information only for the CONTRALATERAL hemifield. It is for this reason that deficits in spatial behavior (attention, sound localization) following a UNILATERAL cerebral LESION are also unilateral, and contralateral to the lesion. By the same token, the strictly temporal fidelity of auditory cortical responses is sufficient to encode the timing of the phonetically important elements of speech
Speech perception 30 years after cisplatin-based chemotherapy in adults: limited clinical relevance of long-term ototoxicity?
Published in Acta Oncologica, 2021
J. Skalleberg, M. Myhrum, M. C. Småstuen, T. A. Osnes, S. D. Fosså, M. Bunne
Importantly, some Cases had quite poor HINT scores both in noise and quiet, indicating that individual patients may experience severe problems with speech perception. Cases had slightly, but statistically significant worse HINT scores with speech from front and noise from either side. This slight difference is likely due to the worse high-frequency thresholds among Cases, leading to a poorer sound localization and Spatial Release from Masking (SRM). SRM refers to the ability to utilize that speech and noise come from different directions. An important part of SRM is the head-shadow effect: with HINT NR/NL the sound reaches each ear at slightly different times and volumes. The brain uses these differences to localize the sound and to hear in background noise. The effect of a difference in volume is most pronounced in the higher frequencies because the shorter wavelengths of high-frequency sounds are more blocked by the human head than those of lower frequencies [45]. Hence, directional hearing and hearing in noise may be slightly poorer among TCS, for example identifying what is said from whom and where in a noisy environment.
Adults with unilateral congenital ear canal atresia – sound localization ability and recognition of speech in competing speech in unaided condition
Published in Acta Oto-Laryngologica, 2021
Malin Siegbahn, Cecilia Engmér Berglin, Malou Hultcrantz, Filip Asp
Binaural cues are crucial for the ability to localize sound accurately in the horizontal plane. Binaural listeners use interaural differences in sound pressure level and time as cues to localize sound in the horizontal plane, and these cues also facilitate speech recognition in background noise [2]. Binaural processing is believed to develop during the first five years of life in normal hearing subjects [3]. It is well established that horizontal sound localization ability is negatively affected by both sensorineural- and conductive unilateral hearing loss. Localization ability differs between individuals; Rosenhall [4] found that the degree of unilateral sensorineural hearing loss (>40 dB) was an important factor in directional hearing, when sound was presented at a comfortable level. Some patients with unilateral conductive hearing loss perform surprisingly well in a localization task in unaided conditions [5]. However, the variability in performance is poorly understood.
Sound localization in patients with idiopathic sudden hearing loss
Published in Acta Oto-Laryngologica, 2023
Ryosuke Kitoh, Yutaka Takumi, Shin-ya Nishio, Shin-ichi Usami
This study has some limitations. It was difficult to examine the long-term chronological changes in sound localization ability because the test was performed relatively early after hearing level fixation. In recent years, it has been reported that patients with unilateral hearing loss can improve their sound localization ability through training [11,18]. However, there is no correlation between the period of unilateral hearing loss and sound localization ability, except for training under specific conditions [18]. In addition, it is difficult to compare the results in this study with those of other studies due to the test conditions, for example, the presented stimulus and arrangement of loudspeakers, differ. In the future, we suggest that unifying the test conditions and the evaluation index should be considered to some extent.
Related Knowledge Centers
- Auditory System
- Auricle
- Cochlea
- Hair Cell
- Middle Ear
- Organ of Corti
- Oval Window
- Synapse
- Eardrum
- Sound
- Organ of Corti