Article

Contribution of monaural and binaural cues to sound localization in listeners with acquired unilateral conductive hearing loss: Improved directional hearing with a bone-conduction device

Department of Biophysics, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands.
Hearing research (Impact Factor: 2.85). 04/2012; 286(1-2):9-18. DOI: 10.1016/j.heares.2012.02.012
Source: PubMed

ABSTRACT Sound localization in the horizontal (azimuth) plane relies mainly on interaural time differences (ITDs) and interaural level differences (ILDs). Both are distorted in listeners with acquired unilateral conductive hearing loss (UCHL), reducing their ability to localize sound. Several studies demonstrated that UCHL listeners had some ability to localize sound in azimuth. To test whether listeners with acquired UCHL use strongly perturbed binaural difference cues, we measured localization while they listened with a sound-attenuating earmuff over their impaired ear. We also tested the potential use of monaural pinna-induced spectral-shape cues for localization in azimuth and elevation, by filling the cavities of the pinna of their better-hearing ear with a mould. These conditions were tested while a bone-conduction device (BCD), fitted to all UCHL listeners in order to provide hearing from the impaired side, was turned off. We varied stimulus presentation levels to investigate whether UCHL listeners were using sound level as an azimuth cue. Furthermore, we examined whether horizontal sound-localization abilities improved when listeners used their BCD. Ten control listeners without hearing loss demonstrated a significant decrease in their localization abilities when they listened with a monaural plug and muff. In 4/13 UCHL listeners we observed good horizontal localization of 65 dB SPL broadband noises with their BCD turned off. Localization was strongly impaired when the impaired ear was covered with the muff. The mould in the good ear of listeners with UCHL deteriorated the localization of broadband sounds presented at 45 dB SPL. This demonstrates that they used pinna cues to localize sounds presented at low levels. Our data demonstrate that UCHL listeners have learned to adapt their localization strategies under a wide variety of hearing conditions and that sound-localization abilities improved with their BCD turned on.

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    • "The sound is affected before entering the inner ear in CHL2) and leads to some undesirable consequences. The acquired unilateral CHL reduces the ability to localize sound3) and the affected individuals' life quality.4) Moderate or even mild hearing loss could be a significant problem for school children5) because educational listening is not easy in the presence of background noise.2) Furthermore, a mild hearing loss in children may cause impairments in the development of communication, behavioral skills,6) learning ability,7) and speech.8) "
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    ABSTRACT: Conductive hearing loss is common among children and adults. This study aims at comparing the results of conductive hearing loss in summer and autumn. Puretone audiometry and tympanometry tests were done for all patients who referred to the Iranian-based audiology center of Imam Khomeini Hospital in Ahvaz. Data on the patients with conductive or mixed hearing loss were analyzed. The impacts of season, age, and etiology of the disease were analyzed on the patients who visited the audiology clinic due to the conductive hearing loss in summer and autumn. One hundred and fifty nine patients in summer and 123 patients in autumn had conductive or mixed hearing loss. Their age ranged from four to 82 years, with the average age of 35. The percentage of the patients, with acute otitis media and chronic otitis media (COM), who visited this clinic, was significantly higher than those with middle ear problems. COM and mastoid surgeries rate was higher in summer than autumn among adults. There is no relationship between season and middle ear diseases between children and juveniles, but COM and mastoid problems are more common in summer among adults visiting this clinic. Most of the patients had mild conductive hearing loss and bilateral middle ear impairments.
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    • "Therefore, in the clinic, hearing aids are used in both ears. Although double hearing aids improve speech perception compared with only a single hearing aid, this is true only in quiet environments, and perception is still quite poor in noisy environments[12478]. In light of this, sounds in a complex auditory environment are likely localized by means of mechanisms other than the binaural sound-signal difference. "
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    • "Factors likely to influence which adaptation strategy is used include the experience of the individual prior to the onset of hearing loss and the extent to which hearing is restored in the affected ear. It is conceivable, for example, that the ability to use binaural spatial cues, whether normal or abnormal, depends on normal binaural hearing during development (Seidl and Grothe, 2005; Grothe et al., 2010; Litovsky et al., 2010; Agterberg et al., 2012). Consequently, in the case of partial unilateral hearing loss, "
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