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Hearing Aids pp 181-215 | Cite as

Spatial Hearing and Hearing Aids

  • Michael A. AkeroydEmail author
  • William M. Whitmer
Chapter
Part of the Springer Handbook of Auditory Research book series (SHAR, volume 56)

Abstract

The questions of whether hearing-impaired listeners are also impaired for the localization of sounds and what benefits hearing aids can provide are important for understanding the wider effects of hearing impairment. We review here 29 studies published since 1983 that have measured acuity for changes in the horizontal-plane direction of sound sources. Where possible, performance is quantified by the root-mean-square error in degrees. Overall, the results demonstrate that (1) hearing-impaired listeners have poorer left–right discrimination than normal-hearing listeners, by 5° when averaged across all experiments, although there is considerable variation across listeners and experiments; (2) hearing aids lead to a deficit of just 1°; (3) directional microphones relative to omnidirectional microphones give a deficit of 3°; (4) custom form factors have no effect relative to the behind-the-ear style; (5) acclimatization gives a benefit of 1°; (6) a unilateral fitting results in a localization deficit of 5° on average, and the deficit can reach nearly 20°; and (7) hearing-impaired listeners are particularly prone to front–back confusions; hearing aids do nothing to reduce these and sometimes increase them. Although statistically significant effects of hearing aids on localization have been reported, few of them are generalizable, as they often occurred for just some source directions, stimuli, hearing aid features, or groups of listeners. Overall, there is no experimental evidence for a benefit from hearing aids for directional acuity.

Keywords

Acclimatization Bilateral aiding Behind-the-ear Directional microphones Front–back confusions Hearing aids Localization Meta-analysis Minimal audible angle Unilateral aiding 

Notes

Acknowledgments

This work was supported by the Medical Research Council (grant number U135097131) and by the Chief Scientist Office of the Scottish Government.

Conflict of interest Michael Akeroyd declares he has no conflict of interest.William Whitmer declares he has no conflict of interest.

References

  1. Aaronson, N. L., & Hartmann, W. M. (2014). Testing, correcting, and extending the Woodworth model for interaural time difference. The Journal of the Acoustical Society of America, 135, 817–823.CrossRefPubMedPubMedCentralGoogle Scholar
  2. Abel, S. M., & Hay, V. H. (1996). Sound localization: The interaction of aging, hearing loss and hearing protection. Scandinavian Audiology, 25, 4–12.CrossRefGoogle Scholar
  3. Akeroyd, M. A. (2014). An overview of the major phenomena of the localization of sound sources by normal-hearing, hearing-impaired, and aided listeners. Trends in Hearing, 18, 1–7.CrossRefGoogle Scholar
  4. Akeroyd, M. A., & Bernstein, L. R. (2001). The variation across time of sensitivity to interaural disparities: Behavioral measurements and quantitative analyses. The Journal of the Acoustical Society of America, 110, 2516–2526.CrossRefPubMedGoogle Scholar
  5. Akeroyd, M. A., & Guy, F. H. (2011). The effect of hearing impairment on localization dominance for single-word stimuli. The Journal of the Acoustical Society of America, 130, 312–323.CrossRefPubMedPubMedCentralGoogle Scholar
  6. Arlinger, S., Gatehouse, S., Bentler, R. A., Byrne, D., Cox, R. M., et al. (1996). Report of the Eriksholm Workshop on auditory deprivation and acclimatization. Ear and Hearing, 17, 87S–98S.CrossRefPubMedGoogle Scholar
  7. Bernstein, L. R., & Trahiotis, C. (2002). Enhancing sensitivity to interaural delays at high frequencies by using “transposed stimuli.” The Journal of the Acoustical Society of America, 112, 1026–1036.CrossRefPubMedGoogle Scholar
  8. Best, V., Kalluri, S., McLachlan, S., Valentine, S., Edwards, B., & Carlile, S. (2010). A comparison of CIC and BTE hearing aids for three-dimensional localization of speech. International Journal of Audiology, 49, 723–732.CrossRefPubMedGoogle Scholar
  9. Best, V., Carlile, S. Kopčo, N., & van Schaik, A. (2011). Localization in speech mixtures by listeners with hearing loss. The Journal of the Acoustical Society of America, 129, EL210–EL215.PubMedGoogle Scholar
  10. Blauert, J. (1997). Spatial hearing: The psychophysics of human sound localization. Cambridge, MA: The MIT Press.Google Scholar
  11. Blauert, J., Brueggen, M., Bronkhorst, A, W., Drullman, R., Reynaud, G., &; Pellieux, L. (1998). The AUDIS catalog of human HRTFs. The Journal of the Acoustical Society of America, 103, 3082.Google Scholar
  12. Brimijoin, W. O., & Akeroyd, M. A. (2012). The role of head movements and signal spectrum in an auditory front/back illusion. iPerception, 3, 179–181.Google Scholar
  13. Brimijoin, W. O., & Akeroyd, M. A. (2014). The moving minimum audible angle is smaller during self motion than during source motion. Frontiers in Neuroscience, 8, 273.Google Scholar
  14. Brimijoin, W. O., Boyd A. W., & Akeroyd M. A. (2013). The contribution of head movement to the externalization and internalization of sounds. PLoS ONE, 8, 1–12.Google Scholar
  15. Brughera, A., Dunai, L., & Hartmann, W. M. (2013). Human interaural time difference thresholds for sine tones: The high-frequency limit. The Journal of the Acoustical Society of America, 133, 2839–2855.CrossRefPubMedPubMedCentralGoogle Scholar
  16. Brungart, D. S., Rabinowitz, W. M., & Durlach, N. I. (2000). Evaluation of response methods for the localization of nearby objects. Perception and Psychophysics, 62, 48–65.CrossRefPubMedGoogle Scholar
  17. Brungart, D. S., Cohen, J., Cord, M., Zion, D., & Kalluri. S. (2014). Assessment of auditory spatial awareness in complex listening environments. The Journal of the Acoustical Society of America, 136, 1808–1820.Google Scholar
  18. Bushby, K. M., Cole, T., Matthews, J. N., & Goodship, J. A. (1992). Centiles for adult head circumference. Archives of Diseases in Childhood, 67, 1286–1287.CrossRefGoogle Scholar
  19. Byrne, D., & Noble, W. (1998). Optimizing sound localization with hearing aids. Trends in Amplification, 3, 51–73.CrossRefPubMedPubMedCentralGoogle Scholar
  20. Byrne, D., Noble, W., & LePage, B. (1992). Effects of long-term bilateral and unilateral fitting of different hearing aid types on the ability to locate sounds. Journal of the American Academy of Audiology, 3, 369–382PubMedGoogle Scholar
  21. Byrne, D., Noble, W., & Glauerst, B. (1996). Effects of earmold type on ability to locate sounds when wearing hearing aids. Ear and Hearing, 17, 218–228.CrossRefPubMedGoogle Scholar
  22. Byrne, D., Sinclair, S., & Noble, W. (1998). Open earmold fittings for improving aided auditory localization for sensorineural hearing losses with good high-frequency hearing. Ear and Hearing, 19, 62–71.CrossRefPubMedGoogle Scholar
  23. Chung, K., Neuman, A. C., & Higgins, M. (2008). Effects of in-the-ear microphone directionality on sound direction identification. The Journal of the Acoustical Society of America, 123, 2264–2275.CrossRefPubMedGoogle Scholar
  24. Dawes, P., Munro, K. J., Kalluri, S., & Edwards, B. (2014). Acclimatization to hearing aids. Ear and Hearing, 35, 203–212.CrossRefPubMedGoogle Scholar
  25. Drennan, W. R., Gatehouse, S., Howell, P., Van Tassell, D., & Lund, S. (2005). Localization and speech-identification ability of hearing-impaired listeners using phase-preserving amplification. Ear and Hearing, 26, 461–472.CrossRefPubMedGoogle Scholar
  26. Durlach, N. I., & Colburn, H. S. (1978). Binaural phenomena. In E. C. Carterette & M. P. Friedman (Eds.), Handbook of perception, Vol. IV: Hearing (pp. 365–466). New York: Academic Press.Google Scholar
  27. Durlach, N. I., Thompson, C. L., & Colburn, H. S. (1981). Binaural interaction in impaired listeners. A review of past research. Audiology, 20, 181–211.Google Scholar
  28. Feddersen, W. E., Sandel, T. T., Teas, D. C., & Jeffress, L. A. (1957). Localization of high‐frequency tones. The Journal of the Acoustical Society of America, 29, 988–991.CrossRefGoogle Scholar
  29. Fisher, R. A. (1922). On the mathematical foundations of theoretical statistics. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences, 222, 309–368.CrossRefGoogle Scholar
  30. Freigang, C., Schmiedchen, K., Nitsche, I., & Rubsamen, R. (2014). Free-field study on auditory localization and discrimination performance in older adults. Experimental Brain Research, 232, 1157–1172.CrossRefPubMedGoogle Scholar
  31. Füllgrabe, C., Moore, B. C. J., & Stone, M. A. (2015). Age-group differences in speech identification despite matched audiometrically normal hearing: Contributions from auditory temporal processing and cognition. Frontiers in Aging Neuroscience, 6, 347.PubMedPubMedCentralGoogle Scholar
  32. Gabriel, K.J., Koehnke, J., & Colburn H. S. (1992). Frequency dependence of binaural performance in listeners with impaired binaural hearing. The Journal of the Acoustical Society of America, 91, 336–347.CrossRefPubMedGoogle Scholar
  33. Gallun, F. J., McMillan, G. P., Molis, M. R., Kampel, S. D., Dann, S. M., & Konrad-Martin, D. L. (2014). Relating age and hearing loss to monaural, bilateral, and binaural temporal sensitivity. Frontiers in Neuroscience, 8, 172.PubMedPubMedCentralGoogle Scholar
  34. Gardner, W. G., & Martin, K. D. (1995). HRTF measurements of a KEMAR. The Journal of the Acoustical Society of America, 97, 3907–3908.CrossRefGoogle Scholar
  35. Geary, R. C. (1935). The ratio of the mean deviation to the standard deviation as a test of normality. Biometrika, 27, 310–332.CrossRefGoogle Scholar
  36. Grantham, D. W. (1984). Interaural intensity discrimination: Insensitivity at 1000 Hz. The Journal of the Acoustical Society of America, 75, 1191–1194.CrossRefPubMedGoogle Scholar
  37. Grantham, D. W., Hornsby, B. W. Y., & Erpenbeck, E. A. (2003). Auditory spatial resolution in horizontal, vertical, and diagonal planes. The Journal of the Acoustical Society of America, 114, 1009–1022.CrossRefPubMedGoogle Scholar
  38. Hafter, E. R., & Dye, R. H. (1983). Detection of interaural differences of time in trains of high-frequency clicks as a function of interclick interval and number. The Journal of the Acoustical Society of America, 73, 644–651.CrossRefPubMedGoogle Scholar
  39. Hartmann, W. M. (1983). Localization of sound in rooms. The Journal of the Acoustical Society of America, 74, 1380–1391.CrossRefPubMedGoogle Scholar
  40. Hartmann, W. M., & Constan, Z. A. (2002). Interaural level differences and the level-meter model. The Journal of the Acoustical Society of America, 112, 1037–1045.CrossRefPubMedGoogle Scholar
  41. Häusler, R., Colburn, S., & Marr, E. (1983). Sound localization in subjects with impaired hearing. Spatial-discrimination and interaural-discrimination tests. Acta Oto-Laryngologica (Supplementum), 400, 1–62.Google Scholar
  42. Hawkins, D. B., & Wightman, F. L. (1980). Interaural time discrimination ability of listeners with sensorineural hearing loss. Audiology, 19, 495–507.CrossRefPubMedGoogle Scholar
  43. Hopkins, K., & Moore, B. C. J. (2010). The importance of temporal fine structure information in speech at different spectral regions for normal-hearing and hearing-impaired subjects. The Journal of the Acoustical Society of America, 127, 1595–1608.CrossRefPubMedGoogle Scholar
  44. Hopkins, K., & Moore, B. C. J. (2011). The effects of age and cochlear hearing loss on temporal fine structure sensitivity, frequency selectivity, and speech reception in noise. The Journal of the Acoustical Society of America, 130, 334–349.CrossRefPubMedGoogle Scholar
  45. Humes, L. E., & Wilson, D. L. (2003). An examination of changes in hearing-aid performance and benefit in the elderly over a 3-year period of hearing-aid use. Journal of Speech, Language, and Hearing Research, 46, 137–145.CrossRefPubMedGoogle Scholar
  46. Jensen, N. S., Neher, T., Laugesen, S., Johannesson, B. J., & Kragelund, L. (2013). Laboratory and field study of the potential benefits of pinna cue-preserving hearing aids. Trends in Amplification, 17, 171–188.PubMedCentralGoogle Scholar
  47. Jiang, D., & Oleson, J. J. (2011). Simulation study of power and sample size for repeated measures with multinomial outcomes: An application to sound direction identification experiments (SDIE). Statistics in Medicine, 30, 2451–2466.CrossRefPubMedPubMedCentralGoogle Scholar
  48. Keidser, G., Rohrseitz, K., Dillon, H., Hamacher, V., Carter, L., et al. (2006). The effect of multi-channel wide dynamic range compression, noise reduction, and the directional microphone on horizontal localization performance in hearing aid wearers. International Journal of Audiology, 45, 563–579.CrossRefPubMedGoogle Scholar
  49. Keidser, G., Carter, L., Chalupper, J., & Dillon, H. (2007). Effect of low-frequency gain and venting effects on the benefit derived from directionality and noise reduction in hearing aids. International Journal of Audiology, 46, 554–568.CrossRefPubMedGoogle Scholar
  50. Keidser, G., O’Brien, A., Hain, J. U., McLelland, M., & Yeend, I. (2009). The effect of frequency-dependent microphone directionality on horizontal localization performance in hearing-aid users. International Journal of Audiology, 48, 789–803.CrossRefPubMedGoogle Scholar
  51. King, A., Hopkins, K., & Plack, C. J. (2014). The effects of age and hearing loss on interaural phase difference discrimination. The Journal of the Acoustical Society of America, 135, 342–351.CrossRefPubMedGoogle Scholar
  52. Klump, R. G., & Eady, H. R. (1956). Some measurements of interaural time difference thresholds. The Journal of the Acoustical Society of America, 28, 859–860.CrossRefGoogle Scholar
  53. Köbler, S., & Rosenhall, U. (2002). Horizontal localization and speech intelligibility with bilateral and unilateral hearing aid amplification. International Journal of Audiology, 41, 395–400.CrossRefPubMedGoogle Scholar
  54. Kramer, S. E., Kapteyn, T. S., Festen, J. M., & Tobi, H. (1996). The relationships between self-reported hearing disability and measures of auditory disability. Audiology, 35, 277–287.CrossRefPubMedGoogle Scholar
  55. Kreuzer, W., Majdak, P., & Chen, Z. (2009). Fast multipole boundary element method to calculate head-related transfer functions for a wide frequency range. The Journal of the Acoustical Society of America, 126, 1280–1290.CrossRefPubMedPubMedCentralGoogle Scholar
  56. Kuhn, G. F. (1977). Model for the interaural time differences in the azimuthal plane. The Journal of the Acoustical Society of America, 62, 157–167.CrossRefGoogle Scholar
  57. Kuhn, G. F. (1987). Physical acoustics and measurements pertaining to directional hearing. In W. A. Yost & G. Gourevitch (Eds.), Directional hearing (pp. 3–5). New York: Springer-Verlag.Google Scholar
  58. Kuk, F., Korhonen, P., Lau, C., Keenan, D., & Norgaard, M. (2013). Evaluation of a pinna compensation algorithm for sound localization and speech perception in noise. American Journal of Audiology, 22, 84–93.CrossRefPubMedGoogle Scholar
  59. Litovsky, R. Y., Colburn, H. S., Yost, W.A., & Guzman, S. J. (1999). The precedence effect. The Journal of the Acoustical Society of America, 106, 1633–1654.CrossRefPubMedGoogle Scholar
  60. Lorenzi, C., Gatehouse, S., & Lever, C. (1999a). Sound localization in noise in normal-hearing listeners. The Journal of the Acoustical Society of America, 105, 1810–1820.CrossRefPubMedGoogle Scholar
  61. Lorenzi, C., Gatehouse, S., & Lever, C. (1999b). Sound localization in noise in hearing-impaired listeners. The Journal of the Acoustical Society of America, 105, 3454–3463.CrossRefPubMedGoogle Scholar
  62. Macaulay, E. J., Hartmann, W. M., & Rakerd, B. (2010). The acoustical bright spot and mislocalization of tones by human listeners. The Journal of the Acoustical Society of America, 127, 1440–1449.CrossRefPubMedPubMedCentralGoogle Scholar
  63. Mills, A. W. (1958). On the minimum audible angle. The Journal of the Acoustical Society of America, 30, 237–246.CrossRefGoogle Scholar
  64. Moore, B. C. J. (2013). An introduction to the psychology of hearing. Leiden, The Netherlands: Brill.Google Scholar
  65. Moore, B. C. J. (2014). Auditory processing of temporal fine structure: Effects of age and hearing loss. Singapore: World Scientific.CrossRefGoogle Scholar
  66. Munro, K. J. (2008). Reorganization of the adult auditory system: Perceptual and physiological evidence from monaural fitting of hearing aids. Trends in Amplification, 12, 85–102.CrossRefPubMedPubMedCentralGoogle Scholar
  67. Neher, T., Laugesen, S., Jensen, N. S., & Kragelund, L. (2011). Can basic auditory and cognitive measures predict hearing-impaired listeners’ localization and spatial speech recognition abilities? The Journal of the Acoustical Society of America, 130, 1542–1558.CrossRefPubMedGoogle Scholar
  68. Noble, W., & Byrne, D. (1990). A comparison of different binaural hearing aid systems for sound localization in the horizontal and vertical planes. British Journal of Audiology, 24, 335–346.CrossRefPubMedGoogle Scholar
  69. Noble, W., & Byrne, D. (1991). Auditory localization under conditions of unilateral fitting of different hearing aid systems. British Journal of Audiology, 25, 237–250.CrossRefPubMedGoogle Scholar
  70. Noble, W., Byrne, D., & Lepage, B. (1994). Effects on sound localization of configuration and type of hearing impairment. The Journal of the Acoustical Society of America, 95, 992–1005.CrossRefPubMedGoogle Scholar
  71. Noble, W., Byrne, D., & Ter-Horst, K. (1997). Auditory localization, detection of spatial separateness, and speech hearing in noise by hearing impaired listeners. The Journal of the Acoustical Society of America, 102, 2343–2352.CrossRefPubMedGoogle Scholar
  72. Noble, W., Sinclair, S., & Byrne, D. (1998). Improvement in aided sound localization with open earmolds: Observations in people with high-frequency hearing loss. Journal of the American Academy of Audiology, 9, 25–34.PubMedGoogle Scholar
  73. Picou, E. M., Aspell, A., & Ricketts, T. A. (2014). Potential benefits and limitations of three types of directional processing in hearing aids. Ear and Hearing, 35, 339–352.CrossRefPubMedGoogle Scholar
  74. Rayleigh, L. (1894). Theory of sound. London: Macmillan.Google Scholar
  75. Recanzone, G., Makhamra, S. D. D. R., & Guard, D. C. (1998). Comparison of relative and absolute sound localization ability in humans. The Journal of the Acoustical Society of America, 103, 1085–1097.CrossRefPubMedGoogle Scholar
  76. Ross, B., Fujioka, T., Tremblay, K. L., & Picton, T. W. (2007). Aging in binaural hearing begins in mid-life: Evidence from cortical auditory-evoked responses to changes in interaural phase. Journal of Neuroscience, 27, 11172–11178.CrossRefPubMedGoogle Scholar
  77. Seeber, B. U., Eiler, C., Kalluri, S., Hafter, E. R., & Edwards, B. (2008). Interaction between stimulus and compression type in precedence situations with hearing aids (A). The Journal of the Acoustical Society of America, 123, 3169.CrossRefGoogle Scholar
  78. Shinn-Cunningham, B. G., Santarelli, S., & Kopco, N. (2000). Tori of confusion: Binaural localization cues for sources within reach of a listener. The Journal of the Acoustical Society of America, 107, 1627–1636.CrossRefPubMedGoogle Scholar
  79. Simon, H. J. (2005). Bilateral amplification and sound localization: Then and now. Journal of Rehabilitation Research and Development, 42, 117–132.CrossRefPubMedGoogle Scholar
  80. Smith-Olinde, L., Koehnke, J., & Besing, J. (1998). Effects of sensorineural hearing loss on interaural discrimination and virtual localization. The Journal of the Acoustical Society of America, 103, 2084–2099.CrossRefPubMedGoogle Scholar
  81. Stern, R. M., Slocum, J. E., & Phillips, M. S. (1983). Interaural time and amplitude discrimination in noise. The Journal of the Acoustical Society of America, 73, 1714–1722.CrossRefPubMedGoogle Scholar
  82. Stevens, S. S., & Newman, E. B. (1936). The localization of actual sources of sound. American Journal of Psychology, 48, 297–306.CrossRefGoogle Scholar
  83. Strelcyk, O., & Dau, T. (2009). Relations between frequency selectivity, temporal fine-structure processing, and speech reception in impaired hearing. The Journal of the Acoustical Society of America, 125, 3328–3345.CrossRefPubMedGoogle Scholar
  84. Tattersall, I. (2008). An evolutionary framework for the acquisition of symbolic cognition by Homo sapiens. Comparative Cognition & Behavior Reviews, 3, 99–114.CrossRefGoogle Scholar
  85. Tobias, J. V., & Zerlin, S. (1959). Lateralization thresholds as a function of stimulus duration. The Journal of the Acoustical Society of America, 31, 1591–1594.CrossRefGoogle Scholar
  86. Treeby, B. E., Pan, J., & Paurobally, R. M. (2007). The effect of hair on auditory localization cues. The Journal of the Acoustical Society of America, 122, 3586–3597.CrossRefPubMedGoogle Scholar
  87. Vaillancourt, V., Laroche, C., Giguère, C., Beaulieu, M. A., & Legault, J. P. (2011). Evaluation of auditory functions for Royal Canadian mounted police officers. Journal of the American Academy of Audiology, 22, 313–331.CrossRefPubMedGoogle Scholar
  88. van den Bogaert, T., Klasen, T. J., Moonen, M., Van Deun, L., & Wouters, J. (2006). Horizontal localization with bilateral hearing aids: Without is better than with. The Journal of the Acoustical Society of America, 119, 515–526.CrossRefPubMedGoogle Scholar
  89. van den Bogaert, T., Carette, E., & Wouters, J. (2011). Sound source localization using hearing aids with microphones placed behind-the-ear, in-the-canal, and in-the-pinna. International Journal of Audiology, 50, 164–176.CrossRefPubMedGoogle Scholar
  90. van Esch, T. E. M., Kollmeier, B., Vormann, M. Lyzenga, J., Houtgast, T., et al. (2013). Evaluation of the preliminary auditory profile test battery in an international multi-centre study. International Journal of Audiology, 52, 305–321.CrossRefPubMedGoogle Scholar
  91. Wallach, H. (1940). The role of head movements and vestibular and visual cues in sound localization. Journal of Experimental Psychology, 27, 339–368.CrossRefGoogle Scholar
  92. Whitmer, W. M., Seeber, B. U., & Akeroyd, M. A. (2012). Apparent auditory source width insensitivity in older hearing-impaired individuals. The Journal of the Acoustical Society of America, 132, 369–379.CrossRefPubMedPubMedCentralGoogle Scholar
  93. Whitmer, W. M., Seeber, B. U., & Akeroyd, M. A. (2014). The perception of apparent auditory source width in hearing-impaired adults. The Journal of the Acoustical Society of America, 135, 3548–3559.CrossRefPubMedPubMedCentralGoogle Scholar
  94. Wiggins, I. M., & Seeber, B. U. (2011). Dynamic-range compression affects the lateral position of sounds. The Journal of the Acoustical Society of America, 130, 3939–3953.CrossRefPubMedGoogle Scholar
  95. Woodworth, R. S. (1938). Experimental psychology. New York: Holt.Google Scholar
  96. Yost, W. A., Loiselle, L., Dorman, M., Burns, J., & Brown, C. A. (2013). Sound source localization of filtered noises by listeners with normal hearing: A statistical analysis. The Journal of the Acoustical Society of America, 133, 2876–2882.CrossRefPubMedPubMedCentralGoogle Scholar

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© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.MRC Institute of Hearing ResearchSchool of Medicine, University of Nottingham Medical SchoolNottinghamUK
  2. 2.MRC Institute of Hearing ResearchNottinghamUK
  3. 3.MRC/CSO Institute of Hearing Research – Scottish SectionGlasgow Royal InfirmaryGlasgowUK

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