Cochlear hearing loss : physiological, psychological and technical issues

Since the first edition was published in 1998, considerable advances have been made in the fields of pitch perception and speech perception. In addition, there have been major changes in the way that hearing aids work, and the features they offer. This book will provide an understanding of the changes in perception that take place when a person has cochlear hearing loss so the reader understands not only what does happen, but why it happens. It interrelates physiological and perceptual data and presents both this and basic concepts in an integrated manner. The goal is to convey an understanding of the perceptual changes associated with cochlear hearing loss, of the difficulties faced by the hearing-impaired person, and the limitations of current hearing aids.

Author Notes

Brian C. J. Moore is the author of Cochlear Hearing Loss: Physiological, Psychological and Technical Issues, 2nd Edition, published by Wiley.

Preface	p. xi
1 Physiological Aspects of Cochlear Hearing Loss	p. 1
I Introduction	p. 1
II Linear and Nonlinear Systems	p. 1
III Structure and Function of the Outer and Middle Ear	p. 6
IV Structure and Function of the Normal Cochlea	p. 9
1 The cochlea, the basilar membrane and the organ of Corti	p. 9
2 Tuning on the basilar membrane	p. 12
3 The nonlinearity of input-output functions on the basilar membrane	p. 16
4 Two-tone suppression	p. 18
5 Combination tone generation	p. 18
6 Responses of the basilar membrane to complex sounds	p. 19
7 Otoacoustic emissions	p. 20
V Neural Responses in the Normal Auditory Nerve	p. 21
1 Spontaneous firing rates and thresholds	p. 22
2 Tuning curves and iso-rate contours	p. 22
3 Rate-versus-level functions	p. 23
4 Two-tone suppression	p. 25
5 Phase locking	p. 26
VI Types of Hearing Loss	p. 28
VII Physiology of the Damaged Cochlea	p. 29
1 Basilar membrane responses	p. 29
2 Neural responses	p. 31
3 Structure-function correlation	p. 32
4 Otoacoustic emissions	p. 35
5 Phase locking	p. 35
VIII Conclusions	p. 36
2 Absolute Thresholds	p. 39
I Introduction	p. 39
II Measures of Absolute Threshold	p. 39
1 Minimum audible pressure (MAP)	p. 39
2 Minimum audible field (MAF)	p. 39
3 Comparison of MAP and MAF	p. 40
4 The audiogram	p. 41
III Descriptions of the Severity of Hearing Loss	p. 42
IV Causes of Hearing Loss Due to Cochlear Damage	p. 43
V Perceptual Consequences of Elevated Absolute Thresholds	p. 44
3 Masking, Frequency Selectivity and Basilar Membrane Nonlinearity	p. 45
I Introduction	p. 45
II The Measurement of Frequency Selectivity Using Masking	p. 46
1 Introduction	p. 46
2 The power-spectrum model	p. 46
3 Estimating the shape of a filter	p. 47
III Estimating Frequency Selectivity from Masking Experiments	p. 48
1 Psychophysical tuning curves	p. 48
2 The notched-noise method	p. 51
IV Characteristics of the Auditory Filter in Normal Hearing	p. 54
1 Variation with centre frequency	p. 54
2 Variation with level	p. 56
3 Summary	p. 59
V Masking Patterns and Excitation Patterns	p. 59
1 Masking patterns	p. 59
2 Relationship of the auditory filter to the excitation pattern	p. 61
3 Changes in excitation patterns with level	p. 62
4 Possible effects of suppression	p. 63
VI Non-Simultaneous Masking	p. 64
1 Basic properties of non-simultaneous masking	p. 64
2 Evidence for suppression from non-simultaneous masking	p. 67
3 The enhancement of frequency selectivity revealed in non-simultaneous masking	p. 69
4 Relation between the growth of forward masking and the basilar membrane input-output function	p. 70
VII The Audibility of Partials in Complex Tones	p. 73
VIII Effects of Cochlear Damage on Frequency Selectivity in Simultaneous Masking	p. 75
1 Complicating factors	p. 75
2 Psychophysical tuning curves	p. 76
3 Auditory filter shapes measured with notched noise	p. 79
IX The Use of Masking to Diagnose Dead Regions	p. 83
1 The threshold-equalizing noise (TEN) test	p. 83
2 The TEN(HL) test	p. 85
3 Prevalence of dead regions assessed using the TEN(HL) test	p. 86
X Effects of Cochlear Damage on Forward Masking and Suppression	p. 86
XI Effects of Cochlear Hearing Loss on BM Input-output Functions 88 XII Perceptual Consequences of Reduced Frequency Selectivity, Dead Regions, Loss of Suppression and Steeper BM Input-output Functions	p. 90
1 Susceptibility to masking	p. 90
2 Timbre perception	p. 90
3 Perceptual consequences of dead regions	p. 91
4 Loudness Perception and Intensity Resolution	p. 93
I Introduction	p. 93
II Loudness Perception for Normally Hearing People	p. 93
1 Equal-loudness contours and loudness level	p. 93
2 The scaling of loudness	p. 94
3 The detection of intensity changes	p. 96
III Effects of Cochlear Hearing Loss on Loudness Perception	p. 97
IV A Model of Normal Loudness Perception	p. 101
V A Model of Loudness Perception Applied to Cochlear Hearing Loss	p. 104
1 Introduction	p. 104
2 Elevation of absolute threshold	p. 105
3 Reduced compressive nonlinearity	p. 105
4 Reduced inner hair cell/neural function	p. 106
5 Reduced frequency selectivity	p. 107
6 Complete loss of functioning IHCs or neurones (dead regions)	p. 108
7 Using the model to account for loudness recruitment	p. 109
VI Effects of Bandwidth on Loudness	p. 110
1 Normal hearing	p. 110
2 Impaired hearing	p. 111
VII Effects of Cochlear Hearing Loss on Intensity Resolution	p. 113
VIII Perceptual Consequences of Altered Loudness Perception	p. 114
1 Consequences of loudness recruitment and reduced dynamic range	p. 114
2 Perceptual consequences of reduced loudness summation	p. 114
3 Perceptual consequences of altered intensity discrimination	p. 115
5 Temporal Resolution and Temporal Integration	p. 117
I Introduction	p. 117
II Modelling Within-Channel Temporal Resolution in Normal Hearing	p. 118
1 Bandpass filtering	p. 118
2 The nonlinearity	p. 119
3 The sliding temporal integrator	p. 120
4 The decision device	p. 122
5 Characterizing the nonlinear device and the sliding temporal integrator	p. 122
III Temporal Resolution in Normal Hearing	p. 124
1 The effect of centre frequency on gap detection	p. 124
2 Temporal modulation transfer functions	p. 125
3 The rate of recovery from forward masking	p. 126
IV Temporal Resolution in People with Cochlear Damage	p. 128
1 The influence of sound level on gap detection and the rate of decay of forward masking	p. 128
2 The influence of audible bandwidth on temporal modulation transfer functions and gap detection	p. 130
3 The influence of changes in the compressive nonlinearity	p. 131
V Temporal Integration at Threshold	p. 135
1 Temporal integration in normally hearing people	p. 135
2 Temporal integration in people with cochlear hearing loss	p. 136
3 Explanations for reduced temporal integration in people with cochlear hearing loss	p. 137
VI Temporal Integration at Suprathreshold Levels	p. 138
VII Perceptual Consequences of Abnormal Temporal Processing in People with Cochlear Hearing Loss	p. 140
1 Consequences of abnormal temporal resolution	p. 140
2 Consequences of reduced temporal integration	p. 141
6 Pitch Perception and Frequency Discrimination	p. 143
I Introduction	p. 143
II Theories of Pitch Perception	p. 144
III The Perception of the Pitch of Pure Tones by Normally Hearing People	p. 144
1 The frequency discrimination of pure tones	p. 144
2 The perception of musical intervals	p. 148
3 The effect of level on pitch	p. 149
IV Frequency Discrimination of Pure Tones by People with Cochlear Hearing Loss	p. 150
1 Difference limens for frequency (DLFs)	p. 150
2 Frequency modulation detection limens (FMDLs)	p. 152
V The Perception of Pure-Tone Pitch for Frequencies Falling in a Dead Region	p. 155
VI Pitch Anomalies in the Perception of Pure Tones	p. 157
VII The Pitch Perception of Complex Tones by Normally Hearing People	p. 159
1 The phenomenon of the missing fundamental	p. 159
2 Discrimination of the repetition rate of complex tones	p. 159
VIII Theories of Pitch Perception for Complex Tones	p. 160
1 The representation of a complex tone in the peripheral auditory system	p. 160
2 Spectro-temporal pitch theories	p. 162
3 The relative importance of envelope and temporal fine structure	p. 164
IX Pitch Perception of Complex Tones by People with Cochlear Hearing Loss	p. 167
1 Theoretical considerations	p. 167
2 Experimental studies	p. 169
X Perceptual Consequences of Altered Frequency Discrimination and Pitch Perception	p. 170
1 Effects on speech perception	p. 170
2 Effects on music perception	p. 172
7 Spatial Hearing and Advantages of Binaural Hearing	p. 173
I Introduction	p. 173
II The Localization of Sinusoids	p. 174
1 Cues for localization	p. 174
2 Performance of normally hearing people in localization and lateralization	p. 177
3 Performance of hearing-impaired people in localization and lateralization	p. 178
III The Localization of Complex Sounds	p. 179
1 The role of transients and across-frequency comparisons	p. 179
2 Performance of normally hearing people	p. 179
3 Performance of people with cochlear hearing loss	p. 180
4 Reasons for large interaural time difference and interaural level difference thresholds in people with cochlear hearing loss	p. 183
IV The Cone of Confusion, Head Movements and Pinna Cues	p. 184
1 The cone of confusion	p. 184
2 The role of head movements	p. 185
3 Information provided by the pinnae	p. 185
4 Localization using pinna cues by normally hearing and hearing-impaired people	p. 186
V General Conclusions on Sound Localization	p. 186
VI The Precedence Effect	p. 187
1 The precedence effect for normal hearing	p. 187
2 The precedence effect for impaired hearing	p. 188
VII Binaural Masking Level Differences (MLDs)	p. 189
1 MLDs for normally hearing people	p. 189
2 Mechanisms underlying MLDs	p. 192
3 MLDs for people with cochlear hearing loss	p. 192
4 Possible reasons for smaller MLDs in people with cochlear damage	p. 193
VIII Head-Shadow Effects	p. 194
1 Benefits of head shadow for normally hearing people	p. 194
2 Benefits of head shadow for hearing-impaired people	p. 195
IX Release from Informational Masking	p. 196
X Diotic Advantages	p. 198
XI Perceptual Consequences of Abnormal Binaural and Spatial Hearing in People with Cochlear Damage	p. 199
8 Speech Perception	p. 201
I Introduction	p. 201
II The Magnitude of the Noise Problem	p. 201
III The Role of Audibility	p. 203
1 The Articulation Index (AI) and Speech Intelligibility Index (SII)	p. 203
2 Use of the AI or SII to predict speech intelligibility for the hearing impaired	p. 204
3 The intelligibility of speech in noise at high overall levels	p. 205
4 Comparison of detection and recognition for speech in noise	p. 206
5 The intelligibility of speech in quiet at high overall levels	p. 207
6 Simulation of hearing loss by selective filtering (frequency-dependent attenuation)	p. 207
7 Simulation of hearing loss by masking	p. 208
8 Conclusions on the role of audibility	p. 209
IV Influence of Dead Regions on Speech Perception	p. 209
V Correlation Between Psychoacoustic Abilities and Speech Perception	p. 212
VI Assessing the Effects of Frequency Selectivity on Vowel and Consonant Perception	p. 214
1 Consonant perception	p. 214
2 Vowel perception	p. 215
VII Influence of Loss of Sensitivity to Temporal Fine Structure	p. 219
VIII The Use of Simulations to Assess the Importance of Psychoacoustic Factors in Speech Perception	p. 221
1 Simulations of loudness recruitment combined with threshold elevation	p. 222
2 Simulations of reduced frequency selectivity	p. 226
3 Simulation of the combined effects of threshold elevation, recruitment and reduced frequency selectivity	p. 229
4 Simulation of reduced temporal resolution	p. 230
IX Conclusions	p. 232
9 Hearing Aids	p. 233
I Introduction	p. 233
II Linear Amplification	p. 233
1 The difficulty of restoring audibility using linear aids	p. 233
2 Prescriptive fitting rules for linear hearing aids	p. 234
III Compression Amplification	p. 236
1 Basic characteristics of automatic gain control systems	p. 236
2 Varieties of automatic gain control systems	p. 241
3 Rationales for the use of multi-band compression (and noise reduction)	p. 241
4 Research on the effectiveness of multi-band syllabic compression	p. 242
5 Methods for initial fitting of hearing aids with multi-band compression	p. 244
6 Methods for fine tuning hearing aids with multi-band compression	p. 252
7 Slow-acting automatic gain control systems	p. 253
8 Comparisons of slow-acting and fast-acting systems	p. 255
9 General conclusions about compression	p. 257
IV Some General Problems with Hearing Aids	p. 257
1 Inadequate gain at high frequencies	p. 257
2 Acoustic feedback	p. 258
3 Peakiness of frequency response	p. 259
4 The occlusion effect	p. 260
5 Time delays	p. 261
V Methods for Improving the Speech-to-Noise Ratio	p. 262
1 Multi-channel noise reduction	p. 262
2 Directional microphones	p. 262
3 Binaural processing algorithms	p. 263
VI Transposition Aids for Severe and Profound Hearing Loss	p. 264
VII Cochlear Implants	p. 266
VIII Concluding Remarks	p. 267
Glossary	p. 269
References	p. 287
Index	p. 327

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