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Figures for Chapter 14 Binaural and bilateral issues

Figures for Chapter 14 Binaural and bilateral issues. Dillon (2001) Hearing Aids. Horizontal localization. Far ear. Near ear. Figure 14.1 Variation of the source direction in the horizontal plane. Source: Dillon (2001): Hearing Aids. Inter-aural time differences.

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Figures for Chapter 14 Binaural and bilateral issues

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  1. Figures for Chapter 14Binaural and bilateral issues Dillon (2001) Hearing Aids

  2. Horizontal localization Far ear Near ear Figure 14.1 Variation of the source direction in the horizontal plane. Source: Dillon (2001): Hearing Aids

  3. Inter-aural time differences Figure 14.2 Interaural time difference for low-frequency sounds as a function of direction measured from directly in front. Data are the average of measurements on people and on a manikin (Kuhn, 1982). Source: Dillon (2001): Hearing Aids

  4. Inter-aural level differences Figure 14.3 Interaural level difference for three source directions in the horizontal plane. Data are calculated from Shaw (1974). Interaural level differences are zero for frontally incident sound. Source: Dillon (2001): Hearing Aids

  5. Vertical localization Figure 14.4 Variation of the source direction in the vertical plane. Source: Dillon (2001): Hearing Aids

  6. Head diffraction Figure 14.5 Head diffraction effects from the undisturbed field to the eardrum for five source directions in the horizontal plane, with positive angles representing sound arriving from the side of the ear in question. Data are from Shaw (1974). Source: Dillon (2001): Hearing Aids

  7. S Effect of head diffraction on SNR N 30o 60o SNR decreased by 9 dB at 3 kHz, and by 8 dB averaged across frequency SNR increased by 11 dB at 3 kHz, and by 9 dB averaged across frequency Figure 14.6 Effect of head diffraction on the SNR at each ear, relative to the SNR in the undisturbed field. The SNR at the right ear is thus 20 dB better than at the left ear at 3 kHz, and 17 dB better when averaged across frequency. Source: Dillon (2001): Hearing Aids

  8. Inter-aural time differences Noise Signal + + Left Right Figure 14.7 Waveforms at the left and right ears when noise arrives from directly in front and a signal (in this case a pure tone) arrives from one side. Source: Dillon (2001): Hearing Aids

  9. S N Bilateral Fitting Demonstrating binaural advantage Figure 14.8 Test arrangement for demonstrating bilateral advantage, showing the location of the speech (S) and noise (N) loudspeakers. Speakers should be 0.5 m or more from the patient. For unilateral fittings to the left ear, the S and N sources should be reversed for both the bilateral and unilateral tests. N S Unilateral Fitting Source: Dillon (2001): Hearing Aids

  10. Bilateral Fitting Unilateral Fitting Detecting negative binaural interactions Figure 14.9 Test arrangement for detecting negative binaural interactions. Speech and noise both come from the same loudspeaker. Source: Dillon (2001): Hearing Aids

  11. 125 250 500 1k 2k 4k 8k 0 20 40 60 80 100 120 Frequency (Hz) Binaural cross-over effect Hearing threshold (dB HL) Figure 14.10 An audiogram for a person who is likely to benefit from the hearing aid cross-over effect if a bilateral fitting is provided. Source: Dillon (2001): Hearing Aids

  12. Poorer ear fitting 125 250 500 1k 2k 4k 8k 0 20 40 60 80 100 120 Frequency (Hz) Hearing threshold (dB HL) Figure 14.11 An audiogram where the poorer ear should be aided if the person chooses to have a unilateral fitting. Source: Dillon (2001): Hearing Aids

  13. 125 250 500 1k 2k 4k 8k 0 20 40 60 80 100 120 Frequency (Hz) Better ear fitting Hearing threshold (dB HL) Figure 14.12 An audiogram where the better ear should be aided if the person chooses to have a unilateral fitting. Source: Dillon (2001): Hearing Aids

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