1. What if cross-hearing is a problem? Necessary to prevent NTE from responding. Necessary to prevent NTE from responding. Procedure: MASKING. Procedure: MASKING. Types of masking: Central versus peripheral Types of masking: Central versus peripheral Central masking: Elevation of threshold of a pure tone presented to one ear when noise is presented to the other ear. Around 5 dB threshold shift. Central masking: Elevation of threshold of a pure tone presented to one ear when noise is presented to the other ear. Around 5 dB threshold shift. What types of maskers? Noise (white versus narrow). What types of maskers? Noise (white versus narrow).

2. Effective masking (EM) Amount of threshold shift provided by a certain amount of noise. Amount of threshold shift provided by a certain amount of noise. 20 dB EM is the amount of noise just enough to make a 20 dB HL 1000 Hz tone inaudible. 20 dB EM is the amount of noise just enough to make a 20 dB HL 1000 Hz tone inaudible. A 25 dB HL tone would be audible in the presence of 20 dB EM noise. A 25 dB HL tone would be audible in the presence of 20 dB EM noise.

3. Methods for masking ‘Shotgun’ method ‘Shotgun’ method Minimum noise method: Use effective masking level in the non-test ear. Just enough noise to shift AC and BC thresholds in the non-test ear by 5 dB. Minimum noise method: Use effective masking level in the non-test ear. Just enough noise to shift AC and BC thresholds in the non-test ear by 5 dB. Maximum masking: BC TE + IA – 5 Maximum masking: BC TE + IA – 5 Danger of overmasking, where masking level exceeds BC TE + IA – 5 Danger of overmasking, where masking level exceeds BC TE + IA – 5

4. Hood’s plateau method Measure unmasked threshold in test ear. Measure unmasked threshold in test ear. Present noise to non-test ear, starting at effective masking level. Present noise to non-test ear, starting at effective masking level. Present tone. Test-ear threshold will probably go up. WHY? Present tone. Test-ear threshold will probably go up. WHY? If the tone is heard, then increase masking noise level in 5 dB steps till tone is not heard. If the tone is heard, then increase masking noise level in 5 dB steps till tone is not heard. If the tone is not heard, then increase tone level till it becomes audible again. If the tone is not heard, then increase tone level till it becomes audible again. At some point, tone will be heard even after masking noise level has increased several steps: PLATEAU At some point, tone will be heard even after masking noise level has increased several steps: PLATEAU This is the masked threshold of the test ear. This is the masked threshold of the test ear.

5. Sufficient masking Overmasking Undermasking Minimum maskingMaximum masking