A method for evaluating temporal, spectral and combined temporal-spectral resolution of hearing

A method for evaluating the spectral, temporal and combined spectral temporal resolution of hearing is presented; it was used to obtain masked hearing thresholds using the fixed frequency Bekesy technique. The masking noise was a broadband random noise with a 3 dB/octave roll off (pink noise). Spectral resolution was assessed by introducing a spectral gap in the masking noise centred al the test tone frequency. Temporal resolution was assessed by introducing temporal gaps, the centre of which coincided in time with the centre of the test tone-pulses. The spectral and temporal gaps were used either separately or simultaneously. Release of masking values were calculated from masked hearing thresholds. One test group comprised 16 normal-hearing subjects, a second group 16 elderly (age 55-75 years) subjects with normal hearing for their age. Temporal gaps were 20, 50 and 100 ms long. Spectral gaps had a bandwidth of 1/10, 1/3 and 1 octave. Each gap or combination of gaps was tested at the frequencies 0.5, 1, 2 and 4 kHz. Release of masking increased with increasing temporal or spectral gaps. If a temporal gap and a spectral gap were combined, the release of masking increased further. Maximum release of masking was obtained with the 100 ms temporal gap combined with the 1 octave notch filter. The overall difference in release of masking between the young and elderly normal-hearing group was 2 dB.