Table 4.

Summary of studies of masked thresholds in temporally-modulated noise in listeners with hearing impairment. The major studies reviewed in this paper are listed in the first column the order in which they are discussed in Section II-D. The second column describes the signals and the third column describes the characteristics of the temporally-modulated noises. The fourth column (Thresh. Match?) provides information concerning the use of threshold matching to simulate hearing loss (with the noise-masking threshold-elevation procedure abbreviated as NM). The fifth column gives the number (No.) of subjects (Ss) and either the range or the mean (X̄) of ages in years of the NH and HI groups. The final column summarizes key comparisons of NH and HI performance.

Study	Signal	Noise	Thresh. Match?	No. and Ages (Years) of Ss	Summary of Findings
Zwicker and Schorn (1982)	600-msec pure tones of 0.5, 1.5, and 4.0 kHz	Bandpass noise; steady-state or square-wave modulated at rate of 14 Hz; overall level of 40 dB SL	NM	40 NH: 17-57 55 HI: Ages Unspecified	Threshold difference between steady-state and modulated noise was in range of 15-25 dB for NH and NM NH listeners and 5-10 dB in HI listeners whose thresholds in quiet exceeded 50 dB SPL at a particular test frequency.
Humes (1990)	4.6-msec tone bursts at 0.5, 1.4, and 4.0 kHz presented in peak or trough of noise	100% sinusoidally amplitude-modulated (SAM) speech-shaped noise with modulation frequency in range of 2.5 to 20 Hz; overall level of 70 dB SPL	NM	10 NH: 17-32 5 HI: 22-67	For NH listeners, threshold differences between detection in peaks and detection in troughs decreased as modulation rate increased: maximum difference of 30-40 dB at lowest modulation rate. Similar trend for HI listeners but maximum magnitude of threshold difference was reduced to 25 dB. Results for NMNH listeners comparable to those of HI listeners.
Halling and Humes (1998)	Pure tones of 0.5, 1.0, and 2.0 kHz	Broadband noise; steady-state or SAM at 7 modulation frequencies in range of 0.5 to 32 Hz; overall level of 70 dBC	No	8 NH: X̄ =23 8 NH: X̄ =72 8 HI: X̄ =73	Release of masking defined as difference between masked threshold in steady-state noise and masked thresholds averaged across the SAM noises. Release of masking slightly greater for young NH compared to elderly NH listeners and substantially larger for elderly NH compared to elderly HI.