Temporal envelopes, derived using the Hilbert transform, from stimuli processed in four ways. Upper panel: ENV&TFS(once-BPF) (continuous line) and ENV(once-BPF) (circles). Lower panel: ENV&TFS(twice-BPF) (continuous line) and ENV(twice-BPF) (circles). The alignment of the circles with the corresponding continuous lines demonstrates that the steps taken to control temporal envelopes were successful. The figure was generated by passing a 200-ms segment of the word “bull” from the sentence “The bull chased the lady” spoken in quiet through the FIR filter centered on 1033 Hz with low and high cut-off frequencies of 965 and 1100 Hz, respectively.
Benefit from TFS with each type of sentence in steady and modulated noise. Benefit was calculated by subtracting the SRT in each ENV&TFS condition from the SRT in the corresponding ENV condition. Bars plot the mean benefit for each condition. Error bars plot 95% confidence intervals of the means. Open circles plot data for individual participants.
Processing steps used to create ENV and ENV&TFS stimuli in five studies. The steps are described in the Introduction. (ERBN: equivalent rectangular bandwidth of an auditory filter in a young healthy adult with normal hearing. CF: center frequency. HWR: half-wave rectification. FWR: full-wave rectification. LPF: low-pass filter.)
Average improvement in SRT in dB for each condition, using different combinations of processing strategy (ENV&TFS, ENV), sentence type (IHR, IEEE), number of band-pass filtering operations (once, twice), noise type (steady, 30-dB-, and 60-dB-modulated), and presentation level (60 dB SPL, 65 dB SPL). Averages were calculated by subtracting the mean SRT in each condition from the mean SRT in the condition with the highest mean SRT (ENV, IEEE, Once, Steady, 60 dB). Participants in both the main experiment and the three control experiments contributed to the averages.
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