1. Results from offline processing
Comparison of dynamic range compression using single-band, multiband, and sliding-band compression schemes
Compression Ratio
Single-band Compression
Multiband Compression
Sliding-band Compression 5 10 20 30
Speech material
“you will mark ut please” concatenated with scaling factors of 0.1, 0.8, 0.1, 0.4, 0.1
Processing
Single-band, multiband, and sliding-band dynamic range compression using Win. len. = 25.6 ms, FFT len. = 512

2. Distortions during spectral transitions: Example of swept sinusoidal input.
Input: constant amplitude, 125 –250 Hz linearly swept frequency, 200 ms sweep duration
Single-band compression output
Multiband compression (18 auditory critical bands) output
Sliding band compression output
CR = 30, Ta = 6.4 ms, Tr = 192 ms.
Time (s)

3. Example: "you will mark ut please" concatenated with scaling factors for variation in the input level. CR = 2, Ta = 6.4 ms, Tr = 6.4 & 192 ms.
Input waveform
Scaling factor
Unprocessed waveform
Processed Tr = 6.4 ms, low Pmc
Processed Tr = 192 ms, low Pmc
Processed Tr = 6.4 ms, high Pmc
Processed Tr = 192 ms, high Pmc
Time (s)
Processing of different speech materials with varying levels: No audible roughness or distortion during informal listening.

4. Results from real-time processing
Example: "you will mark ut please" concatenated with scaling factors for variation in the input level. CR = 2, Ta = 6.4 ms, Tr = 192 ms, low Pmc.
Unprocessed waveform
Offline processed waveform
Real-time processed waveform
Time (s)
Informal listening: real-time output perceptually similar to the offline output
PESQ for real-time w.r.t. offline : 3.5
Signal delay = 36 ms
Use of processing capacity: 41%
(lowest proc. clock for satisfactory operation = 50 MHz, max. clock = 120 MHz)