Optimum Linear Filter for Speech Transmission
John David Griffiths · The Journal of the Acoustical Society of America · 1968
A common speech-communications problem is to maximize speech intelligibility over a noisy channel when the transmitter is peak-power limited. An optimum linear solution is analytically derived, and consists of a speech-processing filter in the transmitter. The degree of improvement due to use of the filter is derived for a number of bandwidths and signal-to-noise ratios. The filter was experimentally verified by articulation tests as the optimum linear configuration, and was significantly more intelligible than other filters that bounded it. Although the optimum filter depends on the noise spectrum, there is no significant difference between it and a noise-invariant filter for white or speech-shaped noise. The use of the filter is equivalent to raising the transmitter power between 1 and 10 dB, depending on the speech bandwidth and the signal-to-noise ratio.