Channel vocoder quality improvements

Spectra of Vocoder Channel Signals

A channel vocoder derives the short time magnitude spectrum of speech by passing the speech through a set of analyzing channels, each consisting of a band pass filter followed by an envelope detector and a low pass filter. Each channel produces a slowly varying output signal which represents a short term average of the speech energy in the corresponding frequency band. The measurement of the po...

Comparative formant and channel vocoder performance

Intelligibility of frequency-lowered speech produced by a channel vocoder.

Frequency lowering is a form of signal processing designed to match speech to the residual auditory capacity of a listener with a high frequency hearing loss. A vocoder-based frequency-lowering system similar to one studied by Lippmann was evaluated in the present study. In this system, speech levels in high frequency bands modulated one-third-octave bands of noise at low frequencies, which wer...

Phase-locked Vocoder 1. Phase Vocoder

The phase vocoder is widely used to provide high-delity time stretching or contraction of audio signals such as speech or monophonic musical passages. Two problems bedevil the re-constructive phase of this technique. First, the frequency estimate is usually multi-valued and one does not know how to choose which of the possible frequencies given by the analysis to use in resynthesis. Second, a s...

Valuing Transit Service Quality Improvements

This article investigates the value transit travelers place on qualitative factors, such as comfort and convenience, and practical ways to incorporate these factors into transport planning and project evaluation. Conventional evaluation practices generally assign the same time value regardless of travel conditions, and so undervalue comfort and convenience impacts. More comprehensive analysis o...