Digital Encoding of Speech and Audio Signals Based on the Perceptual Requirements of the Auditory System
Abstract
The development of a digital encoding system for speech and audio signals is described. The system is designed to exploit the limited detection ability of the auditory system. Existing digital encoders are examined. Relevant psychoacoustic experiments are reviewed. Where the literature is lacking, a simple masking experiment is performed and the results reported. The design of the encoding system and specifications of system parameters are then developed from the perceptual requirements and digital signal processing techniques. The encoder is a multi-channel system, each channel approximately of critical bandwidth. The input signal is filtered via the quadrature mirror filter technique. An extensive development of this technique is presented. Channels are quantized with an adaptive PCM scheme. The encoder is evaluated for speech and audio signal inputs. For 4.1-kHz bandwidth speech, the differential threshold of encoding degradation occurs at a bit rate of 34.4 kbps. At 16 kbps, the encoder produces toll-quality speech output. Audio signals of 15-kHz bandwidth can be encoded at 123.8 kbps without audible degradation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 18, 1979
- Accession Number
- ADA077355
Entities
People
- Michael A. Krasner
Organizations
- Massachusetts Institute of Technology