Mark Franklin Davis

Method and apparatus for adjusting dynamic range and gain in an encoder/decoder for multidimensional sound fields

An audio encoder/decoder system suitable for digital motion picture film soundtracks provides for adjusting playback signal gain and dynamic range by modifying the scale factors of scaled spectral information. In one embodiment of a transform coding system, transform coefficients are expressed in floating-point form and adjustments are made by modifying the exponents in the floating-point representation.

Stereophonic balance control system

The disclosure relates to an audio signal reproduction system having one or more of the following features: (1) a loudspeaker having (a) a flat frequency response and (b) a predetermined power response; (2) two loudspeakers adapted to be positioned relative to one another so that they reproduce a stereophonic image substantially independent of the listeners position along a listening line spaced from the loudspeakers and nonintersecting a line extending between the two speakers; (3) an improved cross-over network having a substantially constant input impedance as a function of frequency; (4) a power sensor for sensing the power applied to a transducer so that audio signals are transmitted over a first signal path through the system when the sensed power is above a predetermined minimum level, and over a second path when the sensed power falls below the minimum level; (5) a power monitoring circuit to prevent a loudspeaker driver from being overdriven; and (6) a circuit for substantially balancing the signal energy levels between two audio channels over a long period of time.

Computerized stethoscopic analysis system and method

This invention relates in general to a method and apparatus for identifying specific medical conditions from detected stethoscopic sounds. More particularly, the invention relates to the processing of such sounds electronically and the display of the time-variations of the spectral composition of such sounds. The invention is embodied in an accessory package designed to enable a host computer to perform computerized stethoscopic analysis.

Audio and Electroacoustics

This chapter surveys devices and systems associated with audio and electroacoustics: The acquisition, transmission, storage, and reproduction of audio. The chapter provides an historical overview of the field since before the days of Edison and Bell to the present day, and analyzes performance of audio transducers, components and systems from basic psychoacoustic principles, to arrive at an assessment of the perceptual performance of such elements and an indication of possible directions for future progress.

Computer simulation of static localization cues

A system for imposing static (fixed‐head) localization cues on an artificial sound source is described. The system is based on the measurement of the peripheral binaural impulse responses at a series of target source positions using small microphones in the subjects ear canals. A computer with associated waveform processing software convolves these impulse responses with widehand noise bursts and plays the results to the subject over headphones. The headphone impulse responses are also measured and deconvolved out of the waveforms in advance by the computer. Both live and simulated localization trials have been carried out, using an identification paradigm with unconstrained source and subject‐response positions. Two‐dimensional, weighted error analysis is used to derive performance scores. Psychophysical localization performance with the simulator is compared to equivalent live performance.