Opens in a new tab

AES E-Library

← Back to search

Journal Article

Increasing the Audio Measurement Capability of FFT Analyzers by Microcomputer Postprocessing

Authors: Lipshitz, Stanley P.; Scott, Tony C.; Vanderkooy, John

Journal of the Audio Engineering Society · Volume 33 · Issue 9 · pp. 626–648 · September 1985

Abstract

A fast Fourier transform (FFT) spectrum analyzer, especially a dual-channel device, can furnish increased measurement capabilities if its data can be sent to a microcomputer for postprocessing. Some of the additional capabilities that the authors have achieved are illustrated, their usefulness in audio measurement is discussed, and their theoretical basis and the means by which they are computed are outlined. The FFT analyzer, in addition to acquiring the data, functions essentially as a rapid Fourier transform calculator and flexible display unit, while the data are suitably reconfigured in the microcomputer and shuttled forward and backward between them. The computation is shown of 1) the analytic signal and its envelope (that is, the "energy-time curve"), 2) the minimum-phase and excess-phase portions of a system's phase response, 3) constant relative bandwidth smoothing (such as one-third-octave smoothing) of FFT spectral data, and 4) the cumulative spectral decay plot (that is, the "waterfall" plot of power versus frequency versus time).

Details

Publication
Journal of the Audio Engineering Society
Volume
33
Issue
9
Pages
626–648
Publication date
September 6, 1985
Affiliation
University of Waterloo, Waterloo, Ont., N2L 3G! Canada (See document for exact affiliation information.)
Type
Journal Article