Acquisition and reproduction of factory noise with low-frequency extended bandwidth: a case study

Abstract

A case study concerning the problem of collecting noise sound signals from a typical factory shop-floor, down from 2 Hz to 20 kHz, and reproducing them in a biologically controlled small reverberant closed-room for in-vivo investigation of the biological effects of noise radiation is presented. The project of the electro-acoustic set-up for recording and reproduction is described, with discussion of the encountered solutions. The resulting system is PC based, with DT2823 data acquisition and Sound Blaster 5.1 cards, preamplifier for B&K 4135 microphone, 2-channel power amplifier, 16 monitor loudspeakers and 1 sub woofer. The operation software is a LabVIEW custom designed software. Signal processing was done both on LabVIEW and on Matlab. The system is capable of recording and reproducing noise sounds with monitoring of saturation. Signal acquisition and processing methodologies are presented and explained. Total signals duration is 1 hour, with frequency and amplitude characterization. Reproduction of sounds at the same levels with spectrum near the original, is the following topic addressed in the paper with a description of the problems of equalization and distribution of sound output. The system is in operation for 6 months in a laboratory of the University of Porto.