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

A case study of the problem of collection of noise sound signals in a typical factory shop floor, down from 2 Hz up to 20 kHz, and subsequent reproduction in a biologically controlled small reverberant closed-room is presented. The purpose is to allow an in-vivo investigation of the biological effects of acoustical noise radiation. The project of the electro-acoustic set-up for recording and reproduction is described, with discussion of the encountered solutions. The resulting system is based on a PC, with a DT2823 data acquisition and a SB Live 5.1 cards, one B&K 4165 microphone with preamplifier, one 2-channel power amplifier, 16 monitor-type and 1 sub-woofer loudspeakers. The operation software was designed under the LabVIEW system. Sound signals processing was done offline, partly in LabVIEW and partly in Matlab. The system is capable of recording and reproducing noise sounds with monitoring of saturation level in the amplitude dynamic range. Signal acquisition and processing methodologies are presented and explained. Total signals’ duration is 1 hour. Frequency and amplitude characterisation of signals was done. Reproduction of sounds at the original levels with spectrum very near the original is the following topic addressed in the paper with a description of the problems of equalisation and distribution of sound output in the room. The system has been in operation for 6 months in a laboratory of the Instituto de Ciencias Biomedicas Abel Salazar, of the University of Porto. Diamantino Freitas Page number 2