Use of graphic level recorders as indicating instruments. I. Meeting the specifications of a sound level meter

Abstract

The recent trend in environmental noise control has been toward regulations based on sound level measurements. Such regulations typically require the use of a sound level meter satisfying certain specifications of ANSI S1.4-1971. If another acoustical instrument, such as a graphic level recorder, is to be used in the enforcement of these regulations, it is essential that it meet the same performance specifications. The ability of two well-known graphic level recorders to the meet the “fast” and “slow” response characteristics for indicating instruments has been determined experimentally. For each combination of potentiometer dynamic range and chart paper width, it was necessary to find settings for the remaining controls which would result in the specified tone-burst response and overshoot. It was also necessary to test the resulting frequency response to insure it remained linear over the operating range of a sound level meter. In some cases it proved impossible to obtain the response of a Type 1, or precision sound level meter, but the less stringent Type 2 specifications generally could be met. However, a comparison of a graphic level recorder set to Type 1 specifications to a sound level meter of the same type disclosed a noticeable difference in response to tone bursts. This observation prompted a more comprehensive investigation of the performance of the graphic level recorder which is detailed in a companion paper.