6 - Measurement techniques for sound level meters

Abstract

This chapter illustrates various measurement techniques for sound level meters. It also highlights the need for individual hearing protection and noise reduction measures. Sound may be characterized by its pressure level and frequency. The frequency range of the undamaged human ear extends from about 20 Hz to 20,000 Hz (20 kHz). A basic sound level meter consists of a microphone, a calibrated attenuator, amplifiers, weighting networks, and an indicating meter. Accuracy of the sound level meter depends largely on the microphone. Most sound level meters incorporate fast and slow response settings. The manufacturer generally specifies preferred microphone orientation. Microphones are designed to respond equally to all frequencies in the range of interest. While the human ear may respond to tones in the frequency range of 20 Hz to 20 kHz, the response is not the same at all frequencies. Instrument calibration is crucial in noise measurement. Sound level meters are often supplied with an internal check of battery level and an internal electronic calibration check. Human response may be expressed in terms of annoyance and other subjective criteria. Response depends on the frequency content and the time patterns of the noise and differs widely among individuals.