ABSTRACT
Sound levels can be measured with a sound level meter (SLM). A sound level meter contains a microphone, an amplifier circuit, a filter circuit, and a detector. The microphone applied in the SLM is a pressure type. More advanced SLMs can identify the microphone and set the correct gain according to the microphone’s sensitivity and frequency response. The detector rectifies the signal, averages it, and calculates an RMS value. There are two forms of averaging. One is linear averaging, and the other is exponential averaging. In connection with the measurement of acoustic sound, exponential averaging is used. Advanced SLMs have gradually become full audio analyzers that can easily be controlled directly, by an external computer, or by a smartphone. In case of measurements for sound insulation between two rooms, background noise is measured and analyzed; reverberation time is measured and analyzed; a noise source is started and stopped; sound levels in different positions are measured, averaged and analyzed.
