The maximum and minimum sound levels are simply the highest and lowest time-weighted sound level measured. Be careful with the Peak, as the terms "Peak" and "Maximum" mean very different things in the world of sound level meters.
The Lmax and Lmin parameters are quite easy to understand. They are simply the highest and lowest values measured by the sound level meter over a given period of time. They are based on the time-weighted sound level in dB, using either the Fast or Slow time constant.
The Lmax and Lmin term used should indicate the frequency weighting and time constant used:
|LAFmax||The maximum level with A-weighted frequency response and Fast time constant.|
|LAFmin||The minimum level with A-weighted frequency response and Fast time constant.|
|LASmax||The maximum level with A-weighted frequency response and Slow time constant.|
|LASmin||The minimum level with A-weighted frequency response and Slow time constant.|
Other frequency weightings, such as C-Weighting or Z-Weighting can be used but are rarely needed in any noise measurement application.
Don't forget, Fast Max (LAFmax) is different to Slow Max (LASmax) and both of these are very different to Peak.
The Peak is not the same as the Maximum Sound Level. The Peak, referred to as the Lpeak or sometimes Lpk, is the maximum value reached by the sound pressure. There is no time-constant applied and the signal has not passed through an RMS circuit or calculator. This is the true Peak of the sound pressure wave.
For a pure tone, the Peak will be 3 dB above the Maximum Sound Level. For varying signals there can be a huge difference and there is no way to calculate the Peak from the Max or any other measurement.
Unlike the Sound Level and the Leq, the Peak measurement is usually C-Weighted rather than A-Weighted. Some older meters used Linear, but C-weighting has replaced that in most standards, including the European Noise at Work regulations. The C-weighted Peak measurement is usually expressed as LCpeak in dB(C).
The LCpeak is used for occupational noise measurement where loud bangs are present. The Peak is not usually used for environmental noise measurement and is useless when any wind is present. A gust of wind will easily give very high LCPeak readings.