Difference between Lmax, Lmin and Peak

Understanding Noise Measurements

Lmax & Peak should not be confused when measuring noise levels. Lmax is the RMS (root mean squared) maximum level of a noise source or environment where peak is the maximum level of the raw noise source.

RMS, or root mean squared, is a measure of the magnitude of the varying noise source quantity. The name derives from the calculation, from either a series of discreete values or a continuous varying function, of the square root of the mean of the squares of the values.

The reason for using RMS values gives a clearer understanding of a noise level, making calculations and measurements easier for a noise source waveform which is changing constantly in its magnitude.
Sound Pressure Level Graph highlighting Lmax, Lmin and Peak

  • Lmax is the highest RMS sound pressure level within the measuring period.
  • Lmin is the lowest RMS sound pressure level within the measuring period.
  • Peak is the crest of the sound pressure within the measuring period. (This is not a RMS level)

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