When measuring noise levels Lmax and Peak should not be confused. 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.

• 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)