The notional constant single level, in decibels, that represents the same sound energy as the actual varying sound over a specified interval of time. The steady level Leq is equivalent in energy to the "real" actual varying noise level over the specified period of time. The Leq is usually expressed as an ‘A’ weighted value in dB unless the frequency response is specified otherwise, e.g. LCeq. The Leq can also be measured in individual octave or third octave bands during a frequency analysis of a noise source for noise control purposes.