This document specifies a method for estimating the loudness and loudness level of both stationary and time-varying sounds as perceived by otologically normal adult listeners under specific listening conditions. The sounds may be recorded using a single microphone, using a head and torso simulator, or, for sounds presented via earphones, the electrical signal delivered to the earphones may be used.

The method is based on the Moore-Glasberg-Schlittenlacher algorithm.

NOTE 1    Users who wish to study the details of the calculation method can review or implement the source code which is entirely informative and provided with the standard for the convenience of the user.

This method can be applied to any sounds, including tones, broadband noises, complex sounds with sharp line spectral components, musical sounds, speech, and impact sounds such as gunshots and sonic booms.

Calculation of a single value for the overall loudness over the entire period of a time-varying signal lasting more than 5 s is outside the scope of this document.

NOTE 2    It has been shown that, for steady tones, this method provides a good match to the contours of equal loudness level as defined in ISO 226:2003^[18] and the reference threshold of hearing as defined in ISO 389-7:2019^[19].