This document is applicable to active acoustic noise-cancelling headphones and earphones that have the function of reducing the ambient noise heard by the user by the level of the output sound from the transducer, which is generated by the ambient noise detection microphone and the noise reduction signal processing circuit.

This document covers headphones and earphones to be worn over-the-ear or in-ear, all of which are referred to as "headphones" in this document.

This document specifies the terms and definitions relating to battery duration of this type of headphones and the measurement and evaluation methods.

The noise detection microphones are mounted in the body, on the surface, or on an accessory of the headphones. Signal-processing circuits are analogue and digital electronic circuits.

This document does not deal with equipment intended for hearing protection. It is also not applicable to music players, recorders, etc. that have a noise-cancelling function.

The battery duration measurement methods can be applied to headphones having no active noise-cancelling function.