Summary

Recommendation ITU-T H.871 complements ITU-T H.870 ''Guidelines for safe listening devices/systems''. Currently there is no international standard for personal sound amplifiers (PSAs). These devices, which are freely available to anyone, require this standard to ensure that these devices are safe for users and do not further damage users' hearing.

PSAs are non-medical devices, intended for people with normal hearing and a) can have a design physically comparable to hearing aids, in which case they are called personal sound amplification products (PSAPs) or b) can also simply be an application on any smartphone or other device, in which case they are called personal sound amplification applications (PSAAs).

As defined in ITU-T H.870, the sound exposure should be limited to an accumulated dose (100 % calculated sound dose (CSD)) over 7 days of in total 1.6 Pa²h which corresponds to 80 dBA for 40 hours to prevent noise-induced hearing loss. When the 100% CSD is reached, the sound level should suddenly drop, and the user will get a suggestion to lower the sound level, since the weekly sound listening dose is exceeded.

When PSAPs and PSAAs do not have the capacity to measure CSD, the output level of the device needs to be permanently limited to 95 dBA, so that a user is unlikely to use the device at a level higher than 80 dBA, since the dynamic range of speech has a crest factor of 12 to 17 dB.

The U.S. Food and Drug Administration has carried out considerable work on these devices and their work is referenced in this Recommendation.