36 CFR Part 1194 Electronic and Information Technology Accessibility Standards (Section 508 Standards)

(f) When products deliver voice output in a public area, incremental volume control shall be provided with output amplification up to a level of at least 65 dB.  Where the ambient noise level of the environment is above 45 dB, a volume gain of at least 20 dB above the ambient level shall be user selectable.  A function shall be provided to automatically reset the volume to the default level after every use.