Mobile telephone for controlling call signal volume/hands-free functions with a microphone and a loudspeaker measures acoustic distance between the loudspeaker and an obstruction.

摘要

A loudspeaker (LP) is adapted for sound reproduction in a hands-free mode and/or for call signaling. Distance between the loudspeaker and an obstruction is measured acoustically. Propagation time is measured for a test sound in order to determine the distance. Propagation time measured in this way controls call signal volume or hands-free volume. Devices for reproducing high-frequency sound signals (HS) compared with a voice signal are set up through the loudspeaker for picking up a reflected signal (RS) via a microphone (MK).