A sound-based proximity detector for use in a mobile telephone apparatus

in the proximity degree detector used in mobile phone equipment, telephone was connected to the signal-processing means (2, 3, 4) so that it could operate -- it has the microphone (1) and the loudspeaker (5) at least. In order for a proximity degree detector to start a loudspeaker and to reproduce a sound control signal, It is reflected from the user (13) of a means to control a signal-processing means (3, 4), the control signal (D) directly received with the microphone (1), and telephone (9), Subsequently, a correlation means to take correlation with the control signal (D+D) received with a microphone (1), and to determine the distance (D≒D) between telephone (9) and a user (13), In order to change the signal level of the audible signal which was in direct proportion to the distance (D≒D) determined between telephone (9) and a user (13), and was reproduced by the loudspeaker (5), data processing and a control means (6) including a signal level control means to control a signal-processing means (3, 4) are included.