PURPOSE: To allow the user to sense a deteriorated radio wave reception in a pleasant sense of use by providing a means detecting an error rate of a reception signal of a receiver and a means decreasing a sound volume of a received voice signal when the detected error rate exceeds a specified value to the system.

CONSTITUTION: When a distance between a base station and a mobile station gets longer, a reception electric field strength of the mobile station is deteriorated, resulting that a radio wave reception environment is deteriorated. Then an error rate detection means 81 built in a CPU 8 of a receiver of the mobile station detects an error rate of the received signal in excess of a specified error rate. When the error rate exceeds the specified value, a sound volume reduction means 82 reduces stepwise (e.g. 4 stages) the sound volume of a speaker 10. Thus, the user senses the sound volume of the received voice signal from the speaker 10 to be reduced as if to be in the case of the analog mobile radio communication system. Furthermore, the digital mobile radio communication system is adopted for digitizing and processing of the voice signal on the way, noise caused in the analog system is not produced and the possibility of interrupted talking is recognized with a sense of natural use with high quality.