Typically there are two reasons why the sound may not be coming out of your LRA-DCRX long range receiver.
First, check the selector switch on the side of the unit. There are three modes you can set the receiver to a) strobe only, b) sound only, and c) strobe and sound. Often times when there’s no sound it is because the selector switch is on sound only.
Second, check the volume control selector. Open the front cover of the receiver and locate the volume adjustment dial. Use a small screwdriver to adjust the sound level.
Take a look at this illustration to get an idea of where the selector switch is located.