Some devices with buzzers, like stationary telephones, have a swallow volume adjustment range for said buzzer.
For instance, this particular model has only two ringer volume settings: dead man’s whisper and scream to rise the dead. I would prefer something in between, and this in fact could be quite easily achieved. Open up the phone case and locate the buzzer. In this case it is a black metal disk. I really like how the circuit board has the ringer output wire soldering points marked as BLACK RINGER. Color coding is so color.
We have two options to reduce ringer volume: electric and mechanical. For electric, we have to solder a resistor to increase the ringer resistance, or fiddle with the amplifier, in other words, this could be complicated even for an experienced technician armed with device schematics. The other way is to literally shut the ringer up. This is simple and could be comprehended by a vast majority of end users. Unscrew the ringer and find a hole in the middle of it. This is where the buzz sound come out from. Wrap two layers of tape around it so that the hole is tightly shut. Now connect the phone line, hold the hangup switch, and call this number. Maybe the ringer volume may be too low. Then punch a hole in tape and try again. Punch more holes until the volume is satisfactory. Try not to touch the membrane inside, as this may damage the device. That’s basically it. Assemble the telephone, put it back in place, connect the phone line and wait for calls.