a hearing aid including a microphone , an adjustable amplifier , and a transducer comprising an acoustic driver driving a diaphragm disposed within an acoustic chamber , all mounted in an in - the - ear housing having a sound outlet passage leading from the acoustic chamber into the user &# 39 ; s ear canal , is provided with a cleaning passage that is accessible from the outside of the housing and that connects to the inner end of the sound outlet passage , through a portion of the acoustic chamber . throughout internal cleaning is effected by pumping a solvent through the continuous conduit formed by the cleaning passage , the acoustic chamber , and the sound outlet passage , without disassembly of the hearing aid .