This beginner's project could be regarded as the audio equivalent of a telescope. Its basic function is to pick up sounds via a microphone, greatly amplify the resultant signal, and then feed it to a pair of headphones. This gives users a sort of "larger than life" version of what they would normally hear, permitting them to detect sounds that would otherwise be inaudible. A sort of hearing aid for those who do not have a hearing defect.

Apart from making sounds louder, it is often possible to place the microphone very close to the sound source, or even actually touching it, so that otherwise inaudible sounds can be monitored. When used in this way the unit acts as a sort of electronic stethoscope, and the barely audible sound from a watch can be made to sound more like a shipyard in full production. It is even possible to place the microphone underwater, perhaps to monitor the wildlife in a pond, provided, of course, the microphone is given adequate waterproofing.