Contact microphones are a great way to record sound without picking up any air vibrations. Made using piezo discs (made of brass disc and crystal), they need direct contact with the source of sound to amplify it- or when used experimentally in certain settings, to even hear the sound at all. Contact microphones are a great way of recording acoustic instruments, such as guitar. After building my contact microphone, I used it to record my double bass, which I will go more into depth about later in this post.

By soldering, the piezo discs are attached to a TRS cable. It is very important when putting the mic together, that the connections do not touch each other. If this happens (as it did in my experience), the microphone will not work. Similarly, if the piezo disc becomes damaged, its sensitivity will be decreased, meaning that more gain will be needed to record, or it will no longer pick up sound.

Here is a visual demonstration of how to put together a contact mic:

Once I’d built my mic, I used it to record double bass. I noticed that it was very hard to pick up sound. I realised this was because the piezo disc must’ve been damaged. However, when using an impedance transformer, the “buzz” was reduced, so I was able to turn the gain up, which allowed me to pick up the sound.