Have you heard the term otoacoustic emissions? They are the noises that your ears generate and emit.
When you hear a tone or noise, the noise waves are transmitted to a part of your inner ear called the cochlea. These noises stimulate hair cells in the inner part of the cochlea that send electrical signals to your brain to be processed. Other hair cells in the cochlea are also stimulated, and these generate waves along the membrane of the cochlea that help to amplify and fine-tune the sounds you heard. These waves also get sent back out of your ear and can be heard if you amplify them.
These noises tell about the functioning of your cochlea. Audiologists use these otoacoustic emissions to see if you have damage to certain portions of your cochlea that could keep you from hearing certain frequencies, or pitches of sound.