Sound energy causes changes in the shape of these cells, which serves to amplify sound vibrations in a frequency specific manner.

The abdominal tracheal air sacs surround the sound muscles and extend into the abdomen, acting as resonant chambers to amplify sound.

Modern experiments have indicated that their effect would have been to absorb the resonance of certain frequencies, rather than to amplify sound.

The carbon transmitter was used to amplify sound by taking a weak signal and using electric current to make it a strong signal.

Built-in microphones amplify sounds from under the house; a dining table can be 'played' like a xylophone; and a mirrored staircase makes a different sound with each step.