Listening Tubes

Principles of Science: Speed of Sound, Wave Reflection

One person speaks into the end of a tube – they can even whisper – while another person
listens on the other end.

The listening tube exhibit demonstrates how sound travels great distances in waves. A sound wave is a vibration in air; it is a transfer of energy from a source (mouth) to an observer (ear). Although there is a slight delay due to the finite speed of sound, the person listening at the other end can hear the message crystal clear, as if they were standing right next to the person speaking. Sound tubes may be over 100 feet long, but the sound waves inside do not disperse because they are contained within the walls of the tube. The sound energy is contained within the tube, and so can be heard from a greater distance.

Listening tubes, sometimes called sound tubes, were once used by ship captains to communicate with their crews below decks. They were also used in houses to communicate between floors—an early intercom system.