# Sound wave in a Vacuum

If a Tuning fork was Struck in a Vacuum what happens to the resonant frequency of the fork and the potential sound wave. Does the wave leave the fork?

No the sound wave cannot emanate from the fork because there are no particles that can carry away the energy of the vibration. This also means that a tuning fork can oscillate for a very long time in a complete vacuum.

The frequency of the vibration will stay the same as it is dependent on the size of the fork not the medium around it.

Since there is no medium, the vibration of the tuning fork itself occurs, but it does not create sound, as sound is due to vibration of the medium, which in this case is absent.

The resonant frequency of the tuning fork remains unchanged. This is because the resonant frequency of the tuning fork depends on factors such as the dimensions and composition of the tuning fork, not on the surrounding medium.

Also, since the tuning fork does not experience the viscous retardation to vibration that it experiences due to air, it can execute undamped or free oscillations, until it depletes its energy as heat, which can radiate through a vacuum. This means that a tuning fork can vibrate for a very long time in vacuum, if no one is holding it (this damps the vibrations).

• The frequency of a tuning fork changes enough due to air pressure to act as a crude barometer. Going from air to vacuum could probably be heard of there was a electromagnetic or optical pickup on the fork. The damping does affect not only ring-down but also the frequency. Nov 4, 2022 at 16:58

The fork won't make sound wave in (missing) air and thus not dissipate there... But the fork is probably in contact with some support. Mecanical "sound" waves will travel through everything in contact (more or less efficiently depending of the quality of the contact and materials). In the vacuum if you let the fork touching your skull (through your skin), or your helmet, you would ear it. Air is not the only support for sound !