What happens to the resonant frequency when the size of the resonating cavity decreases?

When the size of a resonating cavity decreases, the resonant frequency tends to increase. This relationship is based on the physical properties of sound waves and how they interact with a given space.

Resonant frequency refers to the frequency at which an object can naturally oscillate. In the context of a resonating cavity, which typically refers to the air-filled spaces involved in speech production or musical instruments, the size of the cavity significantly influences the wavelengths of the sound waves generated within it.

A smaller cavity can better accommodate higher frequencies, as shorter wavelengths fit more easily into the limited space. Since resonant frequency and wavelength are inversely related—meaning that as one increases, the other decreases—reducing the cavity size results in an increase in resonant frequency. This is analogous to the tuning of a musical instrument, where a smaller instrument or shorter vibrating string produces higher-pitched sounds.

Thus, as the volume of the space decreases, the ability of that space to support lower-frequency sound waves diminishes, leading to an increase in the resonant frequency.