Helmholtz resonance
![A brass, spherical Helmholtz resonator based on his original design, circa 1890-1900.](/Images/godic/202501/17/Helmholtz_resonator2653.jpg")
Helmholtz resonance is the phenomenon of air resonance in a cavity, such as when one blows across the top of an empty bottle. The name comes from a device created in the 1850s by Hermann von Helmholtz, the Helmholtz resonator, which he used to identify the various frequencies or musical pitches present in music and other complex sounds.