Acoustic resonance is the tendency of an acoustic system to absorb more energy when it is forced or driven at a frequency that is the same as one of its own natural frequencies of vibrations. Acoustic resonance is sometimes used to narrow mechanical resonance to the frequency range of human hearing. Since acoustics is defined in general terms concerning vibrational waves in matter, acoustic resonance can occur at frequencies outside the range of human hearing.
An acoustically resonant object usually has more than one resonance frequency. This is especially true at harmonics of the strongest resonance. The object will easily vibrate at these frequencies and vibrate less strongly at other frequencies. It can pick out its resonance frequency from a complex excitation such as an impulse or a wideband noise excitation; it is filtering out all frequencies other than its resonance.
Acoustical resonance is important for instrument builders. Most instruments used resonators, such as, the strings and body of a guitar, the length of tube in a flute, and the shape of a drum membrane. It is also important in hearing.