A sound box or sounding box (sometimes written soundbox) is an open chamber in the body of a

musical instrument A musical instrument is a device created or adapted to make Music, musical sounds. In principle, any object that produces sound can be considered a musical instrument—it is through purpose that the object becomes a musical instrument. A person ...

which modifies the sound of the instrument, and helps transfer that sound to the surrounding air. Objects respond more strongly to vibrations at certain frequencies, known as

resonance Resonance is a phenomenon that occurs when an object or system is subjected to an external force or vibration whose frequency matches a resonant frequency (or resonance frequency) of the system, defined as a frequency that generates a maximu ...

s. The frequency and strength of the resonances of the body of a musical instrument have a significant impact on the

tone quality In music, timbre (), also known as tone color or tone quality (from psychoacoustics), is the perceived sound of a musical note, sound or tone. Timbre distinguishes sounds according to their source, such as choir voices and musical instruments ...

it produces. The air inside the chamber has its own resonances, and these interact with the resonances of the body, altering the resonances of the instrument as a whole. The sound box typically adds

s at lower frequencies, enhancing the lower-

frequency response In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and Phase (waves), phase of the output as a function of input frequency. The frequency response is widely used in the design and ...

of the instrument. The distinctive sound of an instrument with a sound box owes a lot to the alteration made to the

tone Tone may refer to: Visual arts and color-related * Tone (color theory), a mix of tint and shade, in painting and color theory * Tone (color), the lightness or brightness (as well as darkness) of a color * Toning (coin), color change in coins * ...

. A sound box is found in most

string instrument In musical instrument classification, string instruments, or chordophones, are musical instruments that produce sound from vibrating strings when a performer strums, plucks, strikes or sounds the strings in varying manners. Musicians play some ...

s.Medieval and Tudor string instruments
/ref> The most notable exceptions are some electrically amplified instruments like the solid body

electric guitar An electric guitar is a guitar that requires external electric Guitar amplifier, sound amplification in order to be heard at typical performance volumes, unlike a standard acoustic guitar. It uses one or more pickup (music technology), pickups ...

or the

electric violin An electric violin is a violin equipped with an electronic output of its sound. The term most properly refers to an instrument intentionally made to be electrified with built-in pickups, usually with a solid body. It can also refer to a violin fi ...

, and the

piano A piano is a keyboard instrument that produces sound when its keys are depressed, activating an Action (music), action mechanism where hammers strike String (music), strings. Modern pianos have a row of 88 black and white keys, tuned to a c ...

which uses only a sound board instead. Drumhead lutes such as the

banjo The banjo is a stringed instrument with a thin membrane stretched over a frame or cavity to form a resonator. The membrane is typically circular, and in modern forms is usually made of plastic, where early membranes were made of animal skin. ...

or ''

erhu The (; ) is a Chinese two-stringed bowed musical instrument, more specifically a spike fiddle, that is sometimes known in the Western world as the ''Chinese violin'' or a ''Chinese two-stringed fiddle''. It is used as a solo instrument as ...

'' have at least one open end of the sound box covered with animal skin (or a skin-like acrylic material). Open back banjos are normally used for clawhammer and frailing, while those used for bluegrass have the back covered with a resonator. In some arrangements,

loudspeaker A loudspeaker (commonly referred to as a speaker or, more fully, a speaker system) is a combination of one or more speaker drivers, an enclosure, and electrical connections (possibly including a crossover network). The speaker driver is an ...

s are also mounted on a sound box to enhance their output, particularly bass speakers. One notable example of this arrangement is called the

bass reflex A bass reflex system (also known as a ported, vented box or reflex port) is a type of loudspeaker enclosure that uses a port (hole) or vent cut into the cabinet and a section of tubing or pipe affixed to the port. This port enables the sound fro ...

enclosure. However, in these cases the box resonance is carefully tuned so as to make the sound more equal across frequencies, rather than to impart a particular character to the reinforced sound. *

Acoustic guitar An acoustic guitar is a musical instrument in the string family. When a string is plucked, its vibration is transmitted from the bridge, resonating throughout the top of the guitar. It is also transmitted to the side and back of the instrument, ...

* Basic physics of the violin *

Filter (signal processing) In signal processing, a filter is a device or process that removes some unwanted components or features from a Signal (electronics), signal. Filtering is a class of signal processing, the defining feature of filters being the complete or partial s ...

Frequency response In signal processing and electronics, the frequency response of a system is the quantitative measure of the magnitude and Phase (waves), phase of the output as a function of input frequency. The frequency response is widely used in the design and ...

* Resonance chamber

References

String instrument construction {{string-instrument-stub