sound box or sounding box (sometimes written soundbox) is an open chamber within the body of a instrument which modifies the sound of the instrument, and helps transfer that sound to the encompassing air. Objects respond more strongly to vibrations at certain frequencies, referred to as resonances. The frequency and strength of the resonances of the body of a instrument have a big impact on the tone quality 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 an entire . The sound box typically adds resonances at lower frequencies, enhancing the lower-frequency response of the instrument.