A sound box or sounding box (sometimes written soundbox) is an open chamber in the body of a musical instrument 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 resonances. The frequency and strength of the resonances of the body of a musical instrument have a significant 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 a whole. The sound box typically adds resonances at lower frequencies, enhancing the lower-frequency response of the instrument.