A piece of wood used in stringed instruments, including keyboard instruments, which acts as a coupling device between the string and the air in order to AMPLIFY the sound. Since the amount of radiation varies with the size of the board, large ones are usually used to increase the sound output. The board will have many RESONANCE frequencies which are activated by the vibrating string; however, soundboards are designed so that each FREQUENCY produced by the string will sound equally loud.
See: FREQUENCY RESPONSE. Compare: AMPLIFIER, HELMHOLTZ RESONATOR, RESONATOR.
A similar device, called a sounding board, was used in many older churches above the pulpit to REFLECT and therefore amplify the speaker's voice.