Sound-board.
1. (Music.) The upper surface board of a wind-chest in an organ. It is pierced with channels, which communicate with the ducts below the respective pipes of the organ. These channels are guarded by spring valves, which are depressed by their appropriate keys on the manual, allowing air to escape from the wind-chest to the particular pipe or pipes as the keys are moved. The valves play between thin bars of wood, which divide the under surface of the sound-board into a series of parallel partitioned spaces. On the upper side of the sound-board are grooves pierced with holes, which are commanded by the register slides of the respective stops. As the slide is pulled to open the holes, the communication is permitted to the pipes of a given stop, when the valve is depressed by the key of the manual. When more than one slide is opened, the opening of a given valve by the key admits air to so many pipes, which sound the corresponding notes according to their pitch and quality. See sounding-board. 2. A canopy over a pulpit, to direct the sound toward the audience.
3. (Carpentry.) Deadening. A partition or an additional division between two apartments, to prevent the propagation of sound from one to the other.
