ASTM E 1179

This specification states the requirements for sound sources used for measuring the speech privacy between open offices or for measuring the laboratory performance of acoustical components. The sound source shall be a loudspeaker enclosed in a box that has a maximum dimension of 0.30 m (1 ft) on a side, to reduce spurious sound reflections. The measurements shall be carried out in a free sound field. The measurement microphone, amplifier, and level meter used to measure sound pressure levels shall satisfy the requirements prescribed. When the sound source is driven with the qualification signal, the sound output shall be adequate to maintain one-third octave-band sound pressure levels at least 10 dB above the corresponding background noise in each band at each measurement location. The directivity of the sound source shall be verified by driving the source with the qualification signal and measuring the sound pressure levels at measurement points.