Abstract:
An acousto-fluidic sound augmentation system has been developed which provides adequate sound coverage in worship spaces accommodating as many as 1600 persons. Because of the unique religious restrictions of Orthodox Judaism, use of electricity and sound reproduction per se are prohibited while sound augmentation is permissible as long as the original sound is preserved and no apparent sound amplification occurs. A kosher sound system has been built and tested with essentially 0-dB sound-level gain but about 50 dB of power gain when operating with a 10-psi air source. The system frequency response is flat from 700--3500 Hz, and cuts off at 200 and 6000 Hz, respectively. A single-channel output comprises two 180(degrees) out-of-phase ElectroVoice HB640 horns. The monaural sound quality is good enough for recognition of the speaker's voice with good reproduction of sufficient overtones to render singing pleasant. Sounds can be transmitted up to 25 m through 5-cm-diam PVC pipes thereby allowing speakers to be placed far enough away from the inputs to ensure good aural reception at the furthest reaches of worship spaces. The inherent acoustic delay obviates the need for the introduction of artificial delays and consequently results in very natural sound propagation and rendition.