Abstract: A sound-wave receiving applicance comprises a resonance panel and a crystal type piezoelectric microphone responsive to oscillations generated by the soundwaves, said microphone being adapted for connection to an amplifier. The crystal of the microphone is subjected, between two pole members, to a mechanical initial pressure to increase the pressure sensitivity of the microphone relative to the resonance panel. The receiving applicance preferably has means for manual adjustment of the initial pressure which is absorbed by the resonance panel via one pole member. The resonance panel of the receiving appliance preferably is made of a material, such as a cellular plastic, having a higher porosity and a lower specific gravity than ordinary wood.

Abstract: The invention relates to a method to improve the acoustics of a room, preferably a hall, having a relatively minor space (10) from which sound waves, chiefly emanating from a musical instrument, and a relatively larger audience space (12), the outgoing sound waves being re-emitted via an amplifier device comprising a sounding board (20, 22) united with an electromagnet (26), an amplifier (21) and a microphone connected therewith, which device receives impulses from the sound source (14). The sound board (20, 22) and the electromagnet (26) form part of each of a plurality of wall elements (16) of such area and location in the audience space (12) that the sounding boards transmit to the listener a mixture of sound waves directly reflected from the sound source (14) and sound waves indirectly emanating from the amplifier device.

Abstract: A sound resonator apparatus including side walls and a sounding board the grain fiber of which is arranged from end to end of the resonator. A plurality of wooden strips are mounted on the exterior surface of the sounding board and substantially in parallel relationship with the grain thereof.