Abstract: A loudspeaker diaphragm comprising a molded, sintered ceramic body is described. The body is made of ceramic crystalline particles whose maximum size is below 1/5 time a thickness of the body which is in the form of a dome or cone. The dome- or cone-shaped diaphragm may have a flange along an opening side thereof in order to prevent deformation as may occur during firing.

Abstract: A variable-directivity microphone device comprises at least three microphones. First and second microphones spaced apart by specific distances and facing in the same direction and a third microphone facing in the opposite direction. A directivity varying control capable of undergoing displacement between at least three positions, a first mixer operating, while the control is between a first and a second position, to mix, in accordance with the position thereof, the third microphone signal with the first microphone signal and, while the control is between the second and third positions, to cause the third microphone output signal to be zero, and a second mixer operating, while the control is between the second and third positions, to mix the first and second microphone output signals with varied mixing quantity and, while the control is between the first and second positions, to cause the output signal of the second microphone to be zero.