Abstract: A substantially flat and disc-like shaped sound transducer for sensing sound waves in a fluid transmission medium and having directional and omnidirectional response characteristics to the sound waves. The sound transducer having a circular vibratile plate divided into quadrantal portions and having a surface adapted to be coupled to the transmission medium for providing sound wave motion in the portions dependent upon, and in response to, sound wave travel in the transmission medium and having a plurality of electroacoustic transducer elements coupled to the quadrantal portions of the vibratile plate for providing electrical output signals in response to the wave motions in diametrically opposed quadrantal portions. The sound transducer responding to incident sound waves having wavefront travel directions, in the transmission medium, substantially parallel to the coupled surface.

Abstract: A digital flutter reduction system which corrects for a varying time base ror in FM recordings on magnetic tape. Pulse transitions from the outputs of a reference oscillator and a reference tone on a first tape track are compared by a flip-flop whose output is a pulse having a width corresponding to the time base error. The output pulse enables a first counter to provide a digital output which is loaded into a second counter. Pulse transitions from a second tape track containing recorded data advance the second counter over a number of counts indicative of a correction factor. The pulse transitions of the recorded data are delayed in accordance with the correction factor thereby reducing the time base error.