Valve mechanism for an acoustic modulator

Abstract

A valve mechanism for an acoustic modulator which modulates air flowing tugh the acoustic modulator. The valve mechanism comprises a pair of cylindrical shaped members with each member having a plurality of elongated ports. The first cylindrical shaped member is held in a fixed position, while the second cylindrical shaped member is movable with respect to the first member. There is located at the lower end of the second cylindrical shaped member a drive coil which is positioned in a magnetic field such that when the coil is excited by an electrical sinusoidal input signal, movement of the second member occurs, partially aligning the ports of the second member with the ports of the first member which opens the valve mechanism. The sinusoidal input signal causes a frequency 'doubling' to occur, that is the valve mechanism of the present invention completes an open-close-open-close cycle during each cycle of the sinusoidal input signal. This frequency 'doubling' modulation of air flow through the acoustic modulator is accomplished by exposing the same open port area for both the positive going portion and the negative going portion of the sinusoidal input signal. The valve mechanism 'closes' when the sinusoidal input signal is at zero volts.