Resonant electroacoustic transducer with increased band width response

Claim 1

In combination in an electroacoustic transducer including a peripherally-clamped vibratile diaphragm and electromechanical transducer means associated with said diaphragm for converting alternating electrical signals into mechanical vibrations, said peripherally-clamped diaphragm characterized in that its fundamental resonant frequency is greater than 1 kHz, and further characterized in that the clamped diameter of said diaphragm is less than one-half wavelength of the sound generated at said resonant frequency, said electroacoustic transducer characterized in that the band width of the frequency response characteristic in the vicinity of resonance is relatively narrow and is equivalent to a Q factor greater than 20, means for substantially increasing the band width of the response characteristic of said transducer such that the Q factor is reduced to a value less than 8, said means for increasing the band width includes means for damping the acoustic reactance of the peripherally-clamped vibratile diaphragm over a frequency range extending at least ±10% beyond the resonant frequency of said transducer, said damping means characterized in that the damping is not in the form of a mechanical resistance which adds viscosity loss to the vibrating diaphragm, but that said damping is in the form of increased acoustic radiation resistance added to the vibrating diaphragm by means of an acoustic coupler interposed between the radiating surface of said vibratile diaphragm and the medium into which the acoustic energy is radiated.