Abstract: An acoustical transducer enclosure has an acoustic lever acoustically coupled to an electro-acoustical transducer so as to force all radiated sound through the lever.

Abstract: An apparatus and method for determining a transducers principle operating parameters which utilizes two transfer functions; 1) the transfer function from the pressure response (50) to the voltage drop across the transducer (60); and 2) the transfer function from the pressure response (50) to the current flow through the transducer(70). The parameters of simple filter equations are fitted to these measured response curves. The transducers operating parameters are then calculated directly from the fitted parameters of the filter equations. Several methods for measuring the pressure and determining the appropriate filter equations are shown.

Abstract: An acoustic production system having multiple signal sources and a power amplifier driving an acoustic transducer such as a loudspeaker includes an arbitrator in a power limiter circuit to selectively limit the input level of one of the sources to the power amp in response to an overdrive signal from the amplifier. The input level to the power amplifier is automatically reduced in response to the overdrive signal until a predetermined level of limiting has been attained. Once the predetermined level of limiting is reached, the arbitrator outputs a second overdrive signal to prompt additional limiting of the power amplifier output. Preferably, the arbitrator is included in an interior active noise cancellation module combined with an audio entertainment system for a passenger compartment of a motor vehicle.

Abstract: For transducers such as loudspeakers and actuators which must operate at unusually low or high ambient temperatures, a robust resilient annular support member for mounting the vibratable diaphragm extends outwardly therefrom to the main frame. The support member is formed from silicone elastomer or a silicone rubber composite in a molding process which may be a constant temperature process, preferably transfer molding. A diaphragm and a surround member may be bonded together in the molding process by inserting the edge of the diaphragm into the cavity mold. The molding techniques of silicone rubber composites containing pulp and weave fiber grades of commercially available mix materials allow transfer, compression or injection molding of diaphragm suspension system members with good control of the mechanical properties and thickness.

Abstract: An active muffler for use in motor vehicles comprises a sensor, an electronic control responsive to the signal generated by the sensor for producing a drive signal delivered to a transducer which emits cancellation pulses phased 180.degree. from the sound pressure pulses passing through a conduit, where both front and rear sides of the transducer are acoustically coupled to the conduit to improve the efficiency of the transducer operation. Preferably, the acoustic coupling comprises an enclosed chamber including a port for communicating with the conduit which can be tuned to resonate at predetermined frequencies. When both sides of the transducer are so coupled to the conduit, the transducer has increased efficiency over a broad band of frequencies, and the frequency band can be broadened at the low end as required to accommodate the frequencies generated by a source of noise. A tandem transducer mounting arrangement according to the present invention reduces vibration of the housing.

Abstract: A signal processor for sound image enhancement of stereophonic signals provides fluctuating coherence between the left channel and right channel outputs by crossfeeding a high pass portion of the left channel to the right output and a like portion of the right channel to the left output. Preferably, the crossfeed path includes a high pass filter to eliminate crossfeeding of lower frequency range components which are often reproduced monaurally in prerecorded materials. The filtering is compensated for by a shelving filter introduced in the respective channel input to boost the power of the lower frequency components to be added with the crossfed signal to produce the channel output. In the preferred embodiment, an automatic gain control varies the gain of the crossfeed in accordance with the stereo content in the input channels. In addition, the gain control includes a control for user variation of the amount of coherence to be generated at the output.

Abstract: A transducer for use in an active noise cancellation system is particularly adapted for use as a motor vehicle exhaust muffler by physically designing the transducer to optimize magnetic flux with increases in temperature through the operating temperature range of the motor vehicle. The magnet material used to form the transducer is selected, and the load line which provides increased flux with increases in temperature is then equated to the ratio of the area of the gap to the length of the gap between the magnetic poles divided by the ratio of the area of the magnet to the length of the magnet; by equating the area of the gap to the length of the gap ratios at maximum B/H and the selected load range, the desired length of the magnet is derived since the area of the magnet is determined according to conventional criteria.

Abstract: An active muffler for use in motor vehicles comprises a sensor, an electronic control responsive to the signal generated by the sensor for producing a drive signal delivered to a transducer which emits cancellation pulses phased 180.degree. from the sound pressure pulses passing through a conduit, where both front and rear sides of the transducer are acoustically coupled to the conduit to improve the efficiency of the transducer operation. Preferably, the acoustic coupling comprises an enclosed chamber including a port for communicating with the conduit which can be tuned to resonate at predetermined frequencies. When both sides of the transducer are so coupled to the conduit, the transducer has increased efficiency over a broad band of frequencies, and the frequency band can be broadened at the low end as required to accommodate the frequencies generated by a source of noise.

Abstract: An active muffler for use in motor vehicles comprises a sensor, an electronic control responsive to the signal generated by the sensor for producing a drive signal delivered to a transducer which emits cancellation pulses phased 180.degree. from the sound pressure pulses passing through a conduit, where both front and rear sides of the transducer are acoustically coupled to the conduit to improve the efficiency of the transducer operation. Preferably, the acoustic coupling comprises an enclosed chamber including a port for communicating with the conduit which can be tuned to resonate at predetermined frequencies. When both sides of the transducer are so coupled to the conduit, the transducer has increased efficiency over a broad band of frequencies, and the frequency band can be broadened at the low end as required to accommodate the frequencies generated by a source of noise. A tandem transducer mounting arrangement according to the present invention reduces vibration of the housing.

Abstract: A machine analyzer is connected to an active vibration cancellation system in order to identify the operating status of the moving machinery while using a minimum of additional parts and taking advantage of signal processing already occurring in the active vibration cancellation system. A preferred embodiment employs a neural network pattern classifier in connection with detecting operating states such as cylinder misfires in an internal combustion engine.

Abstract: A transducer arrangement for active noise cancellation signals provides an acoustically permeable membrane between ports in direct communication with the noise propagating conduit and the transducers delivering sound pulses to the port. A housing defines at least one chamber exposed to at least one face of a transducer diaphragm, and each chamber is connected in fluid communication with the conduit through at least one port. The chamber is partitioned by the membrane to include chamber portions with a predetermined volumetric relationship. In a preferred embodiment where the transducer arrangement is coupled to a motor vehicle exhaust conduit, the membrane is preferably a silicone impregnated polyurethane film reinforced with aromatic polyamide fibers. Such a member provides a waterproof, acoustically permeable partition between the port and any adjacent speaker face that can withstand high temperatures.

Abstract: A transducer arrangement for active noise cancellation in conduits, for example, in motor vehicles where an electronic control produces a drive signal for a transducer that emits cancellation pulses phased 180.degree. from the sound pressure pulses passing through an exhaust conduit, where both front and rear sides of the transducer are acoustically coupled to improve the efficiency of the transducer operation. Preferably, the acoustic coupling comprises an enclosed chamber partitioned to expose a first transducer side to a chamber portion and a second transducer side to a second chamber portion. A first port couples one of the chambers to the other and a second port couples one of the chambers to the conduit. Each port for communicating with the conduit can be tuned to resonate at predetermined frequencies.

Abstract: A transducer for use in an active noise cancellation system is particularly adapted for use as a motor vehicle exhaust muffler by physically designing the transducer to optimize magnetic flux with increases in temperature through the operating temperature range of the motor vehicle. The magnet material used to form the transducer is selected, and the load line which provides increased flux with increases in temperature is then equated to the ratio of the area of the gap to the length of the gap between the magnetic poles divided by the ratio of the area of the magnet to the length of the magnet; by equating the area of the gap to the length of the gap ratios at maximum B/H and the selected load range, the desired length of the magnet is derived since the area of the magnet is determined according to conventional criteria.

Abstract: An active muffler for use in motor vehicles comprises a sensor, an electronic control responsive to the signal generated by the sensor for producing a drive signal delivered to a transducer which emits cancellation pulses phased 180.degree. from the sound pressure pulses passing through a conduit, where both front and rear sides of the transducer are acoustically coupled to the conduit to improve the efficiency of the transducer operation. Preferably, the acoustic coupling comprises an enclosed chamber including a port for communicating with the conduit which can be tuned to resonate at predetermined frequencies. When both sides of the transducer are so coupled to the conduit, the transducer has increased efficiency over a broad band of frequencies, and the frequency band can be broadened at the low end as required to accommodate the frequencies generated by a source of noise.

Abstract: An active muffler for motor vehicle exhaust conduits comprises a pulse tracking sensor generating a signal input to an electronic control for actuating an acoustic transducer imposing cancellation pulses upon the sound pressure pulse train travelling through the conduit. The system includes a preconditioning circuit for reducing the crest factor of the waveform pulse train travelling through the exhaust conduit by introducing negative pressure pulses into the exhaust conduit. Preferably, a digitally controlled one bit injector includes a fluid outlet in communication with the exhaust conduit and an inlet in communication with a vacuum source such as the intake manifold of the motor vehicle engine. Accordingly, the amplifier and the transducer of the acoustic actuator can be substantially downsized for employment in mass produced motor vehicles.

Abstract: A method and apparatus for muffling motor vehicle engine noise comprises conventional noise attenuation apparatus and techniques as well as a tuning circuit for delivering separate signal outputs to at least two transducers separated along the length of the exhaust conduit. A spacing between the transducers corresponds to the range of tuned exhaust lengths required at various engine speeds within the operating range of the motor vehicle engine. The tuning circuit varies the strength of the signal delivered to each of the transducers to vary the cancellation point within the conduit so as to vary the effective length of the conduit in a manner that maintains a minimum or negative pressure pulse at the valve exhaust port and aids in the exhaustion of combustion gases from the cylinder. As a result, engine performance is improved throughout the operating range of the motor vehicle engine.

Abstract: An electronically controlled intake manifold system for an internal combustion engine includes an intake manifold for conveying charge air to each of the cylinders of the engine, an electronically driven pressure pulse generator operatively connected with the manifold for the purpose of producing pressure pulses within the manifold at one or more frequencies related to an operating parameter of the engine, and a processor using at least one operating parameter of the engine to generate a signal for driving the pressure pulse generator.