Abstract: This invention relates to a system and method for reducing non-linear electrical distortion in an electroacoustic device. Specifically, the present invention relates to a system and method for reducing spatially dependent electrical distortion, for example, distortion caused by differences in electrical displacement between a conductive membrane and a counter electrode at different parts of the conductive membrane. The system and method for reducing non-linear electrical distortion has particular application in condenser microphones comprising, for example, a conductive diaphragm receptive to sound, and a backplate electrically coupled thereto to generate an electrical output. In one exemplary embodiment, the present invention provides an electroacoustic system comprising a conductive membrane and a counter electrode electrically coupled to the conductive membrane. A face of the counter electrode facing the conductive membrane is curved.

Abstract: A microphone housing system is disclosed having a tapered structure enclosed within the housing structure coupled to a rear portion of a microphone element. In the preferred embodiment, the tapered portion has a generally conic shape expanding away from the rear portion of the microphone element. The housing structure surrounding the tapered structure has a plurality of radially disposed opening or slots and fully or partially covered with a sound-resistive material. The housing system provides increased front-to-back signal ratio and increased overall gain and frequency response due to superior rear signal cancellation.

Abstract: An improved system is disclosed for generating a signal encoded with stereophonic information and adapted to be used with a monophonic signal to synthesize stereophonic reproduction. The system includes means for generating the encoded signal as a function of at least a portion of the program information of a monophonic input signal so as to control the amount of stereophonic spread provided during stereophonic reproduction provided by the encoded signal and a monophonic signal derived from the monophonic input signal. The system is particularly adapted for use in the transmission and/or reception of stereophonic television signals.

Abstract: A signal encoding system for generating at least two encoded signals in response to a plurality of information signals containing audio data representative of virtual images of sources of the data so that the encoded signals can be subsequently decoded by a decoding system including a decoding matrix means for decoding the encoded signals so as to regenerate the information signals. The signal encoding system comprises signal encoding means for generating the encoded signals in response to the information signals; and a duplicate of the decoding matrix means coupled to the encoding means for generating a feedback signal corresponding to each of the information signals; wherein the encoding signals are modified in response to the feedback signals so as to reduce the noise artifacts generated by the decoding matrix when the encoded signals are decoded by the decoding system.

Abstract: A signal decoding system for use in a quadraphonic type sound reproducing system is disclosed. In accordance with one aspect of the invention, a multiband expander is used to control the steering of the four information signals decoded from the two input signals. In accordance with another aspect of the invention, the difference between the rear and front signals is used to enhance virtual sound images to one side of a listener.

Abstract: An improved bias generator provides a bias voltage output which is a function of an input current Iprog and provides a bias current to a preselected load which tracks the input signal independently of temperature. The amount the bias voltage output changes with temperature is determined by (1) V(T, Iprog), a voltage-current temperature dependent function of the base-emitter voltage drop of at least one transistor and (2) X, a scalar which is easily provided by setting the ratio of two resistors. The generator can therefore be easily constructed for particular circuit loads which include at least one semiconductive junction such that the biasing current through the load will be substantially independent of temperature.

Abstract: An improved amplifier of the type comprising bipolar transistor means coupled between the input terminal of the amplifier and a differential pair of transistors. Compensation means is provided for generating a compensating signal through the bipolar transistor means such that the bipolar transistor means and compensation means reduce the amount of bias current drawn from the input signal to the amplifier. Other aspects of the present invention include the provision of reducing DC offset voltages between each side of the differential amplifier due to the operation of the device with its input terminals at different voltage levels, and the provision of a zero in the transfer characteristics of the amplifier to mitigate the effects of poles provided in the transfer characteristics.

Abstract: An improved audio signal processing system for use in an audio reproduction apparatus is described. The apparatus is of the type for generating ambient effects and includes at least two channels for respectively transmitting an audio signal to at least two speakers so that one of the speakers reproduces sound in response to the audio signal at a predetermined delay with respect to the other. The improved system comprises gain control means, electrically connected to receive the audio signal being transmitted to the one speaker, for controlling the signal gain of the system in accordance with the signal level derivative of the audio signal.

Abstract: An improved gain control circuit of the "eight transistor gain cell" type is disclosed. The improvements comprise (1) means for operating the circuit as a Class AB amplifier and (2) means for reducing the distortion component in the output signal due to the inherent parasitic base and emitter resistances of the transistors of the gain cell of the gain control circuit.

Abstract: A signal conditioning system comprises an improved gain control module 10 and an improved detector 12 which are adapted to be manufactured in integrated circuit form.

Abstract: An improved signal expansion system and technique is disclosed. The system comprises a detector for sensing an input signal and for producing responsively thereto a D.C. control signal having an amplitude as a function of the input signal, and a gain control amplifier for amplifying the input signal, the amplifier including means for controlling the gain of the amplifier as a function of the amplitude of the control signal. The improvement comprises means for varying the amplitude of the D.C. signal at least in part as a function of the time derivative of that amplitude.

Abstract: An improved audio signal processing system synthesizes from an audio signal, an enhanced audio signal by sensing signal energy of the audio signal within a preselected frequency portion of the audio signal, dividing the sensed signal energy into a plurality of discrete bands according to the frequency thereof and generating, responsively to the signal energy in each of the bands, a like plurality of second signals each of which includes frequency components which are subharmonics of the frequencies of the corresponding frequency band. The second signals are combined so as to provide a combined signal and the latter is added to the audio signal to provide the enhanced audio signal.

Abstract: An adaptive signal weighting system for use in electrical signal transmission along a signal path comprises a variable filter disposed in the signal path having electrical transmission characteristics capable of varying in response to a first control signal the relationship between the spectral region of dominant energy in a transmitted signal relative to the other spectral regions of the transmitted signal. Frequency discrimination means senses the spectral region of dominant signal energy in the transmitted signal and provides the first control signal as a function of frequency of the dominant signal energy. Gain control means disposed in the signal path and coupled in series with the filter means provides a gain variable on the transmitted signal responsively to a second control signal. This second control signal is logarithmically related to the amplitude of the transmitted signal over at least a portion of the frequency range of the signal.

Abstract: A system for detecting and reproducing variable-area-type optically recorded audio signals by cyclically detecting substantially only the position of a boundary of the sound track. In one embodiment, the boundary is detected by imaging the boundary onto an array of photosensors and scanning the array to provide an output signal containing a transition corresponding in the time domain to the position of the boundary. The transition signal is filtered and sliced to provide electrical interpolation to improve the resolution substantially over the special resolution of the photosensitive elements of the array. The system may also include a multitrack capability with means for minimizing the effect of film weave.

Abstract: An improved signal conditioning compander system includes one or more weighting networks designed so that the system provides a substantially flat single-frequency sine wave sweep response through or on the transmission medium throughout the frequency bandwidth of interest.The system provides greater high-frequency weighting than heretofore practical and at the same time permits full level transmission over the entire frequency spectrum transmitted or recorded.

Abstract: An adaptive signal weighting filter for use in a compander performs a frequency response weighting function so that during the encoding process the spectral region of dominant signal energy of the program signal is preemphasized with respect to other spectral regions and during the decoding process the corresponding spectral regions of the encoded signal are deemphasized with respect to one another in a complementary manner.

Abstract: A current mode operational rectifier has an output terminal connectable as a DC current source of a predetermined polarity, and comprises a high gain amplifier having an inverting input terminal for receiving an input signal current from an AC current source and two alternative transmission paths for providing full wave rectification. The first transmission path includes a first transistor having its base connected to the output terminal of the amplifier and its emitter and collector connected between the output terminal of the rectifier and the input terminal of the amplifier. The first transmission path conducts DC current to the output from the input terminal of the amplifier at an instantaneous level substantially equal to the instantaneous level of the input signal when the input signal is of a first polarity. The second transmission path includes matched second and third transistors.