Abstract: A stereo audio processing system for a stereo audio signal processing reproduction that provides improved source imaging and simulation of desired listening environment acoustics while retaining relative independence of listener movement. The system first utilizes a synthetic or artificial head microphone pickup and utilizes the results as inputs to a cross-talk cancellation and naturalization compensation circuit utilizing minimum phase filter circuits to adapt the head diffraction compensated signals for use as loudspeaker signals. The system provides for head diffraction compensation including cross-coupling while permitting listener movement by limiting the cross-talk cancellation and diffraction compensation to frequencies substantially below approximately ten kilohertz.

Abstract: A loudness control circuit emphasizes low frequency components in audio signals. A secondary low-pass filter select low frequency components of the audio signals, inverting a phase of the audio signals. The phase-inverted signals and audio signals are respectively inputted to an inverting input terminal and non-inverting input terminal of an operational amplifier to obtain audio signals whose low frequency components are emphasized. These signals have the same phase as the phase of the inputted audio signals. The output of the low-pass filter is amplified to obtain a signal having low frequency components whose phase is inverted. Both the audio signal whose low frequency components have been amplified and the low frequency components whose phase has been inverted are applied to a speaker to reproduce sounds with their low frequency components dynamically emphasized.

Abstract: The present invention is a multi-chamber two-way center channel speaker for an audio system which has four stereo surround sound channels including a right front channel, a left front channel, a rear surround channel and a center channel. The preferred embodiment of the present invention center channel speaker comprises a VCR shaped cabinet having three parallel interior chambers including a front chamber, a middle and a rear chamber, all interconnected by offset openings. A tweeter and two midranges are installed in the front chamber. The rear chamber is vented through a rear opening. The volumes of the three chambers are expanded. This design and construction makes the three interconnected chambers a bass-reflex enclosure having gradually expanded volume for amplifying the backload of the two midranges.

Abstract: A surround processor includes a time constant processing circuit for smoothing directional information signals from a detector with continuously variable time constants in order to generate one or more control voltage signals. The time constants produced by the circuit are continuously variable and responsive to both the rate of change and the amplitude of the directional information signals, such that as the difference between the controlled voltage signals and the directional information signals increases, the value of the time constants decreases to permit the control voltage signals to closely follow the directional information signals, and as the difference between the control voltage signals and the directional information signals decreases, the value of the time constants increases so that variations in the control voltage signals are smooth. Split-band processing of input audio signals to the processor is also accomplished without the necessity of placing filters directly in the audio path.

Abstract: When a stereophonic broadcasting signal is interrupted because an electric field has weakened, a pilot signal 1 which designates that the electric field is not strong enough to separate an R-channel signal and an L-channel signal from a signal received by the tuner, is also interrupted. This interruption of the pilot signal changes gains and/or phases which act on an R-channel signal and/or an L-channel signal which are applied to a sound field calibrating system.

Abstract: A multi-channel sound simulation system for processing a stereophonic signal having a high frequency component for use with at least a pair of primary loudspeakers and a pair of secondary loudspeakers includes a receiving member for receiving the stereophonic signal and for producing a first primary channel signal and a second primary channel signal. The first and second primary channel signals are adapted to be respectively applied to a first primary loudspeaker and a second primary loudspeaker. The receiving member is further adapted to divide the input signal into a first secondary channel signal and a second secondary channel signal. The first and second secondary channel signals are fed through a roll-off member which inhibits the high frequency component of the signal, thereby producing inhibited first and second secondary channel signals.

Abstract: A method and apparatus for generating control voltage signals in a surround sound processor is disclosed which utilizes a one-shot monostable multivibrator for minimizing intermodulation distortion while following rapid directional changes, yet minimizing intermodulation distortion. The apparatus includes a circuit for smoothing the directional information signals derived from audio input signals each with a continuously variable time constant to generate a corresponding control voltage signal, such that each time constant depends inversely upon the magnitude of the difference between the directional information signal applied thereto and the corresponding control voltage signal generated thereby.

Abstract: A audio surround system particularly arranged for use in a theater provides the enhanced ambience and wide sound image advantages of a stereo enhancement system (SRS system) having directivity servos. A stereo enhancement system known as the "SRS" enhancement system enables a pair of relatively closely spaced speakers to provide a wide sound image lacking in any apparent point source and having enhanced directivity. A first SRS system (10) is modified for use with a set of front speakers (16,22,26) by increasing speed of its directivity servos (80), minimizing "pumping" caused by the increased directivity servo speed, increasing its threshold, and providing a bleed for minimizing reverberation effect. A similar SRS system (34) drives a set of rear speakers (40,46,50) and is differently modified to eliminate certain high pass filters (86,110), increase speed of its directivity servos (80), and to feed only ambience signals to left and right rear speakers (40,46).

Abstract: A directional microphone system gain adjusts the sum of signals that are received from two microphones mounted less than an inch apart. The gain adjustment is generally proportional to the product of the two microphone signals. Analog multipliers are used both for multiplying the signals together and also to form a gate that gain adjusts the sum of the signals.

Abstract: A stereo audio system includes a plurality of drivers and a signal processor circuit. The signal processing circuit has at least a left channel input and a right channel input, and provides at least one processed signal on at least one output. The processed signal is characterized by a coefficient of proportionality representative of complex components of the signals on the left channel input and the right channel input. The coefficient of proportionality is at a maximum and minimum for the complex components on the left channel input and the right channel input being in phase opposition and phase coherence, respectively. Each of the signals on the left channel input, the right channel input, and the at least one output are received by at least one of the drivers, and each of the drivers receives at least one of the left channel input signal, the right channel input signal, and the processed signal.

Abstract: An audio circuit for a television receiver wherein a left-hand speaker is disposed on a left side of a screen of a television receiver, a right-hand speaker is disposed on a right side of the screen, and a central speaker is disposed above and below the screen, or wherein an audio signal accompanies a picture to be displayed on the screen. The audio circuit supplies the audio signal to the left-hand, right-hand and central speakers to produce sound including a frequency component extraction circuit for extracting predetermined frequency components of human voice from the audio signal and for supplying an extracted signal of the human voice frequency components to the central speaker so that the central speaker produces only human voice sound.

Abstract: A multiple-channel audio reproduction apparatus has an audio demodulator for demodulating an input signal to produce audio signals for multiple channels. One or more signal-processing circuits process audio signals of one or more of these channels in a way suitable for reproduction by loudspeakers connected to other channels. Switches feed the processed audio signals to output terminals for those other channels. A switch controller turns these switches on if a loudspeaker is not connected to the channel corresponding to the original, unprocessed signal, and otherwise turns these switches off.

Abstract: In order to permit three-component (left, right and back) audio signals (LS, RS, BS) to be conveyed by a three-channel (left, right and mono) transmission system and still permit stereo and mono compatibility, the signals are encoded so that the three channels carry LS-1/2BS, RS-1/2BS and LS+RS+BS, respectively. Upon receipt, the signals can be decoded back to LS, RS and BS respectively. In a mono receiver without such a decoder, the signal LS+RS+BS on the mono channel is employed, and in a stereo receiver the signals LS-1/2BS and RS-1/2BS on the stereo channels are employed.

Abstract: An audio system having an improved sound field by generating a center audio channel from left and right stereo channels. The center channel is preferably generated by summing the left and right channels, and then filtering the resulting output. The center channel signal is also combined with the left and right channel signals to remove a portion of the monophonic information from the left and right channels thereby maintaining a constant level of monophonic information in the sound field.

Abstract: A sound projection apparatus for a video display device having left and right speakers, first and second ambience speakers, and an amplifier having a right channel and left channel. In this system, connection of the left channel to a speaker produces a left signal; the right channel to a speaker produces a right signal; the left and right channels to ambience circuitry produces an ambience channel; the ambience channel to the positive input of the first ambience speaker produces a first ambience signal and the ambience channel to the negative input of the second ambience speaker produces a second ambience signal. The left and right speakers are forward facing, projecting sound directly from the television to a viewer. The first and second ambience speakers are side or rearward facing, projecting sound indirectly to the viewer. The projection apparatus may be formed as a single cohesive unit, within or near the television.

Abstract: A center mode control circuit includes an amplifying portion (31) for amplifying a center input signal, a switch (34) connected to an input terminal of the amplifying portion, and capacitors (35, 36) selected by the switch and having different characteristic from each other. The modes that are switched are (a) a normal mode for adding a low frequency component of the center input signal to left and right input signals, (b) a phantom mode for adding a full range of the center input signal to the left and the right stereo input signals, and (c) a wide mode for not adding the center input signal to the left and the right stereo input signals.

Abstract: The invention provides surround mode stereophonic reproducing equipment for using the Dolby surround mode and another surround mode other than the Dolby mode by means of selectively switching between them. The equipment is provided with two front power amplifiers for driving front speakers on the right and left, and two rear power amplifiers for driving the rear speakers. The rear speakers are driven jointly by one of the rear power amplifiers while the center speaker is driven by the other power amplifier when using the Dolby surround mode, and the rear speakers are respectively driven by the two rear power amplifiers when using a surround mode other than the Dolby surround mode.

Abstract: Electronic crossover modules and systems in accordance with the invention employ a set of crossover channels in each module together with internal input interconnections which enable input signals to be serially intercoupled but cutoff points to be separately adjustable. Each module comprises two independently settable, variably interconnectable high pass channels and a third low pass channel which also is independently settable, and which can receive signals from the first two channels and/or a different module and also transmit signals to a different module. Using the available input interconnections and a frequency multiplier control in the first channel, great versatility in bi-amp and tri-amp with two channel and/or four channel operation is achieved.

Abstract: A stereophonic signal processing circuit is designed to be provided with a pair of level compression circuits compressing peak levels of a pair of stereophonic input signals into 1/2 power each, an arithmetic mean circuit determining an arithmetic mean between a pair of output signals issued from the level compression circuits, and a level expansion circuit expanding a peak level of an output signal from the arithmetic mean circuit into the 2nd power of the level so that an output signal from the level expansion circuit is reproduced midway between individual reproducing positions of the pair of stereophonic input signals. A delay circuit may be connected between the arithmetic mean circuit and the level expansion circuit. The stereophonic signal processing circuit makes it possible to cause more fully the lateralization of a reproduced sound and can be fabricated at a low cost.

Abstract: Audio-band electromechanical vibration converter characterized in that a yoke having a permanent magnet and a magnetic gap formed therein is displaceably housed by a damper in a casing to which a vibration plate is attached; a coil attached to the casing is placed in said magnetic gap; and the casing gives an output of a mechanical vibration synchronized with a low-band audio-signal.

Abstract: In a stereophonic reproduction system, a true center-channel signal is derived by combining the left and right signals into a monophonic signal, and canceling and overriding this monophonic signal with a second modified monophonic signal, the latter derived by combining properly bandpassed left and right signals that have been compressed, combined, and expanded. True left-and true right-channel signals are subsequently derived by subtracting the true center-channel signal voltage from the left and right signal voltages.

Abstract: In a conventional stereo system, provided the listener remains equidistant from the left and right speakers, the common portions of the left and right signals produce in the mind of the listener the virtual source of sound thought to be located between the left and right speakers. In the present invention, the common components are used to power a third speaker located between the left and right speakers thereby providing a real source of sound, whereby the listener is not required to remain equidistant from the left and right speakers, but instead has considerably more latitude with respect to his position. The present invention takes the left and right signals produced by a stereo decoder, equalizes them, and develops a commonality index on which the allocation of the signals to the three speakers is based. Linear combinations of the equalized left and right signals are applied to the speakers with the coefficients each being a function only of the commonality index.

Abstract: A stereophonic sound system has the conventional components of a stereo pre-amplifier, to receive and amplify left and right audio signals, originating from left and right channel microphones, and feed left and right power amplifiers for left and right loudspeakers and additionally has left and right attack separator circuits (6+18, 8+20) connected to receive input audio signals from the pre-amplifier (70) and acting to separate the attack components from the steady-state components of the input audio signals, the steady-state components being fed to the left and right power amplifiers (42, 44) and the attack components being fed to an attack correlator (30) which compares the arrival times of the attack components from the left and right audio signals and calculates an azimuth angle corresponding to the point of origin (8) of the original sound, an attack distributor (40) is connected to the outputs of the correlator and distributes transient attack signals to one of a series of small power amplifiers (46, 4

Abstract: In a conventional stereo system, provided the listener remains equidistant from the left and right speakers, the common portions of the left and right signals produce in the mind of the listener the virtual source of sound thought to be located between the left and right speakers. In the present invention, the common components are used to power a third speaker located between the left and right speakers thereby providing a real source of sound, whereby the listener is not required to remain equidistant from the left and right speakers, but instead has considerably more latitude with respect to his position. The present invention takes the left and right signals produced by a stereo decoder, equalizes them, and develops a commonality index on which the allocation of the signals to the three speakers is based. Linear combinations of the equalized left and right signals are applied to the speakers with the coefficients each being a function only of the commonality index.

Abstract: This invention relates to an apparatus and to a method for enhancing the perceived sound image of a stereophonic, audio reproduction system whose inputs are a right and a left signal channel by decoding the right and left signal channels into a modified right, a modified left and a center signal channels. Signal information common to the original right and left signal channels is removed within a specified bandwith to produce the modified right and modified left signal channels. The original right and left signal channels are combined and frequencies below a predetermined cutoff frequency are attenuated to produce the center signal channel.

Abstract: A stereo speaker system is shown having at least three individual speakers arranged along a path, with one of the speakers positioned between the other two speakers and connected to receive signals from a selected one of a pair of left and right signal outputs from a stereo signal source such as a stereo radio. Both of the other two speakers are connected to receive signals from the remaining one of said pair of outputs. Balanced stereo images are thus obtained simultaneously at two different locations. The system has particular application in an automobile. Another embodiment is shown which uses more than three speakers.

Abstract: A triphonic sound system in which three independent stereophonically related audio frequency source signals L, R and C are combined to derive three other audio frequency signals M, S, and T which respectively comprise (L+1.4C+R, (L-R) and (-1.4C). In a preferred transmitter embodiment, useful in television broadcasting, the audio signals S and T modulate two quadrature-related sub-carriers of the same frequency to develop two double-sideband, suppressed-carrier signals, the frequency of the subcarriers being sufficiently high as to assure a frequency gap between the lower sidebands of the modulated subcarrier signals and the audio frequency signal (L+1.4C+R). The aforementioned signals, and a pilot signal having a frequency which lies within the frequency gap, are combined and frequency-modulated onto a high frequency carrier for the purpose of transmitting the same to one or more remote receivers.

Abstract: A stereo sound system for reproducing signals from two independent channels through right and left speakers. The two speakers are centrally located and propagate a lesser part of their acoustic output directly into free space. Two acoustic tunnels separately couple the major part of the outputs of the respective speakers and have their issuing ends far removed on either side of the speakers. The tunnels provide advantageous delay.

Abstract: A device for giving an audio signal to a coil associated with an audio-band electromechanical converter uses a mixer, a first-stage low-pass filter, a limited and a second-stage low pass filter to correct distortion of the wave form of a signal from the limiter.

Abstract: A microphone for receiving acoustic vents stereophonically in accordance with a center-side method comprises a plurality of transducers including at least one having a unilateral directional characteristic particularly cardioid or hypercardioid and at least two other electroacoustic transducers having a figure-eight characteristic which are associated with the unidirectional characteristic transducer and have principal axes at right angles to the main axes of the unidirectional transducer. A common line connects a terminal of each of the three transducers and a connecting line interconnects a respective terminal of each. In addition, the connecting line between the two electroacoustic transducers having a figure-eight characteristic include control means comprising either a switch or a controller.

Abstract: An improved method and apparatus for reproducing sound includes a third channel which is derived from the pair of signals representing traditional left and right stereophonic channels and which represents a linear algebraic difference between such a pair of signals. A third loudspeaker associated with the third channel povides acoustic radiation as a supplement to acoustic radiation from two laterally-spaced loudspeakers normally used to reproduce respective left and right signal channels. Acoustic radiation from the third loudspeaker is toward a preferred listening region and in a direction substantially opposite to that from the two laterally-spaced left and right loudspeakers which are positioned and oriented to provide essentially codirectional acoustic radiation toward the preferred listening region.

Abstract: An acoustic apparatus comprised of a means for extracting middle and high frequency components from left- and right-channel signals through respective high-pass filters to reproduce the components, and a means for mixing left- and right-channel signals and extracting a low frequency component through a low-pass filter to reproduce the component, wherein the reproduction power of the middle and high frequency component is set below the reproduction power of the low frequency component.