Abstract: A method of reproducing a sound field using digital signal processors in which 2-channel stereo signals are received and converted into 4-channel sound field signals through a first DSP and the 4-channel sound field signals are adaptively composed corresponding to a headphone mode or a speaker mode, again to be into 2-channel sound field signals through a second DSP thereby reproducing 4-channel sound field feeling by 2 channels.

Abstract: This invention minimizes the space required for a speaker system for a multimedia personal computer display on a desktop. The speaker system has a very thin shape, moderate cost, very good impulse and phase response for a crisp sonic detail and good directionality for use by a single listener seated in front of the multimedia personal computer display without disturbing others nearby. Each component of the speaker system is attached to or incorporated in the right or left side of the computer display. Each component comprises a plurality of small speakers arranged in a vertical, linear array. Preferably, each plurality includes a small folded waveguide which is acoustically coupled to the rear of each of the speakers. The folded waveguide is in a unique sheet configuration and enables directional ports in a treble component and a folded variable impedance maze in a base waveguide. The speaker system provides the required shape, clarity and listener isolation needed in the personal multimedia market.

Abstract: An augmentation amplifier includes a first power amplifier stage having an output adapted to be coupled to one side of a load. A second amplifier of negative unity gain has an output coupled to the input adapted to be of the first amplifier and its input coupled to the other side of the load. The circuit may be switched to bypass the bridge and modular units may be employed together. The system is particularly adapted for a powered speaker system for use with a computer sound card.

Abstract: A signal processing system comprising components such as split-band perceptual coders can receive a peak amplitude limited input audio signal and can process the signal in such a manner that the processed signal preserves the apparent loudness of the input signal but is no longer peak-amplitude limited. In one embodiment, upsampling is used in estimating the resultant peak amplitude and gain factors established in response to the estimated peak amplitude are applied to one or more frequency subbands of the processed signal.

Abstract: A signal distribution and communication arrangement includes a main control unit remotely located and electrically coupled to a volume control panel. The volume control panel is located near a speaker, and the main control unit sends substantially continuous audio signals or an interrupting audio signal to the volume control panel for playing via the speaker. These signals can be sent on the same conductor or separate conductors. When the interrupting audio signal is present, a voltage or current source provides a level from the main control unit to the volume control panel to indicate that a volume override circuit should be engaged. Upon engagement of the volume override circuit, the interrupting audio signal is passed through to the speaker at a prescribed signal level, regardless of the volume control setting on the volume control panel.

Abstract: There is substantially provided a muting control circuit in which there is no difference in muting time between the muting utilizing capacitor charging and that utilizing capacitor discharging. A constant current source is in parallel with an external capacitor. The constant current source operates so as to decrease a charging current in the course of charging the external capacitor 20, whereas it operates so as to increase a discharging current in the course of discharging. Therefore, no substantial difference in muting time occurs.

Abstract: A distortion effector includes a calculation section for performing a predetermined higher-degree expression calculation on an input digital sound signal, and a multiplication section that is provided in series with the calculation section for multiplying the digital sound signal by a coefficient that is adjusted so as to utilize a specific portion of the higher-degree expression which exhibits a smooth distortion characteristic. The digital sound signal is distorted in accordance with a smooth non-linear curve based on the higher-degree expression calculation, to thereby achieve a mild distortion effect. In a multi-effector capable of imparting three or more predetermined effects in such a manner that the effects can be selected to be imparted independently of each other, a registration device is provided for registering, for each of the effects, whether the effect should be made switchable or not.

Abstract: A method and apparatus for active cancellation of vibrational noise produced by a medical instrument in the head of a patient. Vibrations from the instrument, as well as vibrations in the bone structure in the head of the patient, are sensed and processed to generate cancelling noise waves which are then fed into the inner ear through headphones or through vibrators placed on the head of the patient. An equalizer shapes the magnitude and phase spectrum of the vibrational signal picked up from the drill and delivers the equalized signal to the patient. An automatic adaptive controller adjusts the equalizer using control signals consisting of vibrations from the bone structure and the drill.

Abstract: A bootstrapped audio line receiver that receives a differential-mode input signal from first and second differential lines and outputs a single-ended signal on an output line. The line receiver includes a differential amplifier and an input amplifier having differential output terminals and differential input terminals. The input amplifier is connected between the differential lines and the differential amplifier. The input amplifier provides a dc current path to a ground terminal while maintaining a high input impedance to ac signals at audio frequencies. The input amplifier also includes an rf filter that removes rf noise without adversely affecting the line receiver's common-mode noise rejection at audio frequencies. In one embodiment, the input amplifier includes two operational amplifiers connected for unity gain and having two bias resistors connected in series between each input terminals of the input amplifier and a ground terminal.

Abstract: A silent method of, and apparatus for use in, enhancing the quality of sound from an electrically powered audio equipment assembly. The apparatus includes an electrical signal conducting component which forms a part of a home audio equipment assembly. The method includes the step of applying a pulsed digital signal having a wide and continuous range of frequencies within the audio frequency bandwidth to the electrical signal conducting component. The signal is applied at a signal level which is a substantial fraction of the maximum signal level rating of the component for a prolonged period of time.

Abstract: An electronic stethoscope includes a microphone mounted in a resilient collar in a hand-held case. The microphone is coupled to an active filter having independently and continuously adjustable bandwidth and center frequency. A switch bypasses the active filter when the user wishes to hear all of the sounds detected by the microphone. The controls for bandwidth and center frequency are located on one side of the case and can be manipulated by the hand holding the stethoscope. The volume or gain of the stethoscope is adjusted by a third control located on the one side of the stethoscope. The controls can be linear or rotary or combinations thereof. The output signal from the active filter passes through a filter having a frequency response inverse to that of the human ear, is amplified, and is coupled to headphones which plug into a socket on the rear of the case.

Abstract: An audio signal processing system produces an output 24 having an illusory distance effect for a sound source signal S by feeding it via a direct signal path 25 and an indirect signal path 22, 23 passing through early reflection simulation apparatus 1 which feed an output mixing mechanism 9. A control system adjusts the relative delays 3, 4 and relative gains 5, 6 in the direct 25 and indirect 22, 23 signal paths to modify the illusory distance effect so as to substantially maintain the mathematical relationship between the gains and time delays of simulated reflections relative to first sound arrivals at the output 24 encountered for sounds at that source distance in actual rooms. Signal paths 22, 23, 24, 25 may be stereophonic or multichannel using matrix gain coefficients in the early reflection simulator 1, and may produce different simulated distances for different sound positions. A plurality of sound sources S may have different simulated distances while feeding a common early reflection simulator 1.

Abstract: This invention relates to an improved method of on-line system identification for use with active control systems which requires less computation and reduces the problem of coefficient jitter in the filters of the active control system by using a fixed test signal which is designed to have a particular power spectrum.

Abstract: A sound reproduction system is disclosed that uses a single pair of compact speaker enclosures to provide surround sound for a multimedia computer workstation. A pair of stereo speaker enclosures provide the computer screen's monaural center channel to a viewer seated at the workstation, as well as pairs of stereo-imaging and stereo surround channels.

Abstract: A dual-speaker unit providing improved stereo base response and directionality for portable computer applications is disclosed. The small speakers direct low end frequencies into a mixing chamber which directs these frequencies out through a central exit port, thereby providing clearer base response without sacrificing psychoacoustic directionality.The speakers are mounted on the mixing chamber and also rotatable relative to it, for adjustable stereo imaging and compact portability.

Abstract: An ear device protects a user from damaging sound levels while permitting the user to hear and understand conversation in a noisy environment. The device includes an enclosure system for at least partially isolating the user's ear drums from ambient sounds, at least on directional microphone, an adaptive band pass filter and a speaker. The adaptive band pass filter further includes adaptive high pass and adaptive low pass filters which adaptively and independently control the range of the pass band depending upon the characteristics of the noise in the user's environment. A speaker transmits the processed signal to the user. The adaptive filter also includes a detector connected to receive the processed signal which controls the gain of the system to prevent overcompression of the audio signal. The adaptive filter further includes an adaptive compression circuit utilizing multiple time constants to control the response time of the adaptive filter under various conditions.

Abstract: An active noise and vibration control system which minimizes noise output by creating a secondary, cancelling noise and/or vibration field using vibrational inputs. The system includes one or more piezoceramic actuators mounted to the inner surface of a magnetic resonance imaging device. The actuators can be either mounted directly to the device or to one or more noise cancelling members which are resiliently mounted to the device. Transducers are also provided for sensing the noise or vibrations generated by the device and producing an error signal corresponding to the level of noise or vibrations sensed. A controller sends a control signal to the actuators in response to the error signal, thereby causing the actuators to vibrate and generate a noise or vibration field which minimizes the total noise emanating from the device. Alternatively, the system can use noise and vibration feedback simultaneously.

Abstract: A silencing apparatus for effectively reducing noises in the three dimension space which detects physical characteristics of the noise source by the laser doppler sensor unit during the noise source comes close to the telephone booth, and collects acoustic characteristics of the noise source by the sensor microphone array. The control portion generates an inverse-phased signal against the noise source so that the noises are decreased at the error sensor, and stores the noise source information (physical characteristics and the acoustic characteristics) and the generated inverse-phased signal. When the same noise source come closely, the voice is generated from the speaker using the inverse-phased signal stored in the memory. The control potion generates an inverse-phased voice from the speaker when the collected noise by the sensor microphone is actually over a certain threshold level.

Abstract: A swimming training device having a swimming cap removably contained therein a receiving device. The receiving device can pickup one of a multiple of signals from a transmitter controlled by a swimming coach. The cap has a compartment that can be sealed releasably, so that water is kept out during swimming and the device may be accessed for repairs or removal.

Abstract: A signal level display unit which makes adjustment for correcting of deviation unnecessary and enables cost reduction. An input analog audio signal 26 is divided into seven signals having different frequency bands, converted into digital signal by an A/D converter 22, input to a display controller 25, and temporarily stored in a storage unit 32. A preset recovery time which is input to the display controller 25 through an A/D converter 28 is also stored in the storage unit 32. The value of each signal newly input from the A/D converter 22 is compared with the current value stored in the storage unit 32. When the value of a newly input signal is higher than the current value, the value displayed by a liquid crystal indicator 23 is immediately renewed. On the other hand, when no signal having a higher value than the current value is input, the displayed value is renewed after the preset recovery time stored in the storage init 32 has elapsed.