Abstract: An arrangement is provided for converting an electric signal into an acoustic or a mechanic signal comprising a transducer (1) and an electric circuit connected to the terminals of the transducer (1). An adaptive correction filter (3) compensates for linear and nonlinear distortions of the transducer (1) and realizes a desired overall transfer characteristic of the arrangement. An adaptive detector circuit (2) connected between the filter output (7) and the transducer's terminals provides a motional signal of the transducer at output (11) without using an additional mechanic or acoustic sensor. Reference filter (6) and comparator (13) compare the detected motional signal with a desired signal and provide an error signal e(t) for adaptively adjusting both the correction filter (3) and detector circuit (2) to the transducer. This arrangement dispenses from pre-training and copes with nonlinear and changing transducer characteristics.

Abstract: The device of the present invention is designed for the purpose of providing a system for conducting objective assessment of the actual or "real world" attenuation which is provided by insert-type hearing protection (IHP) devices. The device is constructed to serve as the input device to any commercially available noise dosimetry instrument or sound level measuring device. A miniature microphone is mounted on, or embedded in the proximal surface of the IHP which is to be inserted in the ear or upon the ear of the user. The miniature microphone is hard wired to a miniature jack which is mounted on, or embedded in the distal surface of the IHP device. A cable connects to the jack on the outside of the IHP device and to the input of the noise dosimetry instrument or sound level measurement device.

Abstract: A system for controlling distribution of sound in a multi-channel sound system such as a "surround sound" system in a movie theater. Control signals are used to steer, or distribute, portions of the sound signal between designated speakers. In a preferred embodiment the control signals are provided with the sound signals, themselves, and are separated from the sound signals by using a pilot signal or signals.

Abstract: An analog vector processor and method for converting right and left mono and stereo audio input signals through a series of six amplifier blocks and two control blocks using a series of unique signal path connections. The six amplifier blocks are comprised of three dual-amplifiers, two spacial amplifiers, a four-amplifier integrated circuit that inverts and transposes the signal path thus putting the signals out-of-phase. The two control blocks are comprised of a new and unique signal mixer control block that selects a mono, stereo, spacial or binaural signal, and a level control block for dual tracking of the signals. The resultant output signals are of an altered sound field producing a binaural effect thus creating a three-dimensional sound experience. The input signals may be from any sound source or conducting medium.

Abstract: An active control method and apparatus for controlling vibration or sound wherein the computational burden to adaptively update the control filter within the update model is reduced. The apparatus includes means for producing an input signal for input to the update model and the reduction block, means for generating an error sensor, and an output device for canceling sound and/or vibration at a selected location. The method uses a gradient descent algorithm such as the filtered-x LMS algorithm and replaces the long filter model with a shortened length filter model. Error signal information together with the output information from the shortened length filter model are used to update the coefficients of the control filter according to an update calculation method. The shortened filter model only contains frequency response information at the L frequencies of interest.

Abstract: An improved theater surround sound system incorporates a screen top speaker and an overhead speaker driven by corresponding upper surround channels to more accurately reproduce sounds produced from above the listener. These top surround channels are encoded along with the left and right surround channels. A pilot signal is used to direct the sound from the side surround channels to the upper surround channels when needed.

Abstract: An external memory control circuit for a sound field processing digital signal processor capable of obtaining continuous sound listening by shortening the time that sound is cut off upon a change of the sound field algorithm depending on the listening place (i.e., concert hall, meeting hall, church or the like). The external memory control circuit is constructed to utilize a mute function only for the time required to transfer the algorithm itself where a sound field processing circuit is realized using a DSP, thereby reducing the time that sound is cut off and thereby obtaining continuous sound listening even when the sound field algorithm is changed while listening.

Abstract: A multichannel sound reproduction method and apparatus are described for achieving a higher proportion in the overall room size for acoustic/visual use, which can be used for the listening-position-independent reproduction of spatial information in maintaining the given directional information of the individual sound signal sources. In the described method, each signal is split up and, after a summation, part of it with an increased delay, a modified level and a changed phase position is supplied to one of the unchanged signal portions, with the aggregate signals being distributed and supplied to the two surround reproduction channels and to other reproduction loudspeakers distributedly located in the room in conformity with directional allocation and in accordance with the relevant unchanged signal portions.

Abstract: Audio reproducing apparatus reproducing an audio signal corresponding to a picture which localizes a sound image in a direction corresponding to the picture by processing an audio signal in a real-time fashion is supplied with an audio signal from a general-purpose signal source such as a laser disc a digital vibratory gyroscope detects a rotational angle of a listener's head. In response to the detected rotational angle, the audio reproducing apparatus subjects the audio signal to a predetermined signal processing in a real-time fashion. Thus, a sound image is localized in the direction corresponding to the picture projected on a screen from a projector.

Abstract: An arrangement is provided for converting an electric signal into an acoustic or a mechanic signal comprising a transducer (11), a linear or nonlinear filter (1) with controllable parameters, a sensor (12), a controller (24), a reference filter (20) and a summer (17). The filter (1) is connected to the electric input of the transducer and is adaptively adjusted to compensate for the linear and/or nonlinear distortions of the transducer and to realize a desired overall transfer characteristic. The filter has for every controllable filter parameter an additional output (7) supplying a gradient signal to the controller and a control input (10). The summer (17) provides an error signal derived from the sensor output and reference filter output. The controller contains a circuit (53) for filtering the gradient signal and/or a circuit (25) for filtering the error signal, a multiplier (51) and an integrator (57) for producing a control signal to update every filter parameter.

Abstract: A reproduced sound is sent from a speaker as a sound source unit provided in a sound field. An error signal is produced by a microphone on the basis of a difference in sound between the reproduced sound from the speaker and noise coming from the outside of the sound field into the sound field. A digital filter has a fixed transfer function approximated to a transfer function of the sound field, to which a signal for driving the speaker is supplied. Variation of the transfer function of the sound field is detected by the digital filter. A difference signal between the error signal and an output signal from the digital filter is calculated by an adder. The difference signal determined by the adder is inputted into an IMC filter. A signal for compensating the variation of the transfer function of the sound field and variation of the noise is produced by the IMC filter.

Abstract: A hearing aid device is disclosed providing omnidirectional listening assistance for the hearing impaired individual. The person with the hearing impairment may have greater hearing sensitivity in one ear than the other. Sounds emanating on the opposite side of a person than the more sensitive ear may be lost because the more sensitive ear is not directionally situated to receive the sound most effectively. The invention is directed toward detecting sounds in the auditory field associated with the less sensitive ear and transmitting those detected sounds to the more sensitive ear for amplification therein. Where the dominant ear is also partially impaired, a second sound transducer may be added to detect the sound emanating in a second auditory range associated with the more sensitive, albeit partially impaired, ear. The detected signals from the first and second auditory ranges may be combined in this embodiment for amplification in the more sensitive ear.

Abstract: Automobiles having convertible tops and audio systems are provided with a first audio equalization mode for closed car conditions and a second audio equalization mode for open car conditions. The appropriate audio equalization mode is selected automatically upon raising or lowering the convertible top. In order to minimize inadvertent switching of modes, a timer is included in the system to delay switching from one mode to the other. The timer times a period of about three seconds.

Abstract: An AC-3 decoder output signals of five channels, i.e., main signals of left front, center front and right front channels and surround signals of two channels. A first synthesizing section synthesizes the three-channel main signals and a difference signal between the two-channel surround signals, and the resultant synthesized signals are then fed to a main sound field signal forming section which in turn forms main sound field signals. A second synthesizing section synthesizes the surround signals of the two channels and a difference signal between the main signals of the left and right channels, and the resultant synthesized signals are fed to a surround sound field signal forming section which in turn forms surround sound field signals. A composite sound field forming section synthesizes the main sound field signals, surround sound field signals and original surround signals so as to form composite sound field signals.

Abstract: An analog spread spectrum wireless speaker system for use in consumer audio applications for providing reliable and high fidelity stereo sound. The system includes a transmitter that accommodates any analog input from a variety of audio devices such as compact disk players, cassette players, AM/FM tuners and transmits this information in the 2.4-2.4835 GHz band to a receiver at a remote location. The receiver is capable of reproducing the audio signal with good frequency and signal-to-noise performance.

Abstract: Apparatus for reducing acoustic background noise for use with a telephone handset or a boom microphone device or a boom headset or the like. The apparatus includes first and second microphones which are arranged such that the first microphone receives a desired speech input and the background noise present in the vicinity of the speech, and the second microphone receives substantially only the background noise. The background noise from the second microphone is converted into a corresponding electrical signal and subtracted from a signal corresponding to the speech and background noise obtained from the first microphone so as to produce a signal representing substantially the speech.

Abstract: A loudspeaker configuration for a notebook computer includes one or more high frequency "upper" speakers and a low frequency "lower" speaker. The upper speakers are mounted within a display housing and emit sounds over a range including directional sounds having wavelengths less than one-third the upper speaker diameter. The "lower" speaker is mounted within a keyboard housing. The lower speaker is oriented downward onto the desktop or other support surface and displaces a larger volume of air than the upper speaker. Open space between a processor board and a lower housing base surface define an internal speaker-box chamber for the lower speaker. The housing base surface and a support surface for the computer defining an external speaker box for the lower speaker. The internal speaker box and external speaker box define a band pass acoustic filter for sound waves emitted from the second speaker. The sound waves passing through the band pass filter occur to a listener as non-directional sound.

Abstract: A system and method for automatically adjusting the volume of an audio system to compensate for variations in ambient noise. The system includes a microphone for monitoring the ambient audio environment which includes output of the audio system plus environmental noise. The system also includes processing circuitry connected to the microphone. The processing circuitry varies the volume of the output of the audio system in proportion to changes in the environmental noise. The processing circuitry comprises the microphone, located to detect the ambient sound in the listening environment, an analog-to-digital converter connected to the output of the microphone, and a digital signal processor connected to the output of the analog-to-digital converter. The output signal of the DSP is an input to the volume control of the audio system.

Abstract: Method and apparatus for controlling the volume of an internal PC speaker. In the present invention, pulse width modulation (PWM) techniques are used to selectively reduce the signal power generated at the speaker. By substituting a high frequency signal having a symmetric duty cycle for portions of the digital audio signal, the average signal power is reduced. The frequency of the substitute signal is much higher than the speaker bandwidth, contributing negligible power to the output. The ratio of audio signal to high frequency signal determines the output signal level. In the preferred embodiment of the present invention, a three bit counter is used to separate the audio signal into intervals having eight states apiece. A signal providing -6 dB of attenuation is generated by substituting the toggling output from the least significant bit of the counter during four out of the eight states.

Abstract: An artificial head (2) and a plurality of discrete monophonic microphones (8, 10, 12) are used to record one or more sound sources. The signals (14, 16, 18) from each of the microphones (8, 10, 12) then undergo binaural synthesis based upon acoustical properties of a real human head or the artificial head (2), and the signals (4, 6) from the head are equalised using air-to-ear transfer functions of the artificial head (2) or a real head. The resultant signals are combined by summing the individual left (48) and right (50) channels together and then these summed signals (52, 54) are transaural crosstalk compensated (56) to provide final left and right channel signals (58, 60) suitable for recording or playback which provide a three-dimensional sound effect to a listener both via headphones and loudspeakers.