Abstract: The invention relates to a noise attenuation system for voice signals. The invention is based on noise signal measurement during the tonal periods of the voice. The line spectrum structure of the spectrum of the tonal sounds is utilized in the noise measurement. In this way it is possible to measure the noise of different frequency bands with the aid of narrow-band filters.

Abstract: A stereo signal demodulator circuit demodulates a stereo signal by using a PLL circuit including a voltage-controlled oscillator (VCO) for generating a first oscillation signal and a second oscillation signal having a phase different from that of the first oscillation signal by 90.degree.. The voltage-controlled oscillator circuit includes a first amplifier for outputting a signal whose phase is different from that of an input signal by 90.degree., a second amplifier for outputting a signal whose phase is different from that of an input signal by 90.degree., and a third amplifier for outputting a signal whose phase is different from that of an input signal by 180.degree.. The first, second and third amplifiers are connected in series so that an output signal of the third amplifier is different, in phase, from the input signal of the first amplifier by 360.degree.

Abstract: A method for reproducing sounds from signals, which are supplied from a same sound source through a pair of localization filters by using a pair of transducers disposed apart from each other and for controlling the localization of a sound image in such a way to make a listener feel that he hears sounds from a virtual sound source which is localized at a desired sound image location being different from the positions of the transducers. When performing this method, a signal for measurement reproduced at each sound image location is measured at the listener's position as data to be used for estimating head-related transfer characteristics. Then, the head-related transfer characteristics corresponding to each sound image location are estimated from the measured data.

Abstract: A headphone apparatus includes a speaker unit accommodated in an accommodating member of an open-air type, a microphone disposed at a front side of the speaker unit, a circuit arrangement mounted on a circuit board in the speaker unit including a filter for lowering a level of a high frequency component of a signal picked up by the microphone, and a negative feedback loop for feeding back an output of the filter to the speaker unit to thereby lower the level of a low frequency component of circumference noise output from the speaker unit. This headphone apparatus further includes an equalizer having a frequency characteristic substantially opposite to that of the filter, wherein an input audio signal is added to the negative feedback loop through the equalizer and then output from the speaker unit.

Abstract: A noise and feedback suppression apparatus processes an audio input signal having both a desired component and an undesired component. When implemented so as to effect noise cancellation, the apparatus includes a first filter operatively coupled to the input signal. The first filter generates a focused reference signal by selectively passing an audio spectrum of the input signal which primarily contains the undesired component. The reference signal is supplied to an adaptive filter disposed to filter the input signal so as to provide an adaptive filter output signal. A combining network subtracts the adaptive filter output signal from the input signal to create an error signal. The noise suppression apparatus further includes a second filter for selectively passing to the adaptive filter an audio spectrum of the error signal substantially encompassing the spectrum of the undesired component of the input signal.

Abstract: Hook- and-loop-type tapes are selectively attached to a video display unit and to flexible elongated strips of magnetic material so that the strips of magnetic material may be removably mounted around the video display unit in orthogonally intersecting planes to absorb magnetic radiation from the source. Each strip of magnetic material has a grain orientation parallel to its longitudinal axis and may be formed from grain-oriented ferromagnetic material in the range from M3 to M7. A multiple-layer magnetic shielding material is provided by securing first and second layers of such grain-oriented ferromagnetic material together with the grain orientation of the first layer orthogonal to the grain orientation of the second layer. Each strip of magnetic material may also be formed from this multiple-layer magnetic shielding material.

Abstract: A shading correction circuit for correcting the shading distortion of a photoelectric conversion device including a plurality of arrayed photocells, has a memory for storing data on the output characteristics of each pixel, represented by image signals having a given level outputted by the photoelectric conversion device a plurality of image pickup times. Thereby, the data on the output characteristics of each pixel stored in the storing means is read by desirably switching the order of the image pickup for each pixel to provide shading correction data. Noise or irregularities which readily appear on the output picture after shading correction are reduced.

Abstract: An electroacoustic amplifier arrangement comprises a plurality of microphone arrangements each of which includes a microphone coupled to a comparator and coupled via a coupling circuit to a variable gain amplifier. The amplifier arrangement further includes a threshold signal generator. The threshold signal generator has a first and a second input coupled to the input and output, respectively, of the amplifier and is arranged to derive a threshold signal as a function of the signals applied to its two inputs. The output of the threshold signal generator is coupled to a second input of the comparator. The threshold signal generator is arranged to derive a threshold signal as a function of the gain factor adjusted in the amplifier.

Abstract: A signal processing circuit for an audio apparatus has a variable gain amplifier whose gain is varied in accordance with a gain controlling signal supplied thereto. The signal processing circuit comprises a gain setting section having a plurality of tables of input-output characteristics according to a level of loudness selected by a user. The characteristics being for the variable gain amplifier. A table selecting section selects a corresponding one of the plurality of input-output characteristics in accordance with the selected level of loudness. The table selecting section supplies the corresponding input-output characteristic to the variable gain amplifier so as to set the variable gain amplifier for a gain corresponding to the input-output characteristic.

Abstract: An audio mixer system using a serial editor interface is disclosed. Use of a microprocessor control circuit is disclosed to control various functions a plurality of multiple channel VTRs under the control of a mixer. Serial control signals are supplied from a video editor to a serial interface which includes a microprocessor. These control signals are decoded, and the appropriate controls of the VTRs are implemented. These controls include crossfading as well as PREVIEW/REVIEW monitoring.

Abstract: A volume control circuit comprises a variable gain stage (306), having a variable gain, and an up/down counter (324) for counting. The counter (324) has a counter input (321) and a counter output (333) for providing a first word (333) for controlling the gain of the gain stage. A microprocessor interface (326) includes an interface output (323) for providing a second word. A digital magnitude comparator (333) compares the first (323) and second (333) words. The comparator having a first input (333) connected to the counter output, a second input connected to the interface output (323), and a comparator output connected to the counter input (321), provides a count signal (329) if the words do not match and for providing a non-count signal (329) if the words match. Thus, responsive to the count signal (329), the up/down counter (324), counts from the first word, in a direction approaching the second word by a least significant bit to form a new first word, for controlling the gain of the gain stage.

Abstract: A system for low frequency sound production in vehicular passenger compartments, comprising an electrodynamic driver, having a first acoustic mass and a first acoustic compliance; and a Helmhotz resonator, affixed to one side of said electrodynamic driver means and having a second acoustic mass and a second acoustic compliance, the second acoustic mass being affixed to a baffle facing the passenger compartment. The first and second acoustic mass have substantially similar magnitudes, and the Helmholtz resonator and the electrodynamic driver being substantially tuned to the highest and lowest frequencies of a desired passband, respectively, so as to provide a substantially flat pressure vas. frequency characteristic when the passenger compartment has dimensions generally smaller than one eighth wavelength of the lowest frequency.

Abstract: A microphone power supply for use with precision microphones having an attached pre-amplifier, connects to an analyzer with a coaxial cable and is powered by an ICP current source in the analyzer. The power supply provides a polarization voltage and a pre-amplifier power voltage to a microphone and pre-amplifier assembly. The power supply receives an AC audio signal produced by the microphone, buffers the AC signal, and provides the AC signal to the analyzer through the coaxial cable.

Abstract: An active noise control apparatus comprises a secondary sound source for generating sound canceling noise emitted from a noise source, first and second microphones sequentially arranged between the noise source and the secondary sound source at a predetermined distance in a direction from the noise source to the secondary sound source, a coefficient multiplier for multiplying an output signal of the second microphone by a coefficient corresponding to a ratio of a transfer function of the first microphone with respect to the secondary sound source to that of the second microphone with respect thereto, a subtracter for obtaining a difference between a multiplication resultant signal and an output signal of the first microphone, and a signal processor for outputting a secondary sound signal obtained by multiplying the difference signal with a predetermined coefficient to the secondary sound source.

Abstract: A mechanism for facilitating metric conversion of digitized images intended for use with a multi-resolution, multi-application environment is integrated into the encoding and decoding mechanisms of the hierarchical data base, such that stored residual image files contain metric change information. In a preferred embodiment of the invention, the metric conversion operator is executed upon a relatively low spatial resolution file, thereby resulting in a substantial reduction in processing overhead, as advantage is taken of the availability of the reduced size of the lower spatial resolution base file within the hierarchical database, so that a metric conversion may be performed on the relatively small number of pixels within the base file, prior to up-converting the image to a relatively high spatial resolution image, such as a 2048.times.3072 pixel image for driving a high resolution digital thermal color printer.

Abstract: A vehicle detector includes an inductive sensor which is driven by an oscillator to produce an oscillator signal having a frequency which is a function of inductance of the inductive sensor. Presence of a vehicle is detected when measured frequency of the oscillator signal changes by more than a threshold value. The effects of magnetic flux produced by adjacent power lines are compensated by measuring the frequency of the oscillator signal during a plurality of sample periods and characterizing the fluctuation of the measured frequency as a function of phase of a power main signal. During a normal measurement period, the frequency of the oscillator signal is measured, and the phase of the power main signal during the measurement period is determined. An output signal is produced based upon the measured frequency, the phase, and the known fluctuation of measured frequency as a function of phase of the power main signal.

Abstract: An adaptive noise control system comprises a reference microphone (12) (FIG. 2) for generating a reference signal (x(t)) that is correlated with noise emanating from a primary noise source (10), secondary loud speaker sources (S.sub.1, S.sub.2, . . . S.sub.N) for generating a plurality of secondary sound waves, microphones (e.sub.1, e.sub.2, . . . e.sub.M) for detecting a plurality of far-field sound waves in a far-field of the primary noise source and generating a plurality of error signals (e.sub.1 (t), e.sub.2 (t), . . . e.sub.M (t)) each of which is indicative of the power of a corresponding far-field sound wave, and an adaptive controller (14) for controlling the secondary sources in accordance with the reference signal and the error signals so as to minimize the power in the far-field sound waves.

Abstract: A speaker driving device applies a constant voltage of a constant voltage source to a pair of voice coils alternatively by switching the direction of applying the constant voltage based on a binary PDM signal. A .DELTA..SIGMA. modulator produces the binary PDM signal by .DELTA..SIGMA.-modulating a digital audio signal from a digital low-pass filter. The constant voltage is applied to a first voice coil in one direction and is applied to a second voice coil in the reverse direction by switching the direction of applying the constant voltage. The first and second voice coils forms the pair of voice coils. This arrangement causes a current to flow through the first and second voice coils in opposite directions and a diaphragm of a speaker to be driven in two directions opposite to each other. As a result, the speaker is driven more efficiently.

Abstract: An active noise control (ANC) system is disclosed for attenuating engine generated noise that contains at least one sinusoidal noise component having an amplitude and frequency that vary with changes in engine rotational speed. The ANC system includes a means for generating at least one generator output signal that contains one or more sinusoidal signal components, where the frequency of each signal component corresponds to the frequency of a respective noise component. A separate control signal having an amplitude that varies with engine rotational speed is generated to correspond with each generator output signal. Each generator output signal is then multiplied by its respective control signal to produce a corresponding filter input signal. Each filter input signal passes to a respective adaptive filter, where it is filtered to produce a corresponding filter output signal according to the adjustable filtering characteristics of the adaptive filter.