Abstract: A low-cost speech recognition apparatus for AV equipment capable of speech recognition with high accuracy while 2-channel sound is being produced from loudspeakers is achieved. A monaural conversion part converts 2-channel signals to be inputted to the loudspeakers into a monaural signal. A single echo canceller is provided with an output from a microphone and an output from the monaural conversion part (monaural signal). The echo canceller estimates an echo of multichannel sound based on the monaural signal, and then eliminates the echo sound from the microphone output. Thus, with only a single echo canceller, speech recognition can be carried out while 2-channel sound is being produced from the loudspeakers. Moreover, unlike the case where two echo cancellers are provided, the present invention can prevent the occurrence of mutual interference between the echo cancellers that leads to deterioration in speech recognition performance.

Abstract: A built-in microphone device for use in an apparatus having a mechanism section generating internal noise inside a housing of the apparatus includes a main microphone for picking up an external sound; a noise reference microphone for picking up the internal noise; an adaptive filter member for generating a control audio signal based on an output signal from the noise reference microphone using a filter coefficient; a signal subtraction section for subtracting the control audio signal generated by the adaptive filter member from an output signal from the main microphone to generate a subtraction result; and a filter coefficient update control section for receiving an operation signal generated at the time of an operation of the mechanism section, and in response to the operation signal, updating the filter coefficient of the adaptive filter member based on the subtraction result generated by the signal subtraction section and an output signal from the noise reference microphone.

Abstract: A built-in microphone device for use in an apparatus having a mechanism section generating internal noise inside a housing of the apparatus includes a main microphone for picking up an external sound; a noise reference microphone for picking up the internal noise; an adaptive filter member for generating a control audio signal based on an output signal from the noise reference microphone using a filter coefficient; a signal subtraction section for subtracting the control audio signal generated by the adaptive filter member from an output signal from the main microphone to generate a subtraction result; and a filter coefficient update control section for receiving an operation signal generated at the time of an operation of the mechanism section, and in response to the operation signal, updating the filter coefficient of the adaptive filter member based on the subtraction result generated by the signal subtraction section and an output signal from the noise reference microphone.

Abstract: A stereo ultradirectional microphone apparatus for detecting a sound to produce stereo sound signals, comprises: first and second ultradirectional microphones arranged side by side with a given distance in parallel for converting a sound into first and second sound signals respectively, first and second delays for delaying an output of the first and second microphones by a delay time .tau. respectively, and first and second subtractors for subtracting for subtraction between the first sound signal and an output of the second delay and subtracting for subtraction between the second sound signal and an output of the first delay. The delay time .tau. corresponds to a difference between the timings of a sound from a sound source in a direction making a clockwise angel .theta. from the front where a dead angel should be made. The subtraction provides the dead angle. Similarly, a dead angle on the side is also made to obtain a stereo characteristic.

Abstract: A reference microphone is disposed close to a primary microphone through an enclosure wall of an appliance incorporating microphones, and a noise generated by mechanical systems and included in an output of the primary microphone is canceled by an adaptive filter. In a smaller hardware scale than a case of mounting a sensor for noise reference directly to a noise source, a noise component can be canceled more effectively depending on changes of noise environments.

Abstract: In a small-sized pressure gradient type microphone apparatus, a plurality of omni-directional microphone units are encased within a microphone holder. A plurality of acoustic passages having first and second ends are provided within the microphone holder for coupling the sound inlets of the plurality of omni-directional microphone units respectively to an outer space of the microphone holder. The second ends of the acoustic passages opened to the outer space of the microphone holder are arranged to be apart from each other at distances larger than distances between the sound inlets of the corresponding microphone units coupled at the first ends of the acoustic passages.

Abstract: In an echo canceller, a first adaptive filter (1) estimates an impulse response of an echo path between reception and transmission side by an NLMS algorithm to synthesize a pseud echo, while a second adaptive filter (3) determines whether there is an echo path change or a double talk. A voice detector (8) detects a short time power of the received input signal (x) to determine whether far-end speech is present or absent. The voice detector controls the second adaptive filter (3) to execute adaptation of the second adaptive filter for renewal of an impulse response of an echo path when far-end speech is present and otherwise to suspend the adaptation of the second adaptive filter when far-end speech is absent, while a double talk detector (9) controls the first adaptive filter to execute or suspend adaptation of the first adaptive filter according to the determination results of the voice detector.

Abstract: An array microphone is a directional microphone having an improved directional characteric in which both the sensitivity and the sound pressure frequency response are uniform within the recording area and more particularly, the quality and level of sound remain unchanged. The array microphone includes a microphone array including a plurality of microphone units, and a two-dimensional filter for filtering an output of the microphone array in the dimensions of both time and space. When the two-dimensional filter is a digital filter and varied in its two-dimensional filter coefficient and sampling frequency, the array microphone serves as a variable directional microphone whose directional characteristic can be varied with the sound quality and level remaining unchanged throughout the recording area.

Abstract: A howling canceller includes a group of filters for dividing an output of a microphone into a plurality of frequency bands, a transfer characteristic estimation unit for estimating a transfer characteristic (i.e.-impulse response) of a low frequency range in an echo path extending from a loudspeaker to the microphone, an echo signal estimation unit for producing an approximate echo signal of the low frequency range proceeding from the loudspeaker to the microphone, a subtracter for subtracting an output of the echo signal estimation unit from an output of a low-pass filter of the filters, and an adder for adding an output of the subtracter to outputs of the filters other than the low-pass filter.

Abstract: A microphone comprises a pair of electroacoustic transducing high polymer piezoelectric semi cylindrical shaped membranes having a single axis of elongation tangent to the curvature mounted in a housing facing each other. The membranes are electrically series connected to each other with a connection between the facing surfaces thereof and are of prescribed polarizations to generate an output which is substantially twice the voltage developed individually from each membrane when said membranes are caused to flex in opposite directions and substantially zero when said membranes are caused to flex in the same direction.