Abstract: An object of the present invention is to provide a loudspeaker device which has a high moisture resistance and can further widens an audio range of low-frequency range sounds. To achieve the above object, a closed box loudspeaker device of the present invention includes a loudspeaker unit which is attached to an opening in a box and activated carbon fiber which is provided in the box to adsorb gas. The activated carbon fiber has plural pores, which are exposed on a surface of the activated carbon fiber and have a diameter of 2.0 nm or less, and a volume of the pores having the diameter of 2.0 nm or less occupies 60% or more of a volume of the entire pores, so that the loudspeaker device which simultaneously achieves both an enhancement of the moisture resistance and the widening of the audio range of the low-frequency range sounds can be provided.

Abstract: An object of the present invention is to provide a loudspeaker device which has a high moisture resistance and can further widens an audio range of low-frequency range sounds. To achieve the above object, a closed box loudspeaker device of the present invention includes a loudspeaker unit which is attached to an opening in a box and activated carbon fiber which is provided in the box to adsorb gas. The activated carbon fiber has plural pores, which are exposed on a surface of the activated carbon fiber and have a diameter of 2.0 nm or less, and a volume of the pores having the diameter of 2.0 nm or less occupies 60% or more of a volume of the entire pores, so that the loudspeaker device which simultaneously achieves both an enhancement of the moisture resistance and the widening of the audio range of the low-frequency range sounds can be provided.

Abstract: A microphone apparatus comprises two non-directional microphones in case of monaural sound pickup or three non-directional microphones in case of stereo sound pickup, and a signal processing means for processing output signals of the non-directional microphones so that a directivity becomes non-directional in a low frequency region and a first order pressure gradient type in a high frequency region. Accordingly, the microphone apparatus can attenuate the level of unwanted acoustic and vibration noises caused by its onboard moving mechanism as well as wind noise, thus ensuring no declination in the S/N ratio during sound pickup action.

Abstract: A microphone apparatus using two microphones has a circuit for processing output signals of the two microphones so as to obtain non-directional characteristics in a low frequency region and uni-directional characteristics in a high frequency region. When this microphone apparatus is incorporated in an appliance containing an acoustic noise source and vibration source therein, acoustic noise, vibration noise and wind noise are reduced to prevent a reduction of the S/N ratio when picking up the sound, so that the recording of an excellent quality sound can be realized.

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.