Matsushita Electric Industrial Co., Ltd.

Nippon Precision Circuits Inc.

Masataka Saito

I Fusanori

Masayoshi Nakamura

Akira Toyama

Atsushi Nagayoshi

Eiichi Takakura

Kazutoshi Yamaguchi

Koichi Higuchi

Kazuhiko Hakuta

In an APC system waveform dam compression apparatus which generates an optimum prediction coefficient utilizing a block calculation process in a first mode and generating prediction data utilizing a block calculation process based on this optimum prediction coefficient in a second mode with respect to a fixed number of blocked waveform data, to make possible use of suitable data in the first prediction calculation process of each block calculation process. A data holding section for holding data corresponding to at least final first waveform data to be used in a final prediction calculation process of a block calculation process in a second mode, and a first selection section for using data held in the data holding section in place of data memorized in a second delay section in each first prediction calculation process of each block calculation process of the next block are provided in an operating circuit.

Waveform data compression apparatus

The present invention relates to an acoustic reproducing apparatus which is suitable particularly for listening to reproduced sound with noise through an open-air-type head phone. A sound leakage frequency band, when a head phone is loaded is measured in advance, and operation of a filter attenuating that sound leakage frequency band is changed-over. Thereby the sound leakage from the head phone to the outside in the loaded state is controlled. Also, a noise frequency characteristic is measured in advance, the low frequency band is intensified so as to correspond to that characteristic, and operation of the filter for attenuating the high frequency band containing the above-mentioned sound leakage frequency band is controlled to be changed-over.

Acoustic reproducing apparatus

An amplifying circuit of the invention comprises: a high frequency amplifying circuit for amplifying high frequency; a low frequency amplifying circuit for amplifying a low frequency; input filters which are provided on the input side of the respective amplifying circuits so as to pass the frequency components thereof; output filters having the same characteristics as those of the input filters; and an adding circuit for adding outputs of the output filters. Therefore, an output dynamic range of the whole amplifying circuit is equal to the sum of the dynamic ranges of the respective amplifying circuits, so that a large output which is not distorted even if a sound volume is raised is derived. By providing a matching filter on the input side of the low frequency amplifying circuit, even if the low frequency side output filter which needs a large coil is omitted, the frequency characteristics of the output of the adding circuit can be made flat and the amplifying circuit of a small size and a less distortion can be realized.

Audio amplifying circuit

Growing community of inventors

Hirakata, Japan

Masataka Saito