Mitsubishi Electric Engineering Company, Limited

Toshimitsu Seri

Noboru Kyouno

Makoto Koura

An accident sound detection circuit includes an accident sound detection block that detects an accident sound from a sound signal inputted from an environmental sound detection unit and outputs an accident sound detection signal a power spectrum calculator for obtaining a power spectrum in regard to a sound signal when acquiring the accident sound detection signal outputted from the accident sound detection block as a trigger signal, a spectrum pattern calculator for forming a pattern of the power spectrum, and a pattern comparator circuit for comparing the formed spectrum pattern and a set pattern set in a pattern generating circuit beforehand and generating a final accident sound detection signal if the patterns coincide with each other.

Accident sound detection circuit

An accident sound detection circuit includes an accident sound detection block that detects an accident sound from a sound signal inputted from an environmental sound detection unit and outputs an accident sound detection signal, a power spectrum calculator for obtaining a power spectrum in regard to a sound signal when acquiring the accident sound detection signal, outputted from the accident sound detection block, as a trigger signal, a spectrum pattern calculator for forming a pattern of the power spectrum, and a pattern comparator circuit for comparing the formed spectrum pattern and a set pattern set in a pattern generating circuit beforehand and generating a final accident sound detection signal if the patterns coincide with each other.

An accident sound detector counts the number of records of detected accident sounds in a predetermined period of time. The accident sound detector varies the amplification of input sound signals according to the number of records or their variation to limit the number of records, thereby making it possible to increase the recording time of a recording medium without overwriting the records. The detector includes an amplifier for amplifying a sound signal from an ambient sound detector. An accident sound detector circuit and a record controller detect and record an accident sound by comparing an output value from the amplifier to a threshold. A counter circuit counts the number of detected signals of the accident sound detector circuit. A comparator compares the count value of the counter circuit with a reference count value. An amplification controller circuit controls the amplification of the amplifier based on output of the comparator.

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Nagasaki, Japan

Toshimitsu Seri