A detection device comprising: a detector detecting sound waves generated by a bodily motion; an acquiring unit acquiring burst information on at least one of the duration and frequency of a burst during which a cluster of pulses appears in a waveform of the sound waves detected by the detector ; a memory storing reference information on reference values compared with the burst information, the reference values differing from each other depending on the types of bodily motions generating sound waves; and a determining unit comparing the burst information with the reference information to determine which of bodily motions has caused the sound waves detected by the detector , characterized in that : the sound waves are inaudible to a human; and that the detector detects ultrasound having a frequency not less than 20 kHz and not more than 70 kHz, as the sound waves, and outputs an ultrasonic signal (P1) in accordance with the detected ultrasound; the detection device further comprising an audible converter for converting the ultrasonic signal (P1) to a low frequency audio signal, and an A/D converter for converting the low frequency audio signal to a digital detection signal (P2) and for outputting the digital detection signal (P2) to the acquiring unit , wherein the acquiring unit acquires the burst information based on the digital detection signal (P2). a detector detecting sound waves generated by a bodily motion; an acquiring unit acquiring burst information on at least one of the duration and frequency of a burst during which a cluster of pulses appears in a waveform of the sound waves detected by the detector ; a memory storing reference information on reference values compared with the burst information, the reference values differing from each other depending on the types of bodily motions generating sound waves; and a determining unit comparing the burst information with the reference information to determine which of bodily motions has caused the sound waves detected by the detector , characterized in that : the sound waves are inaudible to a human; and that the detector detects ultrasound having a frequency not less than 20 kHz and not more than 70 kHz, as the sound waves, and outputs an ultrasonic signal (P1) in accordance with the detected ultrasound; the detection device further comprising an audible converter for converting the ultrasonic signal (P1) to a low frequency audio signal, and an A/D converter for converting the low frequency audio signal to a digital detection signal (P2) and for outputting the digital detection signal (P2) to the acquiring unit , wherein the acquiring unit acquires the burst information based on the digital detection signal (P2). the sound waves are inaudible to a human; and that the detector detects ultrasound having a frequency not less than 20 kHz and not more than 70 kHz, as the sound waves, and outputs an ultrasonic signal (P1) in accordance with the detected ultrasound; the detection device further comprising an audible converter for converting the ultrasonic signal (P1) to a low frequency audio signal, and an A/D converter for converting the low frequency audio signal to a digital detection signal (P2) and for outputting the digital detection signal (P2) to the acquiring unit , an audible converter for converting the ultrasonic signal (P1) to a low frequency audio signal, and an A/D converter for converting the low frequency audio signal to a digital detection signal (P2) and for outputting the digital detection signal (P2) to the acquiring unit , wherein the acquiring unit acquires the burst information based on the digital detection signal (P2). <EOS>