Monitoring device, sound collecting device, and monitoring method

A sound collecting device used in a monitoring device for monitoring an operation state of a device, the sound collecting device comprising:

• a plurality of microphones configured to convert a sound wave emitted from the device into a sound pressure signal, the sound wave including an audible sound and an ultrasonic wave,
• wherein the plurality of microphones include:
• a first microphone group in which an interval between the microphones is set to a distance suitable for detection of the ultrasonic wave;
• and
• a second microphone group in which an interval between the microphones is set to a distance suitable for detection of the audible sound and larger than the distance in the first microphone group.

A monitoring method for monitoring an operation state of a device by a sound collecting device in which a plurality of microphones are arranged, the monitoring method comprising:

• acquiring, as a primary sound pressure signal, a sound wave emitted from the device through the plurality of microphones, the sound wave including an audible sound and an ultrasonic wave;
• detecting presence or absence of an abnormality of the device, based on a signal, in an audible range, of the acquired primary sound pressure signal;
• and
• in a case where it is detected that there is an abnormality in the device, detecting an abnormal portion of the device, based on a secondary sound pressure signal generated by performing a beamforming processing on a signal, in an ultrasonic range, of the acquired primary sound pressure signal.