A position detecting
system is provided, which is capable of effectively preventing erroneous detection of audio to be measured. The position detecting
system includes a terminal device that inputs an
audio signal from an audio device and a
microphone. The audio device sequentially inputs measurement audio signals that have been formed by two or more audio signals of different frequencies to a speaker and receives a notification
signal, wherein the report
signal indicates that the audio of the measurement
audio signal has been collected from the terminal device. The audio device clocks a time t1 and a time t2, namely clocks after the audio of the measurement
audio signal is output from the speakers SP1-SP2 until the notification signals of the measurement audio signals are received by the
signal receiving unit. The audio device calculates the position of the
microphone by using the times t1 and t2. For each frequency component of the measurement audio signal, when an audio signal exceeding a predetermined level is inputted from the
microphone, the terminal device detects it as a component of the measurement audio signal and transmits a notification signal upon detection of the measurement audio signal.