| 摘要 |
PURPOSE:To enable high-accuracy recognition by calculating the cross correlation value between an input signal and a reference wave in each section which is an integral multiple of the period of the reference wave of the audible tone signal and also calculating the 2nd cross correlation value between the power variation component of the correlation value and a modulated reference wave in each section which is an integral multiple of the period of the modulated reference value. CONSTITUTION:An impulse noise removal part 1 removes impulse noises from the input signal and a cross correlation part 3 calculates the 1st cross correlation value between the input signal and reference wave in each section which is an integral multiple of the period of the reference signal of the audible tone signal to be recognized. Further, a cross correlation part 8 calculates the 2nd cross correlation value between the power variation component of the correlation value and the modulated reference value in each section which is an integral multiple of the period of the modulated reference value of the audible tone signal, and a 2nd correlation decision part 9 normalizes the output of the cross modulation part 8 with modulated electric power outputted by a modulated signal input presence/absence decision part 7 and also extracts a modulated component from the levels of the 2nd correlation value and variation component and the continuance of the variation component to recognize the audible tone signal from the reference component and modulated component. Consequently, the high-accuracy recognition where a noise containing the same frequency components with the audible tone signal is not misdetected as the audible tone signal is carried out. |
