Patent ID: 7869611

Claim:
A test tone determination method comprising the steps of: picking up, by a first microphone and a second microphone that are disposed with a predetermined distance therebetween, a test tone output from a speaker; calculating a first distance from the speaker to the first microphone, a second distance from the speaker to the second microphone, and a distance difference between the first and second distances, in accordance with periods of time necessary for occurrence of a first amplitude and a second amplitude that are larger than a predetermined value in output signals of the first and second microphones; determining whether or not the distance difference is less than or equal to the predetermined distance; determining the first and second amplitudes to be amplitudes corresponding to direct waves of the test tone, when the distance difference is less than or equal to the predetermined distance in accordance with a determination result of the distance difference; performing scanning, with respect to one of the first and second amplitudes that is found later, on a first output signal portion corresponding to a second output signal portion near the other one of the first and second amplitudes that is found earlier, when the distance difference is larger than the predetermined distance in accordance with the determination result of the distance difference; and determining an amplitude found in both the first output signal portion corresponding to the second output signal portion to be amplitudes corresponding to the direct waves of the test tone, when the amplitude found in the output signal portion corresponding to the output signal portion near the other one of the first and second amplitudes that is found earlier is found in accordance with a scanning result.