Patent ID: 8731693

Claim:
A voice input device comprising: a first microphone that includes a first diaphragm; a second microphone that includes a second diaphragm; and a differential signal generation section that generates a differential signal that indicates a difference between a first voltage signal obtained by the first microphone and a second voltage signal obtained by the second microphone based on the first voltage signal and the second voltage signal, the first diaphragm and the second diaphragm being disposed so that a noise intensity ratio that indicates a ratio of intensity of a noise component contained in the differential signal to intensity of the noise component contained in the first voltage signal or the second voltage signal, is smaller than an input voice intensity ratio that indicates a ratio of intensity of an input voice component contained in the differential signal to intensity of the input voice component contained in the first voltage signal or the second voltage signal; and the differential signal generation section including: a gain section that amplifies the first voltage signal obtained by the first microphone by a predetermined gain; and a differential signal output section that receives the first voltage signal amplified by the gain section and the second voltage signal obtained by the second microphone, generates a differential signal that indicates a difference between the first voltage signal amplified by the gain section and the second voltage signal, and outputs the differential signal, the first diaphragm and the second diaphragm are disposed with a center-to-center distance Δr which is set to a value for which a ratio of the center-to-center distance Δr to a wavelength λ of the main noise corresponds to a noise intensity ratio set for a desired application of the voice input device, and for which the noise intensity ratio is smaller than an input voice intensity ratio, wherein the noise intensity ratio indicates a ratio of intensity of a noise component contained in the differential signal to intensity of the noise component contained in the first voltage signal or the second voltage signal, and the input voice intensity ratio indicates a ratio of intensity of an input voice component contained in the differential signal to intensity of the input voice component contained in the first voltage signal or the second voltage signal.