Patent ID: 8600071
Filing Date: 2013-12-03
Classification: B60Q,H04R

Abstract:
1. A vehicle existence informing device configured to inform existence of a vehicle by using a warning sound at a frequency in an audible range, the vehicle existence informing device comprising: a speaker array including at least two speakers arranged so that their respective acoustic outputs mix with each other, the speaker array being configured to radiate a warning sound in air on a carrier wave, which is at a frequency in an ultrasonic range; and a phase control unit configured to advance and delay a phase of an acoustic wave radiated from one of the at least two speakers with respect to a phase of an acoustic wave radiated from another of the at least two speakers; wherein each of the at least two speakers is configured to produce acoustic oscillations according to application of an electrical voltage or current so as to radiate in air said warning sound on a carrier wave, and the phase control unit is configured to switch a positive terminal and a negative terminal of one of the at least two speakers so as to advance and delay the phase of an acoustic wave radiated from the one of the at least two speakers with respect to the phase of an acoustic wave radiated from another of the at least two speakers, and wherein: the phase control unit is further configured to incline a direction of an acoustic wave by an angle θ relative to a front direction of the at least two speakers, by switching the positive terminal and the negative terminal, thereby to delay the phase of an acoustic wave radiated from the one of the at least two speakers with respect to the phase of an acoustic wave radiated from another of the at least two speakers by 180 degrees, wherein the angle θ, a distance d between the oscillators and a wavelength λ of a sound wave satisfy an equation of d·sin θ=λ/2.