Patent ID: 8213646

Claim:
A vehicular stereophonic sound apparatus for presenting an object condition of an object based on sensor information that is representative of an in-and-about condition of a vehicle and for outputting notification sound from a virtual sound source toward an occupant of the vehicle, the apparatus comprising: a right and a left main-speakers installed respectively equidistantly on a right side and a left side relative to a right ear and a left ear of the occupant; a sub-speaker installed on a right-front position of the occupant, such that the sub-speaker is disposed in front of the occupant on a center plane of the occupant; a control unit for outputting a control signal for generating virtual sound based on determination of the object condition to be presented for the occupant according to the sensor information; a positioning unit for positioning a sound image of the object in an actual direction by performing, for a right and a left audio signals respectively directed to the right and the left main-speakers, signal processing that utilizes Head-Related Transfer Function that reflects a position of the object based on the control signal from the control unit; an enhance unit for enhancing the sound image by performing, for the right and the left audio signals respectively directed to the right and the left main-speakers, signal processing according to the position of the object; a delay unit for correcting a difference of sound arrival times to the right and the left ears due to a difference of speaker-to-ear distances between the right and left main-speakers and the sub-speakers relative to the right and the left ears based on the control signal from the control unit according to the actual direction of the object; a filter unit for processing the audio signal directed to the sub-speaker based on the control signal from the control unit according to the actual direction of the object, the filter unit being configured as an FIR filter with a tap number of N; and a volume adjustment unit for adjusting sound volume of the right and the left main-speakers and the sub-speaker independently based on the control signal from the control unit according to the actual direction and a distance of the object, wherein the tap number of N of the FIR filter is determined based on the actual direction of the object, N is set to a lower setting when the actual direction of the object is from a side of the vehicle to a front of the vehicle, than when the actual direction of the object is from a rear of the vehicle.