Patent ID: 7113602

Claim:
An acoustic apparatus comprising; attenuator means for attenuating a first audio signal supplied thereto to produce a second audio signal, low pass filter means for reducing high frequency components of the second audio signal obtained from the attenuator means to produce a third audio signal, differential amplifier means operative to produce a fourth audio signal corresponding to a difference between the first and third audio signals supplier thereto, and speaker means supplied with the fourth audio signal obtained from the differential amplifier means, wherein said attenuator means is provided for attenuating each of left and right channel signals of the first audio signal to produce the second audio signal containing the attenuated left and right channel signals, and said speaker means includes a left speaker supplied with the left channel difference signal contained in the fourth audio signal and a right speaker supplied with the right channel difference signal contained in the fourth audio signal, and the attenuator means is operative to create a virtual left sound source position in front of and at a level higher than an actual position of the left speaker and a virtual right sound source position in front of and at a level higher than an actual position of the right speaker, and wherein said attenuator means is operative to determine the attenuation of each of the left and right channel signals so that the following equations are satisfied: SLO =( L×ARR ( z )− R×ARL ( z ))/( ALL ( z )× ARR ( z )− ALR ( z )× ARL ( z )) SRO =( R×ALL ( z )− L×ALR ( z ))/( ALL ( z )× ARR ( z )− ALR ( z ) × ARL ( z )) L=SL×BLL ( z )+ SR×BRL ( z ) R=SL×BLR ( z )+ SR×BRR ( z ) wherein SLO represents the amplified left channel difference signal, SRO represents the amplified right channel difference signal, SL represents the left channel signal, SR represents the right channel signal, ALL(z) represents an acoustic transfer function from the left speaker to a left ear of the listener, ALR(z) represents an acoustic transfer function from the left speaker to a right ear of the listener, ARL(z) represents an acoustic transfer function from the right speaker to the left ear of the listener, ARR(z) represents an acoustic transfer function from the right speaker to the right ear of the listener, BLL(z) represents an acoustic transfer function from the virtual left sound source position to the left ear of the listener, BLR(z) represents an acoustic transfer function from the virtual left sound source position to the right ear of the listener, BRL(z) represents an acoustic transfer function from the virtual right sound source position to the left ear of the listener, and BRR(z) represents an acoustic transfer function from the virtual right sound source position to the right ear of the listener.