Sound reproducing device, earphone device and signal processing device therefor

An earphone device used in combination with a signal processing device which is supplied with an input audio signal of at least one channel to convert the input audio signal to a 2-channel audio signal with which an acoustic image is located at a predetermined position when the input audio signal is reproduced substantially by a 2-channel speaker device, subjects the 2-channel audio signal to signal processing equivalent to a transfer function from said 2-channel speaker device to both the ears of a listener, thereby converting and outputting the input audio signal to a 2-channel audio signal, comprising:

• a signal processing circuit supplied with the 2-channel audio signals from said signal processing circuit;
• a pair of electro-acoustic transducing means supplied with the output signal from said signal processing circuit;
• and
• detection means for detecting the movement of the head of the listener, wherein said signal processing circuit performs the processing corresponding to an alteration of the transfer function on the 2-channel audio signals in accordance with the output of said detection means to control the location position of the acoustic image which is perceived by the listener.

A signal processing device for transmitting 2-channel audio signals to an earphone device having a pair of electro-acoustic transducing means under a wireless condition, including:

• a first signal processing circuit which is supplied with an input audio signal of at least one channel to convert the input audio signal to 2-channel audio signals with which an acoustic image is located at a predetermined position when the input audio signal is reproduced substantially by a 2-channel speaker device;
• a second signal processing circuit which is supplied with the 2-channel audio signal output from said first signal processing circuit and subjects the 2-channel audio signals to the signal processing equivalent to a transfer function from said 2-channel speaker device to both the ears of a listener to convert and output the input audio signals to 2-channel audio signals;
• and
• transmission means for transmitting the 2-channel audio signals output from said second signal processing circuit under the wireless condition.