Sound image localization apparatus

1. An information processing apparatus, comprising:

a sound image localization apparatus including:

a first head related transfer function (HRTF) filter configured to receive a monaural audio signal and generate a first channel output signal using a first head related transfer function describing a change in sound at a right eardrum caused when a sound occurs from a first direction;

a second HRTF filter configured to receive the monaural audio signal and generate a second channel output signal using a second head related transfer function describing a change in sound at a left eardrum caused when a sound occurs from the first direction;

a first low-pass filter configured to cut high frequency components of the monaural audio signal and pass low frequency components of the monaural signal;

a first delay circuit configured to delay an output of the first low-pass filter by a first delay amount;

a second low-pass filter configured to cut high frequency components of the monaural audio signal and pass low frequency components of the monaural signal;

a second delay circuit configured to delay an output of the second low-pass filter by a second delay amount;

a first mixer configured to mix an output of the first HRTF filter and an output of the first delay circuit and output a first audio signal; and

a second mixer configured to mix an output of the second HRTF filter and an output of the second delay circuit and output a second audio signal, wherein

a difference between the first delay amount and the second delay amount is set such that a second direction of localization caused by the difference between the first delay amount and the second delay amount coincides with the first direction of the first HRTF filter and the second HRTF filter.

2. The information processing apparatus of claim 1 , wherein

the sound image localization apparatus further includes a third delay circuit configured to delay an output of the first delay circuit by a third delay amount.

3. The information processing apparatus of claim 2 , wherein

the sound image localization apparatus further includes a fourth delay circuit configured to delay an output of the second delay circuit by a fourth delay amount.

4. The information processing apparatus of claim 3 , wherein

the first mixer is configured to mix an output of the first HRTF filter and an output of the third delay circuit and output the first channel audio signal; and

the second mixer is configured to mix an output of the second HRTF filter and an output of the fourth delay circuit and output the second channel audio signal.

5. The information processing apparatus of claim 1 , further comprising:

a second sound image localization apparatus configured to receive a second monaural audio signal and output a third audio signal and a fourth audio signal.

6. The information processing apparatus of claim 5 , further comprising:

a third mixer configured to mix the first audio signal and the third audio signal and output a fifth audio signal; and

a fourth mixer configured to mix the second audio signal and the fourth audio signal and output a sixth audio signal.

7. The information processing apparatus of claim 6 , further comprising:

a third delay circuit configured to receive a third monaural audio signal and delay an output of the third monaural signal by a third delay amount.

8. The information processing apparatus of claim 7 , wherein

the third mixer is configured to mix the first audio signal, the third audio signal, and the output of the third delay circuit and output the fifth audio signal; and

the fourth mixer is configured to mix the second audio signal, the fourth audio signal, and the output of the third delay circuit and output the sixth audio signal.

9. The information processing apparatus of claim 8 , further comprising:

a third sound image localization apparatus configured to receive a fourth monaural audio signal and output a seventh audio signal and an eighth audio signal.

10. The information processing apparatus of claim 9 , wherein

the third mixer is configured to mix the first audio signal, the third audio signal, the seventh audio signal, and the output of the third delay circuit and output the fifth audio signal; and

the fourth mixer is configured to mix the second audio signal, the fourth audio signal, the eighth audio signal, and the output of the third delay circuit and output the sixth audio signal.

11. The information processing apparatus of claim 10 , further comprising:

a fourth sound image localization apparatus configured to receive a fifth monaural audio signal and output a ninth audio signal and a tenth audio signal.

12. The information processing apparatus of claim 11 , wherein

the third mixer is configured to mix the first audio signal, the third audio signal, the seventh audio signal, the ninth audio signal, and the output of the third delay circuit and output the fifth audio signal; and

the fourth mixer is configured to mix the second audio signal, the fourth audio signal, the eighth audio signal, the tenth audio signal, and the output of the third delay circuit and output the sixth audio signal.

13. The information processing apparatus of claim 12 , further comprising:

a fifth sound image localization apparatus configured to receive a sixth monaural audio signal and output a eleventh audio signal and a twelfth audio signal.

14. The information processing apparatus of claim 13 , wherein

the third mixer is configured to mix the first audio signal, the third audio signal, the seventh audio signal, the ninth audio signal, the eleventh audio signal, and the output of the third delay circuit and output the fifth audio signal; and

the fourth mixer is configured to mix the second audio signal, the fourth audio signal, the eighth audio signal, the tenth audio signal, the twelfth audio signal, and the output of the third delay circuit and output the sixth audio signal.

15. A method performed by an information processing apparatus, the method comprising:

receiving, at a first head related transfer function (HRTF) filter, a monaural audio signal and generating a first channel output signal using a first head related transfer function describing a change in sound at a right eardrum caused when a sound occurs from a first direction;

receiving, at a second HRTF filter, the monaural audio signal and generating a second channel output signal using a second head related transfer function describing a change in sound at a left eardrum caused when a sound occurs from the first direction;

cutting, by a first low-pass filter, high frequency components of the monaural audio signal and passing low frequency components of the monaural signal;

delaying, by a first delay circuit, an output of the first low-pass filter by a first delay amount;

cutting, by a second low-pass filter, high frequency components of the monaural audio signal and passing low frequency components of the monaural signal;

delaying, by a second delay circuit, an output of the second low-pass filter by a second delay amount;

mixing, by a first mixer, an output of the first HRTF filter and an output of the first delay circuit and output a first audio signal; and

mixing, by a second mixer, an output of the second HRTF filter and an output of the second delay circuit and output a second audio signal, wherein

a difference between the first delay amount and the second delay amount is set such that a second direction of localization caused by the difference between the first delay amount and the second delay amount coincides with the first direction of the first HRTF filter and the second HRTF filter.