Signal processing device, sound-reproduction system, and sound reproduction method for enhancing attractiveness or recognition of a sound, such as an engine sound

1. A signal processing device comprising:

a processor; and

a memory including instructions that, when executed by the processor, cause the signal processing device to perform operations, the operations comprising:

performing a modulation processing of modulating a sound signal by using a modulation parameter based on an interaural phase difference at a listening position of the sound signal,

wherein the modulation parameter comprises a frequency shift amount, and

wherein the operations further comprise increasing the frequency shift amount in the modulation processing in a case in which an absolute value of the interaural phase difference is larger than a predetermined value.

2. The signal processing device according to claim 1 ,

wherein the operations further comprise reducing the frequency shift amount in the modulation processing in a case in which the absolute value of the interaural phase difference is smaller than the predetermined value.

3. The signal processing device according to claim 1 ,

wherein the frequency shift amount comprises a modulation width representing a frequency width to be changed.

4. The signal processing device according to claim 1 ,

wherein the frequency shift amount comprises a modulation period representing a period to be changed.

5. The signal processing device according to claim 1 ,

wherein the frequency shift amount comprises a modulation amplitude representing a signal level width to be changed.

6. The signal processing device according to claim 1 ,

wherein the operations further comprise a phase adjustment on a sound signal that has not been subjected to the modulation processing or the sound signal that has been subjected to the modulation processing.

7. The signal processing device according to claim 6 ,

wherein the modulation parameter comprises a parameter based on the interaural phase difference after the phase adjustment.

8. The signal processing device according to claim 6 ,

wherein the operations further comprise turning off the modulation processing in a case in which the absolute value of the interaural phase difference after the phase adjustment is equal to or larger than a predetermined threshold.

9. The signal processing device according to claim 1 ,

wherein the sound signal is a pseudo engine sound, and

wherein the operations further comprise adjusting the modulation parameter based on vehicle information on generation of the pseudo engine sound.

10. The signal processing device according to claim 9 ,

wherein the vehicle information comprises a change amount of a rotational speed of an engine, and

wherein the operations further comprise:

providing no upper limit for the modulation parameter in a case in which the change amount is larger than a threshold; and

providing the upper limit for the modulation parameter in a case in which the change amount is equal to or smaller than the threshold.

11. The signal processing device according to claim 9 ,

wherein the vehicle information comprises a magnitude of a torque of an engine, and

wherein the operations further comprise:

providing no upper limit for the modulation parameter in a case in which the magnitude is larger than a threshold; and

providing the upper limit for the modulation parameter in a case in which the magnitude is equal to or smaller than the threshold.

12. The signal processing device according to claim 9 ,

wherein the vehicle information comprises a change amount of a vehicle speed, and

wherein the operations further comprise reducing the modulation parameter in a case in which the change amount is smaller than a second predetermined value.

13. The signal processing device according to claim 9 ,

wherein the vehicle information comprises a change amount of a rotational speed of an engine, and

wherein the operations further comprise turning off the modulation processing in a case in which the rotational speed is constant for a predetermined time.

14. The signal processing device according to claim 1 ,

wherein the modulation processing is performed on a frequency band in accordance with characteristics of the interaural phase difference.

15. The signal processing device according to claim 1 , further comprising:

a storage,

wherein the operations further comprise reading out the modulation parameter from the storage.

16. A sound reproduction method for reproducing a sound signal, the sound reproduction method comprising:

performing a signal processing, the signal processing comprising a modulation processing of modulating the sound signal by using a modulation parameter based on an interaural phase difference at a listening position of the sound signal; and

outputting the sound signal subjected to the signal processing via an output device,

wherein the modulation parameter comprises a frequency shift amount, and

the signal processing further comprises increasing the frequency shift amount in the modulation processing in a case in which an absolute value of the interaural phase difference is larger than a predetermined value.

17. A signal processing device comprising:

a processor; and

a memory including instructions that, when executed by the processor, cause the signal processing device to perform operations, the operations comprising:

performing a modulation processing of modulating a sound signal by using a modulation parameter based on an interaural phase difference at a listening position of the sound signal,

wherein the modulation parameter comprises a frequency shift amount, and

the operations further comprise reducing the frequency shift amount in the modulation processing in a case in which an absolute value of the interaural phase difference is smaller than a predetermined value.