Sound output device

1. A sound output device for masking an operation sound generated by equipment, the sound output device comprising:

a memory unit that stores, in advance, a plurality of masking sounds corresponding to operation sounds generated in a plurality of operation modes that are executable by the equipment, respectively, each of the masking sounds changing in sound pressure level over time in correspondence with each of said corresponding operation sounds;

an operation determining unit that determines which of the operation modes is to be executed by the equipment;

a selecting unit that selects at least one of the masking sounds stored in the memory unit in advance, based on the operation mode determined by the operation determining unit;

a sound reproducing unit that reads the selected masking sound from the memory unit; and

a sound output unit that outputs the selected masking sound read by the sound reproducing unit from the memory unit,

wherein:

the sound output unit outputs the masking sounds corresponding to respective operation modes determined by the operation determining unit, the masking sounds changing differently in sound pressure level over time,

wherein the selecting unit selects, from among the masking sounds stored in the memory unit, the masking sound corresponding to the operation mode determined by the operation determining unit, and the sound reproducing unit reads the selected masking sound from the memory unit, and causes the sound output unit to output the read masking sound, and

wherein the selecting unit selects a plurality of the masking sounds from the memory unit, based on operation modes determined by the operation determining unit, and the sound reproducing unit reads the selected plurality of the masking sounds from the memory unit and causes the sound output unit to output said plurality of the masking sounds.

2. The sound output device according to claim 1 , wherein the masking sounds stored in advance in the memory unit further change in frequency over time.

3. The sound output device according to claim 1 , wherein the operation determining unit determines the operation mode to be executed by the equipment based on a user operation or a status of the equipment.

4. The sound output device according to claim 1 , wherein when the operation mode determined by the operation determining unit changes while the sound output unit is outputting a masking sound, the selecting unit selects another masking sound corresponding to the current operation mode from the memory unit, and the sound reproducing unit reads said selected another masking sound from the memory unit and causes the sound output unit to output said another masking sound.

5. The sound output device according to claim 1 , wherein the equipment is an image forming apparatus.

6. The sound output device according to claim 1 , wherein the equipment is peripheral equipment of an image forming apparatus.

7. A sound output device for masking an operation sound generated by equipment, the sound output device comprising:

a memory unit that stores, in advance, a plurality of masking sounds corresponding to operation sounds generated in a plurality of operation modes that are executable by the equipment, respectively, each of the masking sounds changing in sound pressure level over time in correspondence with each of said corresponding operation sounds;

an operation determining unit that determines which of the operation modes is to be executed by the equipment;

a selecting unit that selects at least one of the masking sounds stored in the memory unit in advance, based on the operation mode determined by the operation determining unit;

a sound reproducing unit that reads the selected masking sound from the memory unit; and

a sound output unit that outputs the selected masking sound read by the sound reproducing unit from the memory unit,

wherein:

the selecting unit selects two or more of the plurality of masking sounds stored in the memory unit in advance, based on the operation mode determined by the operation determining unit; and

the sound reproducing unit causes the sound output unit to output the selected two or more masking sounds in combination.

8. The sound output device according to claim 1 , wherein the plurality of masking sounds stored in the memory unit in advance change in sound pressure levels over time in different manners, respectively.

9. The sound output device according to claim 1 , wherein the plurality of operation modes executable by the equipment correspond to operations that can be performed by the equipment, respectively.

10. A sound output device for masking an operation sound generated by equipment, the sound output device comprising:

a memory unit that stores, in advance, a plurality of masking sounds corresponding to operation sounds generated in a plurality of operation modes that are executable by the equipment, respectively, each of the masking sounds changing in sound pressure level over time in correspondence with each of said corresponding operation sounds;

an operation determining unit that determines which of the operation modes is to be executed by the equipment;

a selecting unit that selects at least one of the masking sounds stored in the memory unit in advance, based on the operation mode determined by the operation determining unit;

a sound reproducing unit that reads the selected masking sound from the memory unit; and

a sound output unit that outputs the selected masking sound read by the sound reproducing unit from the memory unit,

wherein the memory unit stores, in advance, a combined masking sound corresponding to two or more of the masking sounds which respectively correspond to operations modes which are executable by the equipment concurrently, the combined masking sound having a sound pressure level which is optimized relative to the sound pressure levels of the corresponding two or more masking sounds.