Sound Processing Apparatus, Sound System and Sound Processing Method

A sound system comprising:

• a first speaker in which a lower limit value of a reproduction band is set to be a first frequency;
• a second speaker in which a lower limit value of a reproduction band is set to be a second frequency beyond the first frequency;
• and
• a sound processing apparatus which generates a first sound signal to be supplied to the first speaker and a second sound signal to be supplied to the second speaker, wherein
• the sound processing apparatus includes
• a first adjustor which adjusts a volume of the first sound signal,
• a second adjustor which adjusts a volume of the second sound signal, and
• a control unit which causes the first adjustor and the second adjustor to adjust the first sound signal gradually changed over a first gradually-change time and the second sound signal gradually changed over a second gradually-change time, wherein the second gradually-change time is shorter than and included in the first gradually-change time.