PURPOSE: To form a comfortable sound space by improving a muffling effect in an optionally selected space.

CONSTITUTION: A cabin 2 as a prescribed space of a vehicle 1 is divided into divided areas 9FL-9RR contained seats 8FL-8RR, and in each divided area 9FL-9RR, microphones 6FL-6RR being residual noise detecting means are placed, and also, in the cabin 2, loudspeakers 5a, 5b as control sound sources are placed, and moreover, selection switches 10FL-10RR for arbitrarily selecting a divided area are placed. In such a state, by reducing the gain of residual noise detecting signals e1-e4 outputted from the microphone in the area except the divided area selected by the selection switch, by a controller 15, the gain and the phase of a control sound outputted from the loudspeakers 5a, 5b are changed, a muffling effect of the selected divided area is made larger than that in the case of extending a muffling effect over the whole car room, and a comfortable separate sound space is formed.