A speaker box is covered with a buffer material exclusive of a portion where
an
acoustic output is derived from a speaker unit. The speaker box covered with the
buffer material is attached to the surface of a wall member such as an interior
member of a vehicle body or a side plate outside the vehicle body in a manner the
speaker box is pressed by a holding member, which is a part of the interior member
or designed member, and secured by bolts. Even when the surface of the speaker
box is vibrated, the buffer material prevents an acoustic output due to the vibration
from being generated so that no unnecessary acoustic signal is generated.
