An acoustic apparatus for mounting in a vehicle including: a frame including an annular portion and a supporting portion extending from the annular portion, the frame being attachable to an opening provided in a partition plate that separates an in-cabin space and an off-cabin space of a vehicle from each other; a diaphragm vibratorily supported on an inner side of the annular portion; a magnetic circuit supported by the supporting portion and having a magnetic gap; a bobbin having a cylindrical shape and provided on the diaphragm such that one end of the bobbin projects from one of two vibration surfaces of the diaphragm; a voice coil wound around a peripheral face of the bobbin and positioned in the magnetic gap together with a portion of the bobbin; and a rear cover member defining an air chamber provided between the rear cover member and the diaphragm, the rear cover member being vibratorily supported and configured to conduct back pressure to the off-cabin space, wherein the bobbin around which the voice coil is wound and the magnetic circuit are configured to be positioned in the in-cabin space across the diaphragm from the direction of the air chamber; the apparatus being characterized in that an air course between the air chamber and the in-cabin space follows a route passing through a space on an inner side of the bobbin; the diaphragm has a through hole that defines a portion of the air course; the diaphragm includes a reinforcing member provided on one of the two vibration surfaces of the diaphragm that is on a side opposite a side from which the bobbin projects, the reinforcing member being provided around the through hole of the diaphragm and having a vent hole that further defines the portion of the air course. a frame including an annular portion and a supporting portion extending from the annular portion, the frame being attachable to an opening provided in a partition plate that separates an in-cabin space and an off-cabin space of a vehicle from each other; a diaphragm vibratorily supported on an inner side of the annular portion; a magnetic circuit supported by the supporting portion and having a magnetic gap; a bobbin having a cylindrical shape and provided on the diaphragm such that one end of the bobbin projects from one of two vibration surfaces of the diaphragm; a voice coil wound around a peripheral face of the bobbin and positioned in the magnetic gap together with a portion of the bobbin; and a rear cover member defining an air chamber provided between the rear cover member and the diaphragm, the rear cover member being vibratorily supported and configured to conduct back pressure to the off-cabin space, wherein the bobbin around which the voice coil is wound and the magnetic circuit are configured to be positioned in the in-cabin space across the diaphragm from the direction of the air chamber; the apparatus being characterized in that an air course between the air chamber and the in-cabin space follows a route passing through a space on an inner side of the bobbin; the diaphragm has a through hole that defines a portion of the air course; the diaphragm includes a reinforcing member provided on one of the two vibration surfaces of the diaphragm that is on a side opposite a side from which the bobbin projects, the reinforcing member being provided around the through hole of the diaphragm and having a vent hole that further defines the portion of the air course.