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 (S1) and an off-cabin space (S2) 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 (G); 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 (G) together with a portion of the bobbin ; and a rear cover member defining an air chamber (S) 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 (S2), wherein the bobbin around which the voice coil is wound and the magnetic circuit are configured to be positioned in the in-cabin space (S1) across the diaphragm from the direction of the air chamber (S); the apparatus being characterized in that an air course between the air chamber (S) and the in-cabin space (S1) 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 (S1) and an off-cabin space (S2) 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 (G); 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 (G) together with a portion of the bobbin ; and a rear cover member defining an air chamber (S) 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 (S2), wherein the bobbin around which the voice coil is wound and the magnetic circuit are configured to be positioned in the in-cabin space (S1) across the diaphragm from the direction of the air chamber (S); the apparatus being characterized in that an air course between the air chamber (S) and the in-cabin space (S1) 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. <EOS>