A display apparatus is provided which optimally restores decreased luminance and extends a life of a light emitting element. An audio system has a first audio signal and a second audio signal that have amplitudes. The communication passage 9 is intermediately provided with a separable portion for suitable separate-off, and the casing 8 for the selective reduction catalyst 6 is supported by a frame 15 on a vehicle body independently of the casing 7 for the particulate filter 5.