To inhibit generation of abnormal sound by preventing a protruding directions of respective bend portions 43, 44 of a root portion of a first, second polygon annular rib 7 provided at a second, fifth thin film portion 5 of an inner duct 4 from rapidly reversing.
In respective vibrating surfaces of a second, fifth thin film portion 5 provided at an inner duct (vibrating film) 4, a shape when seeing a first, second polygon annular rib 7, in particular, respective bend portions 43, 44 of a root portion of a second, fifth protrusion rib, from a perpendicular direction orthogonal to respective vibrating surfaces of the second, fifth thin film portion 5, is shaped to include protrusion portions 51, 52 protruding toward the outside from the both slant portions of the second, fifth protrusion rib. Alternatively, planar views of respective bend portions 45, 46 of the root portion of the first, second polygon annular rib 7 is waveform shaped extending meandering in wave shape in vertical direction substantially orthogonal to a plurality of first to sixth flexion portion 6.
YAMAMOTO TAKAO
NISHIO YOSHITAKA
NAKAYAMA TOSHIAKI
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