Fire or smoke detector with integral alarm signal and two acoustic cavities

摘要

A detector 10 for detecting fires or smoke comprises: a housing 20 defining a transducer receiving portion 50; a transducer 40, such as a piezo disc, received within the housing 20 adjacent the transducer receiving portion 50; a first reflector plate 60 with an aperture 65 and being spatially separated from the transducer 40 to define a first acoustic cavity 70 therebetween; and a second reflector plate spatially separated from the first reflector plate 60 and located distal to the transducer 40 to define a second acoustic cavity 80 between the first and second reflector plates. The housing 20 defines one or more sound apertures 90 in connection with the second acoustic cavity 80 through which sound is emitted. The transducer receiving portion 50 may comprise spatial separators located next to the first reflector plate 60 in the periphery of the transducer 40. The transducer 40 and first reflector plate 60 are preferably separated by less than 3mm.