Patent ID: 8525689

Claim:
An alarm device, comprising: a detector configured to detect an alarm condition and generate a detection signal; an alarm signal generation circuit configured to receive the detection signal from the detector and, in response, generate an alarm signal having a fundamental alarm signal frequency and a plurality of harmonic frequencies; and a speaker assembly comprising a speaker coupled to an enclosure and configured to receive the alarm signal, the speaker having a diaphragm that is driven by a coil to produce sound waves, the enclosure having walls that define an enclosure volume, the speaker assembly configured to have a fundamental resonance frequency that is substantially equal to the fundamental alarm signal frequency, said fundamental resonance frequency being dependent upon dimensions of the enclosure, the speaker assembly as a whole configured such that an audible output of the speaker assembly at the fundamental alarm signal frequency is boosted at least partly as a result of a transfer of energy from at least one of the harmonic frequencies to the fundamental alarm signal frequency, wherein the enclosure is a sealed enclosure, such that said audible output boost at the fundamental alarm signal frequency is achieved without reliance on a Helmholtz effect.