Alert device and method

Abstract

An alert device and method include an elongated cavity (306) and a loudspeaker (302) coupled to a first end portion of the cavity wherein sound produced by the loudspeaker is directed through the cavity to provide an audible sound. The cavity and the loudspeaker are configured and dimensioned to provide the audible sound substantially at an anti-resonant frequency (Fb) between first and second resonant frequency peaks for system impedance in a response spectrum for the loudspeaker and the cavity.

Description

technical field [0001] This disclosure relates to alarm devices and methods, and more particularly to a lightweight, small and low cost efficient speaker siren with improved audibility. Background technique [0002] Typical fire alarms, and those used in homes in particular, are small devices designed to warn people of fire or other hazardous conditions such as smoke or high concentrations of carbon monoxide. A traditional design consists of a cylindrically shaped siren with a sensor and speaker on the front (face). Such designs typically have a thickness of about 10-15 cm, although this can vary from design to design. The sound generator or speaker of these devices is usually a piezoelectric disk because it is compact and inexpensive. A typical acoustic response of a conventional fire alarm / smoke detector device is shown in FIG. 1 . [0003] Referring to Figure 1, a normalized frequency spectrum is shown where sound pressure level (SPL in dB) is plotted against frequency...

AI Technical Summary

Problems solved by technology

One problem with the sound wave generator of a traditional siren is that the main frequency is usually around 3kHz and this main frequency is so high that it is easily attenuated (damped) by walls and doors

Such traditional designs mainly utilize piezo disks with the disadvantages mentioned above, or employ loudspeakers mounted in (folded) horns, which suffer from the same limitations

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