Speaker enclosure design for efficiently generating an audible alert signal

摘要

Various inventive features are disclosed for efficiently generating regulation-compliant audible alerts, including but not limited to 520 Hz square wave alert/alarm signals, using an audio speaker. One such feature involves the use of a non-linear amplifier in combination with a voltage boost regulator to efficiently drive the audio speaker. Another feature involves speaker enclosure designs that effectively boost the output of the audio speaker, particularly at relatively low frequencies. Some of the disclosed speaker enclosure designs rely on an interference effect and/or a resonance effect to transfer energy from higher-order harmonics downward to the fundamental frequency and lower-order harmonics. These and other features may be used individually or combination in a given alarm-generation device or system to enable regulation-compliant audible alerts to be generated using conventional batteries, such as AA alkaline batteries.

主权项

1. An alarm device, comprising:
a sealed speaker enclosure assembly comprising a tubular section, a loudspeaker mounted at one end of and facing outward from the tubular section, and a substantially flat plate that encloses an opposite end of the tubular section, such that a sealed enclosure volume is defined within the tubular section, said loudspeaker comprising a diaphragm driven by a coil; and an alarm signal generation circuit that drives the loudspeaker with an alarm signal that comprises a fundamental frequency and multiple harmonics, said multiple harmonics including a set of low-order harmonics at frequencies above the fundamental frequency and a set of higher-order harmonics at frequencies above the frequencies of the low-order harmonics, said fundamental frequency falling in the range of 400 to 700 hertz; said speaker enclosure assembly configured to cause energy in the second set of higher-order harmonics to be transferred downward in frequency to the fundamental frequency and the set of lower-order harmonics, said transfer caused at least partly by an interference effect in which waves emitted from a rear of the loudspeaker into the tubular section are reflected by the substantially flat plate, causing constructive or destructive interference with waves emitted from a front of the loudspeaker.