| 摘要 |
Low frequency alarm tones emitted by life safety devices are more likely to notify sleeping children and the elderly. Disclosed herein is a life safety device equipped with a novel, compact, circumferential resonant cavity which increases the low frequency (400-600 Hz square wave) acoustic efficiency of an audio output apparatus formed by acoustically coupling an audio output transducer to the resonant cavity. The resonant cavity is a compact circumferential acoustic resonator with a captured mass of air within a ring shaped cavity significantly reducing the overall size of the resonator, thereby permitting the audio output apparatus to fit within the housing of conventional size life safety devices such as, but not limited to, residential and commercial smoke alarms and carbon monoxide alarms. The compact resonator is an acoustic compliant cavity with internal passages transforming axial traveling sound waves to circumferentially traveling sound waves thereby yielding a very compact geometry. |
| 主权项 |
1. A life safety device comprising:
electronic control circuitry; a sensor connected to the electronic circuitry; an audio output apparatus comprising an audio output transducer acoustically coupled to a compact circumferential acoustic resonator; the electronic circuitry drives the audio output apparatus to emit a tone when the sensor senses an environmental condition; the compact circumferential acoustic resonator comprises a transducer coupling port and a ring-shaped cavity, having a proximal end and a distal end, wherein axial acoustic waves emitted from the audio output transducer traverse a transducer coupling port and are directed through the radial port into the ring-shaped cavity where the axial acoustic waves are transformed into tangential acoustic waves; the tangential acoustic waves reflect off a node forming wall at the distal end of the ring shaped cavity, the node forming wall oriented perpendicular to direction of motion of the tangential acoustic waves; and the sensor comprises one of a smoke sensor, a carbon monoxide sensor, a natural gas sensor, an intrusion sensor, a glass break sensor, a temperature sensor, or a vibration sensor. |
