| 摘要 |
The outdoor alerting and warning device of this invention comprises numerous electronic drivers and an axially shallow drum-shaped resonance chamber having an inside diameter equal to a whole-number multiple of one-quarter of the wavelength of a sound wave of predetermined frequency. The drivers are mounted on the exterior of the resonance chamber, on its peripheral portion at regular circumferential intervals around it, with their ports opening into its interior. A coaxial outlet port in one end wall of the resonance chamber, having an area of between one-half and two times the total of driver port areas, opens into the throat of a horn; or each end wall may have such an outlet port, each opening into a horn throat.
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