Communications: electrical – Audible indication – Ultrasonic pest control
Patent
1986-10-10
1988-08-30
Caldwell, Sr., John W.
Communications: electrical
Audible indication
Ultrasonic pest control
340521, G08B 300
Patent
active
047680229
ABSTRACT:
Existing auditory warning systems are in general too loud and it is often difficult to distinguish between a number of different warnings. Further under different conditions warnings may change character due to masking by varying noise. A warning system is disclosed which is based on a microprocessor and waveforms for each warning sound stored in a ROM. The waveforms are read out to DACs and used to drive a loudspeaker by way of programmable attenuators. Each waveform is devised to have at least four quasi-harmonically related frequency components at a power level in the range 15 to 30 dB above threshold. In this way the sounds are distinctive and do not change character with varying noise levels below threshold.
REFERENCES:
patent: 3504364 (1970-03-01), Abel
patent: 4090349 (1978-05-01), Takase
patent: 4644327 (1987-02-01), Patterson et al.
"Programmable Doorbell" Elector, vol. 5, No. 6, Jun. 1979, pp. 6-12 to 6-16.
"The appropriate Sound for Auditory Warnings on Civil Aircraft"; Prepared at Meeting of Acoustical Soc. of America; Atlanta Ga.
Caldwell Sr. John W.
National Research Development Corporation
Queen Tyrone
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