Its entry through the speakers of an emergency. His tone is very strong but high. There is a tornado or fire siren. If you tastes like dog whistles, or mechanical mosquito repellent? Only the high-pitched noise that only some people can hear. Except it was just the correct frequency know that nobody could hear. What is? What were they doing?

One problem with the system. It could be interference power somewhere between the dispatch center where the normal controls and speakers, or it could be a defect in the equipment. Unless the team's location speaker is completely off, which can cause noise, ground loops are bothersome. Taking an AM radio batteries out near one of the speakers is possible to collect this or any other source of noise as well. It would not hurt to take the matter to the local unit of government, talk to a coordinator or administrator of the city and raise concerns, and if you can capture the sound of an AM radio near one, a check of a few to be sure, but if you can pick something up that can be audible almost everywhere in the world, you will get your attention, and is likely to repair. The problem is that if you have something you can show or demonstrate to them, it is likely you politely ignore. It may just be the system is accelerating and expanding the portion of the PWM power supply likely to be in use. You may just need some additional RF shielding. But in any case, the power that is increasingly consumed by the city or county and is paying for that probably should not necessary.

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