Should I have cause for concern? …

Heard it about 9am this morning and its still going on now at 2am although its got louder. Sonic youth: The high-pitched sound alarm for under 25s. To detect the presence of such a signal you’ll need some kind of ultrasonic detector.

There's this high pitched beep that goes off every thirty seconds in the house next to mine. Jamie Merrill sounds it out .

Dog repellers I’ve seen typically output ultrasonic squarewaves just above the audiable frequency (30–40kHz). We have a high pitched buzzing/humming type noise in our house and we cannot tell where it is coming from. Just wondering if its a fire/CO alarm of some sort? Sometimes you can hear it during the day but it is the type of noise that you really have to focus on to hear but when you hear it it is really annoying. It is louder at night and seems to be worse on some nights than others. Experts say that sufferers can become convinced their neighbours are vacuuming or using washing machines because of the high-pitched noises and then call in noise … It's pretty loud. Originally launched back in 2005, the device emitted a high pitched annoying noise that could only be heard by those under 25 (or thereabouts). Is Mosquito, the high-pitched alarm only under-25s can hear, a blessing or a bane? Michael Mitchell, 66, and his wife Kathryn, 52, have been threatened with legal action by the local council after their neighbours complained. No ones stopped it. It's just loud enough to bug me.
Or fire alarm dying batteries?