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Comment by kazinator | Hacker News Reader

If you're locating a chirper by sound, you're not seriously impaired by the lights being out.

Also, you could use a spotlight. If you shine the spotlight somewhere and the chirp stops or changes, search that area.

I think you’re assuming too much from the description. In order to be evil, when it’s chirping, the chirps are many minutes apart, not continuous.

That's the main factor then.

If you're relying on sight to find it, then it's irrelevant whether it makes a sound.

If you're relying on sound, you're impeded by the infrequent occurrence. That's would still be the case if the chirping went on with the lights on.

If the chirping requires near total darkness, because then to search by sound you have to go through the trouble of covering the windows (with something more than the blinds or curtains, if there are any) or else you're restricted too searching by sound only in the night hours, and doing a visual sweep by day or lamplight.

(But then the device only chirps in near total darkness, it may be defeated by a relatively dim night light.)

It's very difficult to accurately locate the direction of a high pitched chirp sound. The frequency makes a ton of difference here.

This is only true of a periodic sound. This is because when the wavelength is smaller than the distance between the ears, there is aliasing in the phase information (ambiguity). However, the overall group delay is perceptible at the onset and cessation of the tone. That doesn't give you much time to latch on to the direction. At high frequencies, though, level differences are useful. You know which ear is facing that chirp and which isn't.

I've found that particularly high pitched sounds can bounce of hard/flat surfaces very well.

It is possible to find it with a bit of hardware like a microphone. Very easily by taking multiple level measurement and some multilateration.

It gets hard when there is more than one.

The problem with identifying it by ear is that you get already some 20-30 cm precision at best unless you've trained in echolocation like some blind people. For such a small device it could well be a whole room.

Ok. We'll get you to clear any further pranks so you can tell us what's funny before we go and do anything rash such as trying to have some fun.

Shut it all down guys, kazinator will take over from here.

What?

He's just saying it's not that hard to determine the location of a chirping sound.

Not whether it's funny or not.

Whoosh.

>If you're locating a chirper by sound, you're not seriously impaired by the lights being out.

Even if you're locating it by sound, you probably don't want to stumble around in the dark while you're trying to find it. So you turn on the lights, and you can't find it because it stopped chirping. Then after you turn off the lights, it starts back up, so you turn the lights back on, etc.

It will stop chirping whether or not you turn on the lights, and then not chirp again for a number of minutes. Unless it is pitch dark, you're not really stumbling; people can find their way around in dark rooms. The searcher can reduce stumbling by tidying the room and possibly even removing some items such as chairs and whatever.

If they are doing those things, I’d say the prank was successful.

I never said the prank is unsuccessful, only that darkness doesn't make it harder to find something by ear. Hearing is hearing, sight is sight.

In the past, I have had a hard time finding by ear which switching power supply in a lab is giving off a squeal.

Seeing the power supplies was of no help; it might as well have been dark.

Basically the "off when the lights are on" aspect just confounds people initially when they don't know that this is the case. They hear something in the dark. They hear it beep again some time later, and then again. They turn on the lights to go looking for it. Unbeknownst to them, doing so deactivates it. It takes time to learn that the chirping is related to it being dark. Once they realize that, it makes next to no difference.

It's still not a bad prank without that embellishment.

Fair enough, you didn’t say that. I just think we disagree on how easy it would be to track this thing down in the dark.

I have a bearded dragon, so I know what it’s like to have loose crickets chirping in your house and having no idea where it’s coming from. Like others have said, the nature of the sound makes it harder to locate.

This is like hunting mosquitoes. You get a couple, turn the lights off, then lie down. Only to hear yet more mosquitoes.

There should be an app that allows one to triangulate sound sources to locate these darn things ..

Not that hard to do: sample the sound using multiple microphones, discard anything after the first thing you get (usually they're misleading reflections), then measure the delay to build a map of vectors pointing to the object. The military already have devices using that principle to locate the sound source of a weapon firing to send it a bomb. The RF variant is also employed in air traffic control and to detect pirate radio transmissions and uses arrays of omnidirectional antennas just like this one: https://cdn.everythingrf.com/live/direction_finders_teaser_o... Although military smaller ones are usually protected from casual view using dome-like covers.

Never change, HN.

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