If I had a device that could use sound waves, or sonar, or echolocation (which I assume are all the same thing…right?) to locate stuff, could someone interfere with that device by making a loud noise like shouting, firing a gun, or turning the television up really loudly? Similarly, if a bat is hunting, would its sonar ability be interrupted by frequent loud noises such as gunshots, or would it still be able to “see” the insect it wants to eat?
Nothing scientific <sorry> but think about talking to someone in a noisy room, your brain can filter out the unwanted noise to allow you to continue the conversation. Up to a point anyway, eg. a loud night club.
as you might expect, yes and no.
Since almost all the research in this area has been in underwater acoustics, let us discuss that area. I realize you seem to be thinking of echolocation in the air (television…), but there is much less research and few applications in the air.
The ocean is even noisier than the air. Sound travels much further. So the typical practice is to correlate received sound with known targets. A discrete loud sound, a shout (think whales), a loud explosion, will fade away and not interfere with detection. A continuous loud sound can be a problem. Detection is much harder in shallow water than in deep water, partly because of the higher levels of ambient noise in shallow water. But it is certainly possible to detect things in the water in the presence of noise. A sonar can be at a single frequency. Rather like a laser on a sunny day. The laser isn’t nearly as bright as the sun, but at the single frequency it might be brighter than the sun at that frequency. So noise can interfere, but that is a problem that has been extensively studied and there are ways around it. Remember, the additional interference you are contemplating is likely to only be a small part of the total noise field. Reflections and refractions are considerably more of a problem. Also extensively studied.
To reiterate what rbroome said…
Devices and animals that use sound for ranging or speed measurements typically use only a small part of the acoustic “spectrum”. Humans hear frequencies about 20 to 20000 Hz. The part of the spectrum useful for sonar is typically much higher. What you think of as noise that’s loud to our ears, is often not so loud in the used sonar spectrum. Add in the ability to “tune in” to certain frequencies (like the example SunSandSuffering gave) and noise is not usually a problem.
Noise is typically not as much a problem as interference is. For example, the Navy has sonar systems that use the same frequencies that whales use. And since the sonar systems are much louder than whales are, they can be a real hazard to them. (There’s been lawsuits about this. Civilian vessels have strict rules about sonar usage, going so far as having professional whale watchers with kill switches on the sonars to prevent deafening them. Military ships have fewer restrictions.)
On the other hand, some of the most complete databases of whale vocalizations are from Navy data that was recorded for other purposes, but happened to be in the acoustic band that whales use.
First, an on topic response followed by related, interesting, response in regards to US Navy sonar, from what I know from first-hand experience.
On topic response:
As someone who had the joyeous of joys of working on a typical depth sounder for navigating into and out of ports. Noise can be a huge factor. Being close to other boats using depth sounding, fishing vessels, silty bottoms, shallow bottoms, turbulent water… all these can and will affect the sonar to some degree. Sometimes making it totally useless. If you were to connect a spectrum analyzer to the, forgot the real term, underwater microphone, you can see the noise floor increase as you get to more active areas. With occasional clear signs of interference. And, see things from splashes, gunfire hitting water (target practice on buoys, etc. Most are not within the range of sonar but can raise the noise floor.
OT Response:
Carriers and the like use a standard depth sounder which sends out a series of pulses, waits for the return, calculates depth. It’s a pretty old and ancient system. So old you would gasp!
There are higher resolution sonar used by the USN for mapping of the sea floor. They use a much more advanced sonar system that probably does not interfere with marine mammals. As the system they use is a commercial system with those considerations.
The smaller ships, like frigates, have the sonar that is designed for locating targets underwater. It is usually in “listen” mode as once you fire it up, whomever you are targeting is going to hear you. Assuming that they don’t have the ancient system from above, they might use that one for navigating in and out of a port. But, there is going to be so many ships being active, sonar and otherwise, that I doubt whales would venture in there.
As for the systems that interfere with whales… that is in debate. Not because I was in the Navy but because the Navy system that was blamed was tested on the west coast and the whales that beached themselves due to sonar where on the east. The news media just put stuff together and went with it. It was, however, determined that the cause of whales freaking out from sonar where from really, really, old ship using a very old system of sonar, older than what the USN uses. The sonar system was not necessarily loud but had a lot of noise to it. Not, a nice, pure monotone pulse. And, maybe the ship was in shallow water and that’s why the whales went nuts.
Needless to say, with literally 10’s of thousands of miles of ocean under my belt. And, as someone who was an operator/maintainer of our sonar system, which was on when ever we over the shelf. We would routinely have dolphin pods swim with us and the occasional whale pod swim with is. All the while, our sonar firing away. Even when we were grouped with the small boys, which would have the higher power sonar, we saw them.
Thanks for the responses! I will consider my ignorance fought.