Different Loudness Sound Waves and Destructive Inteference

[Just a dude]

Summary:: Can smaller volume sound waves completely cancel out larger volume sound waves, and if not to what degree will the larger sound be canceled out.

Hello everyone, just had a question regarding destructive interference.

So I am in the process of writing/designing a sci-fi/fantasy power system and I am now working on the detection/sensing scheme (determining the presence or location of targets) and thought to base my idea on sound theory. The idea I'm working on is that users of said power system passively emit their own unique wave that travels throughout an area and bounces back when it hits the source of another wave to alert them to the position of another user. I was also hoping to create a method in which people who want to stay hidden can use to avoid detection and thought to use destructive inteference as a potential model, where the target can stay hidden by sending out an identical, but opposite wave over an area that cancels out the signal. Note that this is intended to work over large regions such as countries or continents.

In the power system I created the more powerful individuals send out waves with more volume and weaker individuals send out lower volume waves, and I intend for even weaker individuals to have the ability to stay hidden, but I'm not sure how effective it will be in doing so and want to keep things somewhat logically sound.

My question is does can lower volume waves cancel out larger volume waves completely, and if not, to what degree is the cancellation when destructive interference occurs?

 

[chemisttree]

My question is does can lower volume waves cancel out larger volume waves completely, and if not, to what degree is the cancellation when destructive interference occurs?

No. Lower volume sound would merely modulate the louder sound wave.

 

[sophiecentaur]

It is a feasible theoretical situation to have a number of low intensity sources of waves to cause cancellation of the waves from a single high intensity source.
You can apply the basic equations for diffraction / interference of multiple sources. The contributions of the vectors from all sources can add up to zero BUT the region where this can be achieved is very small and (of course) very sensitive to the frequency being used. In practice, sound is a very poor wave example for this to work because the propagation through the air is extremely variable - much worse than radio frequency EM waves - and the existence of objects along the path - makes it a very bad system.

 

[Just a dude]

It is a feasible theoretical situation to have a number of low intensity sources of waves to cause cancellation of the waves from a single high intensity source.
You can apply the basic equations for diffraction / interference of multiple sources. The contributions of the vectors from all sources can add up to zero BUT the region where this can be achieved is very small and (of course) very sensitive to the frequency being used. In practice, sound is a very poor wave example for this to work because the propagation through the air is extremely variable - much worse than radio frequency EM waves - and the existence of objects along the path - makes it a very bad system.

So because since a single low intensity wave itself can't completely cancel out a single high intensity wave a possible solution is to use several smaller ones to achieve the same thing? Yeah ok, I can get behind that.

The wave itself is not actually sound (honestly haven't even thought of what it is) I just thought using those properties would work well. Also the wave itself passes through all objects except those who also emit waves of the same kind, so it should ignore everything else.

I appreciate the feedback btw, is there anything else I can keep in mind or improve on?

 

[sophiecentaur]

is there anything else I can keep in mind or improve on?

You would really need to introduce a different form of wave that is, as yet, unknown. Your model is a bit 'open' at the moment but you should really be asking what sort of accuracy of 'location' is required and how your waves will interact with the 'receiver' and the other items in the environment. You are talking quasi engineering so the rules of engineering apply to some extent.

Having though a bit more about your idea, I realize that you don't actually need to find a location where there is complete cancellation. If you look at this link about Hyperbolic Navigation Systems, you can find out how the Decca Navigator operated. It depends on measuring the time differences between three or more highly synchronised radio signals, received by a boat and doesn't depend on amplitudes being the same. Much better altogether and I'm sure you could blag your way through a good enough explanation to convince readers about it. (The term Hyperbolic should carry a bit of weight!)

A vast amount of money was spent on developing such systems and they could provide accurate enough location information for (in ideal conditions) a fisherman to locate, in mist, the crab pots he put down the previous day. Not as good as GPS, which rapidly displaced it, but well worth having.