Silence

[DNA]

We are all running noisy pumps and some are really loud and annoying to listen to for long periods of time.

I've seen pumps for a long time as an excellent candidate for noise cancelling, but for some reason there is nothing on the market.

You buy one pump and it's loud. When you buy another one that's phase shifted the noise will in theory be less than from a single pump.

Now it's your chance get rich or proof the above statement to be pseudo science.

 

[barjam]

Short answer is that this isn't feasible.

The waves from the pump bounce off objects (and the waves themselves) causing all sorts of complicated interactions that would be nearly impossible to cancel out. Much of the sound isn't even created at the pump anyhow it is created by what the pump is attached too.

Now if you had nothing in the room and the pumps weren't attached to anything *and* the pumps both occupied the exact same point in space (not possible obviously) then it would work.

That last point is why the headphones work to a degree. The sound canceling wave effectively occupies the same point in space as the origin of the sound which is the sum of the waves hitting the ear canal at any given moment.

Another illustration of this problem is my tank (in wall). The, by far, loudest items in my tank are two hydor magnum pumps. Right in front of the tank is like 54db or so. To the left a d up the wall a bit is like 57db (poor mechanical isolation). Now here is the weird thing. There are areas in the room, some quite far from the tank (15 foot plus) that are just as loud as right in front of the tank. A standing wave is being generates. Your idea would generate all sorts of standing waves.

On a side note I replaced the standard mounts on my magnum pumps to the evolution mounts which really cut down on the very annoying noise at 120hz that was bugging me.

 

[mustard]

Think the tank inhabitants don't like the sound?

 

[DNA]

I've dived on the reef and it's quite noisy there so I don't think the fish mind much or they get accustomed to the vibrations from the pumps.

This was and idea to discuss for us humans to have quieter tanks.