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I have a metal sink. I don't want to waste much water so I prefer smaller streams of water. But when the stream is small it makes a big noise. However, when I increase the flow, the tapping sound becomes absent and I can only hear the sound of the water flow.

My question is - why does the additional water reduce the noise of flowing water? I believe it has something to do with damping but I can't imagine the process. Probably the water particles in the middle don't make much noise because they are surrounded by other particles and sound waves are trapped inside. But what about the water around the stream? The stream's diameter is big and therefore there are more water particles on the borders than there are in the smaller stream. And more particles should make more noise.

I can make a video of the process I've described if I didn't myself clear enough. Tell me in the comment if you need it.

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  • $\begingroup$ We used to have something like that at my cousin's home. It is usually due to the resonance effect created by the water flow. If you decrease the water flow, you should not hear the sound either. $\endgroup$ – Gonenc May 12 '15 at 23:38
  • $\begingroup$ I do hear the noise when I decrease the water flow. $\endgroup$ – user1 May 13 '15 at 17:25
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I tried this on my kitchen sink and it's true. A narrow stream almost separated into many dollops makes a loud resounding thudding, but a thick fast column of water is almost silent on the metal.

The reason is that the narrow, weaker, less continuous stream allows the metal to vibrate.

The thick, weighty, continuous stream deforms the metal and keeps it that way, doesn't allow the metal to spring back into shape, and there is no vibration. The greater weight and pressure of the thick stream damps the resonance of the metal.

If you pressed a drumstick into a drumhead continuously, there would be no vibration. But when you allow the drumstick to bounce on the drumhead, there's vibration and sound.

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  • $\begingroup$ The way I read the OP's question implies that there was still a stream of water hitting the sink just at a lower flow rate so I don't know if your observation of discrete droplets is the same as OP. I think you are correct with the remaining argument. Another analogy might be a harmonic of a guitar string. The sound is dampened more the larger the point of contact is that defines the node. $\endgroup$ – Mebert May 13 '15 at 2:07
  • $\begingroup$ Yes, I can make a continuous stream that makes noise but it's a very small range of stream diameters. It's a boundary when the stream becomes separate drops of water (due to gravitational acceleration) just near the surface of the sink so it seems like a continuous stream but at the end it's really not. BTW, if I could, I'd upvote both answers but I need 15 reputation. I'll do it in the future. $\endgroup$ – user1 May 13 '15 at 16:54

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