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Why does tap water make sound?

  1. Aug 21, 2012 #1
    When water is flowing out of the tap, there is a buzzing/hissing sound. I can hear One sound coming immediately out of the tap and the other sound when water hits the ground. What are the reasons for these different sounds. Can someone explain to me in layman terms. Thanks.
     
  2. jcsd
  3. Aug 21, 2012 #2

    Bobbywhy

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    Gold Member

    arv217, Welcome to Physics Forums!

    Have you tried to search using “Google” yet? I did, and in a few minutes found lots of sites that may answer your first question:
    Google search terms: “sink faucet making noise”:

    How To Silence a Noisy Faucet
    http://home.howstuffworks.com/home-improvement/plumbing/how-to-repair-a-faucet6.htm

    This site offers six possible causes of sink faucet noise:
    “Why do your kitchen sink faucets make noise when hot or cold water is turned on?”
    http://wiki.answers.com/Q/Why_do_yo..._hot_or_cold_water_is_turned_on#ixzz24AMLrZax

    For your second question, use Google search terms: “sound of water hitting surface” for several explanations of why you hear those sounds.

    Once you have visited these sites and studied that material, if you have a specific question or a doubt, then post it here. Our members are ready and willing to assist you on your journey towards an increased scientific knowledge.

    Cheers,
    Bobbywhy
     
  4. Aug 21, 2012 #3
    Thanks for the welcome! I tried searching in google before and didn't find anything relevant except for this one: http://physics.stackexchange.com/questions/303/why-does-water-make-a-sound-when-it-is-disturbed

    There are two replies in that site, which I think is most relevant for my second question:
    a high pitched slapping sound when the stone makes contact with the water. This is due to the air between the stone and the water being pushed out, as well as the surface ripples
    and
    I think the high-pitched sound is caused mainly by the breakdown of the tension formed by the water layer on the surface (see http://en.wikipedia.org/wiki/Surface_tension for more detail). So it's similar to slapping a table with your hand.

    These two replies put me in further confusion, that's the reason I posted the question. Now, I will refine my question and put it back:
    Lets Imagine there is a tap and a ground underneath. There is just air between those and nothing is disrupted. I turn on the tap and the water flows down on the ground. The moment I turn the tap on, the first stream of water hitting the ground makes a sound which I understand is because of air being pushed away. But what about the subsequent streams of water flowing from the tap and hitting the ground. Since I assume, there is no air between the water and the ground now, there is no air being pushed away. So how does the subsequent streams of water cause sound.

    Hope I have written it clear!
     
  5. Aug 21, 2012 #4
    Check the power supply! sorry an old adage.
    All sound is a result of compressions and decompression in a media.
    So water flowing in a pipe makes some sound, turning a corner in the pipe,
    more sound. Resistance to flow, the energy has to go somewhere, heat, sound,
    vibration.
    The water escaping a pressurized system at the tap, more sound.
    Once you leave the boundary condition of the pipe, it gets more complicated.
    For the sake of discussion, let's say water falls at 32 feet per second in the sink.
    Much of the energy in the falling water, will change state, mostly sound.
    After the volume of water pushes the air out of the way, the air pushes back.
    The air pushes back at about 1000 feet per second.
    Water displaces air, water flows out of the way, leaving a vacuum, air flows
    back into space, process repeats.
     
  6. Aug 21, 2012 #5

    Bobbywhy

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    Gold Member

    arv217, Thank you for rephrasing your question. It's more clear now. You are correct when describing the mechanism that causes the sound when the first parcel of water hits the ground.
    The sound made by a stream of water from a faucet striking a surface depends on the characteristics of the water stream itself. Below are three types. I suggest you experiment with all three in your sink and observe the sound each produces. You might predict what sound to expect from each before the experiment and then compare your observed results with your predictions.

    1. Fully on
    2. Thin stream laminar flow
    3. Drops only

    Here is a photo of a laminar stream entering water silently:
    http://www.google.com/imgres?hl=en&...w=155&start=0&ndsp=22&ved=1t:429,r:6,s:0,i:98

    Here is a photo of a laminar stream forming an arc and entering the water silently.
    http://www.google.com/imgres?hl=en&...tbnw=184&start=22&ndsp=24&ved=1t:429,r:8,s:22

    Here is a photo of two streams, originally laminar and then becoming turbulent. You may imagine the sound generated as these streams hit the water.
    http://www.google.com/imgres?start=...=144&tbnw=191&ndsp=24&ved=1t:429,r:1,s:96,i:9

    Another example of a laminar flow from a nozzle becoming turbulent:
    http://www.google.com/imgres?start=...2&tbnw=208&ndsp=25&ved=1t:429,r:0,s:146,i:166

    Here is a photo of several nozzles emitting laminar flows and showing the onset of turbulence in detail.
    http://www.google.com/imgres?start=...38&tbnw=187&ndsp=24&ved=1t:429,r:3,s:195,i:15

    Hoping this helps answer you question.
    Bobbywhy
     
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