1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

When will an airflow cause whistling?

  1. Dec 17, 2014 #1
    Is there any good approach to determining if an amount of air passing through a given slit or gap will cause a whistling sound? I'm unsure with what shapes whistling might become an issue, and also at what air velocities.
     
  2. jcsd
  3. Dec 17, 2014 #2
    I don't know. But generally in dust collection (which is allowed to be loud) we try to stay below 5000 fpm through ducts as above that you tend to get lots of noise. Through an open orifice, I have no idea off the top of my head. It also depends on the angle of incidence between the air path and the orifice (think of a flute or soda bottle)
     
    Last edited: Dec 17, 2014
  4. Dec 17, 2014 #3

    boneh3ad

    User Avatar
    Science Advisor
    Gold Member

    There isn't a good approach of which I am aware. To really figure it out you will likely need some aeroacoustic simulations. It's going to depend on the geometry of the orifice, slit, or gap, the geometry of the vessel through which the air is flowing, and the details of that air flow. The whistling is caused by the oscillating of the shear layer that forms at the orifice. The amplitude and frequency of those oscillations as well as whether or not the surroundings are capable of resonating with that frequency are going to determine how audible any whistle is going to be. Depending on the geometry in question, there are going to be a few rules of thumb to help roughly determine the frequency, but that won't give you much information about whether it is going to be audible.
     
  5. Dec 17, 2014 #4

    russ_watters

    User Avatar

    Staff: Mentor

    My suggestion would be to flip through some terminal air device catalogues, find some devices similar to what you are picturing, and see what their acoustic properties are.

    Try: www.titus-hvac.com
     
  6. Dec 18, 2014 #5

    Danger

    User Avatar
    Gold Member

    It isn't restricted to commercial stuff. I've had cannulas (nasal prongs) for my oxygen equipment that whistled so loudly in my nose that I couldn't go to sleep. It seemed to be at their whim: sometimes they did and sometimes they didn't. When they did, I would bend and twist and beat them until they got down to a level that I could eventually ignore.
     
  7. Jan 4, 2015 #6
    The effect is called Helmoltz resonance
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: When will an airflow cause whistling?
  1. Airflow in a computer. (Replies: 23)

  2. An Airflow Question (Replies: 0)

  3. Airflow question (Replies: 3)

  4. HELP Airflow (Replies: 4)

Loading...