Talking Physics

IOPSpark Sound resources

This topic contains 7 replies, has 2 voices, and was last updated by  Owen Grinter 5 months, 2 weeks ago.

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  • #59672
    Profile photo of Andrew Normand

    I am delivering my “Tones Tines and Tings” talk at the IOP South West Physics CPD Day

    https://www.talkphysics.org/events/iop-south-west-physics-cpd-day-2019/

    So I am exploring the new https://spark.iop.org

    Beats feature in my talks. The talk this time will have a new audience participation time, with whistling lollipops given to each member of the audience. We will try and make a beat frequency together.

    The first thing I found on IOPSpark was a SPT classroom activity using audacity. There is a nice way to use audacity with a police whistle to explore ghost frequencies.

    https://spark.iop.org/beats

    Here are some of the ways I demonstrate beats

    You can use two signal generators


    It is probably unlikely to have two signal generators so you can do a similar thing with mobile phones.


    The first way I ever made beats was with two tuning forks.

  • #59685
    Profile photo of Andrew Normand

    What never ceases to amaze me about physics is when you look at a concept you will always find an application for it somewhere!
    To test for poisonous gases in mines they used to have organ pipe with surface air in it and another with air pumped up from the mine. These pipes of same length were played together. If one pipes frequency was changed due to the gas from the mine being of a different density then a beat was heard.

    We used to use beats to tune our cornets in Frodsham Silver Band.

  • #59720
    Profile photo of Andrew Normand

    My son made me this Audacity tutorial to make beats.
    Audacity is a free, open source, cross-platform audio software

    https://www.audacityteam.org/

    The link below is to the PowerPoint
    Acoustic-Beats

    Another resource on the IOP Spark website is Practical Activity 14 – 16 Nuffield Practicals.
    Here beats are in the Introducing Waves page

    https://spark.iop.org/introducing-waves

     

  • #59723
    Profile photo of Andrew Normand

    I was pleased to find a new piece of kit to build on the IOP Spark website.
    I have always like this AQA A Level Physics question.

     

    Some times the path difference questions are based on waves other than EM waves.
    This question is how I became aware of¬†Quincke’s tube. The instructions to make it are here

    https://spark.iop.org/acoustic-interferometer

     

     

  • #59806
    Profile photo of Andrew Normand

    I found this clip of one in action

    https://www.youtube.com/watch?v=HQ94rHcPCQE
    This tube is sometimes called a Herschel-Quincke tube (HQ tube). Usually it is the second name in the double named phenomenon that is lost over time, like Lorentz-Fitgerald contraction. Like I said above with the application of beats in finding poisonous gases in mines. Every time you look in to an effect or phenomenon in physics you find someone has made use of it. I discovered that the HQ tube is used in jet engines to try and remove certain frequencies that are much loader spikes than the general engine rumble.

    This images came from this document
    HQ tube interference 2

    I also found a NASA manual for the Honeywell TFE 731-60 jet engine.

    This was an interesting document. The last page has the security classification of the document.

    https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20020043799.pdf

    Still amazes me that such a simple concept as path difference being used to cancel out the sound with destructive interference.

     

     

     

     

     

     

  • #59807
    Profile photo of Andrew Normand

    Another way I have seen sound of a particular frequency being reduced is using a Helmholtz resonator.

  • #59810
    Profile photo of Andrew Normand

    I have a collection of Helmholtz resonators

     

    My favourite use of my vodka bottles came from a Marvin and Milo card.

     

     

    You can find Marvin and Milo on the new IOPSpark website

    https://spark.iop.org/sound-gas


    You can hear with the same amount of water in each bottle the same tone. I am using an effervescent powder.
    At 0.40 seconds in the video I blow across the top of the fizzing bottle and you can it does not really resonate as the bottom surface is no longer reflecting the sound from a smooth plane surface. It is important to let the water settle down. Now you have one bottle filled with carbon dioxide and one with air. The more dense carbon dioxide gives a noticeably lower tone.

     

     

     

  • #59815
    Profile photo of Andrew Normand

    Hi David,

    Thanks for all these great ideas- I built the Quincke’s tube today to use with my Y12s!

    I have a question- why does the pitch drop for the CO2 bottle? (struggling to think of an explanation!)

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