Sharing thoughtful approaches to teaching physics with the wider world.
A Prelude to the Physics of Music Day
25 April 2020 at 13:49 #62853
A unique IOP full CPD day has been planned on the theme of The Physics of Music.
The day will be hosted at Chetham’s school of music, with talks and workshops from the Institute of Physics and Salford Acoustics. The day has capacity for fifty teachers and fifty students from the school will be joining us for the morning talks.
The Stoller Hall is a box within a box. An acoustically isolated room from the busy sounds of Manchester, with acoustic banners that can change the reverberation time at the push of a button. Part of the days will have the physics of concert hall design. How important things like room modes and reflections of sound are important to the design. The company Arup designed the acoustics of the hall
I first came across the idea of concert hall design in a book called Sound by A E E McKenzie. It was this idea of modelling a concert hall with a ripple tank to see how reflections would affect the sound.
I am afraid these pictures are poor quality as they are from a really old book. You can see bottom picture is the ripple tank showing how the model of the concert hall and the multiple reflections from the ripple tank. The top image is a single wave photograph. Behinf the black circle a spark is fired and this creates a pressure wave. This is filmed using Schlieren flow method. The single wave is better to see how the reflections of the sound move around the concert hall.
You can see the shock wave from a trombone here
The book also had this great image of the refraction of sound. Again the black circle hides the intense flash of a spark from the camera. The lens shape bag is full of sulphur dioxide. The sulphur dioxide is denser than air. The shock wave filmed can be seen to refract as it passes through the lens.
I had heard for long time that a balloon full of carbon dioxide will refract sound. I recently tried the experiment.
The green balloon is just air. The yellow balloon is carbon dioxide. As the yellow balloon passes in front of the singer you can hear an increase in volume as the sound waves refract. We hope on the real Physics of Music Day to have an arrangement of strong singers to try and focus them onto a microphone or sound meter and see if what kind of increase in amplitude we find.
The day first talk of the day will be presented by Trevor Cox, Professor of Acoustic Engineering at Salford university’s acoustics department. The talk will include live examples from students of Chetham’s.
How does the voice work and how has it been changed by technology?
Drawing on examples from opera to hip-hop.
We are very lucky that Salford Acoustics is kindly sharing their time and expertise with use. I have been using resources from Salford acoustics since I started teaching over 20 years ago. You might remember Trevor from Teacher’s TV. There was also the great acoustical investigation for Comic Relief
There are many great resources on their website including great careers information for acoustical and audio engineers.
My favourite lesson starter is the confusaphone!
A great lesson starter for sound and hearing. There is some great physics in how having two ears can help us get directional information from interaural time difference. I learnt from Steve Moulds excellent YouTube about owls have vertically asymmetric ears to get information about distance below them in flight.
Steve also covers interaural time differences.
I have been reading a book on hearing in insects and discovered that a cricket has its ears on its legs to gain a big enough distance between them. Some animals have a head that is too small for a measurable time difference. A gecko is like this and has a hole all the way through its head. Its hearing system does something clever with standing wave and interference in the tube to gain directional information.
28 April 2020 at 23:39 #62893
The full day will at some point go ahead. It is an IOP CPD full day event and like other ones will have a variety of workshops to choose from. For our prelude we had a preview of a few of the workshops with IOP Coaches from the NW team.
First up was Daisy Fox with a very well received session on resonance. Daisy is brimming with physics ideas and good classroom practice.
Here is a link for the Top Ten hints for inclusive teaching that Daisy introduced.
Here is Daisy in action
30 April 2020 at 00:31 #62909
David Farley showed us two great ways to measure the speed of sound in air using the resonant frequency of a pipe and the wavelength of the standing wave inside the pipe.
At 11:38 in the video you are asked to watch a video. The best way we found to deal with the problems of streaming video was to give you the link to it in the chat box.
8 May 2020 at 07:48 #63050
An interesting programme/podcast on Radio 4 this week on Noise Cancelling Headphones. The link is here:
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