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Waves and Sound

TRAPPIST-1: Planetary System/Rock Band

Matt Russo, post-doctoral fellow at the Canadian Institute for Theoretical Astrophysics (CITA)

Astronomers and philosophers since as far back as Kepler and Pythagoras have imagined what the music of the spheres would sound like. With the discovery of seven Earth-sized planets orbiting in the nearby TRAPPIST-1 planetary system, this becomes possible as never before. Aside from being a prime target in the search for life, the TRAPPIST-1 planets are interesting because they form the longest discovered resonant chain. This means that the ratios of the planets' orbital periods form simple whole number ratios. For example, for every two orbits of the outer planet, the next one in completes three orbits and similar patterns exist among the orbits of every pair in this system. Since whole number ratios are the basis of rhythm and harmony, TRAPPIST-1 may be the most musical planetary system ever discovered. Read More...

Good Things Happen in an Affective Classroom

Christine Hudecki, Teacher our Lady of Lourdes Catholic HS

We were just a couple of weeks into the new semester when one of my students started to teach me and the rest of the class. It was a great moment and upon reflection, I think that the student felt comfortable ‘taking over’ because of a number of changes that have I made in my classroom. These were changes that reflect the theme of this year’s conference, Affective Physics: Harnessing Emotion to Improve Learning. Read More...

Can You See Sound?

Bonnie Lasby, Physical and Engineering Science Dean’s Office University of Guelph

This demonstration is a nice way to show that sound is vibration of molecules. The picture below shows the equipment required for this demonstration. The setup consists of an amplifier attached to an input device (laptop, iPod, mp3 player, etc) and a set of small speakers (described below) as well as a bar clamp and red and green laser pointers. Read More...

Making Speakers

Bonnie Lasby Physical and Engineering Science Dean’s Office University of Guelph

I prefer to do this as an activity as opposed to a demonstration, and have found that it works very well for students in Grades 7 to 12 visiting the University. I start with a discussion about sound and then compare a speaker to the human ear. In the discussion on speakers, I also talk about magnets and how they work, and I explain the difference between permanent magnets and electromagnets. After this discussion, I explain how to make speakers using a plastic cup, a magnet, and a coil of wire. Each student makes his/her own speaker and then tests it. Read More...

Air Column End

Diana Hall, Bell High School, Nepean, Ontario

Here’s a really easy way to show students that the pressure at the end of an open-air column doesn’t change exactly at the physical end of the tube. It requires a motion sensor, a tube, and the right-sized insert for the tube. I happen to have a plexiglass tube into which a tub of play-doh fits just nicely. Read More...

A Demonstration of the Production of Sound

John Vanderkooy, Distinguished Professor Emeritus Department of Physics and Astronomy, University of Waterloo

For this demonstration, a small open loudspeaker driver is necessary, driven from a sound source with output power sufficient for a loudspeaker. A ghetto-blaster is convenient if it has an output jack or can be modified to direct the loudspeaker output to an external device. For best results the small driver should be of moderate or better quality. It helps if its compliance is high so that bass notes cause substantial cone motion. Read More...

Physics and Music: Harmonics

Diane Nalini de Kerckhove, Department of Physics, University of Guelph

Diane Nalini de Kerckhove is an Assistant Professor in the University of Guelph’s Department of Physics. She is also a singer/songwriter and recently launched her third CD, “Songs of Sweet Fire”, a collection of Shakespeare songs and sonnets set to her original jazz and blues music.

I have never met anyone who doesn’t like music. After teaching the physics of waves at various levels over the years, I’ve come to realize that demos involving music have a wide appeal with students, especially since most of them have studied an instrument at some point or another. Here are two options for exploring harmonics of standing waves. Read More...

Sound Tube: A Versatile and Inexpensive Physics Demonstration

Debbie Chaves and Bruno Tomberli, Physics Department, University of Guelph, Guelph, Ontario, N1G 2W1

A versatile and inexpensive demonstration tool for every physics teacher is the “sound tube,” also known as the whirly, Hummer and corrugahorn. Its puzzling properties span many different physics topics. Read More...

Seeing the Speed of Sound

Diana Hall, Bell High School, Nepean, Ontario

This demonstration allows students to get an idea for how slow sound actually travels. Read More...

Pressure vs. Particle Movement — The Dance

Diana Hall, Bell High School, Nepean

When discussing standing waves in air columns most textbooks focus on the movement of particles and show nodes at closed ends and antinodes at open ends. When thinking about the loudness of sound we have to remember that the sound is loud when the pressure difference is the greatest and that sound is a longitudinal wave. This occurs at nodes (where particles move the leave) and not the antinodes (where particles move the most). I use my students to demonstrate this difference. Read More...

Superposition Principle-Kicking the Canister

Diana Hall, St. Charles North HS, Illinois

My students have fun predicting which canisters will get knocked down in an interference demonstration. We stretch out a long spring across the classroom floor. We then line up film canisters (or other substitutions) alongside the spring. Students predict which ones will get knocked over and which will be left standing. They must also say why. Read More...

Acoustical Wheel with Christmas Tree Balls

Christian Ucke, Technical University Munich

Figure 1 was taken from an old German physics textbook1 dating from 1906. So-called Helmholtz-resonators are fixed on a cross which can rotate easily on a needle bearing. With the right resonance frequency of the Helmholtz-resonators and enough acoustical power from a loudspeaker, this device starts to rotate anticlockwise (view from above). Read More...

Cheap and Easy Sound Demos with Rods and Tubes

Roily Meisel, Ridgeway Crystal Beach High School

Visible standing waves with a node at each end are fairly easy to demonstrate. You can use a long spring such as a slinky (cheap way), or even order a nice transducer-based demo from one of the scientific supply companies (expensive way). However, I also wanted to demonstrate antinodes at both ends, or even one node and one antinode. Read More...

An Electric Guitar Pickup

Peter Scovil, Waterford, ON

I like music, and enjoy playing the guitar, so the following demo caught my eye (or ear?). It was in the Jan. '95 issue of The Physics Teacher (p.58) by G.R. Davies of South Africa. It is a good example of electromagnetic induction that is easy for students to understand. Read More...

Two Sound Demonstrations

James L. Hunt Physics Department, University of Guelph

The following two sound demonstrations have the virtue of being inexpensive; in fact the first one costs the teacher nothing. Although I have seen the first referred to somewhere, I do not recall seeing the second. Both demonstrations rely on the human ear's remarkable ability to distinguish changes in pitch. Read More...

An Inexpensive Vibrator for Standing Waves

Peter Scovil, Waterford District High School,

At the OAPT Conference this past June at the University of Waterloo, I gave a short demonstration of a vibrator I built from a Radio Shack speaker. It allowed me to produce longitudinal as well as transverse standing waves. This is based on an idea from one of the AAPT conference workshops. Read More...

Big Ben — Lenz’s Law and the Cow

John Childs, Grenville Christian College, Brockville

Two demonstrations from John Childs.

The Classroom Wave

Bonnie Edwards, Our Lady of Lourdes High School, Guelph

How about a physics demonstration with hundreds of moving parts that never needs to be fixed and doesn't require storage space? Hard to believe? Try doing THE WAVE in your grade 12 physics classes. Read More...

Standing Waves — The Can that Comes Back

Pauline Plooard, Fenelon Falls Secondary School

Two quick demonstrations from Pauline Plooard.

Not-so-Simple Harmonic Oscillator

John Wylie, The Toronto French School

Two years ago when I was in The Netherlands for the International Physics Olympiad, the Soviet team-leader, Sergey Krotov1, demonstrated a remarkable toy, crafted to the highest standards by the technical staff at Moscow State University. It consisted of a series of simple pendulums of varying lengths which, when swung together, formed very beautiful patterns. I built one of my own which works just as well, using only bits and pieces that I found in my high school physics lab. Read More...

Making Sound Waves Visible

Bill Konrad, Kent County Board of Education

The demonstration described below was demonstrated at the OAPT conference in London in June 1989. Since there was a fair bit of interest in the details of construction of the apparatus, I thought this column would provide a convenient opportunity to give the specifications. Essentially, a speaker at one end of the closed air column is used to set up a standing wave of sound inside the column. Natural gas enters the device through two copper tubes. The gas is lit and burns at numerous holes drilled across the top of the duct. Due to differences in pressure at the nodes and loops of the standing wave inside the air column, the flames that are generated vary in height giving a visual outline of the wave inside. Read More...

Overhead Projector Wave Simulator

Bill Konrad, Kent County Board of Education

The demonstration described in this column is one I learned as a teacher in summer school at the beginning of my teaching career. It is one that I have found to be very useful in teaching a number of concepts related to waves. Read More...
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