Lesson 7

Woodwinds and Brass Instruments

Straw Oboe Demonstration

The video on the left shows how "Science Bob" makes a straw oboe.

SAFETY:

Practice before class (and away from colleagues that you don't want to annoy) and be careful not to blow too hard that you get dizzy! This is a NOISY demonstration.

If you can't do this demonstration for some reason in real life, you can play the YouTube Video above.

Materials:

Plastic Straws (3)
Scissors (1 pair)

SET UP:
Using a straight (not bendy) plastic straw, flatten just one end by gently using your teeth to crush it flat about ¾ of an inch. Cut the sides of the flattened piece with scissors so that there is a pointy part in the middle as seen in the photos below.

Top View

Side View

Directions:

Blow through the flattened and cut part of the straw.
You will probably have to experiment a bit to get the sound to come out. Practice this before class and don't get dizzy! It should sound like a kazoo.
Add a full length, uncut straw to your reed straw, effectively making the end longer. You can add another straw to the end as well! It will be harder to blow, but the sound will be much lower. Just make sure there are no places air can escape at the boundary.
Finally, using just one straw length, blow through the straw and while the straw is buzzing, cut little pieces off the end of the straw while continuing to blow.

Open Tube

The "Open Tube" we are using is the golf tube.

Using your palm, you can tap on one of the open ends to hear the fundamental frequency.

PXL_20230519_162236459.TS.mp4

Meter Stick DemonStration

Directions:

Hold the meterstick (or ruler) firmly in one hand so that it hangs off the end of a table. With your other hand, pluck the end of the meterstick.

Here, you have a couple of options.

You can allow the vibrations to dissipate, moving the meterstick an inch or so and repeat the whole process, listening to the vibrations as they vibrate more quickly and at a higher pitch.

You can do it all in one swooping motion as seen in the video where you pluck the end and before the vibrations dissipate, move the stick on the table so less hangs over the edge.

Notice: You will hear the change in pitch and notice the vibrations quicken as the length overhanging the edge decreases.

Teacher Tips: Group students in pairs and give each pair a ruler so that they can try this on their own.

PXL_20230519_162728175.TS.mp4

Sound Pipe

Directions: Swing the sound tube, holding one end firmly, so that the other end revolves in a circle. Try it slowly at first and gradually increase the speed. Try to produce 5 distinct frequencies. Many people find the first harmonic and the fifth harmonic to be the most challenging.

Teacher tip: Choose a student (possibly one with a lot of energy) to try to get the last harmonic.

Paper Blow Demonstration

The video below shows in the first 1 min, 22 secs how moving air creates a pressure difference.

LAB: CONSTRUCT YOUR OWN TAKE HOME

Pan Flute INSTRUMENT

Use the tuner to make at least four tuned notes for the instrument

Materials: several straws (4-8 per student depending on time and total number of students), scissors, and tape.

At AoPS Academy, we use a tuner to make sure we were getting the note we wanted. There are several free tuner apps available for phones.

For the straws we purchased (which may not be the same as yours), the following notes corresponded with the following length of the straw:

Length (cm)..........Note - frequency (Hz)

21.3........................G5 - 784

18.9........................A5 - 880

17.0........................B5 - 987

15.7........................C6 - 1046

14.0........................D6 - 1175

12.5........................E6 - 1318

11.5........................F6 - 1396

10.3........................G6 - 1568

Page updated

Report abuse