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Sound experiment ① Various straw whistles
When an object is vibrating, the vibration makes a sound. This time, I will introduce various things that use straws to vibrate the air and make sounds .
Experiment 1: Simple straw whistle
you need : straw, scissors
Very easy, crush the straw flat and cut as shown. After that, hold it in your mouth and blow strongly. The cut part acts as a vibrating reed, so cut it so that it easily vibrates. Also, if you change the length as shown in the picture below, a different pitch will be produced.
A thin straw makes it difficult to make sound. At first, it is recommended to use a slightly thick straw of 6 to 8 mm. Once you get used to it, you can even use a straw for a milk carton for lunch.
The pitch is as follows. Since the sound is produced with both ends open, a standing wave can be created as shown in the figure below.
← 10㎝ →
It is the same as the principle of recorder sound.
If the length of the straw is 10 cm as shown in the figure, the wavelength of this sound will be 20 cm (0.2 m). This value Sound speed C = f (frequency) x λ (wavelength)
When the frequency f is calculated at a speed of sound of 340 m / s
f = 340 ÷ 0.2 = 1700 Hz.
Sound If you change the length will change. If you cut the straw with scissors while blowing in front of the students, the sound will gradually increase. Students are overjoyed.
Experiment 2: Straw whistle with scale
you need : Straw, scissors
In the case of this whistle, one side is blocked, so the standing wave is as shown in the figure.
The wavelength is 40 cm (0.4 m), which is four times 10 cm. Assuming that the speed of sound is 340 m / s
Also, if the official sound speed C = f (frequency) x λ (wavelength),
F = 3400 Hz. It's a little high as a sound
Experiment 3: "UGUISU" whistle 1
It is a whistle that imitates the song of a bird called "Uguisu" in Japan.
you need : Straw 20 cm, scissors, vinyl tape
Mark 6 cm and 12 cm from the top of the straw. Cut 6 cm to the last minute with scissors. Bend the bottom twice and tape it securely. Add water up to the 12 cm mark and you're done.
How to make it sound, but there is a trick.
A) Exhale while pushing up slightly from the 12 cm line.
B) "Relieved" to blow in short sections while still in the state of a
C) While blowing, push up the water quickly and loosen your hands "Kekyo"
Experiment : "UGUISU" whistle 2
you need : Thick straw 10 cm, thin straw 6 cm, scissors, cellophane tape
Make a hole in the center of the thick straw. Crush the tip of a narrow straw flat and attach it so that you can breathe into the hole. Only this.
Make a hole in the center of the thick straw. Crush the tip of a narrow straw flat and attach it so that you can breathe into the hole. Only this.
How to blow
A) Cover both ends of the green straw with your thumb and forefinger and exhale for a long time.
B) Blow short in the same state as a "Relieved"
C) Release only your index finger and blow shortly.
D) Return your index finger and blow shortly "Kyo"
Please connect this smoothly.
There are other versions of C, such as releasing only the thumb and releasing the thumb and index finger.
The frequency is the same as that of Experiment 1 (10 cm).
Experiment 5: Let's make a bug whistle
you need : Film case (small PET bottle), octopus thread, cutter, cardboard
Make a 5 mm x 3 cm hole in the film case. Use thick paper with 2 x 3 cm wings to stabilize the rotation. Attach a string and turn it to complete the bug whistle. You can also use a small PET bottle. Regarding the generation of sound, it seems that the two sounds are combined.
One is due to the standing wave created by the air entering through the opening rotating inside the case, and the other is due to the vibration caused by the air vortex behind the case as it moves through the air (called Karman vortex). ).
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