Cover your mouth with both hands and say your name. Afterwards create a “tube” with your hands, place it around your mouth and say your name again.
Questions:
● Which way does make the sound louder and clearer?
● How did the “tube” work?
● When was it difficult to understand the spoken words and why?
If you cover your mouth with your hand the sound is muffled, if you use a "tube" it is amplified. The sound is louder and more audible in the direction the “tube” is facing.
EXPERIMENT NUMBER 2.
Put the fingers on your larynx and make sounds: you can murmur, sing, make a low sound and a high sound.
Now take a piece of food wrap foil (or paper). Ask them to stretch it, put it over their mouths and do the same again.
Questions:
● What did you feel under your fingers when you made the sound?
● What did you feel on your lips when you placed the foil on them?
● Why is this happening?
The vibration under your fingers and the tickling on your lips are the result of the sound wave propagation.
EXPERIMENT NUMBER 3.
Divide into pairs and come to tables / chairs with strings attached to them.
One student must hold the unattached part of the string in his hand. Ask him to pull it as strong as he can.
The second student strikes or hits a string like during playing guitar.
After that they exchange the roles.
Try pull the string harder or more delicate and hit the string.
Use the whole length of a string or roll it on their hands to make it shorter and hit it.
Try all of those exercises on each kind of string – thick and thin ones.
Questions:
What did you have to do to hear sound?
Why did the string have to be taut?
What sound was created when you didn't tighten the string enough?
Were the sounds made on both strings (thick and thin) the same?
What was the difference?
What sound did you hear when you made the string longer or shorter?
The longer the string, the lower the sound. The heavier the string the lower the sound. The tighter the string is pulled, the higher the sound.
This is because the pitch of a sound depends on the frequency of the sound waves - the number of oscillations in a certain time, for example 1 second. The unit of frequency is the Hertz. The higher the frequency, the higher the sound.
EXPERIMENT NUMBER 4.
Seat at the table with your own groups. Take a membrane bowl
Take a piece of A4 paper card. Roll it to make a tube.
Place one end of the tube close to bottom of the bowl and make loud sounds through the tube. Be careful not to touch the bowl with it.
Observe what is happening with the grains or sugar within the bowl.
Questions:
What did you notice?
Why did the grains move?
The foil acts as a membrane vibrating under the influence of sound waves. The sound wave coming out of the tube vibrates the bowl. The foil, by vibrating, moves the grains, which bounce.
EXPERIMENT NUMBER 5.
Students stand in big circle and hold hand of students standing next to them. First student is asked to tilt on the left side to touch with his arm other student’s arm. After that he returns to his original position. The touched student does the same to other student on his left side and returns to his original position. The exercise is finished when the last student in the circle touches with his arm the first one.
Questions:
What role did you have in this exercise?
Why did you move like this?
What is this movement like?
Remember how the guitar string moved, did you move similarly?
The first student plays the role of the sound source. The next pupils are air molecules that lean towards the next molecule. Their movements resemble the propagation of a sound wave.
The propagation of sound in a medium is based on the propagation of vibrations according to the direction of the wave. You can find some examples here
The grey line on the left is a source of sound. Black and red dots are the gas molecules, e. g. air in which the sound propagates. You can see the densification and dilution of air molecules. Those are the sound waves. The red dots show how air molecules move when a sound wave propagates. This is swinging movement
EXPERIMENT NUMBER 6.
Whisper something to the ear of their colleague sitting next to them.
Afterwards whisper the same sentence to the colleague sitting in front of them.
At the end whisper the same sentence to a person sitting at the opposite side of the classroom.
Question:
What is happening to the sound?
Does the sound disappear as the distance increases?
Every sound wave carries a certain amount of energy. The energy of the wave becomes less and less as it moves away from the sound source. This is because energy is absorbed by other physical bodies, such as air molecules. The longer distance the wave has to travel, the more of its energy will be absorbed.
EXPERIMENT NUMBER 7.
Match in pairs; each pair has two paper cups and string from which they make a phone.
Make your own phones. Instruction: Make a hole in the bottom of each cup with a pen. Pull the rope string through them.
Talk on that phone. Make sure the rope string between the cups is taut as they do that.
Question:
Did you hear your voices on that phone?
What is the working principle of this simple phone?
In what material was the sound transferred?
The sound makes the cup vibrate. The bottom of the cup vibrates and transmits the vibration to the rope string. The string transfers the vibration to the other cup. Its bottom acts as a speaker's diaphragm.