Membranophone and other sound activities

Kids were given tasks to find out

1. Why animals such as rabbits, deer and fox have two long rotating ears? (rotates independently to hear sound from all directions).

2. How mammals such as whales and bats use their listening skills for echo location?

Echo location

Echo location is the use of sound waves and echoes to find the location of objects in space. Bats use this to navigate and find food in the dark. To echo locate, they produce sound waves through nose or mouth, which when hit by an object produces echoes. Bats listen to the echoes and figure out the shape, size and the location of the prey.



Even dolphins use the same technique to find food and navigate in the dark. Dolphins produce high frequency clicks that quickly travel through water. In fact, sound waves travel five times faster in water than they do through air. 


After a healthy amount of interaction about animals,  it was time to test it why we have two ears, and how it helps in our hearing.

Materials needed

1.  small hose pipe ( 3 foot length) -1
2.  a pencil or a small fork or butter knife - 1

Procedure

In this experiment, students were paired up to hear sound through hose pipe. They had to hold the ends of the hose to cover up both ears, and the hose itself was behind the ears.  A partner stood behind a student  and tapped anywhere on the hose with a pencil. Students, tried to guess whether the tapping was closer to the right or left ear. They were told to observe, how far does it have move away from the midpoint of the hose before they can hear closer to one ear than the other.
They tried it several times with partner tapping on different places.

Students tried to listen with one ear closed

Finally, students tried to  listen with only one ear.  Is it difficult to locate the source with one ear?
Yes, they understood the difference between listening with one ear versus two ears. They found it difficult to guess which direction the sound was coming from.

If you listen to the tube with only one ear, you will not be able to detect whether the tapping is slightly to one side or the other of the middle of the tube. However, you may be able to detect when the tapping is close to your ear and when it is far away. 



Explanation


Two ears helps us to locate the source in different ways. Sounds enter into different canals and once they reach the lower part of the brain convert into nerve impulses. A very complex mixing takes place after which some impulses reach one part of the brain, some to the other part of the brain and some to both the parts. This allows us to experience "three dimensional" hearing just like you can see the depth of perception with both the eyes. Directional 3D hearing is not possible with only one ear to hear. We can experience it clearly while watching movies in theaters with stereo effect.

Sound travel through metals

Molecules in solids are closely packed (dense ), hence the vibrations in solids  are easily passed from one molecule to the other. Following is a very simple experiment, but kids will be thrilled to hear the effect. 

Materials

1. Jute yarn or any yarn - 2 

2. Stainless steel table spoon  -1

3. Metal cloth hanger - 1

Procedure

1. Try listening to the yarn by just strumming it. 

2.Tie the yarn to the  2 ends of the metal hanger . You can also use a big spoon if you don't have a metal hanger.

3. Using the metal spoon tell your buddy to tap the metal hanger, or alternatively you can tap the hanger to a cupboard.

4. Closely listen to the sound in your ears.  

 Observation

As you tap the hanger on to a table or tap it with a spoon you will hear the sound louder in your ears. This is due to sound amplifying in the metal hanger  and travelling to your ears through the yarn. 

To make it fun we did the following activities by making membranophone and water whistle. 

Water Whistle

Materials

1. Straw - 1

2. Scissor -1

3. Tall glass - 1 (with water in it)

Procedure

1. Using a scissor , 1/3 of the way down the straw partially cut the straw. 

2. Bend it at the right angle , but do not break the straw.

3. Put the straw inside the glass with 3/4 cup water. 

4. Place your lips on the shorter end of the straw and blow air ...

5. What do you hear?

Observation and explanation

When you blow air across the longer part of the straw you are making the column of air inside the straw to vibrate. This air column creates the whistling sound. You can change the pitch of the sound by moving the straw out of the water. If there is more air inside the straw the pitch is lower.

Water bottle membranophone

It is an instrument that produces sound when the stretched membrane is vibrating. 

Materials

1. Empty water bottle - 1.

2.Latex gloves or big balloon - 1

3. Hole puncher -1

4.Scissor -1

5. construction paper -1.

6. Rubber band -1

7. Straw -1 

Procedure

1. Cut the bottle in half. Make sure it has smoother edges.

2. Take a hole puncher or a nail and make a hole away from the cut edge just enough for a straw to fit in. 

3. Cut the finger parts of the gloves and stretch it across the cut side of the bottle. 

4. Using the rubber band wrap it around and secure the glove in place

5. Unscrew the cap and remove it.

6. Roll the construction paper into a roll and secure it snug fit inside the neck of the bottle.

 

7. Insert the straw into the hole punched before. Blow into the straw and play membranophone music now.

Observation and explanation 

As you blow into the straw you create pressure between the inner wall of the bottle and the outer wall of the construction paper. That pressure forces the membrane to rise allowing air into the top of the tube and escape from the bottom.