# Pete (10) asks “What is the pitch of a sound?”

Thank you team.  Lets first look at the motion of the particles. You suggest that the motion of the particles is in the form of waves. I think that is quite difficult to imagine but I think I have an example that will help illustrate this type of motion. Look at what happens when you drop a pebble in a pond. The pebble, when it hits the water, it creates  one vibration.

In this image the sound is produced by the piston creating the waves. Notice the wavelength, that is important. If we can manipulate the piston, make it go slower or faster  we can change the wavelength. Changing the wavelength is changing the pitch, think about that.  How does the sound change?

Try blowing over, or tapping, some bottles.

Pitch and Frequency ..Test your hearing a little bit more …….

In the video below you can see and hear how the pitch of the sound and the wavelength change together.  We measure wavelength in units called Hertz. 1 Hertz is one cycle per second. In the image above imagine that it takes one second to get from the flute to the ear. Then there are 8 cycles in the top sound is so frequency is 8 hertz and there are 3 cycles in the bottom sound so the  wavelength is 3 Hertz.

You can now test your hearing.    Take Care….make sure you have control of the volume.

Thanks to
Orion Lawlor, for the water ripples video, Published on 9 Jan 2011
Earmaster at https://www.earmaster.com/music-theory-online/
The ISVR from the Institute of Sound and Vibration Research, University of Southampton.
The Sound Video, unknown but thanks.

# “How does sound travel in things other than air?” asks Lilly(12)

Hello Molly, Science Master here. Lets’ check that we understand how sound is produced and what it is. Sound is a form of Energy ( see Science Master Special).  It is transmitted by particles hitting each other.

So what do you think? Could you hear the sound underwater?  Could you hear the sound further along the metal tube?

Lets improve the experiment by making it fairer. How could we do this?

Let us look at the particle arrangement in the air, water and metal.

The average distance between particles for a gas is 4 nanometers (1 nanometer = 10-9 meters), for a liquid it is 0.2 of a nanometer and for the solid 0.0002 of a nanometer.

So. If the first line of particles in the gas starts moving it has to travel 4 nanometers before it hits the second row. For the liquid this would be a smaller distance and for the metal it would be hardly any distance. What does that tell you about the speed of travel of sound?

Does your experiments support your thoughts? Maybe it needs to be modified? How could you modify it to really test your thoughts.

Just a thought of my own. The sound source (drum, spoon tapping, violin) gives the particles around it ENERGY. Those particles in air have to travel a long distance before they hit another particle and pass the sound on. All this time they are losing ENERGY. For the metal the particles only have to travel a little way before passing on the vibration.

Not sure of something Lilly…ask another question.

(Anyone reading this post who wants to ask a question or make a comment please feel free to do so)

Thank you team. Some of the things in the image above make sounds without tapping or blowing. Can you find them? Miwah asked a similiar question where he investigated how the sound a drum made was created. Can you try an make a sound using a ruler. Try holding one end of it on the desk and then bending it slightly by pushing down on the end which is not resting on the desk.

Now let go ….. and here come the questions.  Did you hear anything? What did the end of the ruler do? If there was a sound when did it stop?

Another question. If there was a sound what part of your body detected it? So how did the sound get to you? What is between your bodies sound detection and the ruler?

Now for a little bit of information. How did the ruler move when you let go of it? The word to describe this movement is ‘vibration’. A vibration is a continuous small movement up and down, or side to side. This is what Miwah discovered in the drum investigation. Below is a small video of a plastic ruler being pushed downwards and then allowed to vibrate.

Investigate making other objects making sounds and see if you can ‘feel’ the vibrations.

Any more thoughts , then please make a comment or ask another question.

# Elizabeth (9) asked “If you picked up a shell from the beach and put it close to your ear why does it have the sound of waves?”

Elizabeth, I think we need to do some experiments, firstly did you know that sound can be reflected? Sound can be reflected like light, and like light the surface it bounces off can affect the bounce. Try reflecting sound using a mirror (preferably plastic). You could use a loud ticking clock as a sound source. You then use your ears to detect the reflection. Now cover the mirror with some paper see how it affects the reflection. You might have some difficulty in making the experiment ‘fair’ but never mind (a sound detector would help make it fairer).

Now instead of a shell, place (carefully) a cup over your ear and listen. Replace the cup with a closed cardboard tube and listen. Do you hear anything? You might hear a low quiet whistling sound. Try making the tube shorter/longer and see how it affects the sound.

How was what you heard different from what you heard when you used the shell? What is the difference between the surface of the cup and cardboard tube and the shell surface?

My thoughts are that we are living in a ‘sound’ environment. Putting the cup over our ear cuts out most of the sound but not all of it. We call that an ambient sound. This sound manages to enter our cup and it is bounced around in the cup, but inside a shell the bouncing is slightly different.

Let me know what you think by filling in the Reply box below and post your comment or ask another Question . Anybody can do this.

# Ethan (8) asked “How can you hear things?”

Ethan. There are some other small experiments I would like you to try.

Find a ticking clock and a box that you can put it in.  Listen to the ticking with the lid on and the lid off. could you hear the ticking when the lid was on?  Now with the lid on get a cardboard tube (maybe one from a tube of kitchen roll) , put one end of the tube on the box lid and the other end over your ear. Listen. Is the sound of the ticking louder when you use the tube? Move your ear away from the tube. What happens to the ticking?

Also see Clara’s question on sound.

# Miwah (7) asked ” I hit a drum and it produced a banging sound. How did it do that?”

Miwah, what a great question. It really needs some thoughts from my team.

So Miwah what are your thoughts? What happens to the rice when the sound  occurs?

Is there anything around the rice? If there is will that behave in the same way?

# Science Master Special – Energy

Thanks team. I would like to add a few things.

Firstly the list of different types of energy is not complete. If you can think of some more then ‘Leave a reply’ in the box below.

Secondly it is interesting how the energy conversions can take place. For example a microphone converts sound energy into electrical energy and a loudspeaker does the reverse process, it converts electrical energy into sound energy. Can you think of other examples?

# Mattheiu (Yr 4) asked “If sound can’t travel through vacuums, why are they so loud?”

This is an excellent question. We are told that sound travels through the air to us by the vibrations of the air molecules between speaker and listener. But how does is get to us from a very distant speaker? Or through a vacuum? The magic formula is that one form of energy can be converted to another form of energy, as my team have explained.

If we can convert one form of energy to another then why not convert sound, which is moving air and therefore kinetic energy (the energy of movement) to electrical energy that can be passed down a wire or through a vacuum as an electromagnetic wave to a listener a long way away. When it is received the reverse conversion process can take place where the electrical energy can be converted back to kinetic energy, via electromagnetics and loudspeakers and not forget ears and brain.  Then by controlling the input to the conversion process we can control the loudness. Magic but real.

# “Does sound bounce?” asked Molly (7)

Molly, this seems to be a question that we could investigate. I have asked my team about it.

You will now have to think of some experiment to test the ideas that my friends have come up with. See if you can get a plastic mirror and maybe a sheet of cardboard. The next task is how to see if you get a bounce. You will probably need a friend , a cardboard tube and a device to make a sound (bell, buzzer, horn or something else). Your friend can ring the bell in front of the tube and you can  then listen to see if you can hear a bounce from the mirror or cardboard. Try it and then try it again, see if you can make the test as fair as possible. If you can get it to work, try with other surfaces, paper, carpet, aluminium foil. Have fun.

Let me know how it went.

# Clara (8) asked -“Does sound only travel in air”

A great question and some interesting comments from my team. I think we need to carry out some experiments to test the ideas that my friends have.

Firstly we know that air can carry sound. To consider the radiator pipe idea we need to get a tube of metal and see if, on it’s own, it carries sound. tap one end of the tube and put your ear on the other end. record what you hear. Now fill the tube with water and repeat the experiment. You could also get a rod of metal, with no air, no water and test that. If you had a sound sensor(your school might have one) you could measure the amount of sound that a solid rod, water filled rod and air filled rod carry. Which was best? How did you make the test fair?

The string telephone could be another example of sound travelling from one place to another without using the air. Try to make ‘telephones’ that are ‘sound proof’. For example make sure that when somebody is speaking into the mouthpiece they cannot be heard speaking by those standing around. No ‘air’ sounds. to do this you might have to modify the mouthpiece.

Try this video for further information. If after watching it you have any further questions  ….THEN