Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
Some Useful Words For You To Remember
Pitch – how high or low a sound appears to be
Loudness – how loud or quiet a sound appears to be
Vibration – a to and fro motion, sound is made by vibrations
Muffle – to make a sound quieter
Tuning – to make an instrument sound as it should
Tension – how tight a string is
High – a high sound is squeaky like a mouse
Low – a low sound is booming like a bass drum
Sound
Sound is what can be perceived by a living organism through its sense of hearing. Physically, sound is vibrational mechanical energy that travels through matter as a wave.
How Fast Does Sound Travel?
Sound travels at different speeds according to the material that it is passing through. The denser (thicker) the material the longer it will take the sound to travel.
How Does Sound Travel
Sound travels through different kinds of matter. Sound travels through gases, liquids and solids.
What kind of matter does sound travel best in air, water, wood or metal?
Here’s some cool things to try!!
Hold a plastic bag of water against one of your ears.- Cover your other ear with your hand.
- Have someone hold a ticking clock against the bag of water. Now listen.
- Keep the clock in the same place. Remove the bag of water. Now listen.
- Place a block of wood between your ear and the clock. Now listen.
- Do you hear the clock best through the air, the water or the wood?
- Place the clock 20 cm away from your ear and listen to the ticking.
- Have your partner hold the clock at the 20-cm mark on the meter stick. Place your ear at the end of the meter stick and listen.
- Have a friend hold a metal rod to your ear and place the clock against the rod 20 cm away from your ear. Now listen.
Does sound move differently through some solids than it does through others?
Now let’s make a plastic telephone!!
Materials needed:
Two plastic cups- Some string
- Paper clips
- Sharpened pencil for poking holes
Instructions:
- With the pencil, carefully poke a small hole in the bottom of each plastic cup.
- Tie the paper clip to one end of the string.
- Thread the other end of the string through the hole in the bottom of one of the cups. Be sure to thread it from the inside of the cup. The paperclip will keep the string from going all the way through the hole.
- Then thread the string through the hole in the second cup, but this time do it from the outside of the cup.
- Tie the second paper clip to the other end of the string. The paper clip should be inside the cup, just like the first paper clip.
- Take the plastic cups (telephone) and hold your cup to your ear while your friend talks slowly and clearly into the other cup. Keep the string tight.
How does it work? What is vibrating? How do the vibrations of your friend's voice reach your ear?
Can a third person talk and listen if another cup with a string is attached?
Take the separate cup with the string and attach it to
the first line. Keep all strings tight while one friend talks into
one cup and the other two friends listen.
Can you hear the message
of the third party? How many lines could you attach? Does each
addition weaken the vibrations?
Stopping Sound (Known As Sound Insulation)
Soundproofing is any means of reducing the intensity of sound with respect to a specified source and receptor. There are several basic approaches to reducing sound: increasing the distance between source and receiver, using noise barriers to block or absorb the energy of the sound waves, using damping structures such as sound baffles, or using active antinoise sound generators.
Soundproofing affects sound in two different ways: noise reduction and noise absorption. Noise reduction simply blocks the passage of sound waves through the use of distance and intervening objects in the sound path. Noise absorption operates by transforming the sound wave. Noise absorption involves suppressing echoes, reverberation, resonance and reflection. The damping characteristics of the materials it is made out of are important in noise absorption. The wetness or moisture level in a medium can also reflect sound waves, significantly reducing and distorting the sound traveling through it, making moisture an important factor in soundproofing.
The use of distance to dissipate sound is straightforward. The energy density of sound waves decrease as they spread out, so that increasing the distance between the receiver and source results in a progressively lesser intensity of sound at the receiver. In a normal three dimensional setting, the intensity of sound waves will be attenuated according to the inverse square of the distance from the source. Using mass to absorb sound is also quite straightforward, with part of the sound energy being used to vibrate the mass of the intervening object, rather than being transmitted. When this mass consists of air the extra dissipation on top of the distance effect is only significant for typically more than 1000 meters, depending also on the weather and reflections from the soil.
Damping is the process by which sonic vibrations are converted into heat over time and distance. This can be achieved in several ways. One way is to add a layer of material such as lead or neoprene which are both heavy and soft. These can be used as a sound deadening layer in such areas as wall, floor and ceiling construction in sound studios where levels of air borne and mechanically produced sound are targeted for reduction or virtual elimination. Lead and Neoprene do not address the lower, most bothersome low frequency vibrations and can be very difficult to install as well as costly.
Making a sound wave transfer through different layers of material with different densities assists in noise damping.
Some Cool Links
Click on any of the link buttons below to find out lots more.
Have fun!!!
Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
