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Q & A: Sound Wave Demonstration

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Most recent answer: 04/14/2010
Q:
I am doing a presentation about how sound travels. If you have any info you could scan and send me it would be of great help. Thank you .
- Heidi Jurges (age 17)
Bremerton, WA
A:
Sound travels in waves. A slinky is a good demonstration of what a wave looks like and how it behaves.

You could also have several people stand in a circle with you holding hands. Everyone closes their eyes. When anyone feels one of their hands raised, they are to lift their other hand. If one hand goes down, they lower the other hand. You start it by lifting one of your hands that is holding someone else’s hand. Since it take a moment for people to respond, you can see the wave moving around the circle. If you have enough people you can even have several waves moving in different directions all at the same time.

When you get too many waves, it breaks down into a “noisy” clutter of waves, just like trying to listen to one person in a talking crowd.

EJ

(published on 10/22/2007)

Follow-Up #1: Hearing frequency

Q:
Can sound waves of a certain frequency and pitch hurt the ear but not be heard by others or cause pain to others?
- Pam Brown (age 56)
Landenberg, PA, USA
A:
Pam, The human ear can sense sound waves from 20 to 20,000 Hertz. This is the general frequency but as you get older your ability to hear decreases which means that your range of frequency that you can hear decreases. This happens because there are tiny hairs in your ears the convert the vibrations into nerve signals. As you grow older these hairs start to die and they cannot grow back, causing hearing loss. Usually sensitivity to high frequency sound waves is the first to decrease with age.

Sound waves hurt your ears if they are loud. The loudness of sound is measured in decibels. Usually humans can hear below 75 decibels without any damage to the ear. We're not sure if there are cases where your ears can be hurt by sound that you can't hear.

-Prathum

(published on 04/14/2010)

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