Sound Energy

- waves of VIBRATING MATTER that change speed depending on what they are going through.

Sound is produced when matter vibrates.

When particles vibrate they generate a wave of energy known as sound. Without matter there can be no sound.


Sound CANNOT travel in a vacuum.

This means that sound CANNOT travel through the vacuum of space. Without particles, sound cannot be passed. Sound can ONLY travel when particles hit each other.

The sun is an intense nuclear fusion reactor. If it did this job on Earth it would be unbearably loud! Because there is NOTHING but space between us and the Sun, we cannot hear those explosions. Thank goodness!
That means the "sound" of the death star exploding is really just another imaginary part of Star Wars. Turn down the sound to get the idea.



The speed of sound depends on the medium it is going through.

speed of sound in a vacuum
0 m/s

Sound can ONLY travel when particles hit each other.

speed of sound in a gas (20OC air)
337 m/s

You hear most things because of vibrating AIR. The air causes your ear drums to vibrate and your brain translates the vibrations into recognizable sound.

speed of sound in a liquid (water)
1484 m/s
You can hear sound through LIQUIDS. Listen for sound in the basement the next time you take a bath. If you put your ears below the water when taking a bath and tilt your head to get the air bubbles out, the sound from the basement will pass through the floor and enter your ear drum through the water.
speed of sound in a solid (Iron)
5120 m/s
You could hear sound through SOLIDS. A train can be heard from multiple miles away as it comes down the track. If you place your ear directly on the track. (I recommend facing the correct direction) The sound will pass from the train to the track to the bones of your head.




300,000,000 m/s


(that's about a million times faster than sound in air)




Sound moves as a compressional wave.

A compressional wave (also called longitudinal wave) occurs when matter has been pushed.


Imagine pushing on a slinky. (not shaking it up and down) The result will be a wave of rings that are closer together than the other rings. They travel the length of the slinky, bounce off the end and rebound back toward the source.



The intensity or loudness of sound is called amplitude. It is measured in decibels(dB).



Sound is "heard" when the brain interprets vibrations in the ear.


Think of all of the things that must work correctly in order for you to hear!

Microphones are the technological equal to the ear. Both take vibrations and convert them into electrical impulses.


The frequency of sound waves determines its PITCH

-the number of waves per second (frequency) determines how high or low the sound is (pitch)

- LONG objects vibrate with LONG waves. They are slower in the sense that fewer of them will pass by in one second. We say they have a LOW FREQUENCY. The lower the frequency the lower the PITCH of the sound. Pitch is how high or low a tone is.

Remember: LONG and SLOW make LOW

The opposite is also true. Small object vibrate with short quick waves. The higher the frequency the higher the pitch of the sound. (start at 1 min)




Stopping some of the vibrations will make the pitch lower

Pouring water into the glass will absorb some of the vibrations. If the glass is made to vibrate at a lower frequency, the pitch will be low as well.



Doppler Effect: Pitch changes when noisy objects move.

When noisy objects move TOWARDS you their pitch will be HIGHER than normal.

When noisy objects move AWAY from you their pitch will be LOWER than normal.



EXTRA ** Physics of MUSIC ** EXTRA





Test out your own hearing range with this online tone generator .







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