2. Sound Energy

3. What is sound? Sound is – A form of energy made by vibrations. – When an object vibrates it causes the air particles around it to move. – These particles bump into particles close to them and this continues until they run out of energy.

4. Try this: Put your finger on your neck and say “aah” as loud as you can. Now say it as soft as you can. You can not only hear the sound, but you can feel the vibration inside your throat.

5. Waves transfer energy without transferring matter. Frequency= waves/time

6. How does sound travel? Sound travels through all forms of matter— gases, liquids and solid. These are called the medium. Sound cannot travel through a vacuum.

7. How does sound travel? Sound passes through the medium as longitudinal waves. When the vibrations are fast you hear a high pitch. When they’re slow, you hear a low pitch. High PitchLow Pitch

8. What is pitch? Pitch is how high or how low a sound is. This is a high pitched sound. This is a low pitched sound. Pitch is how high or how low a sound is. This is a high pitched sound. This is a low pitched sound.

9. Remember: Lower frequency (lower pitched) sounds have a long wavelength and are not absorbed as easily as high pitched sounds. – Why you hear the bass of a song through a wall before you hear the treble – Why you hear the rumbles of a movie through a wall before you hear anything else

10. Did you know? Sound travels 4 times faster through water than through air. There is no sound in space. Geologists use their knowledge of how sound travels through rocks to help them find oil fields.

11. Ultrasound - sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz Infrasound - sounds with frequencies below the normal human range of hearing. Sounds in the 20-200 Hz range

12. Sounds from Moving Sources. – A moving source of sound or a moving observer experiences an apparent shift of frequency called the Doppler Effect. – If the source is moving as fast or faster than the speed of sound, the sound waves pile up into a shock wave called a sonic boom. – A sonic boom sounds very much like the pressure wave from an explosion Doppler Effect

18. Louder Softer How else can we change sound? We can make it louder or softer by changing the amplitude of the height of the wave. The higher the amplitude, the louder the sound. The lower the amplitude the softer the sound.

19. Loudness of Sound in Decibels SoundLoudness (dbs)Hearing Damage Average Home 40-50 Loud Music 90-100 After long exposure Rock Concert 115-120 Progressive Jet Engine 120-170 Pain

20. Pitch how high or low the sound seems to a person Loudness- how loud or soft a sound is perceived to be.