1. The Nature of Sound

2. New Vocabulary Vibrations- back and forth movements of matter
Sound- form of energy that you can hear and travels through matter as waves
Compression- region where the particles have been pushed closer together

3. New Vocabulary
Rarefaction- region where there are fewer particles than normal
Overtones- softer, higher tones that are mixed with the basic tones
Timbre- special sound produced by a musical instrument

4. The Nature of Sound
Vibrations, or the back and forth movement of matter, are what causes us to hear our favorite songs.
As you saw in the rubber band experiment, as the band vibrated you hear the noise along with it.
Air carries the vibrations to your eardrums and causes them to vibrate.

5. The Nature of Sound
The vibrations in your ears produce nerve impulses that are carried to your brain.
These impulses are interpreted as sounds.

6. Sound Waves
Sound is a form of energy that you can hear and travels through matter as waves.
Anything that is in motion has energy, and sound is certainly in motion.
Objects that vibrate create a back and forth motion

7. Sound Waves
It is this back and forth motion that pushes against air particles around them and creates sound waves.
The sound waves travel outward in all directions from the source.
The areas that have been pushed closer together are called compression.

8. Sound Waves
Air pressure is greater than usual in this compression region
The region where there are fewer particles than normal is called a rarefaction. Air pressure is lower than usual here.
A sound wave is a series of compressions and rarefaction moving outward from the source of a vibration.

9. Sound Waves
A sound wave can be represented as seen below. The crests represent the compressions and the troughs represent the rarefactions

10. Sound Waves
When a sound wave travels from its source to your ear, the particles that carry the wave do not travel along with the wave. Think of it like surfing. Where would find the majority of surfers… on the wave bro!!!

11. Measuring Sound Waves
The distance from one compression to the next is wavelength.
Wavelength depends on the frequency of vibration of the source of the sound.
High sounds have high frequency
Low sounds have low frequency
Amplitude is the distance from the rest to the crest. It is the measure of the amount of energy in the sound

12. Measuring Sound Waves Large Amplitude = loud sound
Small Amplitude = soft sound

13. Quality of Sound- Timbre
Tones are a form of sound that has a single frequency and a single wave pattern.
Most sounds we hear however have a combination of different waves.
Instruments have complex sounds as well. The sound of a musical instrument is made up of a basic tone and overtones.

14. Quality of Sound- Timbre
Overtones are softer, higher tones that are mixed with the basic tone. This mixing of basic tones and overtones is what gives instruments their unique sounds.
The special sound created by an instrument is called its timbre.

15. Noise
Not all sound is pleasant. Many sounds like jackhammers and broken dishes are unpleasant.
Unpleasant sounds have irregular sound waves. Compare below….