WHAT IS SOUND?!?!? Sound Vibration Is a wave that vibrates particles of matter A rapid back and forth movement

Decibels (dB) = measure of intensity or loudness Examples: 10 dB breathing 20 dB whisper 60 dB people talking 80 dB vacuum cleaner 100 dB power saw 140 dB Firecrackers

Dispersion is the spreading out of energy Just like dispersion of light, dispersion of sound is when it spreads out the further it goes from the source

IS THERE SOUND IN SPACE? Space is a vacuum, which means empty space or very few particles. Vibrations have to travel through matter in order to make a sound. In space there is no ‘air’ or medium for the wave to vibrate, thus no sound can be produced.

WATCH THIS => http://bit.ly/1HG3RIt http://bit.ly/vocalcordssinging How do we produce sound? We use our muscles in our body like our diaphragm to push air up from our lungs into an narrow passage (trachea) then through the larynx which include the vocal cords in them. Vocal cords are actually folds! Our body forces air past the folds, which causes them to vibrate! That action produces sound waves!

Parts On your diagram label . . . Diaphragm Lungs Trachea Larynx/ Vocal cords Oral cavity

Vocal folds This entire structure to the right is the Larynx, but the white bands are the actually the vocal folds. Everyone’s folds are slightly different, which is why we have different voices. The shape changes pitch. (as you have learned)

How Do Our Ears Hear Sound Waves? Vibrations travel though the ear canal Then the sound waves vibrate the eardrum, which moves the 3 bones in the ear called hammer, anvil, and stirrup

Continued- How Do Our Ears Hear Sound Waves? WATCH THIS => http://bit.ly/how-we-hear Continued- How Do Our Ears Hear Sound Waves? The eardrum vibrating causes the three bones in the ear to vibrate, which is detected by the cochlea. The cochlea has millions of little hairs called cilia inside the ear fluid that move with the vibrations. The movement of the cilia against the auditory nerve sends messages for the brain to decipher.

What Affects the Speed of Sound? Temperature and medium effects the speed of sound.

Speed of Sound in Different Mediums If the temperature for all three examples is 20 degrees Celsius: In Air-(Gas) sound waves travel at 344 m/s In Water-(Liquid) 1,400 m/s In Steel-(Solid) 5,000 m/s

Why? In order for particles to vitiate in a wave, one particle must then hit the next particle to pass on the energy and continue the wave. There is not as much space between particles in a solid so the vibration wave would move faster. In a gas there is a lot more space in between so the particle would take longer to hit the next. Think of it like the spacing of dominoes

Speed of Sound in Different Temperatures If you are in the desert and in it 115 degrees F sound will travel faster, then if you are in the arctic and it is -20 degrees F! Why? At higher temperatures particles move faster. So if sound waves push against the already fast moving particles, then it will quickly pass through and vibrate the already fast moving particles.

Stop and Think! What Affects the Speed of Sound? Would sound travel faster in cold air or hot air if the humidity was the same? Why? Would sound travel faster through water or bricks? Why?

Waves Have Common Features:

Frequency A given number of waves in specific amount of time, which determines the pitch. The pitch is a characteristic of high and low sounds. Frequency is measured in hertz. (hz)

FREQUENCY Higher frequency = more waves per period of time.

The Doppler Effect The Doppler Effect is a change in the perceived pitch when the source of the noise is moving. So to Further Explain: All waves, light and sound, travel out from the source, but when the source is moving towards you the waves get bunched closed together making a higher frequency/pitch and the waves trailing behind become spread out making a lower pitch/frequency. http://www.youtube.com/watch?v=Kg9F5pN5tlI

Amplitude Amplitude determines intensity, which is just how loud sound is. Intensity or amplitude of sound is measured in decibels (dB).

Longitudinal versus Transverse What kind of waves can we produce with a slinky? We can produce both transverse and longitudinal waves. In the picture below, (a) is a longitudinal wave (compressional) , while (b) is a transverse wave.  

Seismic Waves (Caused by vibrations inside earth)

ECHO! Sound Waves Reflect off of Surfaces!