SOUND

Sound Quick Quiz What is sound? What is pitch? How do the parts of a wave relate to pitch? How do the parts of a wave relate to the volume of a sound? Through what medium will sound travel the fastest (solid, liquid or gas)?

Reflection and sound Echolocation Sonar Ultrasonography

Some Examples… Constructive Interference Destructive Interference http://www2.biglobe.ne.jp/~norimari/science/JavaEd /e-wave2.html Destructive Interference http://www2.biglobe.ne.jp/~norimari/science/JavaEd /e-wave3.html Standing Wave http://www2.biglobe.ne.jp/~norimari/science/Ja vaEd/e-wave4.html

Resonance Standing waves – those that appear to be still; actually a wave and its reflection experiencing interference as they travel; this occurs a medium’s “resonant frequency.” Resonance occurs when an object that is vibrating at or near another objects natural (resonant) frequency causes that other object/medium to vibrate

SOUND Sound travels as a longitudinal wave Energy from a vibration is carried through the medium as the molecules of the medium move back and forth as the disturbance goes by You hear the sound when (and if) the disturbance reaches the medium near your ear

What determines the sound you hear? Properties of sound include what you hear and how high or low it sounds. Each of these is dependent upon the properties of the wave producing the sound

Frequency Frequency refers to the number of waves that pass a point in a second; The frequency of sound waves indicates the pitch (how high or low) the sound has.

Frequency The lower the frequency, the lower the pitch 700 Hz sound The higher the frequency, the higher the pitch 1400 Hz sound Turn It Off!

Amplitude The amplitude of a sound wave indicates the energy carried by the wave The higher the amplitude, the more intense the sound, or the more loud the sound seems Turn It Off!

The amplitude of sound, or its loudness, is measured in DECIBELs. Weakest sound heard 0dB Whisper Quiet Library 30dB Normal conversation (3-5') 60-70dB Telephone dial tone 80dB City Traffic (inside car) 85dB Train whistle at 500', Truck Traffic 90dB Subway train at 200' 95dB Level at which sustained exposure may result in hearing loss 90 - 95dB Power mower at 3' 107dB Snowmobile, Motorcycle 100dB Power saw at 3' 110dB Sandblasting, Loud Rock Concert 115dB Pain begins 125dB Pneumatic riveter at 4' Even short term exposure can cause permanent damage - Loudest recommended exposure WITH hearing protection 140dB Jet engine at 100', Gun Blast Death of hearing tissue 180dB Loudest sound possible 194dB  

Speed of sound Temperature Elasticity Density The speed of sound is dependent upon the properties of the medium through which it travels; those properties include Temperature Elasticity Density http://www.knowitall.org/nasa/simula tions/sound/howsound.html

Sound travels faster in a more elastic medium; Elasticity- this tells us how FAST particles move back to their original (rest) position after a disturbance passes through. Sound travels faster in a more elastic medium; Fastest in solids, slowest in gases Speed of sound in the ground is four times faster than in air!

Temperature Sound travels slower at lower temperatures Sound travels faster at higher temperatures

Density Density affects the speed of sound when considering mediums that are the same state or phase of matter The less dense the medium, the faster the sound; The more dense the medium, the slower the sound

The Doppler Effect The apparent change in frequency as the wave source moves in relation to the listener This is heard as a change in pitch

Sound Wave Interactions Constructive Wave Interference will amplify a sound or make it louder. Destructive Wave Interference will make the volume of a sound softer.

Draw a sound wave with a high pitch and low volume.

Draw a sound wave with a loud volume and a high pitch

Draw a sound wave with a low pitch and high volume.

TOTD: Draw a sound wave with a high pitch and high volume.

Chuck Yeager On October 14, 1947, Captain Chuck Yeager became the first person to fly a plane faster than the speed of sound. How did Chuck Yeager “cheat” to break the sound barrier?

Speed of sound and the sonic boom "At sea level a plane must exceed 741 mph to break the sound barrier, or the speed at which sound travels. The change in pressure as the plane outruns all the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Altitude, wind speed, humidity, the shape and trajectory of the plane - all of these affect the breaking of this barrier. The slightest drag or atmospheric pull on the plane shatters the vapor oval like fireworks as the plane passes through," he said. "You see this vapor flicker around the plane that gets bigger and bigger. You get this loud boom, and it's instantaneous. The vapor cloud is there, and then it's not there.”