Sound

– form of energy – all sounds are made by vibrations – sound moves through mediums as a compressional wave

How Does Sound Travel? 1.Objects vibrate 2.Vibrations transfers energy 3.Causes collisions of nearby air molecules 4.These molecules then collide with others 5.These collisions and energy transfers form the sound wave

Speed of Sound Most sound waves travel through air BUT sound can travel through solids, liquids or gases Sound travels faster in solids and liquids than gases

Speed of Sound Mediumsound speed (m/s) air (20  C) 343 water1497 gold3240 brick3650 wood3800–4600 glass5100 steel5790 aluminum6420

Breaking the Sound Barrier Chuck Yeager broke sound barrier in 1947 Speed of sound at 68° F (20° C) is 768 mph Breaking the sound barrier Breaking the sound barrier

Anatomy of the Ear

Properties of Sound Intensity – Amount of energy that flows through an area in a certain amount of time – Lower volume, lower intensity – Less intensity, less distance the sound wave will travel

Properties of Sound Loudness – Human perception of sound intensity – Measured in Decibels – 0 dB (faintest sound) – >120 dB (pain threshold)

Cilia of the Cochlea Normal Serious Damage Moderate Sound Damage

Process of Hearing

Properties of Sound Pitch – Highness or lowness of a sound – Higher the pitch, higher the frequency – Lower the pitch, lower the frequency – Pitch expressed as musical notes (C, F sharp, E flat etc..)

Frequency Range Human voice range from 250 to 4000 Hz range Human ear can hear frequencies between 20 Hz and 20,000 Hz Frequency Hearing Test Test your hearing with the following frequencies: Frequency Ranges:

Properties of Sound Ultrasonic – Sound frequencies above 20,000 Hz Infrasonic/Subsonic – Sound frequencies below 20 Hz – Elephant's Subsonic Sounds Elephant's Subsonic Sounds

Properties of Sound Doppler Effect – Change in pitch or wave frequency due to movement – The Doppler Effect can occur when the source of a sound is moving or the listener is moving in relation to the source of the sound

Music – Sounds that are deliberately used in a regular pattern – Natural frequencies All objects have a natural frequency at which they vibrate – Resonance Amplifies the sound of musical instruments

Pythagoras and Music

Sound Quality – Describes differences among sounds of the same pitch and loudness Overtone – Other frequencies besides the fundamental that exist in musical instruments – Different instruments = different overtones

Overtones All are playing the same note Have the same wavelength and frequencies Because of overtones, very different sound

Musical Instruments Strings – Violins – Guitars – Harps – Cello – Usually have resonators Resonator – Hollow chamber filled with air that amplifies sound

Musical Instruments Brass and Woodwinds – Horns – Trumpets – Flutes – Oboes – Brass uses cone-shaped mouthpieces to cause air to vibrate – Woodwinds use wooden reeds to cause air to vibrate

Musical Instruments Percussion – Drums – Xylophone – Drums use membrane stretched across a resonator – Xylophones use tube- shaped resonator

Bellringer (15 minutes) In paragraph form, describe 3 ways that sound is used by humans and animals. Include the definition of acoustics in your paragraph. Be sure to mention the difference between sonar and echolocation.

Using Sound Acoustics – Study of sound Echolocation – Process of locating objects by emitting sounds and interpreting the sound waves reflected back

Using Sound Sonar – System that uses the reflection of underwater sound waves to locate objects

Using Sound High frequency sound waves used in many ways: – Remove dirt and buildup from jewelry – Detects and monitors many medical conditions Pregnancy Heart Disease – Break up kidney stones – Produces images of internal body structures