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Waves and Sound. What are waves?. Wave – a disturbance that transfers energy from place to place. Medium – the material thru which a wave passes Waves travel trough the medium without actually moving the medium with it. Types of Waves:.
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What are waves? Wave– a disturbance that transfers energy from place to place. Medium– the material thru which a wave passes Waves travel trough the medium without actually moving the medium with it.
Types of Waves: Transverse Waves: waves that move the medium at right angles to the direction in which the waves are traveling. Longitudinal Waves: move particles parallel to the direction the wave is moving, “push-pull” waves.
Wave Particle Movement Transverse Waves Compression Wave Waves travel trough the medium without actually moving the medium with it. Basically the medium stays put while the wave moves some distance
Properties of Waves • Amplitude – in a transverse wave – the height away from the “rest” position. The amplitude in a longitudinal wave is the measure of how compressed or rarefied the medium becomes. • Wavelength– the distance between two corresponding parts of a wave. • Frequency– the number of complete waves that pass a given point in a certain period of time. Frequency is measured in Hertz; one Hz is a wave that occurs once every second.
Speed, Frequency, and Wavelength Speed S = x f = 1.5 m x 280 Hz = 420 m/s Wavelength x frequency S = S / f = 5.0 m/s / 2.5 Hz = 2 m x f • Speed (meters/sec)= wavelength x frequency • Frequency (Hz = 1/sec)= speed / Wavelength • Wavelength (meters) = speed / Frequency (Designated by Greek letter lambda )
Interactions of Waves • Refraction– The bending of a wave due to the wave moving from one type of medium into another. • Reflection – Bounce back wave • Angle of Incidenceis the angle of the wave coming into the object reflecting the wave. • Angle of Reflectionis the angle bouncing off and going away from the object.
Interactions of Waves Diffraction– Wave passing a barrier or going through a hole in a barrier bends and causes the wave to wrap around the barrier
Interactions of Waves • Interference – when two or more waves meet, they interact. This interaction is called interference. • 1. Constructive Interference– the combining of waves to cause higher amplitude of any of the original waves. • 2. Destructive Interference– when the combining of the waves produce a new wave with a smaller amplitude than the beginning waves
Standing Waves Standing Waves– the combining of the incoming and reflected wave so that the resultant appears to be standing still Node– the point where Constructive Interference and Destructive Interference cause an amplitude of zero on the standing wave. Antinode– the point where Constructive Interference and Destructive Interference of a standing wave are represented by the crest and the trough. Resonance– the point where vibrations traveling thru and object matches the natural vibrations of an object. I.e. an opera singer hitting a note and shattering a crystal glass.
Seismic Waves • Seismic Waves– waves caused by the release of energy due to earthquakes composed of • P - primary waves • S - secondary waves • L - surface waves
P Waves P waves–- Primary waves are pressure waves & are the fastest moving waves, they travel thru solids and liquids, Push-Pull Waves AKA Longitudinal waves
S Waves S Waves– Secondary Waves are slower than primary waves, they cannot travel thru liquid and are Transverse Waves.
L Waves • L Waves (last waves) Surface wave– the combination on the Earth’s surface of Primary and Secondary waves. • The rolling chaotic movement of the surface • Cause the most damage of the seismic waves
Sound Sonic Boom follows • Sounds are longitudinal waves that require a medium to travel caused by the vibrations of an object. • Speed of Sound – on average: • Air is 767 mph (343 m/s) – about 1 mile every 5 sec • Water is 3,315 mph (1,482 m/s) • Steel is 13,330 mph ( 5,960m/s) • The speed of sound depends on the elasticity, density and temperature of the medium.
A sound wave is a wave of alternating high-pressure and low-pressure regions of air. Sound Waves
The Doppler Effect • The shift in frequency caused by motion is called the Doppler effect. • It occurs when a sound source is moving at speeds less than the speed of sound.
Speed of Sound • Speed of Sound: depends on the elasticity, density and temperature. • Elasticity– the ability of an object to bounce back to its original shape. Sound travels faster in more elastic objects. Typically gasses are the least elastic, liquids are next and solids are the most elastic. • Density – generally speaking, in material of the same state of matter (solid, liquid or gas) the denser the medium the slower the sound travels. Sound travels slower in lead than it does in steel. • Temperature – generally speaking the higher the temperature the faster the speed of sound.
The Speed of Sound • We use the term supersonic to describe motion at speeds faster than the speed of sound. • A shock wave forms where the wave fronts pile up. • The pressure change across the shock wave is what causes a very loud sound known as a sonic boom.
Breaking the Sound Barrier October 15, 1997 – in SuperSonic Car “Thrust SSC” 763 MPH October 14, 1947 – in X1 “Glamorous Glennis” Chuck Yeager– first man to fly faster than the speed of sound Andy Green– first man to drive a land vehicle faster than the speed of sound.
Properties of Sound • Intensity– the amount of energy the wave carries per second per meter squared intensity = Watts / m2 • Loudness – sound level is measured in decibels (dB)
Loudness Every increase of 20 dB, means the pressure wave is 10 times greater in amplitude.
Frequency & Pitch • Frequency – the number of vibrations per second • Human Hearing – between 20 Hz – 20,000 Hz • Below 20 Hz is called infrasound • Above 20,000 Hz is called ultrasound • Pitch - dependent of frequency • high frequency yields high pitch sounds • Low frequency yields low pitch • Resonance – when the frequency of sound matches the natural frequency of an object Tacoma Narrows Bridge collapse
The Frequency of Sound • We hear frequencies of sound as having different pitch. • A low frequency sound has a low pitch, like the rumble of a big truck. • A high-frequency sound has a high pitch, like a whistle or siren. • In speech, women have higher fundamental frequencies than men.
Hearing – Human Sound Need to know these structures & their function: Outer Ear, Middle Ear, Inner Ear, Pinna, Auditory canal, Tympanum, Malleus, Incus, Stapes, Oval Window, Cochlea, Auditory Nerve, Semicircular Canals, Eustachian Tube
Outer Ear Pinna- (the ear flap aka auricle), used to focus the sound waves into the ear canal External Auditory Meatus – the “hole through the temporal bone that opens the space for the ear canal, the middle & inner ears Auditory Canal – (ear canal), focuses the sound onto the ear drum Tympanic membrane – (ear drum), end of the outer ear, beginning of the middle ear. Sound starts the ear drum vibrating.
Middle Ear • Tympanic membrane vibrates, causing the 3 smallest bones in to vibrate, one after the next • Malleus (hammer) is touching the ear drum & vibrates first • Next is the Incus (anvil) • Last is the Stapes • Eustachian Tube: tube that connects the middle ear w/ the pharynx. This allows the pressure on both sides of the ear drum to equalize.
Inner Ear Balance is achieved by the semicircular canals, three canals which help us determine our body’s position in space. The Stirup vibrates the oval window of the cochlea. Cochlea is a long, fluid-filled tube, folded in half and the coiled up like a snail shell. The entire inner surface is lined w/ cilia.. Attached to the cilia is a nerve fiber. Once cilia are vibrated, the attached nerves are stimulated and they send a signal to the brain.
A common way to record sound starts with a microphone. A microphone transforms a sound wave into an electrical signal with the same pattern of oscillation. Recording Sound
In modern digital recording, a sensitive circuit converts analog sounds to digitalvaluesbetween 0 and 65,536. Recording Sound
Numbers correspond to the amplitude of the signal and are recorded as data. One second of compact-disk-quality sound is a list of 44,100 numbers. Recording Sound
To play the sound back, the string of numbers is read by a laser and converted into electrical signals again by a second circuit which reverses the process of the previous circuit. Recording Sound
The electrical signal is amplified until it is powerful enough to move the coil in a speaker and reproduce the sound. Recording Sound
Music • The pitch of a sound is how high or low we hear its frequency. Though pitch and frequency usually mean the same thing, the way we hear a pitch can be affected by the sounds we heard before and after. • Rhythm is a regular time pattern in a sound. • Music is a combination of sound and rhythm that we find pleasant. • Most of the music you listen to is created from a pattern of frequencies called a musical scale.
Consonance, Dissonance, and Beats • Harmony is the study of how sounds work together to create effects desired by the composer. • When we hear more than one frequency of sound and the combination sounds good, we call itconsonance. • When the combination sounds bad or unsettling, we call it dissonance.
Consonance, Dissonance, and Beats • Consonance and dissonance are related to beats. • When frequencies are far enough apart that there are no beats, we get consonance. • When frequencies are too close together, we hear beats that are the cause of dissonance. • Beats occur when two frequencies are close, but not exactly the same.
Harmonics and Instruments • The same note sounds different when played on different instruments because the sound from an instrument is not a single pure frequency. • The variation comes from the harmonics, multiples of the fundamental note.
