is a What you Hear The Pressure Wave sets the Ear Drum into Vibration.

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1 is a Pressure Wae

2 is a What you Hear The ear conerts sound energy to mechanical energy to a nere impulse which is transmitted to the brain. The Pressure Wae sets the Ear Drum into Vibration.

Drum to Stirrup: Simple Machine Amplification Since the pressure wae striking the large area of the eardrum is concentrated into the smaller area of the

3 Drum to Stirrup: Simple Machine Amplification Since the pressure wae striking the large area of the eardrum is concentrated into the smaller area of the stirrup, the force of the ibrating stirrup is nearly 15 times larger than that of the eardrum. This feature enhances our ability of hear the faintest of sounds.

Resonance of the Cilia Neres The inner surface of the cochlea is lined with oer 20 000 hair-like cilia connected to nere cells, each differing in length by minuscule amounts.

4 Resonance of the Cilia Neres The inner surface of the cochlea is lined with oer hair-like cilia connected to nere cells, each differing in length by minuscule amounts. Each hair cell has a natural sensitiity to a particular frequency of ibration. When the frequency of the sound wae matches the natural frequency of the nere cell, that nere cell will resonate with a larger amplitude of ibration which induces the cell to release an electrical impulse along the auditory nere towards the brain.

5 Sound Generation Energy is transmitted as a pressure wae. There is no net motion of the medium. The medium oscillates in simple harmonic motion. The frequency of the wae is the same as the ibrating source. Vibrating String Spherically Symmetric Sound Source (bell).

6 is a Longitudinal Wae

7 Periodic Sound Waes Displacement amplitude of the wae: s max is the maximum position from the equilibrium position: s (x, t) = s max cos (kx ωt) Pressure Amplitude: ariation in gas pressure ΔP = Δ P max sin (kx ωt) Δ P max = r ω s max

8 Pressure Wae Problem The ariation in the pressure of helium gas, measured from its equilibrium alue, is gien by ΔP = cos (6.2x 3000t) where x and t hae units m and s, and ΔP is measured in N/m2. Determine the frequency (in Hz), the waelength, (in m) and the speed (m/s) of the wae.

9 The speed of sound waes in a medium depends on the compressibility, density and temperature of the medium The compressibility can sometimes be expressed in terms of the elastic modulus of the material The speed of all mechanical waes follows a general form: Liquid or Gas: Solid Rod: = = B ρ Y ρ = = T ρ elastic property inertial property (1D string) Dependence on Temperature: T = + o C (331 m/s) C

343 m/s in Air @ 20 C 5960 m/s in Steel @ 20 C 1522

10 343 m/s in 20 C 5960 m/s in 20 C 1522 m/s in Ocean 20 C Speed of Sound in a Vacuum?

11 Wae Equation = λ f This gies the relationship between the waelength and frequency for constant wae speed. The frequency depends on the source and the speed depends on the properties of the medium. The speed of sound is independent of the frequency. When traeling from one medium to another, if the speed changes, the waelength changes but the frequency remains the same.

12 Windy Wae Speed Question How does the wind affect the sound of a fog horn you hear on a windy day? What changes? a) Frequency b) waelength c) speed d) nothing

13 = sound 343 m/s Problem: You see lightening flash and 10 seconds later you hear the thunder clap. How far away was the lighting from your position? d = t (343 m/ s)10 = s = 3.43km ~2 miles (Rule of thumb: diide time by 5 to get miles)

14 Reflect ECHO

Echo s Reerberation A reerberation is perceied when the reflected sound wae reaches your ear in less than 0.1 second after the original sound wae.

15 Echo s Reerberation A reerberation is perceied when the reflected sound wae reaches your ear in less than 0.1 second after the original sound wae. Since the original sound wae is still held in memory, there is no time delay between the perception of the reflected sound wae and the original sound wae. The two sound waes tend to combine as one ery prolonged sound wae.

$Diffract We can hear around corners. Why can t we see around corners?$

16 Diffract We can hear around corners. Why can t we see around corners? If the size of the wae (waelength) is close in size to the object (door way) then the wae will diffract (bend).

17 Refract Sound waes refract (bend) when moing between mediums in which it traels at different speeds.

18 Sound Waes Transmit Energy Power Transmitted on a String: Power Transmitted by Sound: ΔE = = Δt ΔE = = Δt μω A 2 1 ρa( ωsmax ) 2 2 NOTE: A s are not the same!!!!!!

19 ΔE = = Δt 1 ρa( ωsmax ) 2 2 The intensity of a wae, the power per unit area, is the rate at which energy is being transported by the wae through a unit area A perpendicular to the direction of trael of the wae: OR: I = P W 4π r m I = ρ( ωsmax ) 2 I = ΔP 2ρ Δ P max = r ω s max 2 max 2

20 I = P W 4π r m The power transmitted by a wae is proportional to the amplitude of the wae. 2 2

21 Cochlear Cilia Nere Damage Excessie exposure to loud sound can damage your cilia. Normal Ear Damaged Ear

22 Threshold of hearing : I = 10 W / m 10 2 Whisper: I = 10 / W m 6 2 Normal Conersation: I = 10 W / m 4 2 Bursting of eardrums : I = 10 W / m 0 db 20 db 60 db 160 db I Whisper I 0 = 10 10decibels 1bel 2 I W log 2 I 0 = 2 bels = 20 decibels

23 Decibel Index: β 0 10 log I 12 2 Threshold of hearing : I = 10 W / m = db I0 Whisper: 20db Conersation: 60db Loud Music: 120 db Jet: 140 db Rocket: 250dB

25 OSHA Safety Standards OSHA - Occupational Safety and Health Act - The OSHA criteria document reealuates and reaffirms the Recommended Exposure Limit (REL) for occupational noise exposure established by the National Institute for Occupational Safety and Health (NIOSH) in The REL is 85 decibels, A-weighted, as an 8-hr time-weighted aerage (85 dba as an 8-hr TWA). Exposures at or aboe this leel are hazardous.

26 If a sound is twice as intense, how much greater is the sound leel, in db? β 10dB log I 1 1 = I0 β 2 10 log I 2 = db I0 I 2 I 1 β2 β1 = 10dB log 10dB log I I 0 0 β β 10 I log I / = db I0 I0 10dB log I 2 = I1 = = 3.01dB β2 β1 10dB log 2 53 db is twice as intense as 50dB. Log Scale!!

27 The decibel leel of a jackhammer is 130 db relatie to the threshold of hearing. Determine the sound intensity produced by the jackhammer. β 130dB 10 log I 1 10 log I 1 = db I0 1 = db I0 I log 13 I 10 = = I I log I I = I = 10 I0 =10 10 = 10 W / m 2

28 I = P W 2 2 4π r m Intensity 10dB log I β = I0 A point source emits sound with a power output of 100 watts. What is the intensity (in W/m 2 ) at a distance of 10.0 m from the source? What is it in db?

29 I = You Try Calculate the intensity leel in db of a sound wae that has an intensity of W/m 2. a. 20 b. 200 c. 92 d. 9 e. 10 P W 2 2 4π r m 10dB log I β = I0

30 I = P W 2 2 4π r m You Try 10dB log I β = I0 By what factor will an intensity change when the corresponding sound leel increases by 3 db? a. 3 b. 0.5 c. 2 d. 4 e. 0.3

31 Loudness Perception: Phons Perception of Loudness depends on Frequency & Intensity

32 Sound Frequencies A middle C ibrates 252 times per second. Sonic: 20 Hz 20 khz INFRAsonic: f < 20Hz ULTRAsonic: f > 20kHz

33 Ultrasound:Pulerizing Tumors f I ~23kHz 5 2 ~10 W / m Deep Heat f I ~1MHz 3 2 ~10 W / m

34 Ultrasound Intensity of reflected sound wae (echo) is related to change in density in target. Ultrasound beam: 7MHz 1 mm detail I ~10-2 W

35 Weeks

"We do know in animal studies, certain leels of ultrasound can cause

36 "A Womb With a View" and "Fetal Fotos Peek in the Pod Hi Cost Hi-Definition Ultrasound Are there RISKS? "We do know in animal studies, certain leels of ultrasound can cause damages in growing bones, in deeloping bones," said Dr. Dan Schultz of the Food and Drug Administration.

37 Ultrasound Question How far apart are two layers of tissue that produce echoes haing round-trip times that differ by 0.750μs? What minimum frequency must the ultrasound hae to see detail this small? The speed of sound in human tissue is 1540m/s. ( )( 1540 m s s) Δt 2 2 w 4 Δ = = = m d Δ d = d d = t t = Δt/2 2 1 s 2 s 1 s w = fλ f = = λ 1540 ms m w 6 = Hz

38 Freaky Question Which traels further, high or low frequencies? Why? Low frequency waes trael further because high frequency waes are absorbed by molecules in the medium. All dat gets thru da wall is da boom boom Bass!

39 Animal Perception of Sound domestic cats ,000 Hz domestic dogs 40-46,000 Hz African 16-12,000 Hz elephants ,000 bats Hz rodents ,000 Hz Human: 20-20,00Hz

These infrasonic calls, with a frequency of about 21 Hz and a normal duration of 4-5 seconds, carry for long distances (seeral

40 Infrasonic Contact Calls Female African elephants use "contact calls" to communicate with other elephants in their bands (usually a family group). These infrasonic calls, with a frequency of about 21 Hz and a normal duration of 4-5 seconds, carry for long distances (seeral kilometers), and help elephants to determine the location of other Elephants. Calls ary among indiidual elephants, so that others respond differently to familiar calls than to unfamiliar calls. Perhaps elephants can recognize the identity of the caller.

Infrasonic: < 20Hz Scientists first detected infrasound in 1883, when the eruption of the Krakatoa olcano in Indonesia sent inaudible sound waes careening around the world, affecting barometric

41 Infrasonic: < 20Hz Scientists first detected infrasound in 1883, when the eruption of the Krakatoa olcano in Indonesia sent inaudible sound waes careening around the world, affecting barometric readings. The eruption of the Fuego olcano in Guatemala last year generated highamplitude infrasound, mostly below 10 hertz. The pressure readings show that the strength of these sound waes can reach the equialent of 120 decibels.

The brain receies the sound waes in the form of nere impulses.

42 Echolocation: Sonic Vision Dolphin Vocalization Dolphins produce high frequency (100kHz) clicks that pass through the melon. These sound waes bounce off objects in the water and return to the dolphin in the form of an echo. The brain receies the sound waes in the form of nere impulses. By this complex system of echolocation, dolphins can determine size, shape, speed, distance, direction, and een some of the internal structure of objects in the water.

43 SOFAR Channel SOund Fixing And Ranging Acoustic Thermometry of Ocean Climate ATOC: 70 Hertz, with a sound pressure leel of 195 db Dolphin, pinniped species sensitie to high frequencies (aboe 10,000 Hz) Baleen whales sensitie to low-frequencies (below 100 Hertz)

44 Low Frequency Actie Sonar The LFAS system consists of a 35- ton block of 18 huge underwater speakers and dozens of microphones. The speakers emit a consistent low-frequency tone, between 100 and 500 Hertz, at 240dB, which traels out into the water at a depth of seeral hundred meters. The low frequency permits the sound to trael tremendous distances, detecting objects many hundreds of miles away by echolocation.

45 Physical Effect on Marine Life At a 1 mile radius from the ship the noise only dissipates to 180 db which causes a bubbling effect in marine mammals' blood stream which creates embolisms. At 100 mile radius from the ship the noise only drops to 160 db which causes shearing of the tissues in the air sack behind whales' and dolphins' brain. This air sack is highly sensitie since it is used in echolocation. This shearing of tissue then causes hemorrhaging in their brains. Fish hae little hairs in their ears that transmit sound waes from their ear canals to their central nerous system. The 160 db leel shears these hair right off. Granted they grow back in 2 weeks, but they are deaf and are more likely to be picked off by predators and can't find food. Any fish or marine mammals caught in this "death zone" would hae to swim 100 miles to escape the noise and pain.

46 Noermber 28, 2004 Sound bombing" of ocean floors to test for oil and gas for National Security? More than 100 whales and dolphins died in two separate beachings in 24 hours on remote Australian islands

48 Deadly Sonar: NRDC

49 Gray whales migrating off the coast of Southern California

50 Sea Quakes produce powerful pressure waes that rupture the sinuses and middle ear of whales and dolphins.

51 Sound Weapons

$Atomic Blast Wae A fraction of a second after a nuclear explosion, the heat from the fireball causes a highpressure wae to deelop and moe outward producing the blast effect.$

52 Atomic Blast Wae A fraction of a second after a nuclear explosion, the heat from the fireball causes a highpressure wae to deelop and moe outward producing the blast effect. The front of the blast wae, i.e., the shock front, traels rapidly away from the fireball, a moing wall of highly compressed air. The blast wind may exceed seeral hundred km/h. The range for blast effects increases with the explosie yield of the weapon and also depends on the burst altitude.

54 Which is traeling at subsonic, sonic, or supersonic speeds? a) Subsonic b) Sonic c) Supersonic

57 RADAR: RAdio Detecting And Ranging

58 Cosmological Redshift: Expanding Unierse Stellar Motions: Rotations and Radial Motions Solar Physics: Surface Studies and Rotations Graitational Redshift: Black Holes & Lensing Extra-solar Planets ia Doppler Wobbler

60 Case 1: Moing Source Stationary Obserer = 0 O S Obserer Reference Frame

61 Case 1: Moing Source Stationary Obserer = 0 O S Obserer Reference Frame

62 Case 1: Moing Source Stationary Obserer = 0 O S Obserer Reference Frame

63 Case 1: Moing Source Stationary Obserer = 0 O S Obserer Reference Frame

64 Case 1: Moing Source Stationary Obserer = 0 O S Obserer Reference Frame

65 Case 1: Moing Source Stationary Obserer = 0 O wae = w What is the speed of sound to the obserer? =? S O w Speed of a wae is determined by the properties of the Medium!

66 Case 1: Moing Source Stationary Obserer = 0 O wae = w What is the speed of sound to the obserer? S O = w w Speed of a wae is determined by the properties of the Medium!

67 Case 1: Moing Source Stationary Obserer = 0 O = w λ =? w S O f =?

68 Case 1: Moing Source Stationary Obserer = 0 O = w λ < λ w S O f =?

69 Case 1: Moing Source Stationary Obserer = 0 O = w λ < λ w S O f > f

70 Case 1: Moing Source Stationary Obserer = 0 O S source moes in time τ a distance S τ

71 Case 1: Moing Source Stationary Obserer = 0 O S emits another waelength

72 Case 1: Moing Source Stationary Obserer = 0 O S traels a distance Sτ and emits again...

73 Case 1: Moing Source Stationary Obserer = 0 O S and so on...

74 Case 1: Moing Source Stationary Obserer = 0 O S bunching up the waecrests by S τ

75 Case 1: Moing Source Stationary Obserer = 0 O λ is shortened by λ λ τ = S S w λ s = λ( ) w τ = λ(1 S ) λ τ = λ(1 S ) w τ = λ(1 S ) w

76 Case 1: Moing Source Stationary Obserer = 0 O f =? Use = w w λ S w s = λ w f λ λ f = f = f λ ' = f f = f λ λ w s λ( ) w w w S

77 Case 1: Source moing TOWARD (-) and AWAY (+) from Obserer S λ ± w s = λ w f = f w ± w S f = f 1 S (1 ± ) w What if =? S w

78 f = f 1 S (1 ± ) w If = S f = f w 1 S (1 ) w = f 1 (1 1) = 1 0

79 f = f 1 S (1 ) w S = Mach # w If S = f = f 1 S (1 ) w = f 1 (1 1) = 1 0

82 When the duck speed is equal or greater than the speed of waes in water, the waes form a bow wae.

83 Case 2: Obserer Moing & Stationary Source Obserer Moing TOWARD (+) and AWAY (-) from Source λ =? S O w = f =??

84 Case 2: Obserer Moing & Stationary Source Obserer Moing TOWARD (+) and AWAY (-) from Source λ = λ S O = ± w w o f = f w ± o w f = f ± 0 (1 ) w

85 Doppler Shift Problem Gien : = 343 m/ s, = 27 m/ s A siren, mounted on the tower, emits a sound with a frequency of 2140 Hz. What is the difference in the frequency heard by the drier traelling away from the tower at 27 m/s between the directed and reflected sound of the siren? Take the speed of sound to be 343 m/s. O f = f(1 ± ) w O O f Direct = f(1 ) f Reflected = f(1 + ) w w f = 2140 Hz, O

86 Doppler Shift Problem O f = f(1 ) Direct Gien : f = 2140 Hz, = 343 m/ s, = 27 m/ s O =1970Hz f f(1 ) Reflected O O = + = 2310Hz f Direct = f(1 ) f Reflected = f(1 + ) O

87 If both Source and Obserer are moing.. = f f w + o w + : Moing Towards each other - : Moing Away from each other s

1 f = Τ. result from periodic disturbance same period (frequency) as source Longitudinal or Transverse Waves Characterized by

1 f = Τ. result from periodic disturbance same period (frequency) as source Longitudinal or Transverse Waves Characterized by result from periodic disturbance same period (frequency) as source Longitudinal or Transverse Waves Characterized by 1 f = Τ amplitude (how far do the bits move from their equilibrium positions? Amplitude