Transfer Of Sound Energy Through Vibrations PDF
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This document provides an introduction to the transfer of sound energy through vibrations. It covers topics including the nature of sound energy, how sound is produced, how sound is transmitted through a medium, factors affecting sound intensity and pitch, and applications of sound. It also includes the factors that affect the speed of sound and defines key terms such as frequency and wavelength. A summary of the document highlights the fundamental concepts of sound transmission and the various factors involved.
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https://www.mwrf.com/technologies/systems/article/21846964/usin g-sound-waves-to-analyze-mimo Transfer of Sound Energy Through Vibrations Content What is sound energy? How is sound produced? How is s...
https://www.mwrf.com/technologies/systems/article/21846964/usin g-sound-waves-to-analyze-mimo Transfer of Sound Energy Through Vibrations Content What is sound energy? How is sound produced? How is sound transmitted? How does sound vary? Amplitude https://www.nti-audio.com/en/support/know-how/what-is-a-sound-level-meter Frequency Speed Applications https://diyaudioheaven.wordpress.com/tutorials/neutral-sound-an-utopia/ 16.1 What Causes Sound? Lesson trigger During a thunderstorm, lightning causes the air around it to be heated to extreme temperatures. This causes a massive disturbance to the air, which creates the loud booming sound of thunder. Would we be able to hear thunder if The sound of thunder air was absent? passes through air to reach our ears. Can you estimate how far the thunderstorm is from you? What is Sound? Sound is a type of energy that requires a medium to travel in all directions in the form of a wave or sound wave. https://www.thomann.de/blog/en/express-vocal-warm-up/ https://www.quora.com/Will-a-speaker-get-damaged-if-the-wires-for-positive-and-negative-are-reversed How is Sound Produced? Sound is produced when an object vibrates. The vibrating source causes the particles in the medium (e.g. air) around the source to vibrate in a back and forth motion, parallel to the direction of energy. This results in a series of compression and rarefaction, called sound waves. Can you hear all vibrations? Why? What is Sound? A wave is a flow or transfer of energy in the form of oscillation through vacuum or a medium. There are 3 types of waves: Mechanical waves – sound waves, earthquakes, ripples (require a medium) Electromagnetic Waves – microwave, X-ray, radio wave, light (can travel through vacuum) Matter Waves (Particle & Wave Duality) – electron beam 3 Types of Mechanical Waves Transverse Waves – particles https://byjus.com/physics/types-of-waves/ vibrate up and down, perpendicular to the motion of energy. Longitudinal Waves – particles vibrate to and fro, parallel to the motion of energy. Surface Waves – waves travel https://tenor.com/view/longitudinal-wave-transverse-waves-waves-gif-13936583 in a circular motion at interfaces. Which type of mechanical wave is Sound Wave? https://gfycat.com/discover/micrometric-surface-waves-gifs Christmas Lecture by Charles Taylor – Sound requires a medium to propogate https://www.youtube.com/watch?v=YxUERaXBAU8 How is Sound Transmitted? Sound is a longitudinal or compressional wave. Sound energy is transmitted through the medium when the particles in the medium vibrate back and forth, along the same direction as the direction of energy travel, colliding into one another. The particles form a series of compressions and rarefactions. A sound wave is a wave of compression and rarefaction. Direction of energy travel https://www.phy.olemiss.edu/~perera/animations/waves.html How is Sound Transmitted? What happens when we beat a drum? air molecules skin of vibrating 1. When the drum membrane drum moves to the right, the surrounding air molecules are pushed closer together. In turn, the air molecules move and collide with other air molecules. 2. When the drum membrane moves to the left, it creates an area with few air molecules. How is Sound Transmitted? The side-to-side motion (i.e. vibration) of the drum skin causes the air molecules near it to also move from side to side in a regular pattern. This helps to carry the sound energy away in a moving pattern. In some regions, the molecules are bunched up. In other regions, there are few molecules. How is Sound Transmitted? In the example below, sound produced is shown as ripples moving away from the source. Each ripple shows where the molecules are bunched up. In some regions, the molecules are bunched up. In other regions, there are few molecules. http://physics.tutorvista.com/waves/longitudinal-waves.html How does sound wave look like? https://www.youtube.com/watch?v=Bcqp6t4ybxU Wavelength = distance between two adjacent compressions or rarefactions. http://www.gcsescience.com/pwav2.htm Can you tell which sound wave is higher or lower pitch? Can you tell the https://www.docbrown.info/ephysics/wavesound.htm loudness of the sound wave? Common Misconceptions: a) Sound is a Transverse wave Transverse wave vibrate in an up-and-down motion, perpendicular to wave travel. – Sound is a longitudinal wave. b) “Sound particles” – there are no such things as sound particles. c) Particles in medium travel with the sound energy – particles in medium merely vibrate about a fixed position. The energy travels when the particles collide. How does Sound Vary? We can vary the loudness and pitch (how high or low) of sound. Sound wave is a motion of vibrations of particles in the medium. Loudness is displayed on the sound wave in the form of amplitude/size of vibrations. Pitch is displayed on the sound wave in the form of frequency/rate of vibrations. Usually the frequency of sound wave is unchanged as it traverses through the medium. How does Sound Vary? It is difficult to observe amplitude and frequency on a longitudinal waveform. Hence, we use a CRO to convert sound energy to electrical signal in the form of sinusoidal waveform. https://my.element14.com/multicomp-pro/mp720010-eu-uk/dso-2-ch-50mhz-10kpts- 500msps/dp/3107569 Terms on a Sinusoidal waveform on a CRO What is the difference between wavelength and period? Observe the horizontal axes of both diagrams. Wavelength refers to distance while Period refers to time. Other Aspects of Sound There are other aspects of sound which we cannot sense: speed, period and wavelength. Period and frequency are inversely related. Speed of sound is dependent mainly on the type of medium, presence of wind and humidity. http://www.miyazaki-catv.ne.jp/~yuasa1436/Eng3.htm Definitions Frequency, f - (unit = Hz or Hertz or s-1) - the number of complete waves/ cycles/ vibrations in 1 second - Or rate at which sound wave vibrates Period, T - (unit = s or second) - Time taken for 1 complete waves/ cycles/ vibrations Therefore, Period = 1 ÷ frequency T=1÷f How are wavelength and frequency related? A sound wave that has high frequency will have a short wavelength and short period, and vice versa. Frequency (the rate of vibration or number of vibrations per second) Pitch (how high or low a sound is) t = 0s t = 1s f = 2 Hz f = 4Hz Can you determine the T of each sound wave? Frequency and Pitch Use this Online Tone Generator from http://onlinetonegenerator.com/. Check your range of hearing. Refer to http://www.seventhstring.com/tuningfork/tuningfork.html for online keyboard. Have fun! Musical Frequency Note (Hz) Middle C 261.626 D 293.665 E 329.628 F 349.228 G 391.995 A 440.000 B 493.883 C 523.251 Do you notice any pattern? Could you predict the frequency of the next D? It would be twice the frequency of the D (2x293.665 = 587.665Hz) How are these sound waves related? A f2 = 2 × f 1 B A musical note is one octave higher if its frequency is TWICE the original note. It would be two octaves higher if its frequency is FOUR times the original note. You need to understand that When a wave has a large amplitude, it implies that the sound is loud. If the wave energy dissipates to the surrounding as the wave travels further away from the source of sound, then it implies that the amplitude of the wave decreases, and it will be softer and softer. Amplitude, Intensity and Loudness (How much energy the sound wave has) t = 0s Loud t = 1s More energy, higher amplitude Soft Prolonged 85-100dB sound can cause hearing loss Speed of Sound If a sound wave is made to travel through equal length of a concrete slab, a cylinder containing water and an air column, assuming the same temperature and humidity, through which medium will sound emerge first? Explain your answer. The particles in the concrete slab have stronger attractive forces hence they are packed closer together so collision of particles and transmission of sound energy will be at a higher speed. How does Speed of Sound Vary? Sound travels at How sound travels in different media different speeds in different media. Speed of sound in a solid We are disturbed by the sound of drilling in neighbouring flats and houses. The speed of sound is the fastest in solids at Sound travels through solids when solid 5,000–6,000 m/s. particles vibrate and collide with one another very rapidly. This is because the solid particles are packed very closely together. How does Speed of Sound Vary? Speed of sound in a liquid Scuba divers sometimes draw attention to other divers by tapping a metal pointer on their The speed of sound is metallic air tanks slower in liquids at 1,500 m/s. Sound travels through liquids when liquid particles vibrate and collide with one another rapidly. This is because the liquid particles are packed closely together. How does Speed of Sound Vary? Speed of sound in a gas We hear public announcements through megaphones of Public Address (PA) systems. The speed of sound is the slowest at 330 m/s. Sound travels through gases when gas particles vibrate and collide with one another slowly. This is because the gas particles are packed very far apart. Speed of Sound – Echo Method Marin Mersenne was the first to measure the speed of sound in the air in 1640 by measuring the return of an echo. The speed of sound can be calculated by (2 x distance)/ time taken. Speed of Sound – Echo Method Time difference Speed of sound = Distance x 2 ÷ Time difference Speed of Sound – Direct Method The speed of sound is thus calculated as distance / time taken. Speed of Sound The speed of sound in dry air at a temperature of 20°C has been measured to be 340 m/s. What do you think are the factors that affect the speed of sound? 1) Temperature, 2) Type of media (how densely packed the particles are), 3) wind/wave. Higher Temp, air particles vibrate faster and transfer sound energy faster. Denser medium, particles closer together because of stronger attractive forces, transfer energy faster. If wind blows same direction of sound travel, sound energy transfers faster. Speed of Sound Medium velocity m/s air (20 oC) 343 air (0 oC) 331 water (25 oC) 1493 sea water 1533 diamond 12000 iron 5130 copper 3560 glass 5640 Q1) Radio waves of speed 3 x108 ms-1 are reflected off the moon and received back on earth. The time elapsed between the sending of the signal and receiving it back at the earth station is 2.5 s. NO! Sound cannot travel through vacuum. Radio wave is a type of Is radio wave audible? Electromagnetic radiation. What is the distance of the moon from the earth? v=d÷t d = v x t = 3 x 108ms-1 x 2.5s ÷ 2 d = 3.75 x 10 m8 Q5) A person standing between two vertical cliffs and 640 m away from the nearest cliff shouted. He heard the 1st echo after 4 seconds and the second echo 3 seconds later. Calculate (i) the velocity of sound in air and (ii) the distance between the cliff. v = 2d ÷ t = 2 x 640m ÷ 4s = 320ms-1 Distance the farthest cliff, d = v x t ÷ 2 = 320ms-1 x 7s ÷ 2 = 1120 m Therefore the distance between the cliffs, D = 640 + 1120 = 1760 m A sound's pitch depends on: Temperature of air – warm air makes sound sharper than cold air due to the speed of vibration of air particles. Length, width/thickness and tightness (how much it is stretched) of vessel producing the sound – shorter and thinner a guitar string, the faster it will vibrate (higher pitch) when plucked and hence produce a higher pitch; If the frequency is doubled, so is the pitch (one octave higher). http://www.youtube.com/watch?v=wNB9Xqqn2YA http://physicscentral.com/experiment/askaphysicist/physics-answer.cfm?uid=20080506014548 A sound's volume depends on: The more energy put into making a sound or a sound wave, the louder the volume will be. The farther distance a sound wave travels, the more it spreads; energy dissipates and this makes it more difficult for us to hear a sound from afar. The medium a sound wave travels through or bounces off, the stiffer or denser the medium, the louder the sound or echo. Effects of sound barriers on sound wave http://www.megasorber.com/4fold-approach/sound-absorption.html A sound's timbre/tone depends on: The shape of wave form – clear repeated pattern or no pattern Different sounds that you hear include (A) noise, (B) pure tones, and (C) musical notes. Applications Ultrasound sound waves with frequencies above the - normal human range of hearing. Sounds in the range from 20kHz-100kHz Infrasound - sounds with frequencies below the normal human range of hearing. Sounds in the 20-200 Hz range Although the ear is the main tool for hearing sounds, it is possible for other parts of the body to “feel them”. Ultrasound used in sonography to produce a picture of a foetus in mother’s womb. Applications Make soundproof barriers by removing air between walls, or place sound absorbing materials like insulation. Sound travels relatively slowly compared to light; hence our brains can help us locate the source of sound. Mountain climbers use echo to measure distance. Geo phycists use sound to determine the depth of an oil well. Applications SONAR (Sound Navigation And Ranging) is used to detect underwater objects – fishing, locate sunken ships. Seismologist use compression waves to determine the epicentre of an earthquake. Ultrasound is used to clean jewelry, teeth, help animals communicate, aid physicians in making observations of internal organs. Applications Entertainment Communication Silent dog Infrasound is used to send whistle http://www.redrae.co.uk/whistles _and_game_calls.htm signals in army to special machines to transmit vital data. Animals pick up low infrasonic noises which warn them of natural disasters before they happen (earthquake, tsunami) Tsunami Wave length, 500 to 600 km in ocean Tsunami Warning On December 26, they were playing in the sea when Tilly suddenly found the water was bubbling, like on top of a beer. She immediately realized tsunami was coming because the scene reminded her of a geography lesson about Hawaii's 1946 tsunami. Right away, Tilly told her parents, sister and other tourists to escape quickly, but at first they were in half belief. However, seeing Tilly's serious and firm expression, people started to be convinced of the seriousness of the thing and instantly left the beach. At last over 100 tourists were ended up in safety with no death Top 10 Amazing Uses for Sound waves http://listverse.com/2012/11/14/t op-10-amazing-uses-for-sound/ Unethical Applications Sound is able to bend or diffract around corners of the house (where you can’t see around the corners) makes eavesdropping easy though it is not ethical. Phone-tapping Supersonic Flight http://www.youtube.com/watch?v=gWGLAAYdbbc http://skeptikai.com/2012/01/12/can-you-hear-the-music-mp3-players- Noise yield-hearing-impaired-youth/ Loudness of Sound in Decibels Sound Loudness (dbs) Hearing Damage Average Home 40-50 Loud Music 90-100 After long exposure Rock Concert 115-120 Progressive Jet Engine 120-170 Pain Summary Understand how sound is produced and explain the propagation of sound energy through a medium. Explain using Particle Theory of Matter, how sound varies: - loudness, pitch and speed Factors that affect sound: - air temperature, type of medium (solid/liquid/gas/length/ thickness/tautness of material), wind v=f×λ,T=1÷f Calculate speed of sound (Echo/Direct) Summary Audible range for humans Long-term exposure to sound level of > 85dB will damage hearing Applications of Infrasound, Sound and Ultrasound. Unethical applications