Sound And It's Applications | Science PPT | Pritam Priyambad Sahoo
- 2. Sound and it's Applications Done by:- Pritam Priyambad Sahoo Class:- 10 Section:- A Roll no.:- 19 Subject:- Science (Physics) Topic:- Sound and it's Applications Submitted to:- Mr.Prajwal Prasanjeet School:- BMPS Takshila School
- 3. Acknowledgement I would like to express my special thanks of gratitude to my teacher Mr.Prajwal Prasanjeet as well as our principal Mrs.Lipsita Mohanty who gave me the golden opportunity to do this wonderful project on the topic Sound and it's applications, which also helped me in doing a lot of Research and i came to know about so many new things I am really thankful to them. Secondly i would also like to thank my parents and friends who helped me a lot in finalizing this project within the limited time frame. 3
- 4. 4 1. Acknowledgement 2. How is sound produced? 3. Propagation of sound wave 4. Propagation of sound wave in air 5. Series of compressions and refractions 6. Sound needs a medium to travel 7. Sound waves are longitudinal waves 8. Characteristics of sound waves 9. Frequency of sound wave 10. Time period of sound waves 11. Amplitude of sound waves 12. Pitch of sound waves 13. Loudness of sound waves 14. Speed of sound in different mediums 15. Reflection of sound 16. Range of hearing 17. Echo 18. Reverberation Index 1. Ultrasonic waves 2. SONAR 3. Echolocation 4. Noise Cancellation 5. Diffraction horn 6. Harmonic Synthesis 7. Conclusion 8. Bibliography 9. Thankyou
- 5. How is sound produced ? Sound is produced due to the vibration of objects. Vibration is the rapid to and fro motion of an object. Example:- The sound of human voice is produced due to the vibration of the vocal cords And stretched rubber band when plucked vibrates and produces sound. Let us perform an activity to understand this better: Activity:- Stroke the prongs of a tuning fork on a rubber pad and bring it near the ear. We can hear a sound. If a suspended table tennis ball is touched with the vibrating prong, the ball is pushed away repeatedly. This shows that the prong is vibrating and vibrating objects produce sound. 5
- 6. Figure showing vibrating objects produce sound 6
- 7. Propagation of sound ā The sound produced by a vibrating object travels through a medium to a listener. The medium can be solid, liquid or gas. ā When an object vibrates, the particles around the medium vibrates. The particle in contact with the vibrating object is first displaced from its equilibrium position. It then exerts a force on the adjacent particle and the adjacent particle is displaced from its position of rest. After displacing the adjacent particle the first particle comes back to its original position. This process repeats in the medium till the sound reaches the ear. ā The disturbance produced by the vibrating body travels through the medium but the particles do not move forward themselves. ā A wave is a disturbance which moves through a medium by the vibration of the particles of the medium. So sound is considered as a wave. Since sound waves are produced due to the vibration of particles of the medium sound waves are called mechanical waves. 7
- 8. Propagation of sound in air ā Air is the most common medium through which sound travels. ā When a vibrating object moves forward, it pushes and compresses the air in front of it forming a region of high pressure called compression (C). The compression moves away from the vibrating object. When the vibrating object moves backward, it forms a region of low pressure called rarefaction (R). ā As the object moves to and fro rapidly, it produces a series of compressions and rarefaction in the air which makes the sound to propagate in the medium. 8
- 9. Figure showing propagation of sound through air 9
- 10. Figure showing the various series of compressions and rarefractions 10
- 11. Sound needs a medium to travel Sound is a mechanical wave and needs a medium for propagation. Sound travels through solids, liquids and gases. Sound does not travel in vacuum Let us perform and activity to understand this better. Activity:- Suspend an electric bell in an air tight bell jar. Connect the bell jar to a vacuum pump. If the switch is pressed, we can hear the sound of the bell. If air is pumped out through the vacuum pump, we cannot hear the sound of the bell. This shows that sound needs a medium to travel and sound cannot travel in vacuum. 11
- 12. Figure showing the electric bell jar experiment 12
- 13. Sound waves are longitudinal waves ā Sound propagates in a medium as a series of compressions (C) and rarefactions (R). ā In these waves the particles move back and forth parallel to the direction of propagation of the disturbance. Such waves are called longitudinal waves. ā There is another kind of waves called transverse waves. In these waves the particles oscillate up and down perpendicular to the propagation of the direction of disturbance. Let us perform an activity to understand this better . Activity:- Stretch a slinky and push and pull it alternately at one end. If you mark a dot on the slinky, the dot moves back and forth parallel to the direction of the propagation of the disturbance. 13
- 14. Figure showing the slinky experiment 14
- 15. Characterstics of sound waves ā Sound wave can be described by its frequency, amplitude and speed. Sound can be graphically represented as a wave. There is changes in the density and pressure as sound moves in a medium. Compressions are the regions of high pressure and density where the particles are crowded and are represented by the upper portion of the curve called crest. ā Rarefactions are the regions of low pressure and density where theparticles are spread out and are represented by the lower portion of the curve called trough. ā The distance between two consecutive compressions (crests) or two consecutive troughs is called wave length. It is represented by the symbol (lambda). (Greek letter lamda). Its Si unit is metre (m). 15
- 16. Characteristics of sound wave 16
- 17. Frequency of sound wave ā When sound is propagated through a medium, the density of the medium oscillates between a maximum value and a minimum value. The change in the density of the medium from a maximum value to a minimum value and again to the maximum value is one oscillation. ā The number of oscillations per unit time is called the frequency of the sound wave. ā It is represented by the symbol V (Greek letter nu). Its Si unit is hertz (Hz). 17
- 18. Time period of sound wave ā The time taken for the change in the density of the medium from a maximum value to a minimum value and again to the maximum value is the time period of the sound wave Or The time taken for one complete oscillation in the density of the medium is called the time period of the sound wave. ā It is represented by the letter T. The Si unit is seconds). ā Frequency and time are represented as follows: v for one oscillation 18
- 19. Amplitute of sound wave The magnitude of the maximum disturbance in the medium on either side of the mean value is the amplitude of the sound wave. Or The amplitude of sound wave is the height of the crest or tough. It is represented by the letter A. The Si unit is the same as that of density or pressure. 19
- 20. Pitch of sound wave ā The pitch of sound (shrillness or flatness) depends on the frequency of vibration. 20
- 21. Loudness of sound wave ā If the frequency is high, the sound has high pitch and if the frequency is low, the sound has low pitch. 21
- 22. Speed of sound in different mediums ā The speed of sound is different in different media. The speed of sound is more in solids, less in liquids and least in gases. ā The speed of sound also depends on the temperature of the medium. If the temperature of the medium is more, the speed of sound is more. 22
- 23. Reflection of sound Like light, sound gets reflected at the surface of a solid or liquid and follows the laws of reflection. 1. The angle of incidence is equal to the angle of reflection. 2. The incident ray, the reflected ray and normal at the point of incidence all lie in the same plane. Let us perform an activity to understand this better. Activity:- Take two pipes of the same length and arrange them on a table near a wall or metal plate. Keep a clock near the open end of one pipe and try to hear the sound of the clock through the other pipe by adjusting the position of the pipe. Now measure the angles of incidence and reflection. Then lift the second pipe and try to hear the sound. It will be seen that the angle of incidence is equal to the angle of reflection. The incident ray, the reflected ray and normal all lie in the same plane. 23
- 24. Figure showing the reflection of sound 24
- 25. Range of hearing ā Human beings can hear sound frequencies between 20 Hz and 2000 Hz. ā Sound whose frequency is less than 20 Hz is called infrasonic sound. Animals like dogs, elephants, rhinoceros, whales etc. produce and hear infrasonic sound. ā Sound whose frequency is more than 2000 Hz is called ultrasonic sound. Animals like dolphins, bats, rats porpoises etc. produce and hear ultrasonic sound. Bats use reflection of ultrasonic sound waves to detect an obstacle or its prey. 25
- 26. Figure showing bat using its range of hearing to catch predators 26
- 27. Echo ā If we shout or clap in a reflecting surface like tall building or a mountain, we hear the same sound again. This sound which we hear is called echo. It is caused due to the reflection of sound. ā To hear an echo clearly, the time interval between the original sound and the echo must be at least 0.1 s. Since the speed of sound in air is 344 m/s, the distance travelled by sound in 0.1 s = 344 m/s x 0.1 s = 34.4 m ā So to hear an echo clearly, the minimum distance of the reflecting surface should be half the distance, that is 17.2 m. 27
- 28. Reverberation ā Echoes may be heard more than once due to repeated or multiple reflections of sound from several reflecting surfaces. This causes ā persistence of sound called reverberation. ā In big halls or auditoriums to reduce reverberation, the roofs and walls are covered by sound absorbing materials like compressed fibre boards, rough plaster or draperies. 28
- 29. Difference between Echo and Reverberation 29
- 30. Applications of sound 1. Ultrasonic waves 2. SONAR 3. Echolocation 4. Noise cancellation 5. Diffraction horn 6. Harmonic synthesis
- 31. Ultrasonic waves ā Humans can normally hear sound frequencies between 20 and 20,000 Hz (20kHz). ā When a sound wave's frequency lies above 20 kHz, it is called an ultrasonic wave. While we cannot hear ultrasonic waves, we apply them in various technologies such as sonar systems, sonograms, surgical tools, and cleaning sytems. ā Some animals also use ultrasonic waves in a specialized technique called echolocation that alows them to pinpoint objects and other animals, even in the dark. 31
- 32. Figure showing the working of Ultrasound 32
- 33. Sonar ā Sonar stands for SOund NAvigation Ranging. Sonar is used in navigation, forecasting weather, and for tracking aircraft, ships, submarines, and missiles. ā Sonar devices work by bouncing sound waves off objects to determine their location. A sonar unit consists of an ultrasonic transmitter and a receiver. ā On boats, the receiver is mounted on the bottom of the ship. To measure water depth, for instance, the transmitter sends out a short pulse of sound, and later, the receiver picks up the reflected sound. The water depth is determined from the time elapsed between the emission of the ultrasonic sound and the reception of its reflection off the sea-floor. ā In the diagram below, a ship sends out ultrasonic waves (green) in order to detect schools of fish swimming beneath. The waves reflect off the fish (white), and return to the ship where they are detected and the depth of the fish is determined. 33
- 34. Figure showing the use of SONAR in Ships 34
- 35. Echolocation ā In 1944, Donald R. Griffin coined the term echolocation. Echolocation is the use of echoes of sound produced by certain animals to detect obstacles and food. ā Animals that live where lighting is unpredictable use echolocation. Some of these animals are bats, porpoises, some kinds of whales, several species of birds, and some shrews. ā The first step in echolocation is emitting a sound. High-frequency sounds provide better resolution of targets than lower-frequency sounds. Not every animal uses ultrasonic sounds in echolocation, but they are more effective. Still, sounds used in echolocation can be produced in the voice box, the mouth, or some other part of the head. Then, a highly refined auditory system detects the returning echoes (the sounds that bounced of the object). ā In order for echolocation to work, the outgoing pulses of sound need to register in the organism's brain, so it can be compared to its echo. Using echolocation, some animals can effectively catch prey and "see" in the dark. 35
- 36. Figure showing about Echolocation 36
- 37. Noise cancellation ā Destructive interference, if applied correctly, can be very useful. It is very important that an airplane pilot hears what's going on around him, but engine noise presents a problem. So, pilots can use special headphones mounted with a microphone that picks up the engine noise. ā A component in the headphones then creates a wave that is the inverse of the wave that represents the engine noise. This wave is then played back through the headphones allowing destructive interference to produce a quieter background. ā Other applications for destructive interference are "quieting" rides in automobiles and passenger sections in airplanes. 37
- 38. Figure showing the cancellation of Noise 38
- 39. Diffraction Horn ā In order for a speaker to have a large listening area, the width of the speaker must be smaller than the frequency of the sound it's emitting. You might think that it's only the size of the speaker that matters, the bigger the better, but, thanks to diffraction, the sound waves emitting from the speaker can bend around it and disperse sound all over the room. ā One application of a wide dispersion is the diffraction horn, a type of speaker. The width of a diffraction horn is much smaller than the wavelengths of the sounds it emits. ā The first diagram shows the correct mounting of a diffraction horn where the width is parallel to the floor. This allows the widest possibe listening area. The green lines mark the listening area of the speaker. In the second diagram the speaker is mounted incorrectly, and so the listening area is greatly reduced. 39
- 40. Correct and incorrect Diffraction horn 40
- 41. Harmonic Synthesis ā If a clarinet and a trumpet play the same note, they sound very different from each other. Although they might have the same pitch and the same fundamental frequency (same note, for example, 440 Hz), they don't have the same tone quality. Where the two instruments differ is in harmonics. ā Harmonics are tones whose frequencies are integral multiples of the fundamental frequency of the wave. For example, if an A is being played at 440 Hz, the frequencies of the harmonics will be 880 Hz, 1320 Hz, and so on. The harmonics are numbered in order of increasing frequency. Thus, the first harmonic is the fundamental frequency, the second is twice the fundamental frequency, etc. The relative strengths of these harmonics determine the timbre, or quality, of the tone. ā Each instrument is producing harmonics whose relative intensities depend on the type and make of the instrument and how the musician plays it. The graphs of the sound waves for these two instruments are called waveforms. The waveform of a tuner contains no other harmonics, only the fundamental frequency. 41
- 42. 42 ā Each instrument is producing harmonics whose relative intensities depend on the type and make of the instrument and how the musician plays it. The graphs of the sound waves for these two instruments are called waveforms. The waveform of a tuner contains no other harmonics, only the fundamental frequency. However, the waveform of the clarinet contains large amounts of the third, fifth, and seventh harmonics, and smaller amounts of the second, fourth, and sixth harmonics, and of course, the first harmonic, the fundamental frequency. The trumpet's waveform consists of a large amount of the third harmonic, and some from the second, fourth, and fifth harmonics, along with the fundamental frequency. ā Harmonic synthesis is the construction of a sound wave from its harmonic components. In order to come as close as possible to the exact waveform of the instrument, more harmonics must be used in the synthesis of the instrument's sound. Electronic music synthesizers use a series of harmonics whose relative amplitudes can be adjusted to fit the desired instrument's waveform. On more advanced synthesizers, they can adjust the attack, decay, vibrato, tremolo, and release of each note. Bands today use synthesizers all the time in their music because the sound they produce is nearly indistinguishable from the real instrument's sound. ā The reverse of harmonic synthesis is harmonic analysis, where a sound is broken up into it's harmonics. This requires complex math called Fourier analysis, after Jean Baptiste Joseph Fourier, a French mathematician who studied periodic functions.
- 44. Conclusion In this assignment, I have explained about the topic Sound and it's Applications by providing all the details available on it. This project also emphasizes on main ideas related to the topic. Many helped me while making of this project,my teachers, my friends and family. I took the ideas and researched about this topic from the websites and some books which are mentioned in the bibliography. I wish this assignment will be a useful and the knowledgeable one. 44
- 45. Bibliography Books Referred ā NCERT class 10 science book ā Oswal class 10 science book ā And other references... Websites referred ā Google.com ā Brainly.com ā Meritnation.com ā Skillshare.com ā Wikipedia.com ā YouTube.com ā Interestingphysics.com 45