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201241723 mz mandhlazi

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University Of Johannesburg
University Of Johannesburg

This document discusses sound waves and the Doppler effect. It defines a wave and describes the characteristics of sound waves including frequency, wavelength, amplitude, and speed. It explains that sound is composed of compressions and rarefactions that the human ear can detect. The Doppler effect is introduced as the apparent change in frequency of a wave due to the motion of the source or observer. The summary provides key details about sound waves and the Doppler effect in under 3 sentences.

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201241723 mz mandhlazi
How can I explain the concept of SOUND, WAVES AND DOPPLER EFFECT?
201241723 mz mandhlazi
WAVES are everywhere. We encounter them on a daily basis. Examples of waves are:
WAVE - a disturbance traveling through a medium or in a vacuum from one location to another.
is the maximum distance the particles in a wave vibrate from their rest positions. the number of waves produced in a given time -
Frequency= waves/time
201241723 mz mandhlazi
201241723 mz mandhlazi
SOUND It is composed of waves of compression and rarefaction in which the human ear is sensitive
Sound may be described by four perceptual characteristics: Pitch refers to the highness or lowness of a sound. It depends upon the frequency of the sounding object. Higher frequency sounds produce high pitch while lower frequency sounds produce low pitch. Loudness is a physiological sensation that varies from one person to another. It depends on the sense of hearing, the distance from the source and the material through which the sound travels.
Pitch - description of how high or low the sound seems to a person . Loudnesshow loud or soft a sound is perceived to be.
201241723 mz mandhlazi
Sound Waves is a longitudinal wave created by vibrating solids, liquids or gases and capable of producing a sensation in our auditory system. It can travel through a medium from one location to another. It travels at a speed of 331m/s in air at sea level when the temperature is 0 degree.
This music is so loud please turn it UP
Loudness of Sound in Decibels
Just like all longitudinal (compression)waves, sound Waves possess a velocity, frequency, wavelength, phase, period, and amplitude. Sound waves also reflect, refract, diffract, and interfere.
201241723 mz mandhlazi
2. LOUDNESS or intensity -description of how high or low the sound seems to a person -determined mainly by the amplitude of the sound wave a. Decibel (dB)- unit used to measure sound intensity or loudness.
Speed of Sound Depends on: 1. Type of medium -travels better through liquids and solids and gas cant travel through a vacuum. 2. Temperature of medium -travels faster at higher temperature. 3. Density -sound moves well through dense materials. 4. Elasticity -sound waves move fast through elastic materials
Human Hearing sound wave vibrates ear drum amplified by bones converted to nerve impulses in cochlea
Ultrasound sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz - Infrasound - sounds with frequencies below the normal human range of hearing. Sounds in the 20-200 Hz range
DOPPLER EFFECT
The apparent change in the frequency of a source of wave due to the motion of the source and/or the observer Developed by Christian Doppler in 1842 The difference of the true frequency and the apparent frequency is called the Doppler Shift
Doppler Effect The Doppler effect is the apparent change in the frequency of sound due to the motion of source of sound and/or the observer.
Key variables The following symbols will be used in the definitions: fis the true frequency f v vs is the apparent frequency is the velocity of the sound (air) is the velocity of the source vo is the velocity of the observer 了 is the true wavelength 了 is the apparent wavelength
Case 1:observer is in motion and the source is at rest f = [ ( v 賊 vo ) / v ] f ( + ) means the observer is moving towards the source ( - ) means the observer is moving away from the source
Case 2:observer is at rest and the source is in motion f = [ v / ( v 賊 vs ) ] f ( + ) means the source is moving away from the observer ( - ) means the source is moving towards the observer
Case 3:both the observer and the source are in motion f = [ ( v 賊 v o ) / ( v 賊 vs ) ] f NOTE: please refer to case 1 and case 2 and analyze the situation of the observer and the source respectively.
Conceptual understanding When a wave source moves toward a receiver, does the receiver encounter an increase in wave frequency, wave speed ,or both? Does the Doppler Effect occur for only some types of waves or all types of waves?
Doppler Effect change in wave frequency caused by a moving wave source moving toward you pitch sounds higher moving away from you pitch sounds lower
named after Austrian physicist and philosopher Ernst Mach Used to describe speed of objects that are travelling close to, or above the speed of sound. The ratio of the speed of the object and the speed of sound in the medium. M = speed of object / speed of sound
Shock waves this is heard as a sonic boom when an airplane passes over; this is the result of the compilation of sound waves generated by a source that moves at equal or greater velocity than the sound it creates
Sample problems: Doppler effect 1. An ambulance traveling at 20. m/s sounds its siren at a frequency of 256Hz. What apparent frequency will you hear if the ambulance is: ( assume air temperature to be at 25属C ) a. approaching you? b. moving away from you? 2. A car traveling at 30. m/s sounds its horn as it overtakes and pass another car traveling at 20. m/s in the same direction. If the frequency of the horn is 500. Hz, what is the frequency heard by the driver in the slower car: a.) before b.) after the car has passed? Assume sound speed to be at 350. m/s.
LIST OF REFFERENCES This presentation is the combination of sources by the following: Agatonlydelle. (2012). Physics Sounds. Online: http://www.slideshare.net/agatonlydelle/physics-sounds. Accessed online on: 06 march 2014 HMLSS21. (2012). Sound Waves BSU-ARASOF. http://www.slideshare.net/HMLSS21/sound-waves-bsuarasof. Accessed online on: 05 march 2014 Marium S. (2013). DAV Lecture: WAVE INTERACTIONS. Online: http://www.slideshare.net/saramarium1/sound-and-waves-26412647. Accessed online on: 05 march 2014 Moral F. (2014). Teacher at B.R.I.G.H.T. Academy: The Doppler effects. Online: http://www.slideshare.net/teacherfidel/16-the-doppler-effect?qid=c0a01b029c80-4a3c-861c-c18f4e6146e9&v=qf1&b=&from_search=2. Access online on: 05 march 2014

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201241723 mz mandhlazi

  • 2. How can I explain the concept of SOUND, WAVES AND DOPPLER EFFECT?
  • 4. WAVES are everywhere. We encounter them on a daily basis. Examples of waves are:
  • 5. WAVE - a disturbance traveling through a medium or in a vacuum from one location to another.
  • 6. is the maximum distance the particles in a wave vibrate from their rest positions. the number of waves produced in a given time -
  • 10. SOUND It is composed of waves of compression and rarefaction in which the human ear is sensitive
  • 11. Sound may be described by four perceptual characteristics: Pitch refers to the highness or lowness of a sound. It depends upon the frequency of the sounding object. Higher frequency sounds produce high pitch while lower frequency sounds produce low pitch. Loudness is a physiological sensation that varies from one person to another. It depends on the sense of hearing, the distance from the source and the material through which the sound travels.
  • 12. Pitch - description of how high or low the sound seems to a person . Loudnesshow loud or soft a sound is perceived to be.
  • 14. Sound Waves is a longitudinal wave created by vibrating solids, liquids or gases and capable of producing a sensation in our auditory system. It can travel through a medium from one location to another. It travels at a speed of 331m/s in air at sea level when the temperature is 0 degree.
  • 15. This music is so loud please turn it UP
  • 16. Loudness of Sound in Decibels
  • 17. Just like all longitudinal (compression)waves, sound Waves possess a velocity, frequency, wavelength, phase, period, and amplitude. Sound waves also reflect, refract, diffract, and interfere.
  • 19. 2. LOUDNESS or intensity -description of how high or low the sound seems to a person -determined mainly by the amplitude of the sound wave a. Decibel (dB)- unit used to measure sound intensity or loudness.
  • 20. Speed of Sound Depends on: 1. Type of medium -travels better through liquids and solids and gas cant travel through a vacuum. 2. Temperature of medium -travels faster at higher temperature. 3. Density -sound moves well through dense materials. 4. Elasticity -sound waves move fast through elastic materials
  • 21. Human Hearing sound wave vibrates ear drum amplified by bones converted to nerve impulses in cochlea
  • 22. Ultrasound sound waves with frequencies above the normal human range of hearing. Sounds in the range from 20-100kHz - Infrasound - sounds with frequencies below the normal human range of hearing. Sounds in the 20-200 Hz range
  • 24. The apparent change in the frequency of a source of wave due to the motion of the source and/or the observer Developed by Christian Doppler in 1842 The difference of the true frequency and the apparent frequency is called the Doppler Shift
  • 25. Doppler Effect The Doppler effect is the apparent change in the frequency of sound due to the motion of source of sound and/or the observer.
  • 26. Key variables The following symbols will be used in the definitions: fis the true frequency f v vs is the apparent frequency is the velocity of the sound (air) is the velocity of the source vo is the velocity of the observer 了 is the true wavelength 了 is the apparent wavelength
  • 27. Case 1:observer is in motion and the source is at rest f = [ ( v 賊 vo ) / v ] f ( + ) means the observer is moving towards the source ( - ) means the observer is moving away from the source
  • 28. Case 2:observer is at rest and the source is in motion f = [ v / ( v 賊 vs ) ] f ( + ) means the source is moving away from the observer ( - ) means the source is moving towards the observer
  • 29. Case 3:both the observer and the source are in motion f = [ ( v 賊 v o ) / ( v 賊 vs ) ] f NOTE: please refer to case 1 and case 2 and analyze the situation of the observer and the source respectively.
  • 30. Conceptual understanding When a wave source moves toward a receiver, does the receiver encounter an increase in wave frequency, wave speed ,or both? Does the Doppler Effect occur for only some types of waves or all types of waves?
  • 31. Doppler Effect change in wave frequency caused by a moving wave source moving toward you pitch sounds higher moving away from you pitch sounds lower
  • 32. named after Austrian physicist and philosopher Ernst Mach Used to describe speed of objects that are travelling close to, or above the speed of sound. The ratio of the speed of the object and the speed of sound in the medium. M = speed of object / speed of sound
  • 33. Shock waves this is heard as a sonic boom when an airplane passes over; this is the result of the compilation of sound waves generated by a source that moves at equal or greater velocity than the sound it creates
  • 34. Sample problems: Doppler effect 1. An ambulance traveling at 20. m/s sounds its siren at a frequency of 256Hz. What apparent frequency will you hear if the ambulance is: ( assume air temperature to be at 25属C ) a. approaching you? b. moving away from you? 2. A car traveling at 30. m/s sounds its horn as it overtakes and pass another car traveling at 20. m/s in the same direction. If the frequency of the horn is 500. Hz, what is the frequency heard by the driver in the slower car: a.) before b.) after the car has passed? Assume sound speed to be at 350. m/s.
  • 35. LIST OF REFFERENCES This presentation is the combination of sources by the following: Agatonlydelle. (2012). Physics Sounds. Online: http://www.slideshare.net/agatonlydelle/physics-sounds. Accessed online on: 06 march 2014 HMLSS21. (2012). Sound Waves BSU-ARASOF. http://www.slideshare.net/HMLSS21/sound-waves-bsuarasof. Accessed online on: 05 march 2014 Marium S. (2013). DAV Lecture: WAVE INTERACTIONS. Online: http://www.slideshare.net/saramarium1/sound-and-waves-26412647. Accessed online on: 05 march 2014 Moral F. (2014). Teacher at B.R.I.G.H.T. Academy: The Doppler effects. Online: http://www.slideshare.net/teacherfidel/16-the-doppler-effect?qid=c0a01b029c80-4a3c-861c-c18f4e6146e9&v=qf1&b=&from_search=2. Access online on: 05 march 2014