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Table taken from pg. 395 of Nelson Physics 11 Additional values can be found at: oom.com/class/sound/Les son-2/The-Speed-of-Sound Medium Speed of Sound (m/s) Air (20 o C) 344 Air (0 o C) 331 Air (- 20 o C) 319 Glass (Pyrex) 5170 Steel 5000 Water 1496 Wood (maple) 4110
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SOUND WAVES(8.5)
Properties of Sound Waves Are longitudinal waves Require a medium to travel through The type of medium influences the speed
of the sound wave Sound travels faster at higher
temperatures Sound waves can also be affected by
humidity and air pressure
Comparison for Speed of Sound in Different Mediums
Table taken from pg. 395 of Nelson Physics 11
Additional values can be found at:
http://www.physicsclassroom.com/class/sound/Lesson-2/The-Speed-of-Sound
Medium Speed of Sound (m/s)
Air (20oC) 344Air (0oC) 331
Air (- 20oC) 319Glass
(Pyrex)5170
Steel 5000Water 1496Wood
(maple)4110
Experimental Formula for the Speed of Sound in Air
Where v is the speed of sound in air in m/s
T is the air temperature in degrees Celsius
(Formula based on analysing speed-temperature data)
Sound Intensity Humans describe how loud a sound is by
its sound intensity.
Sound intensity is the amount of sound energy being transferred per unit area (Units: )
The larger the amplitude of a sound wave the more energy it is transferring and the louder the sound you will hear.
Sound Intensity Sound intensity levels is often described
in decibels (dB).
Decibels are a measure of sound level and uses a logarithmic scale to show the different in sound intensity.
Loudness levels are dependent on the distance from the source of the sound.
Audible Sound Waves
Type of Sound Wave
Frequency Example
Infrasonic Waves
< 20 Hz Earthquakes
Audible Sound Waves
20 Hz – 20 kHz Dog bark, whisper, etc.
Ultrasonic Waves
> 20 kHz Ultrasounds, Ultrasonic ranging
unit
Loudness and DistanceDistance
(m)Sound Level
(dB)
1 12010 10050 86
100 80200 74500 66
1000 602000 545000 46
10000 40
Further away from an object the quieter the sound becomes.
This is because the amount of energy carried is the same but the area the sound travels is greater. Thus decreasing the sound intensity.
Table taken from pg. 396 of Nelson Physics 11
Sound SafetyContinuo
us dBPermissible Exposure
Time85 8 h88 4 h91 2 h94 1 h97 30 min
100 15 min103 7.5 min106 3.75 min109 1.88 min112 0.94 min115 0.47 min
Hearing damage can occur when exposed to loud sounds for extended periods of time.
Exposure time depends on sound intensity.
Important to wear hearing protection when exposed to loud noises
Table taken from pg. 396 of Nelson Physics 11
Mach Number Mach number is the ratio of the airspeed of an object to the local speed of sound The local speed of sound may vary due to surrounding air temperatures Described by Austrian physicist Ernst Mach Mach 1 = speed of sound
Experiment to Measure the Speed of Sound in Air
Reverences http://
www.physicsclassroom.com/class/sound/Lesson-2/The-Speed-of-Sound
https://www.youtube.com/watch?v=NPPgQcFUrXk
https://www.youtube.com/watch?v=RRFV_gJQbB4
Nelson Physics 11