(8.5)

 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

 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

 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.

Type of Sound Wave FrequencyExample Infrasonic Waves < 20 HzEarthquakes Audible Sound Waves 20 Hz – 20 kHz Dog bark, whisper, etc. Ultrasonic Waves > 20 kHzUltrasounds, Ultrasonic ranging unit

Distance (m) Sound Level (dB)  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

Continuous dB Permissible Exposure Time 85 8 h 88 4 h 91 2 h 94 1 h min min min min min min 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

 Lesson-2/The-Speed-of-Sound Lesson-2/The-Speed-of-Sound  Xk Xk  B4 B4  Nelson Physics 11