Learning object
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This document discusses sound levels measured in decibels. It notes that 0dB is the quietest sound a human can hear, 30-40dB is ideal for a quiet environment, sounds over 50dB can affect sleep, and over 70dB can affect work efficiency. Long term exposure to sounds over 90dB can damage hearing. Exposure to 150dB noise could cause immediate hearing loss. It provides examples of sound levels measured in daily life and explains the speed of sound in air is 340m/s.
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![IThere are A, B and two sounding bodies, for the first time
by a separate body armor sounding voice, as measured by
the instrument is 62dB; the second by B vocal sounding
body alone, fixed in the same place the instrument
measured as 45dB. Here are a few to determine the correct
[]
A. A sound body some distance away Instruments
B. B vocal instrument must be far away from the body
C. A sound body away from the instrument may be near
D. None of the above three analysis](https://image.slidesharecdn.com/learningobject-150223015929-conversion-gate01/85/Learning-object-6-320.jpg)
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Learning object
- 2. People use decibels to indicate the sound intensity level. 0dB is the weakest voice heard. 30 ~ 40dB is an ideal quiet environment . Sound louder than 50dB will affect sleep. Sound above 70dB will affect efficiency. Long-term with 90dB or more will affect the hearing. If suddenly exposed to up to 150dB noise environment, hearing will completely lost.!
- 3. There are a lot of normal things is related to sound levels in daily life.
- 4. Assume that robson square features a noise monitoring equipment. A time display on the digital device displays 49.20, this unit of this number is ________, The velocity of oise propagation in air is approximately __________m / s.
- 5. 1.The unit is dB(decibels) 2.The velocity is 340 m/s explanation: using equation v=(B/ρ)^(1/2) Hint:The speed of sound in air is 340m/s
- 6. IThere are A, B and two sounding bodies, for the first time by a separate body armor sounding voice, as measured by the instrument is 62dB; the second by B vocal sounding body alone, fixed in the same place the instrument measured as 45dB. Here are a few to determine the correct [] A. A sound body some distance away Instruments B. B vocal instrument must be far away from the body C. A sound body away from the instrument may be near D. None of the above three analysis
- 7. The answer is C.