Unformatted text preview: n earthquake which registered 6.7 on the Richter scale had a seismograph
reading ten times larger than one which measured 5.7.
iv. Find two news stories about recent earthquakes which give their magnitudes on the
Richter scale. How many times larger was the seismograph reading of the earthquake
with larger magnitude?
(b) While the decibel scale can be used in many disciplines,11 we shall restrict our attention
to its use in acoustics, speciﬁcally its use in measuring the intensity level of sound.12
The Sound Intensity Level L (measured in decibels) of a sound intensity I (measured in
watts per square meter) is given by
L(I ) = 10 log I
10−12 . W
Like the Richter scale, this scale compares I to baseline: 10−12 m2 is the threshold of
human hearing. i. Compute L(10−6 ).
ii. Damage to your hearing can start with short term exposure to sound levels around
115 decibels. What intensity I is needed to produce this level?
iii. Compute L(1). How does this compare with the threshold of pain whic...
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