In the afternoon,the decibel level of a busy freeway is 85 dB with 90 cars passing a given point every minute.Late at night,the traffic flow is only 8 cars per minute.What is the late-night decibel level?
A)200 dB
B)85 dB
C)170 dB
D)74 dB
E)8.5 dB

Question

Quizplus · Accepted Answer

The decibel level is proportional to the logarithm of the intensity. Assuming each passing car makes the same noise, the number of cars passing a given point is directly proportional to the intensity of the sound. Thus, we can use the formula I1/I2 = (dB2 - dB1) / 10, where I1 and I2 are the intensities of the sound, and dB1 and dB2 are the corresponding decibel levels.

Let's set up the equation for the two scenarios given:

I1 / I2 = 90 / 8   (ratio of cars passing)

85 / dB2 = log(90 / 8) / log 10   (solve for dB2)

dB2 = 74 dB

Therefore, the answer is D, 74 dB.

In the Afternoon,the Decibel Level of a Busy Freeway Is