Math Problem Statement

Question content area top Part 1 Loudness measured in decibels​ (dB) is defined by loudnessequals10 log StartFraction Upper I Over Upper I 0 EndFraction ​, where I is the intensity and I Subscript 0equals10 Superscript negative 12 ​W/msquared. The noise level inside a convertible driving along the freeway with its top up is 80 dB. With the top​ down, the noise level is 96 dB. Complete parts a and b below. Question content area bottom Part 1 a. Find the intensity of the sound with the top up and with the top down. The intensity of the sound with the top up is Ialmost equals    enter your response here ​W/msquared.

Solution

We are given the formula for loudness in decibels (dB):

L=10log(II0)L = 10 \log \left( \frac{I}{I_0} \right)

where:

  • LL is the loudness in decibels,
  • II is the intensity of the sound in watts per square meter (W/m2W/m^2),
  • I0=1012I_0 = 10^{-12} W/m2W/m^2 is the reference intensity.

Step 1: Solve for II

Rearrange the formula to solve for II:

I=I0×10L/10I = I_0 \times 10^{L/10}

Step 2: Calculate II for the top up (80 dB)

Iup=(1012)×1080/10I_{\text{up}} = (10^{-12}) \times 10^{80/10}

Iup=(1012)×108I_{\text{up}} = (10^{-12}) \times 10^8

Iup=104 W/m2I_{\text{up}} = 10^{-4} \text{ W/m}^2

Step 3: Calculate II for the top down (96 dB)

Idown=(1012)×1096/10I_{\text{down}} = (10^{-12}) \times 10^{96/10}

Idown=(1012)×109.6I_{\text{down}} = (10^{-12}) \times 10^9.6

Idown=102.4 W/m2I_{\text{down}} = 10^{-2.4} \text{ W/m}^2

Approximating:

Idown3.98×103 W/m2I_{\text{down}} \approx 3.98 \times 10^{-3} \text{ W/m}^2

Final Answers:

  • The intensity of the sound with the top up is 10410^{-4} W/m².
  • The intensity of the sound with the top down is 3.98×1033.98 \times 10^{-3} W/m².

Would you like a breakdown of logarithmic calculations? Let me know!

Related Questions:

  1. How does doubling the intensity affect the loudness in decibels?
  2. If the intensity increases by a factor of 100, by how many dB does the loudness increase?
  3. What is the intensity level at 50 dB?
  4. How does sound intensity relate to human perception of loudness?
  5. What is the threshold of pain in decibels, and what is its intensity?

Tip:

Every 10 dB increase represents a 10-fold increase in intensity, but only about a doubling in perceived loudness.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Exponential Functions
Sound Intensity

Formulas

L = 10 log (I / I₀)
I = I₀ * 10^(L/10)

Theorems

Properties of Logarithms
Definition of Decibels in Sound Intensity

Suitable Grade Level

Grades 9-12