Math Problem Statement

What distance from the sound source is the volume reduced by 6 dB?

Solution

The image contains the following problem:

Given the formula: L2=L1+20log(r1r2)L_2 = L_1 + 20 \log \left( \frac{r_1}{r_2} \right) where:

  • L1L_1 is the sound level (in dB) at distance r1r_1,
  • L2L_2 is the sound level (in dB) at distance r2r_2,
  • r2>r1r_2 > r_1.

You are asked to determine at what distance the volume is reduced by 6 dB, meaning L2=L16L_2 = L_1 - 6.

Step-by-Step Solution:

  1. Set up the equation for the reduction in sound level: L2=L16L_2 = L_1 - 6 Substituting into the original equation: L16=L1+20log(r1r2)L_1 - 6 = L_1 + 20 \log \left( \frac{r_1}{r_2} \right)

  2. Simplify the equation: 6=20log(r1r2)-6 = 20 \log \left( \frac{r_1}{r_2} \right)

  3. Solve for r1r2\frac{r_1}{r_2} by isolating the logarithmic term: log(r1r2)=620=0.3\log \left( \frac{r_1}{r_2} \right) = \frac{-6}{20} = -0.3

  4. Exponentiate both sides to remove the logarithm: r1r2=100.3\frac{r_1}{r_2} = 10^{-0.3} Using a calculator: 100.30.501210^{-0.3} \approx 0.5012

  5. Solve for r2r_2: r2=r10.50121.996r1r_2 = \frac{r_1}{0.5012} \approx 1.996 \cdot r_1

Thus, the distance r2r_2 is approximately 2 times the original distance r1r_1 when the volume is reduced by 6 dB.


Would you like further details or have any questions?

Here are some related questions:

  1. How does the inverse square law relate to sound propagation?
  2. What happens to the sound intensity if the distance is doubled?
  3. How does the logarithmic scale apply to sound measurements?
  4. What is the difference between sound intensity and sound pressure level?
  5. How does frequency affect sound levels at different distances?

Tip: Sound decreases logarithmically with distance, so small changes in dB can represent large changes in distance.

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Math Problem Analysis

Mathematical Concepts

Logarithms
Sound Intensity
Algebra

Formulas

L2 = L1 + 20 * log10(r1/r2)

Theorems

Inverse Square Law for Sound

Suitable Grade Level

Grades 10-12