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Architecture Engineering QUESTION #2347
Question 1
Sound Pressure Level (SPL) \(L_p\) in decibels relative to reference pressure \(p_0 = 20\,\mu\text{Pa}\) is defined as:
  • \(L_p = 10\log_{10}\!\left(\dfrac{p}{p_0}\right) \text{ dB}\)
  • \(L_p = 20\log_{10}\!\left(\dfrac{p}{p_0}\right) \text{ dB}\)✔️
  • \(L_p = 10\log_{10}\!\left(\dfrac{I}{I_0}\right) \text{ dB where } I_0 = 10^{-12}\,\text{W/m}^2\)
  • \(L_p = 20\log_{10}\!\left(\dfrac{p_0}{p}\right) \text{ dB}\)
Correct Answer Explanation
SPL is defined as \(L_p = 20\log_{10}\!\left(\dfrac{p}{p_0}\right)\) dB, since pressure is an amplitude (not power) quantity. Note that Option C defines Sound Intensity Level \(L_I = 10\log_{10}(I/I_0)\), which numerically equals SPL in a free field for plane waves. Options A would be correct for power ratios. Option D is inverted and gives negative values.