Question

Two sources of noise, adjacent to each other in a room, have sound pressure levels of 30 and 40 decibel (dB). The combined sound pressure level in the room is _________ dB(rounded off to 2 decimal places).
Use reference sound pressure as $20 \mu Pa$.

Answer 1

Correct Answer: 40

Step 1: Convert each dB level to its power ratio. \[ P_1 = 10^{\frac{30}{10}} = 1000, \quad P_2 = 10^{\frac{40}{10}} = 10000 \] Step 2: Sum the power ratios. \[ P_{\text{total}} = 1000 + 10000 = 11000 \] Step 3: Convert the total power ratio back to dB. \[ L_{p_{\text{total}}} = 10 \log_{10}(11000) \approx 40.00 \, \text{dB} \]