Engineering Board Exam Reviewer · Environmental Engineering · medium
A point source produces 90 dB at 10 m. Assuming free-field spreading (inverse square law), what is the sound level at 40 m?
- 84.0 dB
- 22.5 dB
- 78.0 dB
- 72.0 dB
Answer
C. 78.0 dB
Solution
L2 = L1 - 20 (r2/r1) = 90 - 20 4 = 78.0 dB (6 dB per doubling of distance).
More Environmental Engineering questions
- Two noise sources produce 90 dB and 85 dB at a point. What is the combined sound level?
- Three identical machines each produce 85 dB at a point. What is the combined sound level?
- Two machines each produce a sound level of 80 dB at a point. What is the combined sound level?
- Using a global warming potential of 28 for methane, what is the CO₂-equivalent of 10 tonnes of methane emissions?
- A household uses 300 kWh of electricity per month. If the grid emission factor is 0.7 kg CO2/ kWh, what are its annual CO2 emissions from…
- How much CO2 is produced by completely burning 1 tonne of coal that is 75% carbon by mass? (C = 12, CO2 = 44)
- A power plant burns 1000 tonnes of coal per day containing 2% sulfur by mass. Assuming all sulfur is converted to SO2, how much SO2 is…
- Using the Deutsch–Anderson equation = 1 - (-wA/Q), what is the efficiency of an electrostatic precipitator with plate area 5000 m2, gas…
- A cyclone (80% efficient) is followed by an electrostatic precipitator (99% efficient) in series. What is the overall particulate…
- A stack discharges 50 m3/s of flue gas containing 200 mg/m3 of particulates. What is the particulate emission rate?