Daily Question, September 20, 2015 (EIA Discussion): 3 wealth points for replies, plus 5 wealth points for correct answers (single-choice question)
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A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A). Considering only geometric divergence attenuation, what is the A sound level at a distance of 20 m from the fan? () A. 81 dB(A) B. 78 dB(A) C. 71 dB(A) D. 68 dB(A) Correct answer: D. Explanation: If the A-weighted sound power level LwA of a point source is known, and the source is in free space, then the A-weighted sound level at distance r can be calculated using the following formula: LA(r) = LwA – 20 log10(r). If the source is in a semi-free space, then the A-weighted sound level at distance r can be calculated using the following formula: LA(r) = LwA – 20 log10(r) – 8
A.81dB(A)
A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A); considering only geometric divergence attenuation, the A sound level at a distance of 20 m from the fan is (A).
A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A); considering only geometric divergence attenuation, the A-weighted sound level at a distance of 20 m from the fan is (C). A.81dB(A) B.78dB(A) C.71dB(A) D.68dB(A)
A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A); considering only geometric divergence attenuation, the A sound level at a distance of 20 m from the fan is (D). A. 81dB(A) B. 78dB(A) C. 71dB(A) D. 68dB(A)
A fan with a diameter of 3 meters is located at a height of 40 meters above the ground. Its sound power level is 105 dB(A). Considering only geometric attenuation, the A-weighted sound level at a distance of 20 meters from the fan is (C. 71 dB(A)).
A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A). Considering only geometric divergence attenuation, the A sound level at a distance of 20 m from the fan is (D
C.71dB(A)...................................
C.71dB(A)
A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A). Considering only geometric divergence attenuation, what is the A sound level at a distance of 20 m from the fan? () A. 81dB(A) B. 78dB(A) C. 71dB(A) D. 68dB(A) B
A fan with a diameter of 3 m is located at a height of 40 m above the ground. Its sound power level is 105 dB(A); considering only geometric divergence attenuation, the A sound level at a distance of 20 m from the fan is (D). A.81dB(A) B.78dB(A) C.71dB(A) D.68dB(A)