1. 0.5/1 points | Previous Answers My Notes Ask Your Teacher A train sounds its

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1. 0.5/1 points | Previous Answers My Notes Ask Your Teacher A train sounds its horn as it approaches an intersection. The horn can just be heard at a level of 44.0 dB by an observer 10.0 km away. (a) What is the average power generated by the horn? 31.5 (b) What intensity level of the horn's sound is observed by someone waiting at an intersection 48.0 m from the train? Treat the horn as a point source and neglect any absorption of sound by the air X dB Enter a number Submit Answer Save ProgressPractice Another Version

Explanation / Answer

(a)

Intensity of a 44dB sound using = 10dB*log(I/10-12)

so

I = 10(44/10)*10-12

I = 10-7.6 W/m2

P = I*A

P = 1x10-7.6*4*(10000m)2

P = 31.54929 W

P = 31.5 W

(b)

At 48m the intensity = P/A = 31.54929W/(4*482)

I = 0.001090228W/m2

intensity level =10dB*log(0.001090228/10-12)

Il= 90.36 dB

Il= 90.3 dB

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