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Noise Analysis <br />£V <br />n o r t h w e s t <br />rail <br />Noise impacts are determined for three categories of <br />sensitive land uses. <br />Basic unit of measurement is the A- weighted sound level <br />in decibels (dBA). <br />Noise at given location at any moment in time <br />Most common outdoor noise sources generate <br />approximately 60 -90 dBA at 50' range <br />A- weighted sound level metric most commonly used to <br />express noise exposure over extended periods of time <br />Hourly Equivalent Sound Level [Leq(h)] and the Day -Night <br />Sound Level (Ldn) <br />Leq(h) cumulative exposure at location over 1- <br />hour <br />Ldn weighted noise level over 24 -hour period <br />16 <br />14 <br />