# Environmental Science: Numerical Questions – Noise Addition of Noise

Dr. Manishika Jain- Join online Paper 1 intensive course. Includes tests and expected questions.

1. A person is exposed to two sound levels of 80 dB and 100 dB simultaneously. What is the average noise level the person experiences ?

1. ~ 97 dB

2. ~ 87 dB

3. ~ 90 dB

4. ~ 93 dB

Explanation: 𝐿_𝑒𝑞= 10 𝐿𝑜𝑔(10^(𝐿_1/10)+10^(𝐿_2/10) )

𝐿_𝑒𝑞= 10 𝐿𝑜𝑔(10^(80/10)+10^(100/10) )

𝐿_𝑒𝑞= 10 𝐿𝑜𝑔(10^8+10^10 )

𝐿_𝑒𝑞= 10 𝐿𝑜𝑔 [108(1+10^2 )]

𝐿_𝑒𝑞= 10 [𝐿𝑜𝑔 108” + log 1+ log 102” ]

𝐿_𝑒𝑞= 10 [“8 + 0+2” ]

𝐿_𝑒𝑞= 100 dB

 Difference (L2-L1) Added to Higher Sound Value 0 3 1 2.5 2 2.1 3 1.5 4 1.5 5 1 6 1 7 0.8 8 0.6 9 0.5 10 0.4
 Difference (L2-L1) Added to Higher Sound Value 0 or 1 3 2 or 3 2 4 to 8 1 9 or more 0

2. On take - off, an aeroplane generates noise level of 120 db. If 5 such aeroplanes take – off simultaneously what will be the noise level ?

1. ~ 126.98 dB

2. ~ 124.98 dB

3. ~ 123.86 dB

4. ~ 122.98 dB

Explanation: 𝐿_𝑒𝑞= 𝐿_𝑖+10 𝐿𝑜𝑔(𝑛)

𝐿_𝑒𝑞=120+10 𝐿𝑜𝑔(5)

𝐿_𝑒𝑞=120+10∗0.69

𝐿_𝑒𝑞=120+6.9

𝐿_𝑒𝑞=126.9

3. The resultant of two noise levels of 50 dB and 55 dB is:

1. 58 dB

2. 55.41 dB

3. 52.5 dB

4. 56.19 dB

Explanation: 𝐿_𝑒𝑞= 10 𝐿𝑜𝑔(10^(𝐿_1/10)+10^(𝐿_2/10) )

𝐿_𝑒𝑞= 10 𝐿𝑜𝑔(10^(50/10)+10^(55/10) )

𝐿_𝑒𝑞= 10 𝐿𝑜𝑔(10^5+10^5.5 )

𝐿_𝑒𝑞=10 Log[10^5 (1+10^0.5)]

𝐿_𝑒𝑞= 10 (𝐿𝑜𝑔 105+log (1+√10)

𝐿_𝑒𝑞= 10 (𝐿𝑜𝑔 105+ log (1+3.16)

𝐿_𝑒𝑞= 10 (5+0.619)

𝐿_𝑒𝑞= 10 ∗5.619=56.19