Question

70 dB noise lasts for 20 min followed by 60 dB for 70 min followed by 80 dB for 10 min. The $L_{eq}$ value for fluctuating noise level for 100 min is

• A. 71.04 dB
• B. 98.4 dB
• C. 101.2 dB
• D. 110.8 dB

Answer 1

The correct option is A 71.04 dB

$L_{eq}=10\log {\sum }_{i=1}^{i=n}(10{)}^{\frac{L_i}{10}}\times t_i$
${\sum }_1^3(10{)}^{\frac{L_i}{10}}\times t_i=\left[\right(10{)}^{\frac{70}{10}}\times \frac{20}{100}+(10{)}^{\frac{60}{10}}\times \frac{70}{100}+(10{)}^{\frac{80}{10}}\times \frac{10}{100}]$
$=12.7\times {10}^6$
$I_{eq}=10lo{g}_{10}(12.7\times {10}^6)=71.04dB$