Correct Answer - Option 1 : Fluctuating noise over different time periods
Concept-
The Leq Concept:
Leq is that statistical value of sound pressure level that can be equated to any fluctuating noise level over different time periods.
A sound of 80 dB lasting for 10 minutes, followed by a sound of 60 dB lasting for the next 80 minutes and then followed by a sound of 100 dB for the next 5 minutes, will compose a fluctuating noise level, which can be represented by a certain dB value which is indicative of producing the same effect over the entire time period of 10 + 80 + 5 = 95 minutes, as the original fluctuating noise.
This value is called the Equivalent continues equal energy level or the Equivalent Noise Level (Leq).
Thus Leq is defined as the constant noise level, which over a given time, expands the same amount of energy, as is expected by the fluctuating levels over the same time.
This value is expressed by the equation-
\({L_{eq}} = 10\log \mathop \sum \limits_{{\rm{i}} = 1}^{{\rm{i}} = {\rm{n}}} {\left( {10} \right)^{\frac{{{{\rm{l}}_{\rm{i}}}}}{{10}}}} \times {{\rm{t}}_{\rm{i}}}\)
Where
n = Total number of sound samples
Li = The noise level of any ith sample
ti = Time duration of ith sample expressed as a fraction of total sample time.
