Question

If the intensity of a given noise increases two-fold, the noise level in decibels (dB) increases by

1. ~2 dB
2. ~3 dB
3. ~6 dB
4. ~10 dB

Answer 1

Correct Answer - Option 2 : ~3 dB

Noise pollution is a major problem for the quality of life in urban areas. Traffic noise is considered as one of the important sources of noise pollution that adversely affects human health in residential urban areas.

In most cases, the sounds and noises we hear are not steady. Apart from variation in tones, the magnitude or the sound pressure level of a sound or noise changes with time.

Explanation

L = 10 log I/I₀

L’ = 10 log 2I/I₀

Where,

L – intensity of noise

L’ - increased intensity of noise

L’ - L = 10 log 2I/I₀-10 log I/I₀

L’ - L = 10 [log 2I/I₀-log I/I₀]

L’ - L = 10 log [2I/I] (after cancelling I₀ both side)

= 10 log 2

= 10*0.301 (log value of 2 = 0.301)

= 3.01dB

Conclusion: Hence, if noise intensity will increase two-fold then noise level in decibel will increase approximately three-fold. So, option (2) is correct.