Question

The sound level of the chirping made by a bird at a distance of 5 metres is measured at 30 dB. When the same bird is 50 metres away, the sound level is measured at 10 dB. How many times greater is the amplitude of the sound wave at 5 metres away compared to 50 metres away –

• A. 3 times greater
• B. 10 times greater
• C. 20 times greater
• D. 100 times greater

Answer 1

Answer: (B)

10 times greater

Answer 2

$\frac { \mathrm { A } _ { 1 } } { \mathrm {~A} _ { 2 } } = \frac { \mathrm { r } _ { 2 } } { \mathrm { r } _ { 1 } } = \frac { 50 } { 5 } = 10$