(a) What is the threshold of hearing and what is the treshold of pain in the context of hearing ? How are these related to each other ?
(b) What are the value of intensity level for (i) Soft whisper (ii) Quiet library (iii) Normal conversation (iv) Rock band (with amplifiers) (v) Jet plane take off (vi) Rocket launch ?

Explanation

(a) Threshold of hearing, `I_0 = 10^-12 W//m^2`
Threshold pf pain, `I_p = 1.0 W//m^2`
`(I_p)/(I_0) = (1.0 W//m^2)/(10^-12 W//m^2) = 10^12`
That is, the intensity at the threshold of pain is a trillion times that at the threshold of hearing.
(b) (i) Soft whisper : `20 dB`,
(ii) Quit library : `40 dB`,
(iii) Normal conversation : `60 dB`,
(iv) Rock band (with amplifires) : `100 dB`,
(v) Rocket launch : `180 dB`.