(a)

The level of sound is .

Standard intensity of sound is .

Intensity of sound of quiet room is .

Power property of logarithms: .

The level of sound is .

(b)

The level of sound is  .

Standard intensity of sound is .

Intensity of sound of busy street corner is .

Power property of logarithms: .

The level of sound is .

(c)

The level of sound is .

Standard intensity of sound is .

Intensity of sound of quiet radio is .

Power property of logarithms: .

The level of sound is .

(d)

The level of sound is .

Standard intensity of sound is .

Intensity of sound of threshold of pain is .

Power property of logarithms: .

The level of sound is .

(a) The level of sound is .

(b) The level of sound is .

(c) The level of sound is .

(d) The level of sound is .