Question

Describe the sound level to decibel scale.

Answer 1

The lowest intensity of sound that can be perceived by the human ear is called threshold of hearing. For a sound of frequency 10 kHz, the threshold of hearing is, I₀ = 10^–12 W/m². The ratio of intensities of the loudest to faintest sound is 10¹². Humans can hear over a large range of intensities. 

Instead of expressing the intensity I of a sound wave, it is more convenient to express of its sound level β, which is defined as

Here dB is the abbreviation for decibel, the unit of sound level. The unit bel was introduced in honour of Alexander Graham Bell.

(β₂ – β₁): Let β₁ and β₂ are the sound levels corresponding to sound intensities I₁ and I₂ respectively, then