Physics Form 5: Chapter 1 - Loudness of Sound

2. Loudness - Amplitude

The loudness of a sound depends on the wave's amplitude.
The louder the sound, the higher the amplitude. So, amplitude is also a way of measuring the energy has.


The higher the energy, the higher the amplitude resulting a louder sound.


The system used to measure the loudness of sounds is the decibel system, given the unit dB.

Range (dB)	Description	Examples
0 - 30	Very Quiet	This is the threshold of human hearing, up to the sound of a quiet whisper.
31 - 50	Quiet	This is an average quiet house, with maybe the sound of a fridge running or someone moving around.
51 - 70	Normal	Regular daily sounds like people talking.
71 - 90	Loud	This is the point where a sound becomes annoying or distracting. Vacuums or a noisy car on a busy street are at these levels.
91 - 110	Very Loud	Most people will try to avoid being in areas this loud. Prolonged exposure can cause permanent ear damage. Temporary effects, like "stereo hiss", may happen.
111 +	Painful!!!	Even limited exposure to levels this high will cause permanent hearing loss.

Amplifier is a device to increase the loudness of sound by use of an external energy source. It drives the loudspeakers used in PA system to make the human voice louder.