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Loudness or intensity

Sound is a wave and waves have amplitude, or height. Amplitude is a measure of energy. The more energy a wave has, the higher its amplitude. As amplitude increases, intensity also increases. Intensity is the amount of energy a sound has over an area. The same sound is more intense if you hear it in a smaller area. In general, we call sounds with a higher intensity louder.

We are used to measuring the sounds we hear in loudness. The sound of your friend yelling is loud, while the sound of your own breathing is very soft. Loudness cannot be assigned a specific number, but intensity can. Intensity is measured in decibels.

The human ear is more sensitive to high sounds, so they may seem louder than a low noise of the same intensity. Decibels and intensity, however, do not depend on the ear. They can be measured with instruments. A whisper is about 10 decibels while thunder is 100 decibels. Listening to loud sounds, sounds with intensities above 85 decibels, may damage your ears. If a noise is loud enough, over 120 decibels, it can be painful to listen to. One hundred and twenty decibels is the threshold of pain

The loudness of a sound depends on the intensity of the sound.   
A dynamite explosion is loader than that of a cap pistol because of the greater amount of air molecules the dynamite is capable of displacing.  

Loudness becomes meaningful only if we are able to compare it with something. The sound of a gunshot may be deafening in a small room, but actually go unnoticed if fired in a subway station when a train is roaring past. 

Sounds and their Decibels

Source of Sound


Civil Defense Siren


Rock Concert


Lawn Mower




Garbage Disposal


Vacuum Cleaner


Normal Conversation


Light Traffic


Background Noise








Rhythm is a recurring sound that alternates between strong and weak elements.  

Wooden pegs, suspended by wires in a wooden frame to suggest the sound of a large group of people marching in order, will be believable if correct rhythm is supplied. If the rhythmic cadence were ignored the wooden pegs would sound like wooden pegs drummed mechanically on a wooden surface.