According to Webster's New World Dictionary, noise is any loud, discordant or disagreeable sound or sounds. Ambient noise is constantly and spontaneously occurring "background noise." Car engines roaring, dogs barking, wind blowing and birds chirping are some of the sounds that combine to make up the ambient noise.

Levels of sound are expressed in decibels (dB), a numerical expression of the relative loudness of a sound.  View Comparison of Sound Chart.

Here are some examples of how loud certain common sounds are:

• A car engine at 50 feet away averages 70 dB.
• A power lawnmower at 50 feet away averages 90 dB.
• A diesel truck at 50 feet away averages 80 dB.
• A train at 50 feet away averages is 85 dB.
• The United Center during a Chicago Bulls championship basketball game can reach 108 dB.