### Video: Decibel Scale

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#### The DeciBel Scale

Video Transcript

Every sound is characterized by a deciBel rating that provides a measure of how intense the sound is. A more intense sound has a higher deciBel rating and is perceived by a person as being louder.

To understand the concept of deciBels, you must know these two things. First, the deciBel scale is a logarithmic scale. It is based on powers of 10, making it much different than usual measurement scales. When comparing two lengths – 80 cm and 40 cm – you would claim that  80 cm is 2 times longer than 40 cm. DeciBels work differently because they’re based on powers of 10. An 80 deciBel sound is NOT twice as intense as a 40 deciBel sound. Instead, it is 4 powers of 10 more intense – 10 000 X more intense – than a 40 deciBel sound. To understand why, you need to know one more thing …

The deci- of deciBel is a Greek prefix that works much like the milli- of milliliter or the centi- of centimeter or the kilo- of kilogram. Centi- means 1/100th, which is why an 80 centi-meter length is equivalent to 0.8 meters. Now deci- means 1/10th , so an 80 deciBel sound is an 8 bel sound. Here’s some other deciBel è Bel conversions.

So let’s return to the intensity comparison of a 40 deciBel to an 80 deciBel sound. A conversion needs to first be made to Bels. So we have a 4 Bel and an 8 Bel sound. The 8 Bel sound is 4 Bels more than the 4 Bel sound. The difference in the Bel rating indicates how many powers of 10 times more intense one sound is than the other sound. That’s why 80 deciBels (8 Bels) is 104 times more intense than 40 deciBels (4 Bels).

Let’s try another example:  compare 110 deciBels to 50 deciBels. In terms of Bels, we’re comparing 11 Bels to 5 Bels. That’s a differene of 6 Bels. So the 110 deciBel sound is 106 (one million) times more intense than the 50 deciBel sound.

Here’s a summary of the process:
1. Convert deciBels to Bels.
2. Determine the difference in Bels for the two sounds. This is “x”.
3. The higher deciBel sound is 10x times more intense.

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