What is a Decibel?

Discussions about noise inevitably make reference to the decibel scale, also known as dB. Unfortunately, you need a pretty good mathematical and scientific mind to understand what a decibel really means.

Don’t despair. The main thing you have to know is that when measuring noise in decibels, every 10 decibel increase in sound means that the loudness of the sound has doubled. When a measured noise increases from 50 decibels to 60 decibels, the noise is not just 20 percent louder, it’s actually 100 percent louder. For example, a normal conversation with a person is measured at 60 decibels. The sound of a vacuum clear is 70 decibels. And that’s considered a doubling of loudness.

So when the Yonkers City Council increased the maximum allowed daytime noise from 55 decibels to 85 decibels, they increased the maximum level by 8X – 85 decibels is heard to be eight times louder than a sound at 55 decibels. From 55 to 65 is a doubling, from 65 to 75 is a quadrupling, and from 75 to 85 is an octupling!

It’s not hard to understand that the farther away you are from a noise source, the less noise you will hear. But how do we get a better understanding of how distance reduces noise? As with decibels, there’s a dense sounding scientific concept at play. But what you need to know is that when you double the distance from a sound source, the intensity drops to one-fourth of its original level.

Let’s see if we can apply that to the Yonkers noise ordinance. If my neighbor is playing music that is 85 decibels loud to me, that would be the maximum noise they would be allowed to make. If I am standing about 40 ft. away from the neighbor’s speaker and hearing 85 decibels, that means that the sound level right next to the speaker would be about 103 decibels, similar to the sound of a jackhammer or a very loud concert. So under the new noise ordinance, your neighbor could be operating a jackhammer from 7 a.m to 10 pm, and be in compliance with the ordinance!