Dreadful Decibels

Decibels are mysterious units until you become accustomed to them. The best way to do so is to look at tables or images of noises with which we are familiar and see the decibel level ascribed to them. The result is very approximate. In the image above the noise level in an average office is given as 50 decibels. But there are average offices and average offices! To have a more accurate sense of noise levels one must have some experience with a sound level meter, hearing the difference between a 50 decibel and a 55 decibel office. The smallest difference of noise level we can distinguish is about one decibel which indicates the usefulness of this unit.
The reason for using decibels is the vast range of sound which the human ear can hear and the fact that our sense of loudness is not linear, which means that if noise power is multiplied by, say, 10, it does not sound ten times louder to us. But more of this on another occasion. Here, let us say that our extraordinary range of hearing varies from a scale of 1 to 100,000,000,000,000 – the lower level being the absolutely lowest level of audible sound and the upper level being capable of destroying our hearing altogether. So instead of having to speak of a level of sound of say 1,000,000 we speak of the much more convenient 60 decibels. You will appreciate that it is easier to speak of a noise level of 61 decibels which most people can distinguish from a level of 60 decibels than to speak of them in ordinary numbers when instead of 61 and 60 we would have to speak of 1,258,925 and 1,000,000. Hurrah for decibels!