Decibel Unit

A decibel is the degree of pressure increase – or the amplitude – which corresponds with the loudness of a sound. The higher the pressure, the louder the volume. Converting to the human ear, it is indicated as the decibel unit.

To produce a pressure increase there first needs to be some kind of energy or power inflicted on the medium.


Now don’t be intimidated by this formula, or the fact that there is a logarithmic involved in it. We shall see that it is not as difficult as it looks. We are going through the equation starting at the beginning:.

  • β is the number of dBs or decibel;
  • The ten is there to note that this is the Deci-bel scale and not just the bel scale;
  • The logarithmic is there to get the outcome in a more comfortable number;
  • I is the numerator and represents the intensity of a sound wave, it is defined as the power divided by the area in watts per square meter [w/m2]
  • The denominator is ten to the negative twelve watts per square meter and represents the threshold of human hearing. It is the softest sound a human ear can pick up.

One to the negative twelve! This is incredibly small, we are talking about one trillionth of a watt. Can you imagine how unbelievable sensitive the human ear is?. On the other side of the spectrum, the loudest intensity which a human is capable to hear is one (1) watt per square meter. Intensities higher than this will start to hurt. You can see that there is an enormous gap between the softest and the loudest intensity we can hear. From 0.000000000001 to 1, that is why we use logarithmic to convert really big numbers into small, easy-to-interpret numbers.


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