Decibels |

The decibel is a measure of the relative intensity or power level of a signal. |

The reference level against which sounds can be measured is the threshold of hearing which is | 10**-12 watts/m**2 and is given a value of 0 dB. |

A sound is given a measure in decibels by taking ten times the logarithm of the ratio of its intensity with the intensity of the reference level. | 10 log (I/Iref) |

This method of measuring level matches more accurately the psychoacoustical properties of human hearing. |

First of all the dynamic range of human hearing is vast with an effective range spanning the reference level of |

What this means is that the higher limits of intensity are some 10,000,000,000,000 times as loud as the quietest sound we can hear! |

Secondly the logarithmic nature of this measurement means that if two sounds of the same intensity are added together there will not be a numerical doubling of the intensity measurement but only a 3 dB increase. This is in line with the perception of two such sounds where there is not a perceived doubling of the loudness. |

doubling of the intensity represents a 3 dB increase. | A doubling of the amplitude of a signal will result in a 6 dB increase. |