When is loud really "loud"? Sensitivity to noise is a subjective matter and is, therefore, not measurable. One man's annoyance must not apply to another man in equal measure. However, the sound intensity of a noise can easily be specified with an objective physical value: the sound pressure level (SPL). Busy roads can cause for example 70 to 80 decibel, industrial plants even more than 100 decibel. Such background noises call for urgent acoustic insulation in adjacent living and working locations.
For a better understanding of the phenomenon “noise”, we cite the following examples and comparisons. The table shows some typical sounds with the corresponding levels and the sensitivity caused.