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Noise > Terms > Basic Units

This trace actually represents about 2½ minutes of data, but, for the purposes of this section, it could represent 2½ hours or 2½ seconds; the points made would still be equally valid.

You can see that within a very short period of time the level varies by some 15 dBA. For single, short, events it may be acceptable to represent them by the maximum reading on the meter (Lmax); for example, gunshots are often represented by the LAmax "Fast", also some occupational noise limits use Lmax "Peak" and PPG24 represents nighttime events in terms of LAmax "Slow".

Time trace of noise

However, for longer periods (say greater than a few seconds) we need to use something more complex; simply using the maximum level of even reporting the range of values isn't descriptive enough; we want to represent a complete noise environment and some form of global analysis of the noise is required.  This is why statistical analysis and energy averaging are used.

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