A quiet zone is the blank, marginal space at the beginning and ending of each barcode that enables a scanner to accurately read the information. A quiet zone, in most cases, does not need to be very large. In fact, oftentimes it may not even be distinguishable to an individual consumer. In the quiet zone, no signal is produced by the scanning device. Thus, the area is named a “quiet zone” because of this lack of production.
A quiet zone is needed because any information near the barcode could confuse a scanning device, which is making complex measurements in the time it takes a person to blink an eye. No quiet zones may cause the scanner to read the product inaccurately or not read the barcode at all. Those who design packaging must keep this in mind. Without the quiet space, scanning using the method used today would likely not be possible.
In most cases, the quiet zone is no bigger than 0.1 inches (2.5 millimeters) or 10 times the width of the “X” dimension, whichever is greater. The “X” dimension is the narrowest bar found within the barcode. Given these miniscule sizes, most packing has no trouble maintaining this space as a quiet zone.
The quiet zone gives the scanner no feedback at all. Thus, the scanning mechanism is “quiet” when it comes to this area. This is how the zone gets its name. In most cases, a quiet zone does not even have a background color, if one exists on the packaging at all. However, some background colors do not interfere with this area and can be used, if the contrast between the black bars and background color is clearly evident.
However, just because the scanner provides no feedback during this time does not mean that it is idle. Instead, the quiet zone provides the opportunity the scanner needs to adjust itself. Scanning a bar code requires a series of very small measurements between the black bars and white spaces. Often, this is done at a very high rate of speed, as demonstrated by a supermarket checkout scanner. Thus, the quiet zone gives the scanner enough time to calibrate itself for the job.