Given that the measurement of sound in air is almost always concerned with human perception of sound, and that the minimum difference in sound pressure perceptible by the human ear is 1 dB, the reader may assume that no acoustical measurement would require a precision greater than 1 dB. However since measuring instruments are often used to establish whether a sound level is above or below some preset limit, the accuracy of the instrumentation must be higher than this. For example, in the case of aircraft noise certification 0.1 dB can decide whether an aircraft is permitted to operate from a large international airport: 0.1 dB can in this case account for a very significant revenue lost or gained. If field measurements are required with an uncertainty of better than 0.1 dB then primary measurement standards must be maintained with an uncertainty of about 0.05 dB.

Measurement Standards >>