White noise

Professional Definition

White noise is an acoustic signal of a random nature, whose energy spectrum has been limited to a specific range (band) of frequencies, e.g., using band-pass filters.

In engineering practice, we most often encounter noises with a bandwidth of one octave (octave noise) or one-third of an octave (third-octave noise). Limiting the spectrum allows for concentrating the energy of the signal in the range of interest, which is crucial when examining the absorption of materials or the frequency response of rooms in specific registers, without interference from other frequencies.

Acoustics in Simple Words

Imagine a radio that is static on all possible stations at once – that would be white noise (full spectrum). White noise occurs when you turn the knob and tune into only a narrow section of the scale, hearing noise of a specific color (e.g., only low rumbling or only high hissing).

Another analogy is a flashlight with colored lenses. White light is full noise. If you put a red lens on the flashlight, you only allow the "band" of red through. In acoustics, we do the same with sound by passing it through a "sieve" that stops everything outside the range we have chosen.

Summary

White noise is a precision tool in the hands of an acoustician. It allows for analyzing sound behavior "piece by piece," rather than grappling with all the noise at once, which is the foundation of accurate tuning of audio systems and interior adaptations.