A random signal with equal intensity at different frequencies, often appearing as static.White noise is a type of random signal where every frequency within a given range has the same average intensity. When you hear it, it sounds like a steady hiss or static, similar to the sound of an untuned radio. The name comes from an analogy to white light, which contains all visible colors (frequencies) in equal amounts.
The term 'white noise' was popularized in the mid-20th century, drawing on the analogy to white light, though the concept of random signals with flat spectra was studied earlier in physics and engineering.
White noise is generated by a random process where each value is independent of the previous ones. Mathematically, its power spectral density is flat, meaning that if you measure the energy at each frequency, it is constant. This flatness is what distinguishes white noise from other types, like pink noise, which has more energy at lower frequencies.
White noise is used in audio engineering to mask unwanted sounds, in electronic testing to measure system responses, and in random number generation for simulations.
True white noise would require infinite energy, so real-world white noise is always limited to a finite frequency range.
