Unlocking the Mystery: Why is it Called White Noise?

Have you ever wondered why the soothing backdrop of sound often used to mask distractions or aid sleep is called white noise? The term can be slightly misleading without some background information, so let's demystify this auditory phenomenon.

Similar to white light, which contains all wavelengths of the visible spectrum at equal intensity, white noise combines sounds of all different frequencies together. The key to understanding white noise lies in our knowledge of color and light. White light is a blend of all colors of the light spectrum, and similarly, white noise is a constant background sound that brings together a wide range of sound frequencies to which humans are sensitive, at a consistent intensity.

The analogy continues as well when we consider other 'colors' of noise, such as pink noiseThe analogy continues as well when we consider other 'colors' of noise, such as pink noise, blue noise, or our key interest—brown noise. Brown noise, for instance, emphasizes lower frequencies, giving it a deeper sound than white noise. This is somewhat akin to how brown light would have a lower frequency or longer wavelength than white light.

Audio engineers and scientists have adopted this nomenclature from optics because it provides an intuitive way to categorize the spectral density of different types of noise. White noise is a random signal having equal intensity at different frequencies, giving it a flat power spectral density—much like a flat, uniformly white visual field.

Emitting a sound frequency spectrum that a human ear perceives as even, white noise is incredibly effective in masking other noises that might disturb sleep or concentration. It's widely used in various environments, from offices to nurseries, and in products like sleep machines and hearing tests.

Understanding the reasoning behind the terminology offers not just an answer to a common query but also a glimpse into the fascinating intersection where auditory science and optics converge, enriching our knowledge of both the world of sound and light.