Pink noise

Professional Definition

Pink noise is a broadband, stationary random signal whose power spectral density is inversely proportional to frequency (1/f characteristic).

This means that the energy level decreases by 3 dB for each octave increase in frequency. Thus, each octave (e.g., the range 100-200 Hz and the range 1000-2000 Hz) contains the same amount of energy. This is a key difference compared to white noise (where energy is constant for a fixed bandwidth in Hz), which makes pink noise ideal for research using third-octave and octave analyzers that mimic the way the human ear perceives sound.

Acoustics in Simple Words

To understand the difference, think of rain. White noise is the sharp, hissing sound of heavy rain hitting concrete – it is exhausting and seems very high. Pink noise is the sound of a powerful waterfall or wind rustling through the leaves of trees. It is deeper, more “bass-like,” and more pleasant.

This can be compared to stacking books on a shelf. In white noise, we cram the same number of books on each shelf (regardless of its size), causing the upper shelves to be overcrowded. In pink noise, we ensure that the “weight” of knowledge is evenly distributed – the lower, wider shelves carry as much energy as the higher, narrower ones. This way, we, as listeners, perceive this sound as flat and even.

Summary

Pink noise is an acoustic pattern of energy balance. Due to its 1/f characteristic, it is best suited to the logarithmic nature of human hearing, making it indispensable when calibrating loudspeakers and studying the acoustics of rooms.