Broadband energy with approximately equal energy across all frequencies is referred to as what?

Broadband energy that has approximately equal energy across all frequencies is known as white noise. This term is derived from optics, where white light contains all wavelengths of visible light combined together. In the context of sound, white noise encompasses a broad range of frequencies and tends to sound like a constant hissing or static, similar to the sound of a television set tuned to an unused channel.

White noise is often used in various applications including sound masking, tinnitus relief, and sleep aids, because the even distribution of sound frequencies can help to mask other auditory stimuli.

Pink noise, on the other hand, has more energy at lower frequencies compared to higher frequencies, and brown noise emphasizes even lower frequencies. Blue noise, conversely, has more energy at higher frequencies. Thus, these colors of noise represent various distributions of sound energy across the frequency spectrum, but they do not have the flat frequency response characteristic of white noise. This is why white noise is specifically identified as having equal energy across all frequencies.