The name “brown noise” is a misnomer; brown refers to the colour of the graph of its amplitude vs. frequency, and is not a spectral colour at all. Brown noise is the reverse of white noise (random noise).
In white noise the amplitude of the sound at each frequency is constant. On the other hand in brown noise amplitude decreases as the frequency increases. So, it is smooth and sounds like a rumble or thunder.
While white noise is used for masking noise in office, brown noise is used for masking everyday sounds in home. E.g. if white noise is used in a room where there is a fan, it will sound like the fan is still running even when it is turned off. On the other hand, if brown noise is used in a room where there is a fan, it will sound like the fan is slowly getting turned off even when it is turned on.
Brown Noise is the one which has more energy in the lower octaves, than in the higher octaves. The use of Brown Noise is helpful when studying, reading or painting.
It gives the feeling of security, making one feel calmer. Brown Noise is supposedly very helpful in the treatment of tinnitus.