Objects that vibrate in a randomised fashion produce sounds that we describe as noisy. This is because the sounds produced contain a random assortment of frequencies.
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A term that describes sounds that have a diffuse spread of spectral energy. It is often contrasted with pitched sounds. Noisy sounds may be hard to define in terms of pitch because their spectral energy covers a wide range of frequencies and is not concentrated, but diffuse.
This image shows the complete spread of sound energy across the spectrum.
