# Why does the milk frother on my coffee machine make so much noise?

I have a Sunbeam home espresso machine with a steam wand. The steam roars out straight from the end of the wand. When it's first placed in the cold milk it really screams! Once the milk has a bit of a whirlpool action going it's much quieter, so I guess that the noise is because of fast-moving steam hitting stationary cold milk. Something something fluid dynamics?

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My bet: So much noise: superheated steam at high velocity, lots of kinetic energy to dissipate as noise. Noise waning: Once the froth starts to form, froth/foam has really good noise muffling properties. –  SF. Dec 13 '12 at 10:17
@SF. I think the temperature must also play a part... not sure how much of a part though, perhaps only in its effect of the viscosity of the fluid? –  a different ben Oct 9 '13 at 3:28