eli5: Why does the pitch of the “mixing noise” decrease over time as a stir a hot drink?

Question

I’ve noticed this with lots of hot liquids. Once I start stirring, the clanking noise of whatever I’m stirring with just gets lower and lower in pitch, possibly as the beverage cools off. What is that? Thanks

In: Physics

Answer 1

As the powder dissolves, it changes the density of the liquid, which affects the pitch as the spoon hits the glass or cup.