Pitch change when flowing bath water becomes hot

Question

If I run the bath and close my eyes, I can tell when the water exiting the faucet goes from cold to hot. The loud rushing sound deepens by half an octave. What causes the tone to drop?

In: 67

Answer 1

Hot water has a lower viscocity – it’s less ‘thick’. This gives it different physical properties, such as producing more bubbles, hence the difference in sound.