When running some water to warm up before turning on the shower head, I can tell when the hot water has arrived by the distinct change in the sound as it splashes on the shower basin. The splash sounds soften when the water starts to run hot.
This is the same context where I noticed this. One of those weird things that would be really easy to google but I never did. Wasn't expected to get that random mystery solved today but I'll take it!
I've heard this as the shower warms up while spraying at the (plastic) shower curtain. However, I thought that it was because the plastic gets more flexible as things warm up.
