This app listens when you pour hot water into a cup and analyzes the noise to estimate the water temperature.
The accuracy reaches ±4 degrees when tested under optimal conditions but is generally lower. The accuracy is higher at high temperatures and the app can be useful for e.g. brewing different teas at their correct temperatures but it is not intended to be used for temperatures less than 50°C (122°F).
How does it work?
The properties of water and air vary with temperature. This results in changes in how noise is generated from pouring water. Most people can actually tell the difference between hot and cold water by listening to pouring noise (1). This app uses a pre-trained machine learning model to analyze pouring noises to get an estimate of the temperature. The longer time you pour the more noise it receives and it can give better estimates.
(1): doi:10.1111/joss.12052