Why there is a small bump at the bottom of the thermos flask, the other people say to thermal insulation.
As for hum, this is a kind of "resonance" phenomenon on the acoustic. Two voices objects with the same frequency, if each other not far away, then make a voice, another also are likely to follow, this phenomenon is called "resonance". If the container is damaged, make some kind of destruction of the integrity of the original air column, then, resonant voice will also change. Therefore, people often by listening to hum to check whether the thermos is damaged, whether the heat preservation effect is good
At the bottom of the thermos is a small bump, is a production, in order to extract left in the wake of the air in the silver coating
At the bottom of the thermos is a small bump, is a production, in order to extract left in the wake of the air in the silver coating
