# Could someone double check if my understanding about the area could one watt be spread over?

This tutorial illustrates how large of an area could one watt be spread over and still be intense enough for the human ear to hear it.

It would be a trillion square meter.

according to which, if there exsists an acoustics lab in a circle shaped building which has about a radius of 560km, a source generates sound wave at one watt, any human inside the circle would could hear that sound. is my understanding right?

Welcome to StackExchange! The area that is being referred to here is the area over which the power is "passing through". Using the Germany example, the simplest way to explain what I mean is that if the power is emitted uniformly in all directions, which is at least somewhat close to how speakers usually operate due to diffraction and their small size. The "three times the land area of Germany" would be the surface area of a sphere that is centered on the source of the power, and the distance you could stand from the source and just be able to hear it would be the radius of that sphere, which would be $$\sqrt{\frac{10^{12} \text{m}^2}{4\pi}} \approx 282 \text{ km}$$. While this is mindblowing, I think that it somewhat obscures the more relevant quantity, which is what is the minimum power that an ear can register. If you know the surface area of someone's tympanum, you can multiply that with the minimum intensity and obtain the minimum power that a person's ear can register.