At a point 13.0 m from a source of spherical sound waves, you measure a sound intensity of 790 mW/m2 . How far do you need to walk, directly away from the source, until the intensity is 220 mW/m2

11.6 m

Explanation:

The intensity of sound is inversely proportional to the square of the distance from the source. If we denote intensity with I and distance with d,

This can be resolved for any two situations as

Therefore, you need to walk 24.6 - 13 m = 11.6 m away from the source.

answer; equivalent to a one(1) horsepower motor;

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia