“Wave theory? We don’t need no stinking wave theory!”
Don’t worry, we are not going to get too technical right off the bat. Waves are simply a means of transferring energy from one place to another. Sound energy, once initiated, travels in all directions meaning three dimensionally.
Now the wave surface, which indicates where a pressure change has gotten to at a particular time, will, in anechoic or free-field conditions (that is without any acoustics involved), be spherical (see Fig. 1.1).
FIGURE 1.1 Sound waves are spherical.
Imagine two people sitting on the top of two poles a mile up in the sky, as ...