This has been called the microwave hearing effect. These sounds, e.g., buzzes, clicks, tones, etc., vary as a function of the modulation. The incident average power density at the head needed to induce the effect is quite low, in microwatts per square centimeter. The transmitting antenna can be many feet away. The salient characteristics of the primary cellular telephone systems in use today are shown in Table 1.
Microwave hearing is a robust effect.
In the context of this paper, the most important point that came out of the microwave hearing research that I did in the 1960s is the finding that my human subjects were reporting headaches. I found that I also was getting headaches when I was in the microwave field, and I do not get headaches. At that time I could not do experimentation on the headache phenomena. Little was known about headaches and there were no suitable animal models. I was sufficiently concerned about the headache phenomena that I stopped doing microwave hearing research with humans.