Health effect of electromagnetic and acoustic waves on brain function
The question is extremely broad.
Electro Magnetic signals
Even this subquestion is very broad. Electro magnetic signals encompass a lot of phenomenon, some of them represent health risks, some of them don't. It is funny to wish to limit the health effect to brain in your question as to reduce the scope of the question given how variable are difference electro magnetic waves can have on matter overall.
Ionizing radiations
Ionizing radiations will obviously represent health risks. But even non-ionizing radiation can pose health risk.
Non Ionizing radiations
Microwave
You are probably aware that you should not put your cat in a microwave!
Retina damage
Intense light can cause photochemical damage to the retina. See here.
Intense infra-red
High intensity infra-red affect cells (see König et al. 1997)
Cell Phone
Overall, there is likely no impact of cell phone radiation on our health. If there were any, it would be minimal.
See this Veritasium video: Do Cell Phones Cause Brain Tumors?. You should also have a look at the skeptics.SE post Do mobile phones have anything to do with brain cancer?.
Cell phone towers
Likely has no health effect. See Do cellphone towers cause health issues?
Other electro magnetic signals
For more information, you should have a look at WHO &gt; Electromagnetic fields and public health: radars and human health
Sound wave
Some sound can cause hearing loss. The frequency of this sound, the intensity and duration of exposure to the sound are all important in determining the degree of the hearing loss. Have a look at this article from the American Hearing Society for more information.