I have been leaving my cover off because there tends to be a 25 degree diference with it off. Yes, it is much louder. Last week my friend came over and told me I was crazy for leaving my pc cover off because the radiation emitted is extremely high and could cause cancer. The next thing he did to prove his point was he used a radiation meter to demonstrate his point. He was right like usual. The amount of radiation coming from my open computer, microwave, and cell phone were so high that it went beyond the limits of the meter. My friend owns a research company that is developing anti-radiation technology for cell phones so he was speaking as a true expert in the field.