Dr. GERBER: It's approximately four times the natural radiation dose that we all receive annually in the Unites States, as a result from background radiation due to radon and other materials.
The essential ingredients of good open-plan office acoustics are evenly distributed sound-absorptive materials and a minimum level of background noise throughout.
The survey also includes information about the home background of pupils - with signs that homework had increased in all age groups, less reading materials were available in homes and 9 and 13 year olds were less likely to be watching six hours of television a day and more likely to be using a computer.