Posted By NickW Just wondering about the information provided by suppliers of ear plugs and defenders etc for protection over the range of frequency octaves. rarely is there any protection given for frequencies of 31 Hz or below or 16 KHz and above. So what if you have high levels in these regions even after accounting for 'A' weighting? This has bugged me for some time. I asked an acoustic specialist and he pulled his face, casting scorn on the suppliers. cheers

Posted By John Murgatroyd Just because you can't hear the sound doesn't mean it is safe to be exposed to high levels of it. And if you have high levels of infrasonic sound the same applies, with the exception that high levels below a few hertz can damage internal organs. http://www.hse.gov.uk/lau/lacs/59-1.htm