Hi Tracy, a sound level meter (SLM) is the most accurate way to determine noise levels, a noise booth is sealed and rated for the amount of noise attenuation. If you have an room where you cannot ensure background noise levels are sufficiently low all the time, taking a quick noise level reading using an SLM before, during and after the test supports the results. I don't know, but I'm sure there is a British Standard that has a recommended maximum background level to be able to carry out the test. In order to measure this accurately I would suggest a sound level meter......rather than an phone ;)................... *Damien Eaves BSc(Hons), Dip.Occ.Hyg., CMFOH, AMIOA, MWMSoc* Chartered Occupational Hygienist 07932 317867 01246 555856 Validate Consulting LtdOSHCR Registered Consultant www.validateconsulting.com <http://www.validateconsulting.com> This message is intended for the recipient to whom it is addressed, the message and any of its attachments are confidential and may be privileged or otherwise protected from disclosure. If you are not the intended recipient, please contact the sender and delete this message and any attachment. If you are not the intended recipient you must not copy this message or attachment or disclose the contents to any other person. Validate Consulting Ltd has taken every reasonable precaution to ensure that this email and any attachments have been swept for viruses. Validate Consulting Ltd does not accept any liability for damage sustained as a result of software viruses. Validate Consulting Ltd advises that any email messages and attachments are swept for viruses before opening. ******************************** Please remove this footer before replying. OCC-HEALTH ARCHIVES: http://www.jiscmail.ac.uk/lists/occ-health.html CONFERENCES AND STUDY DAYS: http://www.jiscmail.ac.uk/cgi-bin/filearea.cgi?LMGT1=OCC-HEALTH