Hi Alan, Your confusion over 3 and 6dB is understandable.
Sometimes "sound intensity" and "sound pressure" are improperly used interchangeably. Intensity is proportional to the square of pressure. If the intensity is doubled, one would say that there is a 3dB increase in sound intensity; 10*log(2I/I). However, if the pressure is doubled there is a 6dB increase in sound pressure; 10*log(2p/p)^2. Also, when doubling (or halving) the DISTANCE between source and receiver, one would subtract (or add) 6dB when dealing with a point source. However, for a cylindrical source there is a 3dB difference when doubling/halving distances. Good luck, Paul Hare From: [email protected] [mailto:[email protected]]On Behalf Of Hudson, Alan Sent: Thursday, January 23, 2003 4:15 AM To: EMC-pstc (E-mail) Subject: RE: Acoustic noise calculations for multiple shelves John Woodgate wrote: > The noises are uncorrelated (largely), so you add 3 dB, not 6. Now I'm confused! I always thought it was noise *level* (similar to voltage level) not noise *power*, and hence it was 20*log(ratio) not 10*log(ratio). So I've been using 6dB for doubling noise, not 3dB. I'll need to consult some basic texts, methinks. Regards, Alan -- Remove ".paper-bag" from address if replying by email. ******************************************************************** This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. ******************************************************************** This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
