Subject: Re: Safety Switch From: Tom Maglione <maglione(at)MEDIA.MIT.EDU> Date: Thu, 3 Mar 2005 18:17:50 -0500To Aaron and List, What you need is called a Limiter. This is a special form of a compressor which remains linear in the majority of its (bipolar) range; however, when the signal amplitude reaches higher thresholds, the Limiter goes into extreme compression like 10:1 or 20:1. This means that signals over the threshold which increase by a factor of 10 are translated to the output as an increase of only 1 or 1/2, corresponding to 10:1 and 20:1 limiting ratios. Really hard limiters have an infinite limiting ratio. I just double checked and you can find out much more by searching on the web, including some low-cost stereo analog limiters used for some FM radio and other audio systems. Limiters are also sometimes used in the recording studio. I hope this helps, happy limiting! Tom Maglione -----Original Message----- From: AUDITORY Research in Auditory Perception [mailto:AUDITORY(at)LISTS.MCGILL.CA] On Behalf Of Aaron L Hastings Sent: Thursday, March 03, 2005 11:42 AM To: AUDITORY(at)LISTS.MCGILL.CA Subject: Safety Switch Hello All, I am wondering whether or not people include some type of safety switch in their playback systems and if so what do they use? We have a playback system which consists of a LynxONE audio card, a TDT attenuator, and Etymotic earphones. We play sounds that are typically as high as 70 dB SPL. It is physically possible for our system to play sounds greater than 90 dB and we would like to include a safegaurd so that sounds sent to the attenuator, will not be played at levels greater than XX dB. Does anyone have any advice / experience with this issue. Issues that I see at present: Anyting that we insert into the loop will increase noise A kill switch might also introduce a loud (damaging) noise depending on how it is designed A compressor would introduce non-linearities and it may not be noticed when it is actually affecting the signal and when not Thanks for any input Aaron