From victora@mda.vnd.TEK.COM Fri Oct 11 22:46:36 1996 Return-Path: Received: from inet1.tek.com (inet1.tek.com [134.62.48.21]) by ursula.ee.pdx.edu (8.7.5/CATastrophe-2/10/96-P) with SMTP id WAA22483; Fri, 11 Oct 1996 22:46:35 -0700 (PDT) for Received: by inet1.tek.com id ; Fri, 11 Oct 1996 22:46:17 -0700 Received: from tektronix.tek.com(134.62.48.24) by inet1 via smap (V1.3) id sma043447; Fri Oct 11 22:38:10 1996 Received: from tekgen.bv.tek.com (tekgen.bv.tek.com [128.181.44.33]) by tektronix.tek.com (8.7.5/8.7.3) with SMTP id WAA22735 for ; Fri, 11 Oct 1996 22:40:14 -0700 (PDT) Received: from Ariel 3 (ariel3.vnd.tek.com) by tekgen.bv.tek.com (4.1/8.0) id AA19324; Fri, 11 Oct 96 22:38:02 PDT Message-Id: <9610120538.AA19324@tekgen.bv.tek.com> Date: Fri, 11 Oct 96 22:38:09 -0700 From: "Victor J. Albert" Organization: Tektronix X-Mailer: Mozilla 1.1 (Windows; U; 16bit) Mime-Version: 1.0 To: thunder5@ee.pdx.edu Subject: weighted scales Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Status: RO X-Status: Decibels anyone? caraudio@ix.netcom.com(Car Audio And Electronics magazine ) wrote: >In <53kv6s$39o@lectura.CS.Arizona.EDU> bmtong@CS.Arizona.EDU (Bo-Ming >Tong) writes: >>In article >, >>George Panagiotopoulos <079555@bud.cc.swin.edu.au> wrote: >>>I dont understand how ppl can have more than 120 db in the car. >>>Isnt that the loudness of a jet engine at close range?? >> >>In car audio we talk about C-weighted decibels. When we talk about >>hearing damage it's A-weighted decibels. C-weighted is measured >>evenly across 20-20kHz. A-weighted is concentrated in the midranges >>and the low treble (e.g. 500-10kHz). Even huge amounts of bass is >>not very damaging to the ears. Depending on how you tune your system, >>a 120dBC may sound only 100dBA and the maximum recommended exposure >>time to 100dBA is 0.5 hours. A jet engine sounds 140dBA in close >range. > >Actually, most car applications (sound-offs, dB contest, etc) use an >*un-weighted* scale for measuring SPL. >C-weighting is *not* evenly across 20-20kHz, it begins rolling off at >about 100Hz and is -6dB at 20Hz. On the high side, C-weighting starts >rolling off at 2.5kHz and is -11 dB at 20kHz. >A-weighting is about the same on high end but rolls sharply off from >1kHz down and is about -25 dB at 55Hz (and off the -side of the scale >at 20Hz) >I am not sure where people get the idea car audio uses C-weighting, >could it be that cheesy meter RadioShack sells that only has A & C >scale selectors? ;>) > >Terry Miller >Contributing editor, CA&E >-- >============================================== >Car Audio And Electronics magazine >21700 Oxnard Street Suite 1600 >Woodland Hills, CA 91367 >(818) 593-3900 >Editorial email: CarAudio@ix.netcom.com >(Please include Name/Address/Phone) >---------------------------------------------- >http://www.webmill.com/avcom/caraudio >---------------------------------------------- >Direct subscription orders/inquires/questions >to: 1-800-289-0611 >Subscriptions: $19.95 per year >==============================================