3 dB
 User Name Stay logged in? Password
 Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read Search

 Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

 Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
 24th May 2012, 03:28 PM #1 doctordata   diyAudio Member     Join Date: Apr 2010 Location: Brisbane 3 dB Like to start this thread to take away a lot of misassumptions about Voltages , Watts and the coupling of those lovely things to our human ears . I read this forum almost daily and I’m still surprised ( but understanding ) members asking questions , that would be all “answered” under our human ear “3dB” rule . I can explain this Logarithmic stuff , but there must be a teacher out here on this forum that will do much better than me ! so come one , please explain the 10log and 20log stuff ! Cheers , Rens __________________ If you measure, you know; if you guess, you don't
 25th May 2012, 11:54 AM #2 DF96   diyAudio Member   Join Date: May 2007 I'm not sure what you mean by the human ear "3dB rule". Decibels are a way of describing ratios. Because adding and subtracting are easier for humans to do than multiplying and dividing, we make use of the properties of logarithms (which are the inverse of exponentials). The maths is taught in a high school near you. The Bel is simply the base-10 log of a ratio. It was found to be inconveniently high a measure, so instead we use a tenth of a Bel - a decibel. To get a ratio in dB you take the log and multiply by 10. In electronics we are mainly interested in power ratios, so take the base-10 log of the power ratio and multiply by 10. The result is the power ratio expressed in dB. Power goes like voltage squared. To square a number you double its log, so to get a power ratio in dB from a voltage ratio (e.g. a voltage gain) you take the base-10 log of the voltage ratio and multiply by 20. This is only strictly correct if the same impedance is used, but there is a convention in electronics that when we are only interested in voltage gain we use dB anyway and ignore the impedance difference. So 6dB could mean a strict power ratio of 4, or it could mean a voltage ratio of 2. The context should make it clear which is meant. In the case of equal impedance the two ideas are the same. I don't know if this deals with your question, but it is an area where people seem to get confused and sometimes confidently assert wrong ideas which they have picked up.
 25th May 2012, 11:58 AM #3 jan.didden   diyAudio Member     Join Date: May 2002 Location: The great city of Turnhout, BE I had a column in one of the previous diyaudio newsletters explaining all this in somewhat more detail. In case you missed it, it should still be on teh forum. Not sure what the '3dB ear rule' is - never heard of it. -3dB of course simply being the point where the voltage level has decreased by 3dB to 0.707 times the starting value. Is that what you mean? jan didden __________________ Advertising is the rattling of a stick inside a swill bucket - George Orwell Get more Linear Audio for less! Check out my Autoranger and SilentSwitcher
 25th May 2012, 12:02 PM #4 hitsware diyAudio Member   Join Date: Mar 2002 I think the ' rule ' is that 3db is the minimum audible change in level. __________________ https://www.youtube.com/watch?v=sBic-7oJ_Cs
 25th May 2012, 01:47 PM #5 jan.didden   diyAudio Member     Join Date: May 2002 Location: The great city of Turnhout, BE That's not correct. There are documented tests that fractional dB differences are audible. What may be meant is that 3dB difference is perceived as doubling of sound level (not sure it actually is though). Probably need to look up on the Fletcher-Munson or similar graph. jan __________________ Advertising is the rattling of a stick inside a swill bucket - George Orwell Get more Linear Audio for less! Check out my Autoranger and SilentSwitcher
 25th May 2012, 02:01 PM #6 richie00boy   Did it Himself diyAudio Member     Join Date: Nov 2003 Location: Gloucestershire, England, UK 10dB is percieved as doubling of sound level. 3dB being the most commonly noticeable change is something I have heard said before. It's kind of a good step. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
 25th May 2012, 03:08 PM #7 DF96   diyAudio Member   Join Date: May 2007 3dB is half power, but I'm not sure what that has to do with ears.
 25th May 2012, 03:27 PM #8 StigErik   diyAudio Member     Join Date: Feb 2008 Phon curves are a better way to describe perceived sound level. 10 phon is a doubling, meaning from 10 to 20 there is a doubling, and from 70 to 80 ... and so on. As it happens, 10 phon is 10 db @ 1 kHz. But not necessarily 10 dB at other frequencies.... Equal-loudness contour - Wikipedia, the free encyclopedia __________________ dipoles dipoles dipoles dipoles dipoles dipoles dipoles dipoles and dipoles
hitsware
diyAudio Member

Join Date: Mar 2002
Quote:
 Originally Posted by janneman That's not correct. There are documented tests that fractional dB differences are audible. What may be meant is that 3dB difference is perceived as doubling of sound level (not sure it actually is though). Probably need to look up on the Fletcher-Munson or similar graph. jan
That's not correct
3db is 'measureable' as doubling of level,
but is the (commonly) least perceptable
change. Hence the logarithmic scale used.

 25th May 2012, 10:07 PM #10 StigErik   diyAudio Member     Join Date: Feb 2008 Wrong. Its easy to hear much smaller changes in level than 3 dB. __________________ dipoles dipoles dipoles dipoles dipoles dipoles dipoles dipoles and dipoles

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is Off Forum Rules
 Forum Jump User Control Panel Private Messages Subscriptions Who's Online Search Forums Forums Home Site     Site Announcements     Forum Problems Amplifiers     Solid State     Pass Labs     Tubes / Valves     Chip Amps     Class D     Power Supplies     Headphone Systems Source & Line     Analogue Source     Analog Line Level     Digital Source     Digital Line Level     PC Based Loudspeakers     Multi-Way     Full Range     Subwoofers     Planars & Exotics Live Sound     PA Systems     Instruments and Amps Design & Build     Parts     Equipment & Tools     Construction Tips     Software Tools General Interest     Car Audio     diyAudio.com Articles     Music     Everything Else Member Areas     Introductions     The Lounge     Clubs & Events     In Memoriam The Moving Image Commercial Sector     Swap Meet     Group Buys     The diyAudio Store     Vendor Forums         Vendor's Bazaar         Sonic Craft         Apex Jr         Audio Sector         Acoustic Fun         Chipamp         DIY HiFi Supply         Elekit         Elektor         Mains Cables R Us         Parts Connexion         Planet 10 hifi         Quanghao Audio Design         Siliconray Online Electronics Store         Tubelab     Manufacturers         AKSA         Audio Poutine         Musicaltech         Aussie Amplifiers         CSS         exaDevices         Feastrex         GedLee         Head 'n' HiFi - Walter         Heatsink USA         miniDSP         SITO Audio         Twin Audio         Twisted Pear         Wild Burro Audio

 Similar Threads Thread Thread Starter Forum Replies Last Post tiefbassuebertr Full Range 10 8th December 2015 01:41 PM rick57 Multi-Way 44 22nd December 2013 01:50 AM gmphadte Solid State 6 20th September 2011 11:10 AM 8cube Multi-Way 21 8th November 2007 07:45 AM moving_electron Multi-Way 27 9th March 2004 03:47 PM

 New To Site? Need Help?

All times are GMT. The time now is 07:14 AM.