They all do. You are mistaken. A 3db change in volume is *easily* detectable by anyone. A figure of 1db would be more relevant as a rough guide to a "not always immediately detectable when drunk".
Kevin Aylward snipped-for-privacy@anasoft.co.uk
Especially if that change happens at "20kHz" :)
Cheers Robin
Yeeeeees! That's a 3dB drop. :)
Actually neither one of us should be saying "drop." If I had specified power drop and you had specified voltage drop it would have been clear that we are both right.
Try to make it work without transistors sometime. In the days when we all used vacuum tubes/valves and transformers, getting the maximum amount of power out of one transformer and into the next transformer was important, thus the matching, and thus the 3dB power drop.
When semiconductors and especially op amps hit, it became feasible to have a low output impedance feeding a high input impedance (and occasionally the reverse, with trans impedance amps). When that hit, not only wasn't there a power drop, the power transfer was annoyingly close to zero, and everyone started thinking in terms of voltage rather than power. Once you start measuring voltage in a Low Z to high Z line, the drop when you add a load approaches the convenient number zero. Filters, however, still needed a -(something)dB point, and the old -3dB stuck.
A common occurrence nowdays is for newly minted recording engineers to think that adding together two close to identical phased signals (think two microphones right next to each other in front of the bass guitar amp) add up the same way as adding together two random phased signals (think two microphones close micing two violins playing in unison). Loads of fun watching them trying to figure out why they don't add up the same way...
-- Guy Macon
For sine waves and instant changes, yes. Try it with an orchestra with one minute of silence between the two playings. I believe that you will find that with changes of less than 3dB SPL, you will be wrong about which one was louder about half the time.
Hi, Joerg.
slide rule calculators. No abacus though.
My last slide rule is in the drawer for sentimental reasons, a gift from my father when I was 10 and such devices were used every day by many engineers. I used it for a few years before electronic calculators became ubiquitous.
pestered me about it at a client's lab and one of the
fail when the battery died. I told him my slide rule
The "calculated by hand" I remember is my father at the kitchen table with a scratch pad and a thin-paged book full of 5 digit logarithms. That was where, with some amazement, I learned about interpolation. The long slide rule was just for approximate work, he explained. I just wish I knew what he was doing that required enough accuracy to justify all that effort.
and buttons. That almost made me sick.
That reminds me of a gift from somebody faintly aware of my fondness for pendulum clocks. Its plastic pendulum, whose motion was derived from the electronic innards, went back and forth linearly, not sinusoidally. What an abomination! I still shudder thinking of it.
-- --Larry Brasfield email: donotspam_larry_brasfield@hotmail.com Above views may belong only to me.
A Larry said, the -3.01 db value falls out of the maths. For a single RC combination, phase moves between 0 and 90 degrees : at -3.01 db the phase is half way - 45 degrees.
Also, -3db frequency in radians per sec = 1/( C R ) { farads, ohms )
When you sketch a Bode diagram, for example when checking the stability of a feedback loop, you just draw straight lines to the -3db frequency asymptote intersection points Larry mentioned, and you are close enough in engineering terms.
So we got 70+ good years out of the -3db concept and that value still pops out at me when I am writing the transfer function for some network on paper. However, programs like Spice present a mass of result data and those special frequencies are less special to us.
Engineering is all about getting a feel for the thing you work with, and the -3db frequency is like this : its an *interesting* frequency for an engineer. You generally know your circuit resistance- an estimate of your capacitance and you calculate the "hot frequency" at -3db. At 3db changes are happening : rolloff slopes are starting or finishing.
This was especially so in the valve/tube days where you would increase gain by increasing load resistance, to the point where the -3db frequency was as low as you could allow.
3 db was a nice fit with the audio world too, because tests on humans showed that a 3 db change was just discernable to the ordinary listener. Of course, many careful listeners can do better than that.Roger Lascelles
Hah ! Quite likely. Aren't we humans fantastic !
The ear quite happily deals with immediate dynamic range issues by offering TTS ( temporary threshold shift ). It's like somone on high figured we might need it and gave it to us !
Graham
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Indeed. I don't think TTS accounts for 3dB SPL being the minimum detectable change under the test coditions above, though. Below
65 or 70 dBA SPL there is no TTS. SeeOne real-world application of the 3dB rule is buying a new stereo. All other things being equal, will you be able top hear the difference between a 200W amplifier and a 400W amplifier? Probably not.
Have you seen those horrible radios that are styled -- in plastic! -- to look like vintage tube radios with their beautiful wooden cabinets? They even come with 100% fake plastic "tubes" even though internally they're regular transistor radios. :-(
Sure you can, if you switch between them in an A/B test.
Sure, the ear brain is not very good at absolute measurements. Remembering one level then another 1/2 hour later might well be a bit difficult, but that is irrelevant to the issue as to whether or not 3db is the minimum detectable as an accurate representaion of the ability of hearing.
Kevin Aylward snipped-for-privacy@anasoft.co.uk
John Larkin posted a photo of one. IIRC, he said it cost all of $10.
Just for fun I tracked down the source in China. ;-)
Best regards, Spehro Pefhany
-- "it\'s the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reminds me of the story of the forest ranger that was patrolling the campgrounds and came upon this pair of snakes that was making whoopee on the rustic picnic table.
When confronted, they said that anybody should be able to multiply on log tables.
Jim
[DerF]
or possibly a power thereof, at frequencies above
How many frequency responses have you seen that were flat up to the 3 dB cutoff frequency? Does this mean you are among the crowd that considers +/- 3dB to be flat?
Yes, I'm afraid so.
[Derf]-- --Larry Brasfield email: donotspam_larry_brasfield@hotmail.com Above views may belong only to me.
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TTS (
and
Tube or SS?
- YD.
-- Remove HAT if replying by mail.
Hello Spehro,
And they haven't even bothered to mimic a tube sound which would have cost next to nothing.
Regards, Joerg
Hey retard- no one gives a damn about calculating anything by hand or any other of your pseudo-mathematical bs ( remember the math it took you
50 years to learn by rote?). The practical significance is, in most cases, that the gain drops as F3db/F, or possibly a power thereof, at frequencies above 3dB, and it's flat up to 3dB. Get it? Quite sad you will go to your grave in such a confused and worthless state- too bad for you there is no such thing as a career in sitting on a park bench blithering to yourself.
Correction: you used it for *many* years before the calculator came on the scene, you old fart.
Noah had a similar problem when he told the animals on the ark to "go forth and multipy." A pair of snakes stayed behind. They couldn't follow the order because they were adders.
In the olden days, 3dB was comparable to the IL . So yeah.
Yeah, 1dB either way doesn't amount to a hill of beans to anyone who uses the Log scale of measurement. +/-3dB is an industry standard error band on signal level for RF.
Well- of course you pretend...
That's the whole point of the original joke.
He made a table out of logs, because even _adders_ can multiply on a log table.
-- Sheesh! Rich ------ "That reminds me of a friend of mine who went north to work on the Alaskan pipeline. Before he went up there, he was just a skinny little runt. When he got back, he was a husky fucker."
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