| hey Tweak, Could u
either explain to me in brief or point me to
a good article that explains to me all the
measurements like Htz, dcb, Khz etc. Cause i
have no idea what you're talking about when
u talk about sound measurements in ur
articles. Thanks Tweak, much appreciated.
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| Thanks for pointing that out. The audible
sound spectrum for humans begins at 20 hz
(hertz, the guy wo named the term) (VERY low
Bass) to 20kHz (kilohertz) very high, upper
threshold of what we hear) A typical "thud" from
a subwoofer is at about 50-70hz The Vocals are
usually around 1-2kHz where our ears are most
sensitive. Hi hats may go up to 18kHz or so and
there are artifacts that may go beyond our range
of hearing. db stands for decibels which is a
measurement of loudness. We typically hear a
noticeable difference in volume every 3 db. If
you look at a graphic equalizer, you will se
markings for hertz and db. A well known
mastering technique is to boost 4kHz by 2-3db.
Makes everything sound "clear". |
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| So im not sure i understand the relationship
between Hertz and Decibals. Htz is related to pitch?
and decibels loudness? |
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| A decibel in and of itself is not actually a measure
of the loudness of a sound - it is actually a number
representing the relative loudness of two different
sounds. (Even in that, it is actually the relative
*amplitude* of two different signals - in terms of
audio, though, this directly related to the loudness of
a sound). If you want to get a little technical, a
decibel is equal to 10 * log (X/Y) [and that's a base-10
log). X and Y represent the signal levels of two
different signals. Let's say you have signal X twice as
loud as signal Y. X/Y is then going to give us a result
of 2. 10*log(2) gives us roughly 3dB. Going the other
way, if Y is twice as loud as X, you get 10*log(0.5),
which is roughly -3dB. Note that this is a purely
numerical analysis. Just because you have a 3dB
difference between two signals does *not* necessarily
mean that it will sound twice as loud - that is a vey
subjective measurement. Anyways, since a decibel is not
actually a measure of the loudness of a single signal,
you have to give a reference point. A commonly used
scale for signals is to measure them in dBv, which
provides the amplitude of your actual signal referenced
to 1 Volt. Thus if your signal is 3dBv, from the
previous math we know the signal is then double the
reference, thus 2 Volts. If you do some searches on your
favorite engine, you'll turn up more info on both
frequency (Hz) and the decibel system, but hopefully
this is a useful primer for you. |
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| Thanks Colin, let me ask you a follow-up then, since you
seem quite articulate on the subject. The markings on a
mixer that go from infinity to +10db, what is their
reference point? How would you use that to calibrate a
mixer? |
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| No problem, Rich. The only reason I'm articulate is due to
my schooling - and as an electrical engineer, most of what I
know I've not really applied yet to home recording and the like.
I've only just started to get into it now (hence my recent
questions to you regarding mixers and audio interfaces). That
was actually on my list of "Questions to be answered", so when I
do come across/research the answer, I'll let you know. Truth is
I don't know, right now, what the reference is on the mixer.
What I think right now, though, would be that it is referencing
the signal input (whatever you've plugged into the mixer input
channel, as well as the input gain trip) to the signal output.
That is, you plug your microphone in and set the gain trim. By
adjusting the mixer slider, it is telling you the ratio of what
it will output, from what you've input. Thus 3dB should be a
quantitative doubling of the signal. |
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| The rule of thumb is Set the fader at 0db and bring up the trim
so the meter pegs at 0db. My question is that if an output is rated
at +4, then unity would be +4 and the output might be hotter than
0db. I think there is a technical step missing in my thinking here.
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| Hey Tweak... I did do some checking, and in fact the sliders are
comparing output to input, on a mixer. As for the -10/+4 levels, that's
unfortunately over my head right now (still a recording newbie :).
Again, if I find out, I'll let you know! |
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