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So a while ago I promised everyone a quick and easy guide to
making computer audio recordings sound good enough for indie movie use.
Now that we’re entering the translation phase of L&P I suppose now
would be as good a time as ever to release it. There are only two important aspects to good recording;
picking up the signal, and not picking up any other noise. Everything
else revolves around that Signal to Noise Ratio (SNR). Once the audio is successfully
digitized many things can be done to modify it, however, for the sake of a
consistent product from a distributed talent base it is best not to attempt any
digital audio editing and let one person who is acting as audio editor for the
whole project do all of the work. Thus, this guide is only about getting
a high quality (that is, a good SNR) signal into the computer. The most obvious sources of noise (where noise is anything
audible that isn’t the desired signal) are obvious: Anything that moves Centralized-air comfort systems People elsewhere Communications (telephone, IM, cell phone, neighbor’s
dog, etc) Computers (especially the one doing the recording) For the most part, simply disabling/stopping/removing/otherwise-silencing
the noise maker is enough, but the case of the computer being used as the
recording medium is a little trickier. Lucky for us there is radio shack,
where $7 is enough to buy a 1/8” miniphono extension cable. To
eliminate the noise from a computer (quiet as it may be, the mic will still
pick it up, and it will detract from the SNR) simply extend the microphone cord
such that the recording can be made in a partitioned off area (optimally another
room). Additionally, laptops often run with their fans turned off or on
low speed with occasional bursts of high speed for cooling, if you have a
laptop and decent timing (wait for high speed to end then hit record) the issue
can be solved without any extensions at all. Other harmful things to the SNR are less obvious, but for
the most part they’re just as easy to fix: Gain too low Gain to high TPS problems Echoes RFI Gain is the % of possible volume that the computer regards
various input signals as. If the gain is too low the recording will sound
quiet (ie low signal) and require normalization, which will amplify the
background noise as well. If the gain is too high the microphone will
supply a signal larger than the computer regards as 100% volume and clipping
will occur (think plateau instead of rolling hills). A good example of
this throughout the beginning of jbocradi episode 1. The key to correctly
setting the gain is rehearsal (which is a good thing to be doing anyway), open
Audacity (yay open source) and click the recording level meter, this will give
you real time feedback about the sound levels coming in from the mic.
Now, rehearse. The loudest part of your dialogue should bring the meter
to between the -6 and 0 marks. If it exceeds 0 the gain is too high, and
audacity will alert you to this fact by keeping the far right bars (just past
the 0 mark) illuminated red. To reset this meter simply click it twice
and try it again with a lower gain (the adjustment bar beside the mic icon).
If the meter never gets above -6 turn up the gain. TPS reports are the sharp explosive noises made by the
letters T, P and S. Think about a time you’ve overheard whispering
from the next room, you only hear the TPS reports, everything else is too quiet.
Ordinarily your brain just cancels the extra volume, but microphones aren’t
that smart. The beginning of jbocradi ep 1 has a few TPS problems. In
reality this is the exact same problem as having too much gain, but since these
letters are so much louder, if you dial down the gain to accommodate you end up
losing over all quality because it will later have to be equalized back
up. The solution is a wind canceling microphone attachment. They
can be had for $3 at radio shack. They’re large and black, and look
ridiculous on small mics (see the pic of mine), but they work miracles for TPS
canceling. Installation is simple, especially if you’re up to speed
with modern prophylactic techniques. Also, B causes TPS reports, but that
wouldn’t have been as funny. Echoes are familiar to everyone, and they’re easy to
get rid of, just make sure the room that you have extended the microphone into
is large and full of oddly shaped things (preferably soft ones). Sofas,
beds, tables, pillows, desks, and shelving units make excellent echo cancellers
because they break up the planarity of echo-causing walls. RFI stands for Radio Frequency Interference, and can cause all
kinds of weird noises to be recorded that the person never hears. I’ll
spare you the physics of why this happens, but the tip to be garnered here is
don’t have a cell phone in the same room as you’re recording, even
if it’s set to silent and vibrate has been turned off. If it is
activated by someone calling it, it will respond by blasting a very “loud”
RF signal back to the nearest tower, but in so doing it will cause a small
current in the wires of your sound system which (once amplified) is enough to
cause odd clicking/buzzing noises. Once you’ve taken care of all of these easy things,
the next step is to go buy a nicer microphone, especially if you have a very
deep voice like I do. I hope this guide helps! --teryret. |
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