Episode: 2006
Title: HPR2006: Basic Audio Production - Compression
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr2006/hpr2006.mp3
Transcribed: 2025-10-18 13:13:55

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This is HPR Episode 2006 entitled, Basic Audio Production, Compression and in part on the series,
Podcasting out or, It is hosted by Acho Jordan and in about 32 minutes long, the summer is,
yet another explanation on Sound Compression in the 8.0.
This episode of HPR is brought to you by AnanasThost.com.
Get 15% discount on all shared hosting with the offer code HPR15, that's HPR15.
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Hi everyone, this is Nacho Jordi for Hacker Public Radio and today I want to discuss a few
basic audio production techniques. Today's episode will be focused on compression, but first of all,
I'd like to tell you what's the rationale behind this series of podcasts. Maybe you think it's
a two specialized issue to discuss in Hacker Public Radio, but I think everybody could benefit
from knowing the basics of audio production. If only as an item of general culture, because
a lot of what passes as music out there, sadly, is like a joke in my view.
It's some undocumented people you see out there, listen to stuff,
I could be down in like five minutes with audacity if you only have the notions of what
as sampling is, and I think if this kind of knowledge were more mainstream, people would not get,
would not be so fooled, because it's not a matter of taste of the musical genre you like,
it's about stuff well done or stuff that is marketed as good and it's just a sonic piece of crap.
So I would try to make my part in the demystifying these concepts, which are not that complex,
and a lot of people sadly, is a bit afraid of the wall of music and music creation and music
in spite of the technical advantages of our age, just because there's like an aura of complexity or
technicality, and that's not that big of a deal if I can understand this stuff, anyone can do it really.
And at the very least, if you're listening to this, obviously you have some degree of interest in
podcasts, so I think this audio notions can be of use to anyone. Other of my motivations
to speak about this is that the best way to learn something is to teach it, I still struggle
with this kind of audio production notions, especially when I'm producing my own stuff,
because it's difficult, I mean, mostly when I record my music, it's difficult to keep the
perspective when you're composing the music and performing, and also doing the production is
difficult to keep the perspective, and yeah, like I said, the best way to learn is to teach,
so going through a discipline of explaining these concepts will also benefit me.
I'm not the most savvy person of this stuff, I still struggle with it sometimes, like I said,
and I'm not either the person that is going to provide the best explanation, but
I know there's a gazillion tutorials that explain these concepts out there, but
I think it's always good to hear stuff in a different way, sometimes it's a learning strategy
I use quite often, it's for example, when I want to learn about a certain concept or a certain
idea, I have something I do is looking for it in YouTube and then watching, like I don't know,
5, 6, 8 videos of different people explaining the same thing, because each of them is going
to do it in their own terms and sometimes the teaching style of one of them can connect with you
more than other, or simply one of those persons maybe uses an image, a metaphor that connects
with you and the learning experience happens, so I'm going to make my contributions and people
will find my summaries of all, another will maybe get some take away,
and the main, like I said, this intent to cover the basic audio production techniques,
which are not in the end, the main tools you use to beautify sound are like three or four main
techniques, no more, you don't do it, most of the times you can make 90% of the time,
you can get away with that stuff, provided that the source, the sound you've recorded is of good
quality, that's something that all the professionals stress a lot, the better the recording quality,
the quality of the source, the less travels and the less tweaking around you're going to have to
do with the sound, but the basic techniques you can apply to a sound there, the basic would be
equalization or EQ, compression, reverb and normalization, that's the main,
then you have more specialized stuff like in effects, like distortion, for example, you can apply
to a guitar track or a vocal track to give it more presence, well the effects are endless,
but like I say the main trimming and beautifying of a sound, you can do it with this basic
technique, equalization, compression, reverb and normalization, today I'm going to focus on compression,
so basic digital editing of audio is done with them usually with a program that kind of programs
called digital audio work stations or those for short, those those with the usual way they work
most of them or all of them probably is that they create a visual representation of the sound
waves which once with that representation of sound you can manipulate the sound and change
stuff and they use a cotton paste and other modifications, in the world of Linux the main
dose you can find are are door and audacity perhaps and also others
like LMMS which is more focused on electronic music and also Rose Garden that one I haven't
I'm not so familiar with it but I've heard a lot of good things about it but I think it's no longer
maintained but it's still available for downloads so maybe it's also interesting for some of you
but yeah the main contenders would be perhaps are door and audacity what's the main difference
between those those probably of course each of them have their own navigation systems and user
interfaces but the main difference in the regard of functionality is that are door allows
changing parameters live I mean as while you are listening to the sound you can turn at knob
and check out as you're listening to the stuff how how does it work while audacity
applies the it's different effects
through you can do it while you're listening to the sound you have to apply the effect there appears
a process bar and then you can see the you can listen to the result and then usually if you
if you don't like it you have to undo it and try different parameters.
Audacity is very useful for simple audio projects that require only one or two tracks for example
this podcast I recorded in audacity or door would probably be overkill and other is better
is for for full fletched audio projects like when you're doing a song and you can easily
end up having like 30 tracks or 100 tracks or whatever the RAM memory is and your patience is the limit
so those are the main doors in elinux and what what can you do to sound with
with one of these those well you can do the basic techniques I have mentioned before
and today I'm focusing like I said in compression which is a very misunderstood technique
and to describe it in short what compression compression is and something you do to the volume
of a sound with intention to make it more clear pleasant pleasant or to make to even out the volume
in different sections of a track.
the the the volume is represented as is shown in the in the hate that the waveform the graphical
representation of the waveform shows so high volume means a high
waveform and the volume means the smaller heights the waveform in most of those looks like some kind
of a visual it's like symmetrical and like I say the higher the peaks in the image the higher
the volume when the when the volume of a of a recording is very very events out usually the spikes of
the of the fishbone will be buried together and it looks like more like a tube
that's the the graphical representation of volume as the other aspect of sound as important
is would be per had the pitch higher or low pitch and that is represented by the extension of
those peaks and low pitch sounds are are take longer to to extend to to produce themselves
so they they they take longer space in the horizontal axis while high pitch sounds on the contrary
they get very short space to to to evolve but this time we're focusing on volume so with it's
something that you can appreciate in the vertical dimension of the of the waveform
and what with compression what we are going to do is like even out those those the spikes of the
sound and even out therefore the the the difference between the the higher and the lower volume
sections of a sound why and why why is that important
and because a barrier recognizes a volume changes as relative changes
for example if you have a song when you have where you have a splash drums crash sound and you
want it to be impressive impressive the best way to do what's if that is making sure that that splash
is preceded by a very quiet part
there there's a certain controversy now in in some production production called the loudness
because a lot of music producers have for some reason the wrong idea of
of making everything loud as loud as possible and all you get with that is that the
by the waking by the way in which we perceive sound if everything is loud
and there comes a point where where you your ear gets numb and you just get a ear fatigue
so the controversy was very this controversy for example had a very high
agitated debate around Metallica's latest album and also Black Sabbath's latest album
have been very criticized for for that because it's it's a wrong idea you need contrast like in every
art otherwise you you your senses get get numb they they look out
but when
so we need a certain differences between high volume and low volume
but if if that differences are too extreme in within the same audio clip it can hurt your ear
so we need to even out things a little and that's what compression does
they ain't thinking of the graphical of the graphical representation of sound it's like we
we took spatula and squashed the higher picks so they are not so prominent so they are
closer to the lower picks that way we reduced the the difference between high volume fragments
and low volume fragments that difference is called dynamic range of the of the sound
and we we avoid that disgusting effect when there's too much variation the the audio clip is
difficult to listen to
and so how can we manipulate the sound with compression what are the tools available
in our spatula sound and well depending on how with this the shape of the sound
clipping we are working on depending on the shape of the spikes of the fishbone
you'll need to modify the compression parameters in a different way
something that that helps me as a rule of thumb to understand compression
it's seeing the compression parameters as something you do to the sound
and you you understand this a bit better later for a long time I saw compression parameters
as something you measured on the sound as something you gauged and calibrated in the in the sound
but it's not it's not a good way of I would mental model the very good mental model is you have
a sound and you are doing stuff to to it
so the first parameter and most straightforward you can apply in compression is the threshold
you see a level of decibels which is the unit of measure of volume decibels and then say okay
at this level we consider the volume is going too far so we are going to start to
to stop it to stop the compression we'll start to to acts upon the sound from this from this
level on when the sound reaches when the pick gets gets this height or higher we're going to to
stop it so we said a line it's a threshold that that's only you can you can get a little
differences and just but train different threshold levels
then another parameter would be the attack
attack is measured in milliseconds is and is the time the the compression takes to to start
once the sound has crossed the line the threshold
how long are we going to take to react to that how long before we attack the sound no that's
what I what I mentioned before we are attacking the sound so it's going to the volume has
gone too far walk then we will whoa whoa whoa stop stop it stop it and we don't let the volume go
as as high as it would if we weren't intervening so we attack we tell it okay when when
the volume crosses the line wait a certain number of milliseconds and then
reduce the reduce that that volume make the make the growth of the volume less prominent
and why can this be useful why do we sometimes want to wait before applying the attack
like depending on in musical production depending of the stone we're working on we sometimes want to
like to create a certain accent and the sound waves in the moment they start
there's a section of the nice called the transients which is the the the most powerful and the
biggest accent lies and sometimes we want that part to pass through but then cut it down before
it's like I said it can be can too much volume can be can painful so for example for example when
you're working on a drum on a drum track it's very very often we want the first the tiny first part
of the drum hit we want that part to come across so we get the rhythm the rhythmical hit but then
we want we want it to not to to be too noisy after after the initial hit in that case we would
say that a short attack time just just a small window where we let those milliseconds of the first hit
come across but but then we take we want to take it out of the sonic space for example to my drum
for other musical instruments to get more more protagonism
so another parameter that you can use is the release which is the opposite to attack it's also
measuring music on and it works the the other way around when when the sound that had crossed
our threshold our our our line volume acceptable when the sound goes below the threshold
how long are we going to take to stop applying our our correction
so do we stop stressing the sound right away or already continue a compressed even though the volume
is not that high anymore this other parameter I have to admit that I still don't understand is the
is the is the parameter that I have more difficulties with
and a possible case use for example is for in any music production if you have a
I like to stick guitar for example where you don't want to the difference of sounds to be too accentuated
you you don't want to to reduce the compression quickly because it would sound unnatural it wouldn't sound
guitar like in other in other musical genres for example in electronic music a there's no you
don't have to try to sound natural because everything is electronic everything is a artificial digital sound
so it's different and also another thing with with this release is a in the inside certain kind of
sounds I think they in the low the low pitch sounds as like I said low pitch sounds it take
take longer to two year evolve so if you in a low low pitch sound you reduce the release too
the sound can distort so there you would need a slower release for example you are playing compression
to a bass bass guitar the chances are probably you will use a slow release to avoid distortion
but my understanding of this parameter is very limited so so I'm sorry if I wasn't
100% exacting something in this parameter and then finally another important parameter you
can play with is the ratio the ratio means a how how much are we going to
to modify the volume when once the compression starts in what measure are we going to
to slow it down to reduce the the volume to hold its horses the ratio the measure of ratio is a
fraction a proportion usually it's like 1 to 10 or express as I want 1 to 10 or 10 to 1 or 1 to 7
depending of the dough and it just means a it's like saying the dough okay from now on we are going
like to apply a tax to the volume that comes in so if if the sound wants to to grow one
decibel it has to give me seven decibels so that would be a compression ratio of one seven
that's a pretty pretty hard compression parameters as you can imagine the sound has to get very
very very loud because before it actually gets loud when the compression allows it to get louder
so that's another parameter that's important and you can you can play for example with this
threshold and ratio ratio values you get a lot of possibilities that of course an
theoretical explanation is limited you have to play with it and get a feeling for how everything
sounds because for example you can choose to to set a low threshold most most of the sound is
going to be compressed but give it a lower ratio like okay most of the sound is going to be
affected but not but the the way we affect the sound is not very very acute or you can do it
on depending on the sound you're working with you can you can do the opposite you can set a very
high threshold so the compression will only start when the decibel level is very high but then
how much once it reaches that threshold how much you want the compression to do you want to
squash the volume and don't let it go almost any higher or are you going to be more gentle
it depends on a lot of factors and what you're trying to do is in music production or is it even
outside some human voice for podcasts and also in addition to knowing the techniques it's important
it's always good to to remark that you have to use your ears as the first rule of course
is it helps knowing how the tools work is going to help your ears but remember that the fact that
though makes a creates a graphic representation of a sound doesn't mean that you
you mix a sound with with your eyes you you have to use your ears and then no rule is as good as
what you're going to hear and once you get a feeling for it you probably will all these rules
parameters will become unconscious but it's it's good to to know them like like I say I'm still
learning about it and I've probably done a few hundred of hours of compression and still
I'm not the best gifted person at this stuff but I like to see I'm improving and I also still on the
other side surprise myself by finding things effects that I cannot understand what happens
considering a certain parameters we're going to have a certain effect and then finding
the I didn't have a clue so I don't know if it's me or it's that the world of sounds has something
about it and it's strange it keeps you coming for more and I don't know it's very interesting and
it's wonderful this this age of hours that has allowed people to do this range of possibilities
of the things you can do with sound and it's it's great so yeah that's all I have for you today
I hope this primer on compression can have been useful for some of you thank you and for listening
and have a great day bye
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