How do you know if a sound is compressed?
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Posted on Feb 29, 2004 05:57 am
Styx
Member Since: Jan 17, 2004
This may sound like a stupid question, but i would like to know if you can tell if a sound is compressed. I have built in compresser effects on my mixer which i use, but i dont know how much an effect its making on the signal.
thanks
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flame...bringing sexy backMember
Since: Jul 01, 2002
Feb 29, 2004 09:40 am well, a compressor should stop you having too loud a signal, and having too much difference in volume through human error...
not that thatll help ya much probably...
why not record the same thing twice, whatever it may be, and try it with and without?
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Feb 29, 2004 10:38 am there is a distinct sound to compression. you've got to learn to hear it, AKA train your ear. what made it possible for me to hear was throwing a stereo compressor on a drum bus (all the drum tracks) and playing with all the settings. drums immediately start to take on a bombastic character when a compressor is used on the whole bus, and i found that easy to hear.
you could use all sorts of relative terms about how it sounds like it's opening and closing, exploding and returning, squished or dry, etc. once you can hear what it sounds like (which would probably be extreme settings at first), you can decide if you want to use it where it's obvious as an effect, like jamie said just transparently for dynamics control, or not at all (hopefully the most frequently used setting).
learn about what exactly a compressor does, then play with it. i have a hunch that very many people who do recording stuff can't truly hear what compression does, so this definitely is not a stupid question.
flame...bringing sexy backMember
Since: Jul 01, 2002
Feb 29, 2004 10:47 am cant wait to get my compressor. thatll be my next toy...
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Feb 29, 2004 10:50 am use plugins while you wait!
EdvoMember
Since: Feb 18, 2004
Mar 01, 2004 08:59 am To Styx: If you have possibility, record some dynamic source sound (e.g. shouting vocal) , apply compression and raise level of compressed untill the cource and compressed will be the same volume, listen to both and you will hear the difference.
Mar 01, 2004 01:05 pm compressors still confuse me...you mean raise the output gain of the compressor until it matches the source volume level, edvo?
EdvoMember
Since: Feb 18, 2004
Mar 01, 2004 01:52 pm fortymile
Something like that :), but easyer to do it with software. Record some highly dynamic track, copy object to the next track, compress it with some plugin, approximately equate volumes of both tracks and compare by listening.
WaltChief Cook and Bottle WasherMember
Since: May 10, 2002
Mar 01, 2004 02:19 pm The attack and release timing will make more noticable difference in the sound. Using a compressor as an effect with small or sharp attack and release times will alter the sound of the recorded signal. Using a compressor for just dynamic control as mentioned above is relitively difficult to detect without first hearing the un-compressed signal.
EdvoMember
Since: Feb 18, 2004
Mar 01, 2004 02:31 pm That is why I said to leave the uncompressed track for sake of comparison.
Mar 01, 2004 06:10 pm how do you set a compressor to gate a snare? sharp attack/sharp release?
juesContributor
Since: Dec 30, 2002
Mar 01, 2004 06:59 pm a compressor and a gate are two completly seperate things forty.
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Mar 01, 2004 08:23 pm another good tool available in most decent compressors is a 'bypass' option that will show you the original sound. set the output volume on the compressor to match that of the bypass signal (original, unaltered signal) to have a clear idea of what you're working with. i have watched in horror as people used a compressor to simply make a sound or a whole mix louder, and thus think that it sounds better. it's deceptive, loudness is!
Mar 04, 2004 01:02 pm I mainly use compression to keep everything at the same level as far as dynamics go. Proper compression is best noticed in a bass line(at least in my opinion), but it also works wonders for vocals and guitar as well(really any audio). Think of it this way, you listen to a slightly heavier band who's singer sings though much of the song, but also screams at times as well. Lets say in the verse the singer will scream at the trailing end of a particular vocal line but up to that point of the scream he was just singing a nice melody. If you do this in real life, the scream will be louder than the singing obviously cause of the force in your voice involved to make the scream happen. Now lets say you insert that line in a mix with no effects at all. If you mix it so that the softer vocals are in just right place in the mix, as soon as the singer screams, the scream will be much louder than everything else if its not controlled and it will jump out at you in a bad way. When you have a mix where certian instruments and vocals fade out or become too loud, it makes it hard to enjoy the mix. Compression will take all the quieter audio and bring it up to a higher level and also take the peaks of the audio(aka a scream or whatever) and squish it down to keep it at the same decibel level as the rest of the audio. In the end proper compression will provide a very consistent mix where any particular instrument or vocal wont become too loud or soft at any particular part in the mix but it keeps everything smooth. The scream (or whatever) will still have plenty of power, but it doenst actually overpower the mix cause it fits in just like the rest of the vocal line did up to that point. One last comparison. Ever really pay attention to the bass in a high quality mix? The bass notes are very full and seem to ring forever and really fill up the mix. This is from proper comression as well. If you recorded yourself hitting single bass notes and you could view the signal, you would see that the audio sorta looks like a sideways triangle cause the initial hit of the not will be the loudest(base of triangle) but it will naturally fade out and taper off cause the vibration of the string eases(this is why the audio tapers down to a point and resembles a triangle). With compression you can have the trailing end of the note hold at the same decibal level as the initial hit, meaning that the bass not wont fade away in the mix but it will hold its ground. Otherwise the initial hit of the note will be the only part of the bass line that really comes out well in the mix and then the rest will fade away to a point where its not really in the mix as well as it should be. Also, you can use the attack/release setting to achieve the effect your were talking about(snare drum). What they do is determine how fast the auido moves up to its peak performance, use the compression to determine how long it will be held, and release will determine how fast it drops off. Just be careful cause this is what makes the most noticeable effect, and sometimes it can be a bad effect cause if its too abrupt on both ends, you can make the audio sound unnatural or lifeless. Sorry for the long post, but I hope it helps a bit.
Mar 04, 2004 01:24 pm oh...
i actually knew that jues. that was a very awful mistake i just made there.
gate opens when levels reach certain level, right right. i gotta start recording again! use it or lose it!
Mar 04, 2004 11:50 pm or maybe i'm wrong. what IS a gate? i guess maybe i thought it was a compressor with the ... threshold (?) set real ... er, high?
Mar 05, 2004 12:04 am No you had it pretty much correct. The gate doesnt open until the signal reaches a certain decibel level. It is also a useful tool. If your recording a track(say vocals) and you dont want the breathing between words or phrases to be included in the mix, set your gate roughly to where the singers voice performs as far as decibels go, and then anything below that level will not be allowed through and most likely any breathing will be at a lower level than the singing, so it will be ommited. This is just one example, but gates can be used many different ways to clean up the audio. But remeber, as soon as the gate opens up, it will allow other things to pass through, so its not totally perfect. Gates are different from compressors in the sense that they dont really adjust or modify the signal much, but gates just decide when the signal actually gets through. So with a gate, you can supress any kind of backround noise or whatever(remember, only to an extent) to make the recorded signal as clean as possible, and then you can add compression to make sure all the levels throughout the track are consistant and make sure that everything that should be heard is heard properly.
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Mar 05, 2004 12:12 am noise gate is the secret to good toms!
Mar 11, 2004 12:48 pm but am i wrong in saying you can set a compressor to act as a gate?
thought i read that somwhere. the only gates i've used have been preset ones, so i don't know...
flame...bringing sexy backMember
Since: Jul 01, 2002
Mar 11, 2004 01:05 pm a lot of compressors will have a gat function i believe...
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Mar 11, 2004 04:03 pm perhaps some compressor units will have gate functions as well, but compression and gating are two different tools.
Mar 11, 2004 05:35 pm many compressors have gates as well...my 266xl does...and many others do to, it's a pretty common combination.
Mar 16, 2004 11:49 pm I'm a member of a site called "Active Bass". A lot of bass players over there were having trouble understanding compression. I wrote what basically amounted to an aricle on compression. I went into great detail, but also provided a simplified explanation. It seemed to help some of them grasp it... Here's the link if you want to read it: activebass.com/fretbuzz/f...2&th=384594
peterMember
Since: Jun 11, 2004
Jun 11, 2004 02:38 am hi all!
a gate/expander is the reversed compressor.
a compressor pushes down the signal over the threshold. a gate/expander pushes down the signa UNDER the threshold.
peter
WaltChief Cook and Bottle WasherMember
Since: May 10, 2002
Jun 11, 2004 07:34 am Forty,
I wish I could help more, but I am afraid that I can only reiderate things I have read. I know no other way to explain it.
First question: Can a compressor be set as a gate? Using the term "compressor" as a physical componant or software plug it depends on if the compressor has a gate function built in. Most Plugs that have gating, compression, and expansion are called "dynamic processors" instead of simply "Compressors" to indicate multi functional.
The task of compression has four basic peramaters.
1. Threashold. The volume level usualy expressed in dB that compression will start. e.g. above 20dB all signal will be compressed.
2. Ratio. How much the signal will be compressed above the threashold. e.g. a 4:1 ratio will compress a 24dB signal down to 21dB for the above threashold of 20dB. In this example even though the input amplitude rose to 24dB the output signal of the compressor is pushed down to 21dB.
3. Attack. The amount of time the compressor will wait before starting compression. First example a drum hit. The rise time of the signal on a drum hit will be very fast, going from say 0 dB to 28dB in say 15 milli seconds. If you were to set the attach time to say 28 milli seconds in this exaple you would get a drum hit that would shoot up to 28 db and 13 milli seconds later would be pushed down to 21 dB. Again using the examples above of a threashold of 20db and a ratio of 4:1. This can be either a desired or undesired effect. A mismatch of attack to the amplitude charisteristics of an insturment is often thought of in terms of "pumping". Another term might be an unatural rise and fall of volume at the begining of a note, tone, or hit.
Release time is the same as attack time on the other end of things. It is the wait time before compression ends after the signal falls beneath the threashold.
Hope this helps.
Jun 11, 2004 07:43 am Greetings...First time poster - long time lurker...you guys are smart!
I need to muddy the water a bit more. I'm beginning to understand much from this thread concerning compressing and gating. My question is: how does the concept of limiting relate to all of this? What exactly does a limiter do?
peterMember
Since: Jun 11, 2004
Jun 11, 2004 08:24 am jim,
a limiter is the extreme compressor. read walts reply about ratio; a limiter has a ratio if infinite:1.
i.e if the signal is 24 db above the threshold, 21 db comes thru. but now also a signal of 50db would result in a 21 db signal output.
in other words, a compressor and a limiter is the same thing, only different settings.
peter
Jun 11, 2004 08:32 am if you want to understand the compressor
you should read an article dB wrote
it's in the recordingtips section
MauzgrrrrrrrMember
Since: Mar 29, 2004
Jun 11, 2004 12:07 pm Compressors are really confusing. I reccomend buying a cheap one to fiddle with. The FMR RNC is really amazing and worth every penny. I have not tried other compressors but it sounds way better than the digital compressors. I just fiddle with the knobs until is sounds good and then write down the settings. No idea what I am doing but at least I find it easier to get a good sound. Why is compression so elusive? I hae read a million reviews and it still gives me anxiety attacks!
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Jun 11, 2004 12:33 pm it's difficult because you can't fully describe 3-dimensional concepts such as the aesthetics of sound with 2-dimensional words. this is why you can read 8 articles on compression and maybe 2 will converge to help you understand the basic concept. but we also don't have an expert at our home recording setups tweaking the knobs and saying, "hear that? hear that?"
WaltChief Cook and Bottle WasherMember
Since: May 10, 2002
Jun 11, 2004 11:56 pm Minkus really has the answer. There is no substitute for playing with it and listening to it. It can be a frustrating process for sure. The other thing that helped me a lot was using Cubase dynamics and Ozone Multiband compressors. Both plugs have visual displays showing what is happening real time. In adverse to Cool Edit Pro which has a kabillian peramaters to play with and no visual display of the results.
MinkusMazBane of All ExistenceMember
Since: Mar 27, 2003
Jun 12, 2004 02:45 am wow that ozone plugin has a linear phase crossover? that must be cool to play with!
Jun 18, 2004 01:29 pm Thanks for all the detail explainations! I picked up a lot of stuff from this thread. Good question styx! It seems as though working with compressors is not as cut and dry as I thought.
