Gain on home made audio CDs

[Dave2002]

I have made some recordings of a live performance with choir and orchestra and imported them into Audacity. As far as I can see the levels are about right, and there's hardly any overloading, but some peaks go close to the limit. Clapping - which I'm less worried about, maybe pushes over the limit.

I was given a similar recording made last year on CD, and I thought the levels on that CD were very low. Is there any extra gain parameter to use when actually burning CDs, or should I just burn the Audacity files to CD "as is", even if this does give a seemingly low level of output? Maybe I'm just noticing the real effect of wide dynamic range - even in amateur performances - of recordings of classical music. I am concerned that some listeners may say that the volume level of the final recording will be too low, yet the evidence from the tools I'm using is that it's very representative of the actual levels in the recording venue. I certainly do not want to normalise the levels or do anything to tinker with the levels in order to create the CDs for this year's performances, though some listeners may prefer to have a more compressed sound and higher mean levels.

[johnb]

Dave, as far as I know, "normalising" an audio file in audio editing software adjusts the levels overall. It doesn't introduce compression. Usually you should be able to specify a peak (or RMS) level and the software then adjusts the level of the audio in the file to meet that requirement.

[MrGongGong]

Dave, as far as I know, "normalising" an audio file in audio editing software adjusts the levels overall. It doesn't introduce compression. Usually you should be able to specify a peak (or RMS) level and the software then adjusts the level of the audio in the file to meet that requirement.

Yes you are right.
Normalising would normally have no effect on the dynamic range of the recording and give you a better signal to noise ratio.
You can, of course, do this 'manually' but increasing the gain.
Of course if you original recording has very low levels normalising will also increase the volume of everything including what you might regard as "noise".
Personally I would avoid using compression unless you really know what you are doing and how it works as you are likely to ruin what is a perfectly serviceable recording. I would pay someone who knows mastering to do this if necessary and choose someone with a deep understanding of the type of music that has been recorded.
The exception to this is where you have loud applause, if I was making a simple record of a performance I might compress JUST the applause before adjusting the overall volume so that more of the music has a decent level of signal.
One thing to look out for if you are using a normalisation plug-in is the software regarding clicks (one of my recording machine sometimes makes loud click when I switch it to record) as the peak signal to normalise to, easily avoided by looking at the waveform for them.
Some people () get very confused and hot under the collar about these things without really understanding them.

[Dave2002]

john and mrgg

You are both expressing pretty much my own opinions. I'll actually have to get on and make a few trial CDs to see (hear) if my hunch about perceived volume levels is correct. I just suspect that I will end up with a "quiet" recording - which isn't really quiet at all, but has - perhaps to my surprise - a rather wider dynamic range than I expected even with amateur forces. This is of couse pretty much in line with what books on recording classical music have been saying for at least 50 years. Many people who listen to a lot of recorded, and particularly pop, music, don't understand that loudness and dynamic range are not the same thing, and might prefer a higher mean level - which would imply compression.

I'll just go ahead and burn the CDs more or less "as is", and see how they sound via my CD player. My guess is that I may have to turn the volume up quite a bit on replay. The applause is seemingly louder, probably because some of the audience was closer to the microphones than the performers. I would consider taming that for the CD if I include it at all - I may taper it off.

Of course my preconceptions could turn out to be wrong - I'll have a better idea of this in a day or two.

[ChrisBennell]

This is an interesting subject. Some months ago I bought an external sound card for my desktop PC - a SoundBlaster Omni Surround 5.1 - I have been very pleased with the results. The audio is very clear and well defined with good bass presence. I record a lot of music from several internet sites, using Audacity, and often output the tracks to CD using Flac files, and Nero software. I have noticed some differences in setting the volume, though. The best results in Audacity now come with setting the output volume at maximum - (which was not the case using the PC internal sound card). But the sound now never reaches the peak levels on the Audacity display-graph. I also set the output from the Internet site at maximum - this seems to produce the best results. The resulting Flac files are perfectly acceptable - as is the sound from the CDs which I end up with. I have investigated whether it's possible to tweak the sound somewhere else to get Audacity to record at a higher level - but I have drawn a blank. Never mind though, the results are fine - from Bach to Mahler. I did find a recording of Janacek's On an Overgrown Path was extremely quiet, but in the end I put that down to the music and the performance (by Leif Ove Andsnes)

[Dave2002]

First draft of the CD has been made. I didn't want to tinker around with the levels within movements, or even within one piece, but one item was recorded on a video microphone, rather than an audio microphone, and once the video was imported into Audacity and the sound channel extracted (just drag the icon for the vido into Audacity ...) it sounded OK, but was decidedly lower in volume than the other items. I fixed this for the "production" CD draft by selecting all that music, then using the Amplify effect. That actually suggests a level of amplification to use to bring the peaks up to the maximum possible, and does seem to work quite well. The end result is not greatly impressive, but at least the levels are reasonable.

The next thing I want to do is to gain more control over the tracks. In order to get silence between tracks I actually got some files of silence, and inserted them - but of course that puts in unnecessary tracks. I could of course, extend the music by pasting the silence in at the end - that might be a reasonable way to get gaps between tracks. Some commercial CDs seem to have tracks which count down inserted between adjacent musical tracks - I don't know how to do that. Most of the tracks could have a standard 2 second gap between them, but there are some which I'd like to be continuous. I think that can be done using cue sheets, but I need to do more to figure that all out.

[MrGongGong]

I fixed this for the "production" CD draft by selecting all that music, then using the Amplify effect. That actually suggests a level of amplification to use to bring the peaks up to the maximum possible, and does seem to work quite well. The end result is not greatly impressive, but at least the levels are reasonable.

The next thing I want to do is to gain more control over the tracks. In order to get silence between tracks I actually got some files of silence, and inserted them - but of course that puts in unnecessary tracks. I could of course, extend the music by pasting the silence in at the end - that might be a reasonable way to get gaps between tracks. Some commercial CDs seem to have tracks which count down inserted between adjacent musical tracks - I don't know how to do that. Most of the tracks could have a standard 2 second gap between them, but there are some which I'd like to be continuous. I think that can be done using cue sheets, but I need to do more to figure that all out.

That's otherwise known as "normalising".
Audacity is a bit clunky but you might find that it does this fine (if you set the maximum level as previously mentioned) without you having to do it manually by trial and error.

I haven't used Audacity for a while but I seem to remember there is an "insert silence" command so you can avoid having to paste in silence.
One does have to be a bit careful about the "colour" of the silence though as you can end up with perceptible changes of ambience (Cage was RIGHT !!)

I don't know what you are using to burn the CDs with but things like Nero or Toast will allow you to create gapless playback WITH track marks where you want them (I think the track mark Metadata in Audacity works for some burning software as well) so you can get rid of the 2 second gaps.

Sounds like you have sussed it though, if you have heaps to do working out shortcuts (or batch processes) can save you loads of time