Hey guys,
I haven’t been using Audacity for long but am finding it pleasantly simple and easy to use…
But I have noticed something today which I’m not sure should be happening (I could be wrong as I don’t have much knowledge in this area of audio).
I wanted to raise the volume of a 3hour live show I have.
I merged about 30 FLAC files using GoldWave and made a WAVE file which is 1836171 KB.
I then raised the volume of that file in “Audacity” by 9.8db so the highest peak of the recording was at -1db (no clipping).
Then exported the raised volume file as a new WAVE file (raised volume) and it is 1836168 KB.
I’m not very technical with audio so here’s where I am confused.
Why is the file with raised volume 3KB smaller than the original WAVE file with lower volume ?
Is this technically correct ?
I don’t understand it as the research I have done on the function I used in Audacity says that it does not do anything but raise the volume without causing clipping / damage or changing the data etc.
When you have 2 WAVE files which are supposedly exactly the same except one is louder volume shouldn’t the louder volume file contain more info, therefore be bigger ?, not smaller ?
Any help / explantion appreciated.
Thanks
OK, I think I might have the answer to my own question, but I’d like to hear from anyone who has more knowledge about audio than I do (probably most of you !).
As I explained I created a single WAVE file by merging 30+ FLAC files with GoldWave (the single WAVE file is 1836171 KB).
I then used “amplify” in Audacity to raise the volume 9.8db and exported as a WAVE file (the new higer volume WAVE file is 1836168 KB which is 3KB smaller than the lower volume WAVE file).
I think I might have just worked out where the higer volume WAVE file is losing 3KB.
The original WAVE file was created by merging 30+ FLAC files with GoldWave.
When you open that single WAVE file in GoldWave it shows marks where the iniividual FLAC files have been merged.
Once that file has it’s volume raised in “Audacity” and is exported as a new WAVE file and is then again opened in GoldWave it no longer shows the marks where the original FLAC files are merged.
Can somebody with more knowledge than me confirm this is why the “louder” volume WAVE file is actually 3KB smaller than the original “lower volume” file ?
PS - Does “Amplify” in “Audacity” raise the volume equally over the entire file, without changing anything else about the file ?
I do not want anything to change except for the volume being raised 9.8db.
Thanks
Your explanation sounds likely. The data that’s storing where all the “merge” points are takes up space, and Audacity ignores data like that so it will throw it all away when you save the file with Audacity. That’s where your 3kB went, most likely (3kB sounds bigger than it needs to be, but I don’t know anything about how goldwave stores data).
To explain why the file with more volume takes up the same amount of space (or at least should, once the “merge” points are thrown out), think of a sound file like this: Each data point is made up of a (probably) 16-bit number, regardless of it’s value. The upshot is that it takes the same amount of space to store a zero sample as it does to store a full-amplitude sample. This is because WAV files are encoded with a PCM format, so each sample has the same resolution, regardless of amplitude.
Visualize it like this, here is what a 4-sample signal might look like:
[00010] - [01520] - [-00323] - [-01047]
It takes up 4 ‘cells’, each cell taking up 16-bits worth of data. The signal itself has nothing to do with the final file size, the overall length is the only thing that matters.
Mp3 files (and other compressed audio) can be smaller because they use less space to store smaller amplitude portions of a signal. This makes them take up less space, but they’re harder to read and edit.
Does “Amplify” in “Audacity” raise the volume equally over the entire file, without changing anything else about the file ?
Yes, as long as you aren’t clipping the signal, amplify changes only the volume of the entire highlighted portion, nothing else.
Thanks for your info.
Since my original post I have been told that the WAVE file should be the same size (KB), both the original “lower volume” file and volume raised “higher volume” file.
OK I did some “testing” and did the same thing with “Adobe Audition” as I did with “Audacity” and the “Adobe Audition” process also dropped 3KB, so I am more certain now it is to do with the “cure points” being removed in the final conversion to WAVE.
I ran a simple last test.
Simply opened the large WAVE file with Gold Wave (which consists of 30+ FLAC files merged in GoldWave).
Then deleted the cue points and saved it.
The file size dropped by 3KB.
<<<The file size dropped by 3KB.>>>
After you do this enough, you really do ignore minor file size changes, especially if you routinely bump files back and forth between different operating systems. Push a Windows file to a linux machine and then on to a Mac, the same file will be different sizes at each stop. It’s all put down to different operating system housekeeping requirements.
It’s the same show.
You can even get differences in file sizes if you take a file from a really small hard drive and put it on a much larger one. Sometimes that housekeeping will expand the file size because each hard drive has minimum requirements. There is a class in early digital technology where they make you create a four-byte file. Push that 4 bytes off to a hard drive and it magically takes up 2K because 2K is the smallest data blob that the hard drive knows about.
The only time you really pay surgically sharp attention is when you’re doing backups in one OS. If those don’t match down to the byte, you got problems.
In your case, knowing the housekeeping requirements of different types of sound files goes a long way. Sound files aren’t all sound.
Koz
Thanks for your input, I totally know what you mean about 3KB being such a small difference.
I just don’t always pay attention to this sort of thing, so when I noticed the difference I wanted to know what was causing it !
It’s nice to learn a little bit here and a little bit there of why these things happen, even though my ears will never hear the difference.
Thanks
And just when you get comfortable with the minor variations, technology comes up behind you and smacks you with a fish.
“Well, of course it failed. Didn’t you see the file size difference?”
[sigh]
Koz