I’ve tried to find answers to this but I always run into a dead end. I would like to amplify the volume in songs using audacity but when I amplify, the maximum is negative! I understand this is to prevent clipping but I don’t understand why the field can’t just be expanded. When I import a song, it’s usually already clipped by Audacity in places. All I want to do is amplify without clipping. Is there some basic idea that I’m missing or is there a solution to this?
Audacity 1.2.x will clip audio at 0dB (digital audio should not go above 0dB).
Audacity 1.3.9 can support audio above 0dB for 32 bit audio, though it may not be able to import/export audio above 0dB.
The Amplify effect in both Audacity 1.2 and 1.3 will prevent you from accidentally amplifying audio above 0dB, though you can override this by clicking the check box (but not recommended).
Audacity should not be clipping audio on import if the peak amplitude is 0dB or lower. 16 and 24 bit files will always clip at 0dB as there are no “bits” to handle amplitudes outside of the range of +1.0 to -1.0
Alright, but how do I make the song louder without clipping?
Use a dynamic compressor effect.
Don’t use the compressor effect that is in Audacity 1.2.6
You can try the compressor that is in the latest 1.3 version, or the SC4 compressor by Steve Harris (I think it’s available in the plug-ins pack from the main Audacity web site).
Ok, thx I’ll try that.
To make a song louder without clipping (so it sounds like a song heard on an FM radio station, for example) you need to compress the dynamic range of the song. As Steve has noted, don’t try this in 1.2! Try Effect > Compressor. Depending on how much you want to squash the dynamic range of the song you will want to use different settings in this effect. As a starting point, try: Threshold -12 dB; Noise Floor: -70 dB; Ratio: 6:1; Attack Time: 0.2 secs; Decay Time: 1.0 secs. Check “Make-up gain for 0 dB after compressing” and “Compress based on peaks”. Listen to the result. Too much? Undo and try again with a higher threshold (try -6 dB). Too little? Try again with a lower threshold (try -18 dB). You might also try different Ratio settings. A higher ratio will squash the loud parts more, and vice versa.
Expect to spend a little time learning to use the Compressor and finding settings that you like.
Alternatively, you could try downloading and installing the “Compress Dynamics” plug-in from http://pdf23ds.net/software/dynamic-compressor/ . Once you’ve downloaded it put it in Audacity’s plug-ins folder then restart Audacity. It will show up as “Compress Dynamics” below the line in the Effect menu.
–Bill
<<<I would like to amplify the volume in songs using audacity but when I amplify, the maximum is negative!>>>
All digital audio is negative. “0” 's official name is 0dBFS. Zero dB full scale. That’s where the digital channel is so loud it runs out of numbers. You can only go down. As pointed out, 32-bit sound has provision to go above that, but the result is not useful outside of Audacity.
And yes, certainly Chris’s Compressor (Compress Dynamics) may be just the ticket for you. Easy to use and highly recommended.
Koz
Chris’s dynamic compressor is certainly good, but if you are trying to “pump up the volume” it may not be the best tool for the job. It will raise the level of quieter sections of audio, and is ideal for “evening out” the volume level in recordings (great for listening to Classical music in noisy environments).
For “maximising to volume” on rock/dance/hip-hop/other contemporary music, you need a compressor that squashes down the peaks more aggressively, hence my previous recommendations. In short, it depends on the type of material you are working with and the effect that you want to achieve.
Thx for the replies. I tried the compressors but it makes it sound more hollow and not any louder. Maybe I’ve just got the wrong idea about how digital music works. Is it that the song just contains relative volumes (and no actual loudness) and that the soundcard or HIFI-system determines how loud it plays?
The actual “loudness/volume” that comes out of the headphones/speakers is indeed determined by the soundcard / HIFI-system / amplifier. The digital audio is just a string of numbers. How loud is a cassette tape? It’s completely silent until you play it.
“Dynamic Compression” narrows (compresses) the difference between high amplitude signals and low amplitude signals, which means that you can get more of the sound close to maximum. There is an explanation about maximising loudness on Wikipedia: Loudness war - Wikipedia
Ok, I think I understand it a bit better now 
Yes and no …
The taped recording does have greater or lesser energy levels recoded into it - which affects the “loudness” - not visible on a tape.
Similarly with a vinyl record - but here you can actually see the loud bits if you know what you are looking for (very useful when it come sto trying to set a sensible input recording level to maximize the amplitude while still avoiding clipping.
And similarly with a digital recording …
The volume that your hear as Steve rightly points out is largely controlled by the volume control on your amp or portable player - BUT if you have a"quiet" recording to start with and then turn up the volume on playback you are also likey to amplify any “noise” that is present in the recording.
So your objective when recording with Audacity is to set the recording level so you get a nice big signal showing on the record level meter BUT without it ever getting to the far right hand end - if you do the recording will clip and Audacity will show you a red bar at the end of the meter. Then you will have to start all over again (if possible) and re-record with a slightly lower amplitude.
So, back to your original question: if you have recorded a nicely saturated signal as abiove, then you shouldn’t need any further amplification prior to exporting the music file. If you still feel the need to amplify then Effect > Amplify helps you out here, as when you invoke it it suggests the highest level possible to avoid digital clipping. You might want to choke it back a little a bit as some portable players apparently can’t cope with such a fully saturated signal.
WC
And from re-reading your thread - I’m pretty sure that you want Effect > Amplify and not any type of compressor.
You would typically use a compressor where you are recording for playback in a noisy environment like a car - it makes the quiet bits louder and the loud bits quieter, so you don’t have to keep adjusting the volume control (apparently).
Personally I like my loud bits loud and my quiet bits quiet (even in the car) - compression trashes the dynamic range of a lot of classical music …
WC
When the new Bentley is delivered I’ll happily go back to the original uncompressed recordings, but while I’m still tootling around in the old Morgan Aero I do rather appreciate the benefits of a little subtle dynamic compression.
With a Lotus Elise it’s hardly worth turning on the radio at all - unless you are doing 25mph or less … 
WC