Normalize versus Amplify

[Justafingerpicker]

What are the particular advantages or disadvantages of each option?

Rule of thumb, I like to normalize to roughly 95-100% when I'm making a compilation CD, because I don't want to have to fiddle with individual track volumes when playing the CD -- I try to keep them comparable. But when I go into "amplify", the settings they're asking me for might as well be in Greek -- I have no clue what the decibel settings are telling me, what I should be looking for or anything else, so it's all purely trial and error; I end up playing with Normalize because I understand what I'm seeing there.

Any advice or clarification would be helpful.

[ignatz]

Normalize sets both stereo channels to the same level, while amplify does not. If you have a quiet passage in the left channel and a simultaneous loud signal in the right channel, you might not like normalize in that case because it would bring the left channel way up and might not sound faithful to the original. Amplify in the same situation would amplify each channel by a set amount and would not bring one channel up more than the other.

There may be other differences I am not aware of.

In the real world, it may not matter which you use. If you are satisfied with normalize, stay with it.

[billw58]

http://wiki.audacityteam.org/wiki/Amplify_and_Normalize

-- Bill

[Justafingerpicker]

Bill, that's the part I saw, but I have no clue besides trial and as to what those numerical settings will do -- bigger? smaller? trust the default?

[billw58]

From the wiki:

The Normalize effect offers the option to "Normalize maximum amplitude to" a chosen level.

The Amplify effect offers two interdependent options (meaning that changing one changes the other): "Amplification (dB)", and "New Peak Amplitude (dB)". The slider can also be used to choose the amplification level without entering any text input.

In the Normalize dialog, you choose the new maximum amplitude. 0 dB is maximum, negative values mean that the selection is amplified to less than the absolute maximum. You can also choose to remove DC offset.

In the Amplify dialog, you can specify how much to amplify the selection (positive values make it louder, negative values make it quieter); or to specify the new peak amplitude (max value of 0 dB, negative values mean that the selection is amplified to less than the absolute maximum). The Amplify dialog will not let you cause clipping unless you check the "allow clipping" option.

the settings they're asking me for might as well be in Greek

You might want to get comfortable with the concept of decibels - http://en.wikipedia.org/wiki/Decibel

-- Bill

[Justafingerpicker]

You might want to get comfortable with the concept of decibels - http://en.wikipedia.org/wiki/Decibel

-- Bill[/quote]

I'm noddingly familiar of what is being measured by the dB number. What is not so clear is, what number I should be looking for as a viable target? Do I simply trust the default number that Audacity presents in it's dialog box (ie, has it taken a measure and determine the maximum I can increase amplification without distortion?)

[steve]

What is not so clear is, what number I should be looking for as a viable target? Do I simply trust the default number that Audacity presents in it's dialog box (ie, has it taken a measure and determine the maximum I can increase amplification without distortion?)

If you are wanting to set the overall track volume to a good level immediately before exporting your finished file, you can either trust the default (which will bring the peak level up to exactly 0 dB), or set the target level just a little bit lower. Many people (including myself) prefer to set the target a little below 0 dB.

My reasoning for leaving a little bit of headroom on the final exported file is based on a number of factors:
There's no guarantee that audio playback equipment will reproduce 0 dB - several studies have shown that some high quality CD players by reputable manufacturers will clip just below 0 dB, particularly with audio that has significant amounts of high frequency content.
If the exported file is converted to a lossy format (for example MP3), then there is a high probability that 0 dB peaks will be clipped due to the conversion process.
A file that is normalised/amplified to -1 dB peak level will sound virtually the same as squeezing out that last 1 dB, but dramatically reducing the possibility of clipping.

When exporting as WAV you will probably be OK to set the peak level to 0 or -0.1 dB, but if you may be making an MP3 version at any time, then in my opinion you should definitely allow at least 1 dB of headroom. Some people like to go as low as -3 dB, and although that is a very safe setting I think that it is possibly a little over cautious.

Ask 5 people this question and you are likely to get 5 different answers, though most would recommend a target level somewhere in the range of 0 dB and -3 dB.

[waxcylinder]

This person amplifies to -2 dB (and IIRC ignatz does too)

WC