Amplify by percent is now available as a plug-in. You can get it here: Amplify by percent
See here for how to install plug-ins: Missing features - Audacity Support
When amplifying, you need to have two reference levels.
On a typical guitar amp there are multiple controls that affect the output level. Gain, Drive, Bass, Mid, Treble, Master… will all affect the output level, as will the input level of the signal being fed into the amp. The “Master” volume cannot be calibrated to an actual measurement because the output level depends on all of the other controls and other factors. Instead of providing a measurement, it simply provides two reference points:
- 0 = silence (infinite attenuation)
- 10 (or 11) = “maximum”
Note that the upper reference is an arbitrary figure (something that Nigel Tufnel failed to appreciate). It could just as easily be 8, or 100, or 42, or it could even be A,B,C,D,E,F…
For amplification in dB, the two reference levels are:
- -infinity = silence (infinite attenuation)
- 0 = No change (same level).
Note that in this case, both reference points are fully defined. “0” is not arbitrary but means “zero” change. The meaning is not ambiguous, “6 dB” is “6 dB” regardless of the make/model of amplifier and regardless of what signal is being processed. The dB scale represents a ratio, thus one signal can be said to be …dB greater or less than the other.
One of the problems with using a percentage range is that the numbers are not very practical.
Let’s say you want to double the amplitude:
In dB that is +6 dB
In % that is 200%
(seems reasonable)
Halving the amplitude:
-6 dB
50 %
(seems reasonable)
Reducing the amplitude to 1/10th
-20 dB
10 %
So probably a reasonable amplification range would be 0 to 200%? (if we want to make a signal bigger then we need greater than 100%).
So let’s say that we have a waveform that has been recorded rather too quietly and we need to amplify it. Say the initial level is -24 dB.
- We will need to amplify by +24 dB to bring the level up to 0. (note that we only need to change the sign from “-” to “+” to work out the required amplification).
- The same level represented on a linear scale is 0.063096. To bring this up to 100% we need to amplify by 1584.89 %. Not only is that harder to work out, it is also much bigger than our “reasonable” range of 200%.
For many audio processes, “dB” is a practical and universally accepted way of representing the level of a signal with reference to either another signal, or a fixed reference point. In many of these cases “%” would just be impractical.
Examples of how “dB” is more practical than “%” abound.
I have a microphone which has a noise floor (the “hiss” level) of -72 dB. As a percentage that works out as about 0.0251%.
For sounds, if we use “dB” then for most practical purposes we have numbers between about -100 (dB) which is very very small, and +100 (dB) which is very very large. If we use percentages instead of dB, to cover the same range we would need “silly numbers”: 0.001% = -100dB. 10000000% = 100dB.
Whether you like it or not, if you wish to do more than very basic audio editing you need to become familiar and comfortable with using “dB”.
Of course, many users do not want to do more than very basic audio editing, which is why I made the plug-in: Amplify by percent