It is helpful to know whether your volume is correct before exporting your recording to an MP3 file. There is a plug-in for Audacity called ReplayGain which allows you to do this.
The latest version of ReplayGain.ny both analyses and has the facility for Equal Loudness Normalization (i.e. amplifying to the required level), and appears in the Effect menu in versions of Audacity 2.1.0 and later.
There is an earlier version of ReplayGain.ny which analyses the volume only and indicates by how much you need to amplify + (or de-amplify -) to achieve the desired volume of 89 dB. This version appears in the Analyze menu in 2.0.3 and in the Effect menu in 2.1.0.
To install this plug-in,
- Save the file to your computer - your desktop or somewhere where you can easily find it.
- Now browse to the folder in which Audacity is installed. It's probably in C:\Program Files\Audacity) and then open the Plug-Ins folder.
- Drag the file you saved into the Plug-Ins folder.
- When you start Audacity, look for ReplayGain under the Effect or Analyze menu. If you don’t see it, go to Analyze | Manage, find ReplayGain and “enable” it. It will then appear in either the Effect or Analyze drop down menu (depending on the version you have installed).
N.B. Please be aware that this plug-in does not warn you if amplification will cause clipping when you Normalize. Check by View | Show Clipping and then View | Fit in Window. If red vertical lines are showing, this means that the audio has reached a level of volume where your voice may be distorted. If this happens, click 'Undo' to undo the Normalization, and use the Effect | Amplify feature without the 'Allow Clipping' box checked.
There is an explanatory video here which walks you through how to use this plug-in.
The author of this plug-in (these plug-ins) explains the use of the plug-in in the Audacity forum here.