Restoring an old tape


I am not an expert so my question is quite basic.
I have an old recording from my grand mother which was on a tape and is now transfered to an MP3.
When she is talking the volume level fluctuates from -45db to 0db making it very difficult to understand. It was probably an issue with the microphone.
How could it be processed to make it more understandable ?
I tried normalize and that reduces all the volume but it doesn’t boost the lowest volume.

Thanks in advance for your help


Dynamic-range-compression reduces variations in volume level , (but 45dB is a big ask)
Try this “LevelSpeech2” plugin … Improved "leveling" for speech - #27 by Trebor , it’s a compressor&limiter designed for speech.

Do you still have the original tape? It is possible much of the damage happened in the playback and/or conversion to mp3. (For example if whoever transcribed it had the Dolby noise reduction turned on and the original was made without Dolby).