Need help with something regarding an MP3

The annoying [bubbly] background-noise is compression-artifacts : they are caused by using a low bit-rate , (nothing to do with AGC).

A free plugin called DtBlkFx can be used to reduce the bubbly compression artifacts somewhat …

DtBlkFx plugin showing the 'Motor-Cycle' settings used.png
Motor-Cycle.xml (504 Bytes)