I use Aard 2 with Freedict & Wiktionary dictionaries which works pretty well for me: https://github.com/itkach/aard2-android

Available on F-droid

You can aldo hit “isolate” so only trusted connections work

I use this on a daily basis on Android, works pretty well & is available through Fdroid:

https://github.com/LittleTrickster/PDF-Doc-Scan

Personally I don’t know of any specific research but afaik the reason why our voices sound terrible to us when recorded is because they’re missing the bass that’s transmitted through the skull, i.e. they sound higher pitched on recording. So I’d try increasing the amplitude of the lower frequencies on the EQ, it’ll take a bit of fiddling to get the right balance.