loooong processing time

Hello,

I am using vosk models (tried english and italian) with nerd-dictation (https://github.com/ideasman42/nerd-dictation)

after starting recognition, for any short sentence to be recognized, it takes _ages_ before producing any output.
(by ages, I mean from 30 to 90 seconds; in the meantime, the computer is frozen).
after getting the first output the terminal starts responding again and I'm able to stop it.

I am running Ubuntu 20.04.1 on a i7 .3GHz 8 core CPU with 15.4 GB RAM

any suggestion is highly appreciated..