A suppressed firearm is typically being considered such when stripped of it's rights, liberties, or other freedoms.. Most generally it isn't allowed to speak out loudly too.
This^^^It's suppressed as soon as the decibel rating drops when using the device versus open bore
I knew someone years ago that was arrested for manufacturing, and selling illegal silencers. It turns out that they were SO bad, he had to be convicted of conspiracy to manufacture silencers, rather than the manufacture of the silencers. I think they have to reduce the sound by a certain number of decibels to be considered a silencer. Otherwise, virtually every flash hider and muzzle break on the market would be a silencer.