Hi, I was like you looking for how to install more voices and found on MaryTTS’s GitHub repository the way to get voices.
To do this, go to this link. Then press CTRL + F to search for your voice (in your case cmu-bdl-hsmm). Look for the link to your voice in the location tag. Copy the link and go to your Home Assistant instance → MaryTTS addon → configuration → paste the link in the “voice” text field.
Now you have a new voice installed on your MaryTTS addon.