A few years back, I passed the Amateur Radio Technician class test and received my amateur radio license. It was about the same time that I wanted to play around with Asterisk, the open source PBX. I was really interested in getting a free voice recognition solution functioning with it. After a lot of trial and error (mostly error) I finally was able to get it working. The two most valuable resources I used were the following two URLS:
1) http://www.voip-info.org/wiki-Sphinx
2) http://turnkey-solution.com/asterisk-sphinx.html
I couldn’t just get Asterisk working with every single word in the English dictionary, I needed a smaller list of words. Since I had just gotten into ham radio I thought it would be fun to be able to call into an Asterisk and have it lookup a callsign in the FCC database for me. Since most people use the NATO phonetic alphabet to phonetically spell out their callsigns on the air, I figured I could use that as my starting dictionary.
At one point, the callsign lookup was fully functional. I could call the phone number and Asterisk would pick up. It then prompted me to say a letter from the phonetic alphabet. Asterisk would call a Perl script that utilizes Sphinx2 to do the voice recognition. After I said a letter, it would repeat it back to me with a female voice and then ask me if that was correct. Then I could either say yes or no. When I had finished entering all of the letters I could say “finished”. The server would then use Perl and Curl to look up the callsign. The callsign web page that got returned was parsed by grep and sed to pull out the first name, last name, call sign, and license class. This was stored in a temporary file. Asterisk would then call another Perl script that uses Festival to read back the retrieved data. It was a bit difficult to understand the Festival engine the first time, so Asterisk would ask if I want to repeat the results back as many times as I want. All in all, the voice recognition worked pretty well, although I don’t think it was very practical for this application. It just seemed to take too long to lookup a callsign. It was a really fun project though, and I learned a lot about Asterisk, Sphinx, Festival, and Perl.
I originally planned on posting up a tutorial explaining how to duplicate my setup exactly. I fear now that I won’t be able to remember how I had set this up since it was years ago. If I have some time I will try to locate my config files and post them at least. They might not even work now considering Asterisk is probably at a much newer version now.