This is the only change that you need to make. I tried a few files from https://www.phpcaptcha.org/download/#translations
The French and German files played but neither of the two Portugese files worked. Instead the message “there was an error generating the audio file” was played.
You will need to raise this problem with the secureimage project.
The second portuguese files (Contributed by Messias Nascimento) will work but you need to change the permission of the pt and pt2 directories to allow the web server to read them. From a terminal window in the audio directory give them the same permissions as the en directory
chmod --reference=en pt
chmod --reference=en pt2
The files in the first portuguese translation (Contributed by Flavio Lucio – ITECH SOLUTION) seem to have the wrong bit rate.