When I look in the Google play store (android apps market), I see that there are a lot of apps to make secure phone calls. However, all the apps I have seen so far all seem to use data packets over 3G/WiFi to encrypt the calls. Therefore it is not possible to make direct calls over the 'regular' phone network to a landline (or the app provides VOIP - and 3G/WiFi -for making a call to a landline).
So my questions are:
-Is there any app that actually encrypts the sound of your voice, and uses this 'encrypted sound' to make a regular voice call (not using data channel)? -Are there any open source implementations for Android for 'encrypting sound' (Systems like secure voice: http://en.wikipedia.org/wiki/Secure_voice)?
P.S. Feel free to correct me if I'm using wrong terms, I'm here to learn :)