I worked with portable voice changers some time ago for my Borg Costume (before phone apps.), but I found that the ones that were available then
only worked as a "Voice Additive" sound effect circuit.
It seemed to distort the spoken words to the point of not being able to even understand what is being said.
If someone was stand near me, they could hear and understand the actual words from my mouth and the
changer itself just played the modified sound.
While speaking into the microphone with the speaker in another room, the person listening couldn't even clearly understand what was being said unless they where right next to me.
Maybe today, things are better with portable voice changers and the voice modifications are clear enough to understand....but so far as seen on youtube, they haven't improved.
It's still more of a sound effect (background) being added to your actual voice which is being heard...
With phones, maybe there is a good "app for that" where you don't have to even hear the person speaking, but the after "modification effect" is clear enough to understand in a different location without the benefit of actually hearing spoken word as well?
Maybe the use of a descent portable mixer would do the trick.
Mix a good clear, amplified voice with the distorted "modified sound" so that the spoken words
are mixed along with the changed sound and adjusted accordingly.
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