Why is the sound perfect when connected to my SatNav, but non existent at all other times?

[AC Question]

When travelling the Swees android is connected to the satnav for safer driving. Sound between the two at this time is loud and clear, but when in a pocket or hand held, the sound is really. bad. I can just about hear the caller but they can't hear me. I suppose that should be a blessing as far as they're concerned, but it just makes me want to fly the phone off the nearest clay trap! Any help would be appreciated.

 

[dpham00]

What is "Swees"?