Before your suspicious suspicions get the best of you and make you paranoid, take a moment to look for some more mundane explanations for the phenomena.
It’s possible that it’s just coincidence, or someone nearby is on their phone and using it in a hands-free mode like speakerphone. It could be static feedback from radio stations, or an anomaly with your own phone signal (i.e., “co-channel interference” when two transmitters are broadcasting on the same frequency). Most cell phones will ring if deliberately tapped lightly in order to provide tactile feedback and also act as an audible confirmation of successful acquisition by another user – so if you have been carrying your mobile device around with you all day without hearing any new calls come through, this is a good sign that you’re not being tracked.
