Quick question - headphone click sound

When I use my Bose QC15 headphones with my phone, if I launch an app or press one of the nav keys, I hear a clicking sound through the headphones, like it is turning off and on almost.. I know that sounds odd, but I was wondering if anyone else has this issue and has a possible solution?
Also, when audio is playing this noise stops. It is only when there is no audio playing.
Thanks.

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