I had to add an external mic to mine... Simply to plug the external mic into the rear of the unit and run the wire up under the A pillar and Headliner. The issue is that the internal mic is in the head unit and picks up all the noise in the cabin .. ie blower motor etc and with the noise cancellation distorts... The mic sells for less than $3.00 on ebay and is plug and play... 3.5mm portable microphone

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2005 E53 4.4i