It should be silent. A friend with an E60 sport (loud, runflats, etc.) sounds silent. Mine, when I had runflats was silent. My hunch it is the mic-- either bad or installed backwards. Mics are cheap, so if the dealer won't do it under warranty, you can do it yourself.

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SOLD
2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input