On a recent road trip we wanted to have a laptop to play movies while on the road. We brought an Apple MacBook Air, a power inverter (to plug in the laptop's charger into the cigarette lighter), and a 3.5mm audio cable to connect the laptop's audio out to the car's audio in.
We noticed that when we played a movie (and thus audio), this "cycle" created a lot of noise in the car that nearly drowned out the movie's own audio. You could hear the movie, but only just. You had to crank the volume way, way up to hear much (but then the noise was too loud as well). The noise wasn't "static" noise per se - more like a deep hum.
However, when we unplugged the power inverter, the audio played normally!
My questions are:
What was it about this cycle that caused this problem?
And how can I avoid this problem?
- Car: 2014 BMW 3-Series
- Power inverter: Plugs into the car's cigarette lighter (in the center console) and has a 110-120V plug (and some other unused connectors, such as USB, etc.)
- Laptop: Apple MacBook Air (2012 probably)
- Audio cable: Normal male-to-male 3.5mm cable