50Hz hum from macbook air headphone port I bought a pair of Brainwavz M1 headphones today and when using them with my Macbook air there is an intermittent buzz regardless of whether or not there's sound playing and irrespective of the volume of the air.

I'm fairly sure that it's 50 Hz noise from the power but curiously when I unplug the charging cable the noise is still there but not quite as loud. 

If I touch the body of the laptop the humming stops whether plugged into power or not. 

The headphones have a rated impedance of 32 ohms. 

Is there anything I can do to stop it?
Most of the Macintoshes I've had over the years have had a buzz in the headphone port. It is especially noticeable with low impedance headphones. Some have even had a click when the sound is turned on (i.e. when an alert sound plays, or a song is started in iTunes).

You could try taking it to the Genius bar, they might replace it if it is still under warranty. There could be a short somewhere, or it could just be considered "normal" which is why audiophiles use digital output.