Help to identify the cause of this noise please?

[Sold5]

Hi hope someone can advise - this noise happens some mornings when I start the car and disappears after about 1km driving. I recorded the noise and put it on vimeo here

. Printouts of the car diagnostics are attached also. My mechanic listened to the recording on my phone but said he doesnt recognise the noise. I can't reproduce it for him as it only happens about once a week or so. Thanks in advance for any ***istance!

 

[mlkehunt]

it must be the mothership proximity warning

but joking aside, the noise seems to be directly affected by engine rpm, is it a "physical" noise/function of resonance or is it coming through your speakers(think interference/bad ground)? quickest and easiest thing to do is to take your aux belt off and start the car up to see if anything changes

 

[Sold5]

It's coming from the engine as far as I can tell. The only problem with taking the aux belt off and starting the car is that I never know when this noise will happen, it only happens once a week or less on average.