Static noise from speaker

[Timatanga]

Hi,  just bought an A3 saloon from Arnold Clark. Within days i noticed a static crackling noise which seems to be coming from the front speakers but still not sure which one exactly. Took it to their garage and told they couldn't find a fault.  They sent it to their audi garage who also said they couldn't find a fault.  I picked the car up and within minutes the noise was there. Took the technician out and a few times i heard the noise he said he couldn't. Not impressed and just looking to see if anyone else had this issue and if so could hopefully point me in the right direction to finding fault. 

Thanks.