The aircraft was in the cruise at FL340 when the crew became aware of a sudden “whirring” noise emanating from beneath the cockpit and forward galley area. This was accompanied by a distinct electrical burning smell in the cockpit. After a discussion with the Senior Cabin Crew (SCC) member the commander decided to divert. The commander and co-pilot donned oxygen masks, declared a PAN and initiated a descent and diversion with ATC clearance. The aircraft landed without further incident and there were no injuries to the passengers or crew. The cause of the noise and source of the burning smell was found to be a bearing failure within the avionics bay cooling extractor fan.
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