BMW F20 116i N13 High pitch sound when accelerating

Hi,
I've become concerned about a noise that occurs when accelerating in my 2012 BMW F20 116i with an N13B16 engine. It’s a high-pitched sound that gets louder as the RPMs rise. When I let off the gas, the noise fades. Do you have any ideas what this might be? Turbo? The car has just undergone a major service (timing chain, water pump, pulleys, multi-ribbed belt, spark plugs). I’d appreciate any information on this.
approx. 190,000 km.