Sounds like pinking (knock) rather than anything mechanical to me...
Usually caused by lower quality fuel but most modern engines have knock sensors which adjust ignition and fuelling to account for it. However you can still get some transient "knock" under load.
Have you had a change of filling station recently, with a possibly poorer fuel...or have you left the fuel in the tank for a long time (like over winter). Modern fuel ages and reduced in octane value if not used...
