There appears to be an odd design quirk with the PS4. If you place the console horizontally on a flat surface, you’ll notice it wobbles slightly.

PS4 Feet

The positioning of the rubber feet on the PS4

The reason for the teetering motion is attributed to the placement of rubber feet on the underside of the console; there are two fins that run down the centre of the PS4 and another on one edge and they cause the unit to be unbalanced on a flat surface. Some may not see that as a great issue but it can actually cause a lot of noise due to the vibration from a fast spinning Blu-Ray.

I resolved it by some domed soft rubber feet which I added to each corner.┬áThe difference they make is quite extraordinary – the PS4 is a lot, lot quieter in use (well, whilst the Blu-Ray is in use anyway).