Hi Yeelight,
after a few days of use of your Yeelight RGBW LED bulb I noticed a slight hum when the bulb is at maximum intensity, so to speak like a fridge but obviously much more modest.
I know if it is a normal thing?
Yes, it’s normal. This noise is generated by the transformer. If you listen carefully to power adapters around, e.g. AC adapter for your PC or charger for your smartphone, then you will probably also heard the same kind of noise.
We have tried to improve this by adding more strictly check in factory, but it’s hard to eliminate it 100%. Really sorry for this issue.
No problem, I just wanted to know. Thanks for the reply.
I do have multiple hue in my house,
Philips did change them all for new bulb for the same reason…
The yeelight are more silent then the HUE 
You’re right, because in the end it is very quiet compared to Philips HUE.
I love Yeelight Bulb!