Buzzing ceramic bulb

[addouk]

Hi all, after some advice please.
After having a basking lamp in my viv for a year I read that a ceramic heat lamp is better for my little red foot.. So today I bought a ceramic 150w bulb and a ceramic bulb fixture (the one I had before was a black plastic one and I found out that this could melt due to the new bulb being ceramic).
The heat lamp is attached to the roof of the viv, and is also in a cage to protect my tort and keep it in place. I also have it connected to a thermostat to keep the temperature regulated.
My question is, on a night when the temp is turned down.. The bulb is making a buzzing sound. Is this normal? I haven't noticed if it does it when the temperature is up during the day with me only purchasing it this afternoon.
If I turn the temp up now the buzzing stops.
Am just concerned that it's not going to explode!
I have read that other people have had buzzing ceramic bulbs but haven't been able to find any solutions or if I should be concerned.
Thanks in advance x

 

[ZEROPILOT]

When the bulb is cooled off. Off for a few minutes, make sure that it is screwed in tight.
I have a halogen light in my kitchen that was on a rheostat. It buzzed untill I replaced the rheostat with an on off switch.
Something about the ballast not liking the lower voltage.