My PC emits machine-like sound when I turn it on?

[xie]

My PC emits machine-like sound when I turn it on. It sounds like a machine, but last only less than 30 seconds.
I guess it's due to my PC often gets electrical shut down.
It's it really bad for PC to be turned off suddenly?
What is the long term effect?
What should I do?
Thanks.

 

[jimmymae2000]

That's one of your fans starting, mine does the same thing.