Why there is a constant voice notification on my Mac? Every minute there is a woman's voice saying 'helo' (it doesn't sound like 'hello'…) coming from my MacBook (OS X 10.10).

It is freaking me out. I tried closing all my Apps and rebooting my Mac, but it keeps coming out all the same. I tried turning off the Wi-Fi, but it is still there! This voice starts even though I don't log into the desktop after rebooting!

Is it a weird virus on Mac or my Mac has been cursed?
Are you sure that you have not accidentally turned on voice commands?

https://discussions.apple.com/thread/1879370

Try command+F5.