Hobbyking 20A UBEC
1st pic front view of esc
2nd pic backside view
3rd pic frontside view
4th pic front view

* Esc has 25V 470uF capacitor
* On backside esc has 1 microcontroller I.C. and 2 transisters and resisters,diodes
* on frontside esc has light weight metal piece to absorb heat(i believe)
* below metal piece there 6 transisters.

NOTE:
- i can not see any component(buzzer or speaker) that can produce voice!!!!
- One more thing is you can repair your esc by replacing capacitor but i haven't tried it and i am not sure whether it works or not.

In esc there is no buzzer/speaker, bep sound comes in motor. Below metel pice the componeni is not transister they are mosfect......

sorry pics uploaded.
@rajsigma
i wonder but manual says ESC beeps!!

UPDATE
After using uncle google finally i found the answer.there have been a lot talk regarding this but the answer is it's MOTOR that beeps.even there is no buzzer or speaker in motor but like speaker it has coil that makes it sound prouducing component.however tune and beep pulse comes from ESC.thank you rajsigma for clarify this earliar.