The manual says that if the input voltage is high enough, it will try to play the waveform on the internal piezo speakers.
The manual also says you SHOULD NOT use the Hz position with more than 30V rms, but this is for safety reasons. It doesn't say the meter will fail.
Martin tested the meter on his Youtube channel and tested the Hz on mains 240v AC and it didn't die, but naturally it doesn't like it, that switch position is for low voltage stuff. To measure AC frequency, you go to V and press the yellow button.
Martin's review is below.. bear with him as he does some minor mistakes but he corrects himself in the following videos. He did these reviews straight as he gets the meter without checking the manual, so some things were confusing to him.
I personally like this style, but some may not be very patient.
Part 1 design, lcd screen, dc voltage, resistors, diodes, capacitors etc
Part 2 data logging (own software and ultradmm) , ac voltage, frequency voltage
Part 3 Insides, battery consumption
Part 4 Cold / Hot tests (how stable and accurate remains when outside the specified operating temperature) , calibration
Really, you guys should read the manual.. it's mixed with information for the other meters in the series but it's not that hard to read and understand. You can get the English version from uni-t's site:
http://www.uni-trend.com/manual2/UT61English.pdf