I have a westinghouse LCM27W4 monitor. turned on one day and got garbled sound with a buzzing over speakers.

SOURCE: Buzzing sound coming from monitor speakers

Check your leads, chances are it's a faulty/dodgy lead coming from your macbook to the system.

SOURCE: My Westinghouse LVM-37w1 monitor has a weak power supply.

You can request parts at this email address: [email protected]
You can also call this particular contact number: 866-839-5888

SOURCE: Sound for Westinghouse L1975NW Monitor does not

Hello, I wuld love to help you out a bit more but I need some more information so we can troubleshoot. You can contact me at [email protected] so I can further assit you.

SOURCE: My sound is not working with speakers on

Sounds like you have some drivers missing.

~To download drivers and specific software;

Always get your drivers from the manufacturer of your Laptop, Notebook or Desktop.

If you were to log on to the manufacturer's web site, usually one is able to download if available, by model number, All available Driver downloads as required.

If the driver is not available, perhaps your manufacturer does not support the OS you are installing.

This is the best way of ensuring up to date drivers for your system and they are free of charge!

There are no XP drivers to be found with Microsoft as XP is no longer supported.

Some manufacturers may have a limited number of Drivers still listed.

I hope this helps.

SOURCE: monitor turns off. buzzing sound

Obviously there is some sort of interference. Do you have any speakers next to it? If so try moving them and see if that helps.
That's normally vibration in one of the transformers (especially prevalent in CRT monitors). Not much you can do about it other than buy a new monitor or learn to live with it. Sorry.