Makes a periodic horrible loud noise while cooking or defrosting especially an item that is frozen. It's getting worse each day. The noise is kind of like growling noise but hard to describe. The microwave is an over the range MW and about 4 or five years old.

An internet search will produce lots of information. Try this link

https://www.google.co.uk/search?q=Cooking+frozen+beef+ribs%3F&rlz=1C1CAFB_enGB673GB676&oq=Cooking+frozen+beef+ribs%3F&aqs=chrome..69i57j0l5.17311j0j8&sourceid=chrome&ie=UTF-8

I personally wouldn't cook meat from frozen due to unpredictability of cooking times though extended defrost times at ambient can be undesirable due to promoting bacteria growth and the necessity of high temperature cooking to make it safe.
Defrosting in the refrigerator works well and is good food safety even though it takes a long time.

The exhaust fan may be loose, {check mounts} also, the turnable motor that rotates the plate often gets noisey before seizing, {remove plate to see if noise goes away} and finally the magnetron gets very loud near end of life.

were both items the same density? Was one maybe thawed more that the other? A microwave cooks by rapidly heating the water molecules within the product that you are heating. If you heat two of the same product, it should cook them both evenly, however say you put in a frozen hamburger and a thawed hamburger, the frozen one will only begin to defrost while the thawed one will actually cook

hIi would return this should be under warranty

Call GE answer center 1-800-626-2000 ask for tech help, Have your Model # orr your data plate ready.

You either have a bad magnetron tube (5 or 10 year parts warranty item through GE Factory Service 1-800-432-2737 or www.geappliances.com) or a shorted high voltage rectifier. I think the light being out is a secondary problem.

Well, it's tough to say more surely without hearing it, etc.

I'd say to use it (and always stay close to it when you do) until and unless some other symptoms occur.

And this is not a cop out - sometimes watchful waiting is called for.

It's always recommended that you never leave a running microwave unattended, but in this case even more so.

Be especially aware if either of the fans quits or if any odd smells occur.

The noise is probably from the high-voltage transformer. When it is overloaded, the excess magnetic field it produces vibrates its wire coils. Odd that it only happens for a brief time. It is either defective itself (in which case it may go a long time) or it is getting overloaded by the magnatron/capacitor/diode on its output (in which case it will get worse shortly)
Hope Ya Fix it

In order to try to set your mind at ease I will have to explain the Basics on how a Microwave Oven Functions.
When a Microwave Oven is set to COOK ...START. It cooks at 100%. There is no lowering of the heat as with a Range ( Cook Top) Control. So in order to do the other things such as DEFROST, WARM, or anything other than 100% COOK. A COOK ON- COOK OFF system was utilized. To DEFROST, the Microve COOKS at 100% for 30% of the TIME, then IDLES for 70% of the TIME. COOK ON 30% of the TIME, COOK OFF 70% of the TIME = DEFROST This is why you can hear the CYCLE. More power is required during the ON CYCLE, thus the lower vibration. The Vibration occurs when the High Voltage Transformer is turned ON ( COOK ON).
The VIBRATION seems to have got louder with age. This is somewhat normal as there is a vibration from the High Voltage Transformer present every time the Microwave is used. screws and other metal parts seem to get loose with this vibration. There is no solution, unless you can tighten EVERY screw, nut, and bolt in the unit.
Sorry!