I have the early version of the 99 (use it now and then) and I will describe it as a smooth low noise machine. It can get noisy if it hasn't been oiled in ages, placed on a wobbly table or if there's no felt bits under base. It's only when it's pushed to it's limits sewing thick leather on full speed it get's noisy, other wise it's a maintanance issue. I like the sound on my 99, as well as my 201.
The 185J are much the same as teh latest version of model 99, with the stitch length lever and indicator to the left (in stead of simply the lever). When I look at the 185 it looks very much like an update of the 99 to go along with the aluminium bodied version of the 201, and there are even a few 15s with the more angular look.
The only problem I have seen with 185 is the plastic casing, it is sometimes cracked, and if you find an intact case and lid be careful with it. If it's in a wooden base it's preferable, they seem to have weathered better over the years. A lot of the 185s are directly wired to the motor, it can't be disconneced. It should run fine though, I haven't owned one my self, but the bobbin case and parts underneath looks exactly the same. The motor belt was originally green on these machine, replacements are either black or a murky orangey color. My 99 (version with the stitch length knob) sounds very different than the 185 in
this video. It might have to do with oiling, plastic casing, motor (mine has been rewired and greased), or simply the sound becomming very boxy in the recording and in my computer. Either way it sounds a bit dry.