help fan or refelctor making a loud whistle sound

Hey guys have a 2 X 4 grow lab with a 4" vortex fan exhausting my refelctor and room. Recently a loud whislte has been coming up every now and then from the room. I've had no problems until recently I put in a Lasko 40" Tower fan in the room. SInce I put in the oscialtating fan a loud whislte shoots out from the room. I just took out the tower fan out just to pin point the noise. Its a loud noise, have had the room set up for 2 years never a whislte. I retaped the ducting connections from the vortex fan to the reflector and the ones out of the vortex. I even taped up the reflector sealed just to make sure it wasnt the refelctor. Its a cheaper sun system reflector yiled master, thats not really sealed at all. you just put in a sheet of glass and supposed to be sealed. I also took out the glass aswell just to pinpoint the noise. I also just added the an intake fan bringing fresh air into the room. I noticed that the neg. Pressure would kind of suck in the tent, so I thought the neg pressure was maybe causing the noise, but I cant seem to fig it out. I have heard that in-line fans like the vortex or can fan can start to malfunction or the bearings get rusted and start making whistles or humming noises. But I havent even used mine for all that long. Any help would be great. I just got everything going how I would like and then this loud ass whistle comes up.!!! Hopefully some one has had something like this come up and give me some good advice. I would really appreciate it. THANKS PEACE>

PS I have the lasko tower fan in another room waiting to see if it starts to whistle on me THANKS AGAIN PEACE!!!

i don't really see your problem. i would just unplug everything and try things one by one to find that damn whistle.