What to do about ventilation duct noise???

My office at work is plagued by white noise from the building's ventilation system. The ductwork is exposed and runs along the ceiling and wall. There is a large vent just above my desk, which drones on throughout the day, all year long. Noise, both turbulant and mechanical, emanates not just from the vent, but also from the entire length of ductwork.
This is a pity, as I spend a lot of time here and thus listen to lots of music. As a matter of fact, my job is also affected by the noise. I am a psychiatrist and often have trouble being heard over the subtle roar (I have a soft voice, "soothing", in the words of my patients).

Cheap fixes, like taping cork panels over most of the vent, help a little, but they inevitably fall off after a while. Plus, it is not a terribly professional look. I have no control of the heating or cooling in the building, and would not be able to make substantial changes to the existing ductwork without being arrested or at least chastised savagely.
Any thoughts from all you audio savants?
Are your ceilings high enough that you could install a plenum (a large air cavity) that is lined with some type of sound damping material and then have several ducts come off that plenum? It might mean putting in a dropped ceiling to hide the fix, but if you are willing to go that extent it should reduce the noise dramatically. You would probably need about 8 inches to work the duct work in (might be able to do 6 inches, but it would be tough).

I had a similar problem and the only remedy within reason was MOVING. The remodeling needed for a cure was beyond question because of the cost.

If you have the time take a look at this site re noise and its psychological effects on people. (www.anstendig.org) I'd like a pro's opinion. Read what they have to say about the effect of vibration and mechanical sound on us. What do you think Doc?

Also, the term "white noise" I believe, refers to something like white light, in that the energy is distributed uniformly throughout the spectrum/frequency range. White noise exhibits a flat distribution of energy with frequency. Pink noise, on the other hand, has higher energy in the lower region. Typically it means a 3db reduction per octave as you go up.. Anyway I doubt you have "White noise" coming out of those godforsaken ducts. Just plain old garden-variety crappy noise and it's going out of those ducts straight into you and your patients!

Hope you solve your problem Doc. Pehaps unorganized sound (noise) can be as unsettling and destructive as organized sound (music) can be soothing and meaningful. I do, in a general way, agree that there is geat power in what is heard. Music, sermons, hypnosis... (read those articles). I would like to hear your opinion.


I remain,
Listen throug it as though it was analog tape hiss and be thankful you don't have digital ducts!
Might want to look into some specialized sound control devices-I'm thinking stalactite shaped that could be used near the vent. Sort of an artwork-sculpture effect. You've got a difficult situation as you would need the owner of the building to approve ductwork modifications and they need to be done with expertise to avoid unbalancing the system. I'd be tempted to pay the pro's for advice on this one.
Pbb, touche'.
Thanks all, for the input. I work in a hospital, and our department just had a big budget cut. As such, I am thinking that the powers that be would be less than enthusiastic about spending money on my ductwork. Rives, I like your suggestion, as it is a DIY kind of thing which would not alter the underlying ducts. Any idea of how effective it would be simply to affix acoustical tiles along the length of the ducts and part of the vent? I am not too worried about actual airflow, as I am willing to suffer for my music.
Clueless, I have glanced at the website you mentioned, and will plunge into it later this week. I will get ahold of you once I form an opinion, a skill that I am quite good at.
Not too effective. You need to create a place for the air to go and settle so to speak. An area that is considerably (2x) larger than the area that feeds it is recommended. Even larger is preferred. Then you want ducts going out from that--the more area the better. What you are trying to do is reduce the air speed coming out of the duct while at the same time shunting the internal noise of the duct. The acoustical tiles, if I understand you correctly, will likely leak air, increase airflow and actually increase the noise. I could have misunderstood what you were trying to do, but if I understand correctly, it's not advised for reducing noise.