RichardP Posted September 12, 2004 Share Posted September 12, 2004 I am having some HVAC ducts and ceiling vents in my living room/HT area replaced with larger ones. The ducts installed during construction were too small, and the room gets hot in the summer. The standard foil/insulated flexible ducts feed the room now. As the ones to be replaced are directly over my listening position (in vaulted ceiling about 12' high), should I seriously consider any sort of special acoustically-quieter ductwork or vents? Ductwork will have to be a flexible type, due to cost considerations and small space in ceiling. Is there any such product as acoustical flexible duct, that is substantiallyl quieter than standard foil/insulated duct? Does anyone know of any HT acoustics sites that would describe such products? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
artto Posted September 14, 2004 Share Posted September 14, 2004 The main source of noise from HVAC ducts is primarily from the vents. And the noise they produce is directly related to the velocity of the air flow. Your main problem with duct vents is that they can allow airborne sound transmission to and from other areas in the building, as well as mechanical sound transmission through the structure. Vents can be internally baffled with sound absorption kind of like a ported cabinet, making the air flow around the sound absorption baffling. Low velocity air flow works best with this. Ducts should be physically isolated from the building structure (such as some closed cell foam between the duct and any building structure). Ducts could also be physically detached from other ducts in the building with some kind of flexible coupler diaphragm. http://www.clevaflex.com/hvac.html Quote Link to comment Share on other sites More sharing options...
RichardP Posted September 14, 2004 Author Share Posted September 14, 2004 Thanks for the reply. Looking at my post, I was not fully clear about which noise I was concerned with. The only concern in this situation is the noise of the air coming out of the vents. If you are saying that the vents are the main source of noise, then should I consider a specific type of vent? My plan was to go with appropriate-sized standard square louver vents, which is what is already there. If the duct size is matched to the correct vent size, and vents are left wide open at all times, is that as quiet as it can get, or would any other special vent type reduce the rushing sound any further? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
spkrgeek Posted September 14, 2004 Share Posted September 14, 2004 just attended a course at CEDIA that covered this - install difussers rather than vents. Artto was correct - the velocity of the air moving through the vent makes the noise. a long (rectangular) diffuser allows the same volume of air to pass through a larger space at a lower velocity. good luck. Quote Link to comment Share on other sites More sharing options...
Joe Shmoe Posted October 14, 2004 Share Posted October 14, 2004 I would go with a diffuser also, that would quiet it down a bit, but if the main duct line is too small it may not help a whole lot. I believe the term is "static pressure" the larger the duct the less pressure and therefore more quiet? Of course that would also mean less heat or AC. Quote Link to comment Share on other sites More sharing options...
michael hurd Posted October 16, 2004 Share Posted October 16, 2004 To elaborate on what artto said, the velocity of air is causing the noise. A larger diameter duct will have less velocity and therefore less noise. Quote Link to comment Share on other sites More sharing options...
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