HVAC Research

Hey Everyone, I have a few questions I was wondering if I would be able to get some help with. I am doing some undergrad research here at school with one of the Architectural Acoustics professors, and am helping him to gather information on managing sound transmission from HVAC systems. I have a general knowledge of how they should be designed for acoustical spaces, because I am an audio technology minor and we have a Recording Studio on campus where I have class (basically how enlarging/adding a higher concentration of supply and return ducts will decrease inherent noise within the space.) incorporating this with some of what I have learned in past Fluid Mechanics classes, I have been able to conclude that pretty much maintaining the necessary flowrate for a designed space is a must, and should be accomplished by increasing duct and supply/return diffuser sizes in order to allow for an increase in velocity. Although I understand the basics of how to control the HVAC noise in an acoustical space, I was wondering for some added information and clarification on certain things so that I may expand on my research and works: 1) are my conclusions right/am I missing something about the basics? 2) would it be practical to introduce a type of Helmholtz Resonator into the duct system, specifically designed and tuned for the bandwitdh containing human speech? 3) is it possible to introduce multiple Helmholtz Resonators into the same system? 4) and lastly, will the use of specific supply and return diffusers introduce any noise? (i.e. floor, ceiling, circular, strip, grate, etc.) Thanks for any help, it will all be appreciated!

vthokies wrote:

1) are my conclusions right/am I missing something about the basics? 2) would it be practical to introduce a type of Helmholtz Resonator into the duct system, specifically designed and tuned for the bandwitdh containing human speech? 3) is it possible to introduce multiple Helmholtz Resonators into the same system? 4) and lastly, will the use of specific supply and return diffusers introduce any noise? (i.e. floor, ceiling, circular, strip, grate, etc.)

the air volume has to remain sufficient to cycle the air in the rooms as needed but the velocity does not have to increase nor is it desirable to increase the velocity at the room entry/exit points. you could put resonators in the ducts but is that what you are targeting? better to use them to damp any system resonances and use proper silencing techniques to avoid room to room transmission of sound. yes, the registers/diffusers can introduce noise.