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50 r 910 AUG 41992 To further attenuate the noise, I would recommend the following: 1. Measure air flows and balance the supply, de- creasing flow through the first diffuser, if possible. 2. Line the return air ductwork to attenuate trans- mitted noise. Extending duct length would also help, however physical constraints limit this possibility. 3. Lay batt insulation above the low ceiling (be- low AHU) to attenuate the radiated noise. 4. If possible, line the main supply air duct to the first branch take -off and replace that branch serving the first diffuser with a lined branch duct (offset if possible) to attenuate noise. Verify proper operation of extractor to balance flow. Next, we examined the second floor judges' office suite. You stated that both noise and thermal comfort had been a problem in these areas. This area is served by a split DX system with the AHU located in a storage room. Return air is dumped into the store room with the room acting as a return air plenum. This presents a code problem, in that no combustible material is allowed in a return air plenum. In addition, with an unducted return opening in the back of the unit, the radiated equipment noise is greater than for a ducted unit. There also appears to be the possibility of insufficient return capacity. Both air and equipment noise were noted from the return grille located.in the door to the store room. On the original remodelling drawings, it appears that the doors to the store room were intended to be louvered doors. The secretarial/reception area was very cool ("normally cold" as described by one employee) and noise from the supply diffusers was objectionable. The two conference rooms are normally warm when occu- pied and the two corner offices may be warm. I would recommend that first, air flow (volume) measure- ments be taken for all of the diffusers on this system. In addition, the testing and balancing contractor should note locations and verify proper operation of all exist- ing volume dampers, extractors and air devices on this system. In particular, verify the operation of the indi- vidual office volume regulators with the wall mounted controls. Based upon this data, we will examine possible modifica- tions required to attenuate noise and provide proper comfort with this system.