TECHNICAL FEATURE levels to be selected. The inlet pressure at the air terminal unit will determine the sound power level of that terminal unit. Without stating the inlet pressure, the sound levels for a terminal unit cannot be determined. This can be an acceptable method to give the selection requirements for all the air terminal units on a project. * Inlet and discharge pressure can be given for each air terminal, which would give the requirements for both allowable pressure drop and also at what point to provide sound levels. The schedule for determining the individual performance required for each terminal can be obtain using manufacturers' air terminal selection software. * State what the noise criteria (NC) should be based on. Currently, the AHRI Standard 885-2008 with Addendum 1 is the standard to be used for calculating NC. Using the latest or most current version will ensure the most consistent noise levels in the occupied space. An alternative is to specify the maximum acceptable power levels for both radiated and discharge sound power levels. * Check to make sure the specified flow range for an air terminal unit is obtainable. Air terminal units operating ranges for comparable inlet sizes between different manufacturers are not all the same. Specifications should include the minimum and maximum flow for the primary air valve based on obtainable flows. The flow sensors of varying manufacturers will allow different minimum and maximum flow rates. Designers should make sure to verify both the flow range of the sensor and controller to be included in a schedule. * Clearly state the requirements for the insulation required for the air terminal units on a schedule. This is commonly overlooked by specifying engineers but can make differences on performance and efficiency of the systems. Bibliography 1. 2011 ASHRAE Handbook-HVAC Applications, Chapter 48, Noise and Vibration Control. 2. 2009 ASHRAE Handbook-Fundamentals, Chapter 8, Sound and Vibration. www.info.hotims.com/49808-17 SEPTEM BER 2014 ashrae.org ASHRAE JOURNAL 35