Rectangular Sound Attenuator Series SA-20

SA attenuator have been rated, tested and derived from tests meeting the requirements of BS 4718: 1971 as tests conducted by SRL of UK. No deviations of insertion loss with airflow were recorded over the range of velocities employed in this catalogue. Static insertion loss figures are provided in Table 3. Full regenerated noise data is available for SA attenuators to enable installed insertion loss to be calculated. Table 2 gives guidelines for maximum face velocity against design noise level requirements, in order to limit attenuator regenerated noise. Pressure loss data assumes that the airflow to the attenuator is uniform over the face, in a duct-to-duct layout. Units installed in situations leading to poor inlet or discharge conditions could incur pressure losses higher than catalogued. In most applications the requirement to keep the pressure drop across the attenuator to a reasonable level automatically ensures that the flow noise generated within the attenuator is insignificant compared with the permissible sound power which emerges. If however, extremely low levels have to be obtained, or if the sound power from the fan is relatively low, the flow noise generated by the attenuator can be significant and can reduce its effective insertion loss. It is for this reason that when an acoustic consultant specifies the attenuator performance he will normally specify the insertion loss which is required. This then enables the attenuator manufacturer to select a unit of such a size that the flow generated within it will not reduce the effective insertion loss below the required level. Assuming correct installation, acoustic and aerodynamic performance of splitters only will be as for a cased attenuator. Description Space noise levels can be affected by attenuator self noise. As a guide it is recommended that the face velocities indicated are not exceeded. For systems with fewer than three outlets or less than 5m of ductwork, size for 5NC lower. For design levels of NC30 or below the selection should be checked by SAFID