Rectangular sound attenuator

Transcription

1 Rectangular sound attenuator Description The type sound attenuator was designed to fit rectangular ducts. The attenuator was developed specifically to reduce noise in certain octave bands primarily in heating, ventilating, and air conditioning systems. The attenuator is sector panel designed, and comes in a wide range of configurations and materials, and is available for either exterior or interior applications. Applications Applications include heating, ventilating, and air conditioning; custom air handling units, generator enclosures, and exhaust stacks, manufacturing equipment, and almost any other situation where noise pollution is a concern. Material & finish Casing of galvanized sheet steel. The sector panels are made of high quality absorption material, with laminated cleanable surfaces (type: Therwoolin) Mounting is supplied as standard with a duct flange connection for direct mounting in rectangular ducts. Function Main features Rectangular sound attenuator Comes in a wide range of configurations and materials Excellent attenuation qualities Efficient and aerodynamic internal baffles, designed to achieve very low pressure drops Quick selection *) Code Gross air speed (m/s) Sound attenuation L w Medium frequency (Hz) *) Based on gross connection surface area 1.0 m

2 Dimension diagram 1. Pa Recommended sound level limit Alternative Technical data In case the sound attenuator total pressure is in the recommended required attenuation limit, it s no need to do additional calculation of attenuation. (Diagram 1.) In case of a more precise calculation demand ithe required attenuation LW (db) can be determined regarding the air speed and the surface area (Diagram 2.). The required attenuation of the sound attenuator must be min. 8dB lower in frequency bands than the noise level after the sound attenuator. Correction diagram 2. Gross connection surface area m 2 Pa Recommended sound level limit ,0 0,2 0,1 db Alternative m ,4 1,0 0,7 0,2 q=0,2 m /s q=1,0 m /s 0,7 1,4 10,0 8,0 7,0 6,0 1,0 0, m/s

3 Manual selection guide Selecting the correct sound attenuator 1. Select the proper sound attenuator in Table 1 with respect to the connecting air duct dimensions and required attenuation in the band 125 Hz (poss. 250 Hz). Check the attenuation even in the higher frequency bands. (In case of fan-generated noise we recommend mainly the lower frequency bands (6, 125 and 250 Hz). Use diagram 1 according to the example and read: 2. Calculate the gross connection surface area (m2) of the selected sound attenuator. The total pressure drop (Pa) of the unit can be determined considering the actual airflow, the air velocity (m/s), and the sound attenuator type/length. If the total pressure drops turns out to be too high, the required sound attenuator can be optimized by the repeated use of Selection chart 1. and Diagram 1., by selecting a different surface area, and/or sound attenuator type or length.. The total pressure drop according to Diagram 1 is valid only at identical duct cross-section dimensions, with straight connections on both sides. If mounted differently the total pressure drop has to be corrected. 4. The Selection chart was designed to easily return and select different alternatives, thus optimizing the sound attenuator. (See example below) 5. A longer 2 sound attenuator will provide a lower total pressure drop Dpt at the same level of frequency bands (at Hz), than a shorter 5 type. See our examples below. 6. At the connection after the fan it is necessary to ensure that the air velocity should be close to equal on the entire cross-section surface of the sound attenuator. Example Airflow: 2.16 m/s Gross connection surface area: 0.70 m2 Required attenuation: 125 Hz db Alternative x Pressuredrop: 6 Pa The required attenuation is in the recommended limit. Air velocity:.2 m/s (Based on gross connection surface area) Alternative x Pressuredrop: 1 Pa The required attenuation is in the recommended limit. Air velocity:.2 m/s (Based on gross connection surface area) The necessary sound attenuator data are to be determined in accordance with the acoustic sizing guide in the Technical support sheet. Self-noise If the total pressure drop of the sound attenuator in Diagram 1 falls within the recommended self-noise limited values, it is not necessary to perform separate calculation relating to the self-noise. In case of more precise calculation requirement, the self-noise can be determined in Table 2 by frequency bands. LW (db) considering the speed of the air flow, as well as the cross-section (Diagram 2). NOTE! The self-noise level of the sound attenuator should be minimum 8 db lower by frequency bands than the noise level after the sound attenuator

4 Sound attenuation selection chart Width 500, 750, 1000, 1250, 00, 1750, , 800, 1100, 1400, 1650, 1950, , 900, 10, 00, 1800, 2100, , , , , 1050, 1400, 1750, 2100, 2450, , 10, 1600, 00, 2400, 2800, 0 Length *) Based on gross connection surface area 1.0 m 2. Sound attenuation db Medium frequency (Hz)

5 Dimensions L H H B L B Dimensions L = Length B = Width , 750, 1000, 1250, 00, 1750, 0 550, 800, 1100, 1400, 1650, 1950, , 900, 10, 00, 1800, 2100, , , , ) The dimension of the height is optional. Max. height 00 mm. 700, 1050, 1400, 1750, 2100, 2450, , 10, 1600, 00, 2400, 2800, 0 Specification Ordering code XXX -X -XX -X Product acronym Thickness of attenuator 2 Interval of attenuator 05 Rockwool 0 mm 1 When fireproof izolit is required. 50 mm mm Exampel: x If other sizes are required, please contact Airvent