Sound Attenuation due to End Reflection

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The attenuation due to the end reflection at some typical duct dimensions with sharp ends and different frequencies are indicated in the table and diagram below:

¹⁾The duct dimension is the diameter of round ducts - or square root of area of rectangular duct.

• 1 mm = 0.03937 in

Sound at lower frequencies reflects more than sound with higher frequencies. Rounded ends reflects sound less than sharp ends. Reflection in funnel shaped ends like trumpets or similar can be nearly neglected.

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