Ducts - Noise Generation

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When air flows through ducts noise are generated. The noise can be calculated with the empirical equation below:

L_w = 10 + 50 log( v ) + 10 log( A )         (1)

where

L_w = sound power level (dB)

v = air velocity (m/s)

A = duct cross sectional area (m²)

Example - Noise generated in Ducts

The noise generated in a 200 mm circular duct with airflow 10 m/s can be calculated as

 L_w = 10 + 50 log( 10 m/s ) + 10 log( π ((0.2 m) / 2)² )

    = 45 db

The noise generated in a 200 mm circular duct with airflow 20 m/s can be calculated as

 L_w = 10 + 50 log( 20 m/s ) + 10 log( π ((0.2 m) / 2)² )

    = 60 db

Note! - the noise is generated inside the duct. Compared to the noise from the fans - the noise generated by the duct can in general be neglected.

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Related Topics

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