Use

Determine the insertion loss due to break-in from outside of a duct into the duct system.

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User Inputs

  1. Width (mm)
  2. Height (mm)
  3. Length (m)
  4. Duct walls: 0.6, 0.8, 1.0 1.2, 1.6 mm thickness

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SoundSurfer Input

Sound Pressure Level (blue node) at a location outside the duct.

Algorithm

Insertion loss is based on ASHRAE 2019 HVAC Applications Chapter 49 Noise and Vibration Control Table 33.

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Reference should be made to the Handbook to assist in determining the appropriate length of ductwork over which break-in occurs (noting that it would often not be the full length of the duct).

The most common application of the element will be plantroom noise (say a thermal plantroom) breaking into a duct which straddles the plantroom to an occupied space.

Refer to the full text of ASHRAE 2019 HVAC Applications Chapter 49 Noise and Vibration Control for full description of application.

Output

Attenuation (dB) from the duct break-in applied to the input Sound Pressure Level (blue node), with resultant Sound Power Level (red node) output octave bands in dB(A), dB(Z) and dB(C). Output being the sound pressure level outside the duct less the attenuation provided through the duct walls and the resultant sound power level inside the duct.