🔌 Achieved Insertion Loss
📈 Margin vs. Required
Sizing Checks
Full Calculation Table
| Parameter | Value |
|---|
How to Size Acoustic Lagging for a Pipe or Duct
Enter the noise reduction needed, calculated as the difference between the unwrapped pipe or duct surface noise and the target level in the adjacent space.
Choose a fiberglass wrap, mass-loaded vinyl composite, or a heavy multi-layer system based on the performance needed.
Enter the diameter or equivalent dimension and the lagging thickness being considered.
Click Calculate to see the estimated insertion loss for the selected system and whether it meets the required reduction.
Typical Insertion Loss by Lagging System Type
| System Type | Typical IL at 25mm | Typical IL at 50mm | Best For |
|---|---|---|---|
| Fiberglass wrap | 4–8 dB | 7–12 dB | Mid-to-high frequency, moderate reduction needs |
| Mass-loaded vinyl composite | 8–14 dB | 12–18 dB | Broadband including low frequency |
| Heavy multi-layer system | 12–18 dB | 16–24 dB | Demanding, high-reduction applications |
General estimating values. Actual performance varies significantly by manufacturer and specific product construction; confirm with manufacturer octave band data for final design.
Sizing Acoustic Lagging for Pipes and Ducts
Acoustic lagging, sometimes called pipe or duct wrap, is applied to the exterior of a pipe or duct to reduce noise radiating from its surface into the surrounding space. This is commonly needed where noisy piping, such as refrigerant lines sized with a refrigerant piping calculator and routed near a compressor, or pump discharge piping, or ductwork carrying high-velocity air, passes through or adjacent to noise-sensitive occupied spaces.
How Lagging Reduces Radiated Noise
Lagging reduces radiated noise through two primary mechanisms: absorption, where sound energy entering the lagging material is converted to heat through friction within the porous structure, and added mass, where a dense, limp barrier layer increases the transmission loss of the combined pipe-plus-lagging assembly according to the mass law, which states that transmission loss increases with the mass per unit area of a barrier. Sound transmission loss for building and mechanical elements is measured under standardized laboratory conditions, and the National Research Council Canada operates dedicated sound transmission testing facilities that generate much of the reference data used across North American acoustic design. Simple fiberglass wrap relies primarily on absorption and provides good performance at higher frequencies but relatively modest low-frequency reduction. Mass-loaded vinyl composite systems add a dense barrier layer to the absorptive material, substantially improving low-frequency performance since mass-based transmission loss is more effective at low frequencies than absorption alone.
Selecting the Right System for the Noise Source
The appropriate lagging system depends heavily on the frequency content of the noise being controlled. If the noise source has significant low-frequency content, such as pump or compressor vibration transmitted into piping, or low-frequency fan noise in ductwork, a mass-loaded system will typically outperform simple fiberglass wrap of similar thickness by a meaningful margin. Treating the source with an appropriate lagging system sits within the broader hierarchy of engineering noise controls that NIOSH has documented and refined over five decades of occupational noise research, which consistently favours controlling noise at its source over relying on protective measures downstream. Use the octave band calculator to characterize the source spectrum before selecting a lagging system, particularly for demanding applications where the wrong system choice could leave a low-frequency problem unresolved despite an apparently adequate overall insertion loss rating.
Thickness and Diminishing Returns
Insertion loss generally increases with lagging thickness, but not in a perfectly linear fashion; each additional increment of thickness typically produces a smaller additional insertion loss gain than the previous increment, since the system's performance approaches practical limits set by its fundamental construction. Doubling lagging thickness rarely doubles insertion loss. This calculator provides an estimate reflecting this diminishing-returns pattern; always confirm the specific manufacturer's published performance data for the actual product and thickness under consideration for final design.
Combining Lagging with Interior Duct Treatment
For duct breakout noise specifically, exterior lagging works alongside, not instead of, controlling the sound power level inside the duct in the first place. If the internal duct sound power level is very high, even well-performing exterior lagging may not achieve the total reduction needed on its own. Use the duct breakout noise calculator to determine the required total reduction, then decide whether interior duct lining, exterior lagging, or a combination of both is the most practical path to the target. Since interior lining and exterior acoustic lagging are typically sized as separate line items, it also helps to check duct wall thermal performance separately with a duct insulation calculator, as a combined thermal-and-acoustic approach often achieves the target more reliably and at lower overall cost than an extremely heavy single-layer lagging system alone.
Frequently Asked Questions
Simple fiberglass wrap relies primarily on absorption to reduce noise radiating from a pipe or duct surface and provides modest insertion loss, generally most effective at higher frequencies. Mass-loaded vinyl composite systems combine a dense, limp barrier layer with an absorptive layer, adding significant mass, which improves low-frequency performance considerably compared to fiberglass wrap alone, since mass-based transmission loss is generally more effective at low frequencies. For sources with substantial low-frequency content, use the octave band calculator to confirm this before selecting a mass-loaded system for the extra performance.
Many acoustic lagging products are designed to provide both acoustic and thermal performance simultaneously, particularly fiberglass-based systems that already function as thermal insulation, with an added mass-loaded vinyl layer providing the acoustic benefit. However, some dedicated acoustic products prioritize noise reduction with limited thermal value, and some thermal insulation products provide limited acoustic benefit. When both thermal and acoustic performance are required, confirm the specific product's ratings for both properties rather than assuming one automatically provides the other.
For a cylindrical pipe or duct, the ratio of lagging thickness to underlying diameter increases as diameter decreases, meaning the same absolute thickness represents a proportionally thicker treatment relative to circumference on smaller diameters. This generally produces a modestly higher insertion loss on smaller diameter pipes and ducts compared to larger ones using identical lagging material and thickness, though the effect is secondary to the lagging system's own construction and is not a substitute for selecting an adequately performing system in the first place.
Acoustic lagging can significantly reduce duct breakout noise by adding transmission loss to the duct wall, but it works best as part of a complete noise control strategy, since breakout noise ultimately depends on the sound power inside the duct reaching the wall in the first place. If the internal duct sound power level is very high, even well-performing lagging may not achieve enough total reduction alone, and reducing the internal noise level through source control or interior duct lining, calculated with the duct breakout noise calculator, alongside exterior lagging often provides a more reliable combined solution.
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