NVH Calculations

How to Calculate Acoustic and NVH Product Metrics: Formulas Worked Step by Step

The four formulas that govern acoustic and NVH product manufacturing, each computed step by step with real units and inputs you can source from a spec sheet.

Acoustic and NVH product math starts with the sabin, the unit of sound absorption. Total absorption A equals the sum of each surface area S in square feet times its absorption coefficient alpha at a given frequency band. A 400 square foot foam wall with alpha of 0.85 at 500 Hz contributes 0.85 times 400, or 340 sabins. Coefficients come straight from ASTM C423 test reports, always tied to a frequency (125, 250, 500, 1000, 2000, 4000 Hz). Never average a single NRC number into a band calculation. The Sound Absorption Area calculator sums these contributions across mixed materials so you avoid mixing coefficients from different test conditions.

Reverberation time follows from absorption through the Sabine equation, T60 equals 0.049 times V divided by A in imperial units, where V is room volume in cubic feet and A is total sabins. A 10,000 cubic foot test space needing a T60 of 0.4 seconds requires A equal to 0.049 times 10,000 divided by 0.4, which is 1,225 sabins. If your panels deliver alpha 0.90 at the target band, you need 1,225 divided by 0.90, roughly 1,361 square feet of treated surface. That number feeds directly into panel count and drives the Acoustic Panel Yield estimate for the job.

Damping material usage is governed by mass and coverage, not acoustics. Constrained layer damping typically targets a treatment mass equal to 30 to 50 percent of the base panel mass for meaningful loss factor gains. For a 2.0 kg steel panel at 40 percent, you apply 0.80 kg of viscoelastic compound. Convert to area using coverage density: a 3 mm butyl sheet at 4.8 kg per square meter covers 0.80 divided by 4.8, or 0.167 square meters per panel. The Damping Material Usage calculator ties target mass ratio, sheet density, and part count together so you order the correct roll footage with scrap allowance.

Vibration isolator sizing rests on static deflection and natural frequency. The isolator's natural frequency fn in Hz equals 3.13 divided by the square root of static deflection in inches. To isolate a 1,800 RPM machine (30 Hz forcing frequency) you want a frequency ratio of at least 3, so fn near 10 Hz, giving a static deflection of (3.13 over 10) squared, about 0.098 inches. Load capacity per mount equals total supported weight divided by mount count: a 1,200 lb unit on four mounts is 300 lb each. The Vibration Isolator Load Capacity calculator checks that the selected spring rate yields both the load rating and the deflection you need.

Transmissibility tells you how much vibration actually passes through. T equals 1 divided by the absolute value of (frequency ratio squared minus 1) when damping is low. At a ratio of 3, T equals 1 over (9 minus 1), or 0.125, meaning 87.5 percent isolation. Push the ratio to 4 and T drops to 0.067, about 93 percent. Below a ratio of 1.4 you get amplification, not isolation, so an isolator tuned wrong makes vibration worse. Always confirm the forcing frequency in the field before locking a mount selection to a computed deflection.

Panel yield turns raw sheet into finished parts. Yield equals good parts divided by gross parts from a sheet, driven by nesting efficiency. A 48 by 96 inch foam sheet is 4,608 square inches. Cutting 12 by 24 inch panels (288 square inches) gives a theoretical 16 parts, but a 0.25 inch kerf and edge trim drop usable area to about 4,200 square inches, so 14 to 15 clean parts, an 88 to 94 percent yield. The Acoustic Panel Yield and Acoustic Material Scrap Rate calculators let you model kerf, trim, and defect fallout together to get true parts per sheet.

Decibel arithmetic is logarithmic, so treatments never add linearly. Combining two sources of 85 dB gives 85 plus 10 times log base 10 of 2, or 88 dB, not 170. A barrier rated at 20 dB insertion loss on an 85 dB source leaves 65 dB only if flanking paths are sealed; a 2 percent open area leak caps real reduction near 17 dB. Use the Decibel Reduction Risk Estimate to sanity check claimed reductions against leakage before you promise a spec, since a single unsealed penetration can erase 3 to 5 dB of designed performance.

Chamber capacity closes the loop between product size and throughput. Capacity equals usable interior volume divided by part envelope plus clearance. A 200 cubic foot test chamber with parts needing a 6 cubic foot envelope plus 40 percent handling clearance fits 200 divided by 8.4, about 23 parts per cycle. At a 45 minute reverberation-decay test cycle that is roughly 30 parts per hour on a single chamber. The Acoustic Test Chamber Capacity calculator combines envelope, clearance factor, and cycle time so your production math matches what the lab can physically qualify per shift.

Published 2026-07-01.