Calculator Inputs
Enter material, frequency, and measurement data. The calculator can estimate theoretical loss, infer missing power or intensity, and compare measured performance.
Example Data Table
Example below uses a surface density of 20.0 kg/m². Values follow the mass law estimate for a single panel.
| Frequency (Hz) | Surface Density (kg/m²) | Estimated TL (dB) | Transmission Coefficient τ |
|---|---|---|---|
| 125 | 20.0 | 20.96 | 0.008019 |
| 250 | 20.0 | 26.98 | 0.002005 |
| 500 | 20.0 | 33.00 | 0.000501 |
| 1,000 | 20.0 | 39.02 | 0.000125 |
| 2,000 | 20.0 | 45.04 | 0.000031 |
| 4,000 | 20.0 | 51.06 | 0.000008 |
Formula Used
Surface density: m is in kg/m², ρ is density in kg/m³, and t is thickness in meters.
Measured sound transmission loss: use incident and transmitted power or intensity. A larger ratio means better sound isolation.
Transmission coefficient: τ is the fraction of sound power that passes through the barrier. Lower τ means better acoustic isolation.
Mass law estimate: this predicts the transmission loss of a single, limp, non-resonant panel. It is widely used for first-pass design checks.
Average theoretical TL: the calculator averages transmission coefficients first, then converts the average back to decibels. This avoids incorrect direct averaging of decibel values.
How to Use This Calculator
- Choose how measured data should be interpreted: auto, power, intensity, or transmission coefficient.
- Enter material density and panel thickness to compute surface density.
- Define the frequency range and step size for the analysis.
- Provide panel area if you want the calculator to infer missing power or intensity values.
- Enter measured incident and transmitted values when available.
- Submit the form to view results above the form, including summary metrics, frequency tables, and a Plotly graph.
- Use the export buttons to save a CSV file or a PDF report.
- Review the note on mass law limitations before using the estimate for final acoustic design decisions.
Frequently Asked Questions
1. What does sound transmission loss measure?
It measures how much sound energy is blocked by a wall, panel, door, or barrier. Higher decibel values indicate better resistance to sound passing through the assembly.
2. Why does the calculator use surface density?
Surface density combines material density and thickness into one value. In basic acoustic mass law, heavier panels per unit area usually deliver higher transmission loss at the same frequency.
3. Can I use intensity instead of power?
Yes. The calculator accepts either sound power or sound intensity ratios. If panel area is provided, it can also derive one from the other for convenience.
4. Is the mass law equation always accurate?
No. It is a first-order estimate. Real assemblies can deviate because of resonance, coincidence, leaks, framing paths, damping, joints, and multilayer interactions.
5. Why is transmitted energy shown as a coefficient?
The transmission coefficient gives the passing fraction directly. It helps compare barriers, estimate transmitted power, and understand how much energy survives after crossing the panel.
6. Why not average decibel values directly?
Decibels are logarithmic. Direct arithmetic averaging can distort the result. A better method averages transmission coefficients first, then converts that average back to decibels.
7. What frequency range should I test?
Common acoustic studies use octave or third-octave bands between low and high speech or machinery frequencies. The best range depends on the noise source you want to control.
8. Can this calculator replace laboratory testing?
No. It is excellent for screening and design comparisons, but certified building products still need standardized laboratory or field testing for dependable published ratings.