Sound Transmission Loss Calculator
Estimate the sound transmission loss of a single-leaf wall using the mass law: TL = 20 * log10(f * m) - 47.3 dB.
Transmission Loss
32.70 dB
Transmission Loss vs Frequency
Formula
## Mass Law for Sound Transmission Loss The mass law gives the theoretical TL of a single homogeneous panel. ### Formula **TL = 20 log10(f m) - 47.3 dB** - *f* = frequency (Hz) - *m* = surface mass density (kg/m2) Doubling the mass or frequency increases TL by about 6 dB. This is the field-incidence mass law, valid below the coincidence frequency.
Esempio Risolto
20 kg/m2 concrete panel at 500 Hz.
- 01TL = 20 log10(500 * 20) - 47.3
- 02TL = 20 log10(10000) - 47.3
- 03TL = 20 * 4 - 47.3
- 04TL = 80 - 47.3 = 32.7 dB
Domande Frequenti
Why does the mass law fail at certain frequencies?
At the coincidence frequency, bending waves in the panel match the airborne sound wavelength, causing a dip in TL. This frequency depends on panel stiffness and thickness.
How can I exceed the mass law?
Use double-leaf constructions (two panels with an air gap), add damping, or use different-thickness panels to avoid common coincidence frequencies.
Is thicker always better?
Heavier is better within the mass-law regime. Very thick panels of the same material are also stiffer, which can lower the coincidence frequency and reduce TL at mid frequencies.
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