Sound Transmission Loss Calculator Formula

Understand the math behind the sound transmission loss calculator. Each variable explained with a worked example.

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Formulas Used

Transmission Loss

tl = 20 * log10(frequency * surface_mass) - 47.3

Variables

VariableDescriptionDefault
frequencyFrequency(Hz)500
surface_massSurface Mass Density(kg/m2)20

How It Works

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.

    Worked Example

    20 kg/m2 concrete panel at 500 Hz.

    frequency = 500surface_mass = 20
    1. 01TL = 20 log10(500 * 20) - 47.3
    2. 02TL = 20 log10(10000) - 47.3
    3. 03TL = 20 * 4 - 47.3
    4. 04TL = 80 - 47.3 = 32.7 dB

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