Sound Absorption Calculator Formula

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

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Formulas Used

Total Absorption

total_absorption = area1 * alpha1 + area2 * alpha2 + area3 * alpha3

Average Absorption Coefficient

avg_alpha = (area1 * alpha1 + area2 * alpha2 + area3 * alpha3) / (area1 + area2 + area3)

Variables

VariableDescriptionDefault
area1Surface 1 Area(m2)100
alpha1Surface 1 Absorption Coefficient0.05
area2Surface 2 Area(m2)80
alpha2Surface 2 Absorption Coefficient0.3
area3Surface 3 Area(m2)50
alpha3Surface 3 Absorption Coefficient0.6

How It Works

Room Sound Absorption

Total absorption determines how quickly sound energy is removed from a room.

Formula

A = sum(S_i * alpha_i)

  • *S_i* = area of surface i
  • *alpha_i* = absorption coefficient (0 = perfect reflection, 1 = perfect absorption)

    • This value feeds into the Sabine equation for reverberation time.

    Worked Example

    Room with concrete walls (100 m2, alpha=0.05), carpet floor (80 m2, alpha=0.3), acoustic ceiling (50 m2, alpha=0.6).

    area1 = 100alpha1 = 0.05area2 = 80alpha2 = 0.3area3 = 50alpha3 = 0.6
    1. 01A = 100*0.05 + 80*0.3 + 50*0.6
    2. 02A = 5 + 24 + 30 = 59 m2 Sabine
    3. 03Average alpha = 59 / 230 = 0.257

    Ready to run the numbers?

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