Calculate the sound absorption coefficient (α) of a material based on incident and absorbed sound intensities.
Last updated: March 2026 | By ForgeCalc Engineering
Sound absorption is the process by which a material, structure, or object takes in sound energy when sound waves are encountered, as opposed to reflecting the energy. Part of the absorbed energy is transformed into heat and part is transmitted through the absorbing body.
The sound absorption coefficient (α) is a dimensionless number between 0 and 1. A value of 0 means the material is perfectly reflective (no sound absorbed), while a value of 1 means the material is perfectly absorptive (all sound absorbed).
Where:
• α (alpha) is the sound absorption coefficient
• Iₐ is the absorbed sound intensity (W/m²)
• Iᵢ is the incident sound intensity (W/m²)
A Sabine is a unit of sound absorption. One Sabine is equal to one square foot of 100% absorbing material. It is named after Wallace Clement Sabine, the pioneer of architectural acoustics.
Yes! Most materials absorb sound differently at different frequencies. For example, thin carpets absorb high frequencies well but are almost useless for low-frequency bass.
The Noise Reduction Coefficient (NRC) is a single-number rating of how much sound a material absorbs. it is the average of the absorption coefficients at 250, 500, 1000, and 2000 Hz.
Acoustic panels are usually made of porous materials like fiberglass or foam. When sound waves enter the pores, the air molecules vibrate and lose energy through friction against the pore walls, converting sound into heat.
Related Tools
Calculate acoustic impedance.
Calculate signal attenuation.
Calculate beat frequency.
Calculate Bragg's Law.
Calculate critical damping.
Calculate damping ratio.