Use this calculation for a first-order acoustics estimate when the stated geometry, propagation model, averaging convention, reference quantity, and SI units match the measurement or design problem.

Surface Mass Kg Per Square Meter

A finite measured or assumed value greater than or equal to 0, expressed in kg/m2.

Frequency Hertz

A finite measured or assumed value greater than or equal to 0, expressed in Hz.

The implemented rule is: Approximate random-incidence mass-law transmission loss in dB for a thin homogeneous panel below coincidence: 20log10(surface mass × frequency) −47.^[1]

Loss Decibels

The calculated loss decibels, expressed in dB.

This is an idealized calculation rather than a complete acoustic simulation or measurement. Reflections, boundary conditions, directivity, damping, frequency dependence, near-field behavior, background noise, transducer response, temperature, humidity, and geometry can change a real result. The mass-law estimate is not valid near panel resonances, coincidence, leaks, flanking paths, or where construction is not a limp homogeneous barrier.

Confirm important results with calibrated measurements or a model that includes the actual geometry, materials, boundaries, source directivity, and frequency-dependent losses. Preserve the reference quantity and weighting whenever a result is expressed in decibels.

• Air Absorption Loss

  Atmospheric attenuation in dB from a specified frequency-dependent attenuation coefficient and path distance.

• Inverse Square Law Level Change

  Free-field point-source sound-level change in dB when observation distance changes from r1 to r2.

• Tissue Attenuation Frequency Loss

  Pulse-echo attenuation in dB from a specified tissue coefficient, transducer frequency, and one-way depth.