Acoustic Transmission Loss Calculation

Acoustic Transmission Loss: How to calculate the Sound Insulation?

Acoustic Transmission Loss (TL) measures the effectiveness of a material or structure, like a wall or partition, in reducing the amount of sound energy transmitted through it. This metric is essential for designing soundproofing solutions in buildings, industrial spaces, and other environments where noise control is crucial.

The calculation of acoustic transmission loss is based on the work of Davy,2009 below the critical frequency, complemented by methodologies developed by Sharp,1973 in frequencies higher than the critical frequency. This method is proposed by Kosala,2019.

Understanding the Three Frequency Zones in Acoustic Transmission Loss

The acoustic performance of materials (thin and isotropic) depends on the frequency of the sound wave relative to the material's critical frequency (f_c). The following zones highlight how sound behaves across different frequency ranges:

• Zone 1: Below the Critical Frequency

  In this zone, the mass law governs transmission loss. Materials with higher mass density and thickness provide better soundproofing.
  In the this frequency range, the transmission loss increases of 6dB by doubling the frequency. Doubling the mass follows tha same law (+6dB)

• Zone 2: Around the Critical Frequency

  In this transition zone, the damping factor and the critical frequency significantly influence transmission loss. Material properties, such as elasticity and internal friction, become critical in this range.

• Zone 3: Above the Critical Frequency

  For frequencies higher than 1.2f_c, transmission loss increases by approximately 9dB per octave. This zone is dominated by the material's damping factor. Materials engineered with high damping properties, such as viscoelastic composites, are particularly effective in this range.

Remarks about the calculations

This calculation has some assumption, take care about it when doing a calculation

The first modes of the plates are not taken into account in the calculation. Especially the first mode could have an impact on the sound insulation curve in low frequencies.

The impact of shear modes are not calculated, that could have an impact especially in high frequencies

Applications of Acoustic Transmission Loss

Understanding the frequency zones of acoustic transmission loss is crucial for:

• Building Design: Ensuring walls, floors, and ceilings meet noise control standards in residential, commercial, and industrial spaces.
• Product Development: Designing materials with tailored acoustic properties for maximum sound insulation.
• Regulatory Compliance: Meeting industry noise reduction standards for health and safety.

Learn More

For further insights into acoustic performance and soundproofing solutions, explore the module to calculate the critical frequency or browse our acoustic product database to have an overview of acoustic performances of real products.

Reference:
Davy, 2009"Predicting the Sound Insulation of Walls"
Sharp, 1978"Prediction Methods for the Sound Transmission of Building Elements"
Kosala, 2019 "Calculation models for analysing the sound insulating properties of homogeneous single baffles used in vibroacoustic protection "

This calculation is provide for information, we are not responsible of possible damages if you use the results