These interactive tools demonstrate why installed building assemblies may perform differently from product ratings. They are screening and teaching aids, not substitutes for laboratory characterization, INSUL-style assembly prediction, ASTM/ISO field testing or project-specific acoustic engineering.
1. Composite Partition Transmission Loss
Combine two elements of a partition by area and linear sound transmission. Example: a 12 m² wall rated 50 dB with a 2 m² door rated 30 dB. Ratings entered below are assumed to be frequency-specific transmission-loss values at the same frequency, not STC or OITC single-number ratings.
Composite transmission loss: 38.2 dB
Formula: TLtotal = −10 log10[(S₁·10−TL₁/10 + S₂·10−TL₂/10)/(S₁+S₂)]. This ignores flanking and interaction effects.
2. Air Leakage and Effective Transmission Loss
Model a partition with a perfectly open hole. Even a small open fraction can limit the effective transmission loss of an otherwise high-performing assembly. This is a simplified upper-bound illustration, not a door-seal prediction.
Effective transmission loss: 30.0 dB
Formula: τeffective = (1−p)·10−TL/10 + p, where p is the open-area fraction and the opening is assumed to have zero transmission loss. Actual cracks and seals are frequency-dependent and do not behave exactly like ideal open holes.
3. Room-to-Room Sound Level Estimate
Estimate receiving-room average sound level from a diffuse-field approximation. Enter a measured or assumed sending-room level, frequency-specific partition TL, separating area and receiving-room equivalent absorption area.
Estimated receiving-room level: 32.8 dB
Formula: L₂ ≈ L₁ − TL + 10 log10(S/A). Assumes suitable diffuse sound fields, steady-state conditions, no significant flanking or background noise, and compatible frequency-band data. Do not interpret the result as a predicted NIC or ASTC.
4. Mass-Law Transmission Loss Illustration
An idealized limp, homogeneous panel can exhibit increasing transmission loss with mass per unit area and frequency. This is not a reliable predictor for stud walls, insulated cavities, glazing systems, doors or multi-leaf assemblies.
Approximate mass-law TL: 28.6 dB
Illustrative random-incidence approximation: TL ≈ 20 log10(surface mass × frequency) − 47 dB. Real panels have stiffness, resonances, coincidence effects and mounting conditions that this equation omits.
What These Tools Cannot Predict
They do not account for junctions, structure-borne flanking, coincidence dips, cavity resonances, installation workmanship, leakage impedance, or the spectral weighting and test conditions required for STC, ASTC, NIC, NNIC, OITC, AOITC or OINIC. A numerical transmission-loss estimate is not an STC rating. For exterior barriers, diffraction and meteorology require a separate model; a single-number barrier attenuation calculator without those inputs would be misleading.
See the acoustic standards and ratings reference, other acoustics calculators and independent commercial field testing. For installed assemblies, OSAT can investigate leakage and flanking paths and verify corrective work through appropriate field measurements.
