What is the difference between NR and TL?

Transmission Loss (TL) is a property of the partition alone — it measures how much sound energy the material blocks. Noise Reduction (NR) is the actual dB difference between the two rooms, which also depends on how absorptive the receiving room is. A very reverberant receiving room has low absorption, which reduces the effective NR even if the wall TL is high.

A sabin is a unit of sound absorption equal to 1 m² of perfectly absorbing surface (metric sabin) or 1 ft² (imperial sabin). A room's total absorption A is calculated by summing the product of each surface area and its absorption coefficient: A = Σ(Sᵢ × αᵢ).

Can NR be higher than TL?

Yes. If the receiving room is highly absorptive (large A relative to partition area S), the term 10 log₁₀(S/A) becomes negative, and NR exceeds TL. Conversely, a very live (reflective) room results in NR lower than TL.

What TL value should I use for a standard drywall wall?

A single-layer 5/8″ drywall on wood studs typically has a Sound Transmission Class (STC) of about 33–35 dB. Double-stud walls with insulation reach STC 50–60 dB. Use frequency-specific TL data for precise results; STC is a single-number rating for convenience.

Does this formula account for flanking paths?

No. The NR = TL − 10 log₁₀(S/A) formula models direct transmission through the partition only. Real-world NR is often 5–10 dB lower due to flanking (sound traveling via floors, ceilings, or ductwork). Always add a flanking margin in practice.

Is this the same as hearing protection Noise Reduction Rating (NRR)?

No. Noise Reduction (NR) evaluates sound level attenuation between rooms across an architectural wall partition, whereas NRR is a laboratory rating for personal hearing protection gear like earplugs or earmuffs.

Noise Reduction Calculator

Enter wall transmission loss and receiving room absorption to calculate the noise reduction in decibels.

Partition & Room Parameters

Units:

Transmission Loss (TL) dB

STC rating of the wall or partition (e.g. 35–55 dB for typical walls)

Partition Area (S) m²

Area of the shared wall / floor / ceiling between the two rooms

Room Absorption (A) metric sabins (m²)

Total absorption of the receiving room (sum of area × absorption coefficient for each surface)

Noise Reduction (NR)

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Formula Breakdown

Transmission Loss (TL) — dB

Partition area (S) —

Room absorption (A) —

10 × log₁₀(S / A) —

NR = TL − correction —

NR Reference Guide

< 25 dB Minimal isolation — speech clearly audible through partition

25–35 dB Basic isolation — loud speech audible, normal speech muffled

35–45 dB Good isolation — typical open-plan office partition target

45–55 dB High isolation — recommended for private offices and hotel rooms

> 55 dB Excellent isolation — recording studios and critical listening rooms

Summary

Noise Reduction (NR) is the difference in sound pressure level between a source room and a receiving room separated by a partition. It equals the Transmission Loss of the partition minus a correction for the receiving room's absorption: NR = TL − 10 log₁₀(S / A), where S is the partition area and A is the total absorption of the receiving room in sabins (m² or ft²). This calculator applies that standard formula so architects, acousticians, and engineers can quickly evaluate partition performance.

How it works

Enter the Transmission Loss (TL) of the wall or partition in dB.
Enter the area of the shared partition (the wall between the two rooms) in m².
Enter the total absorption of the receiving room in metric sabins (m²).
The calculator computes NR = TL − 10 × log₁₀(S / A).
Adjust any value to instantly see how changes affect noise reduction.
Use the unit toggle to switch between metric (m²) and imperial (ft²) inputs.

Use cases

Evaluate how much noise a concrete or drywall partition reduces between offices.
Size acoustic treatment (absorption panels) in a receiving room to meet an NR target.
Verify that a proposed wall assembly meets building code or OSHA noise requirements.
Compare partition materials side-by-side by entering different TL values.
Estimate apartment or hotel room sound isolation from corridor noise.
Design recording studio control-room / live-room separations.
Calculate industrial noise barriers separating a machine room from a work area.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu