Door Manufacturer in China for Global Projects
STC 37 means that a specific complete door specimen achieved a calculated Sound Transmission Class of 37 under defined laboratory test conditions.
For TOF DOOR, steel-door specimen TFTS-02, with a reported size of 1000 × 2100 mm, was tested under ASTM E90-23, and its STC rating was calculated under ASTM E413-22. The report states that the result applies to the whole door assembly system.
However, STC 37 does not mean:
The correct interpretation is simple:
STC 37 is a laboratory rating for the tested door assembly—not a universal rating for a core material, door thickness or product family.
STC stands for Sound Transmission Class. It is a single-number rating used to compare how building elements reduce airborne sound under the applicable test and calculation method.
ASTM E90 covers laboratory measurement of airborne sound transmission loss through building partitions and elements, including doors. During testing, a specimen is installed between a source room and a receiving room. Sound transmission loss is measured across multiple one-third-octave frequency bands.
ASTM E413 provides the method used to convert suitable sound-transmission data into a single-number classification such as STC.
STC is therefore not a direct reading from one sound level. It is a classification calculated from the specimen’s performance over a range of frequencies.
Not at every frequency and not in every real-world situation.
A door’s transmission loss changes with frequency. The STC number summarizes the measured curve into one practical comparison value. It should not be presented as a promise that every voice, machine, vehicle or music source will be reduced by exactly 37 dB.
This matters because different noise sources have different frequency characteristics. Speech, music, mechanical equipment and traffic do not challenge a door in exactly the same way.
For buyers, STC is useful for comparing tested constructions, but the complete frequency data and the project’s actual noise source may matter when acoustic performance is critical.
TOF’s report for TFTS-02 identifies:
This distinction is important. The laboratory did not assign STC 37 to rock wool as a material. It measured sound transmission through the submitted door assembly.
The assembly included more than the internal filling. Its performance was influenced by the door leaf, steel skins, internal construction, frame, seals, clearances, hardware and specimen installation.
Core material can contribute to acoustic design, but it is only one variable.
Sound may pass through or around a steel door through:
Rock wool may be used in an acoustically engineered door because its fibrous structure can support the design. That does not make “rock wool” an STC rating.
Likewise, PU, paper honeycomb, EPS or aluminum honeycomb should not be assigned a whole-door STC value without a relevant complete-specimen test.
TOF DOOR has three steel-door specimens tested under ASTM E90-23, with ratings calculated under ASTM E413-22.
| Tested specimen | Reported size | Calculated result |
|---|---|---|
| TFTS-01 | 1000 × 2100 mm | STC 29 |
| TFTS-02 | 1000 × 2100 mm | STC 37 |
| TFTS-03 | 1000 × 2100 mm | STC 30 |
TOF’s controlled specimen records identify different leaf and core constructions for these samples. The independent laboratory reports establish the STC results for the submitted specimens; they do not establish a universal rating for each core family.
The comparison supports three practical conclusions:
This is why a quotation should identify the construction connected to the test evidence rather than simply state “rock wool soundproof door.”
ASTM E90 is a laboratory method. The test rooms are arranged so that the specimen is the primary sound-transmission path.
Real buildings are more complicated. Sound can travel through walls, floor slabs, ceilings, ducts, joints and unsealed interfaces. Installation errors may also reduce the performance of the opening.
ASTM explains that ratings obtained under E90 do not relate directly to sound isolation in buildings and represent an upper limit to what may be measured in a field test. ASTM E413 also notes that a field result may be lower because of flanking transmission or construction errors. Field measurements are addressed by methods such as ASTM E336.
Therefore, the responsible wording is:
The tested door assembly achieved STC 37 under laboratory conditions.
It is not responsible to state:
This door guarantees STC 37 in every building after installation.
Steel thickness, total mass, leaf depth, internal reinforcement, core continuity and the way the layers are connected all affect how the leaf responds to sound energy.
Acoustic seals must be continuous and properly compressed when the door is closed and latched. A high-performing leaf cannot compensate for an uncontrolled air gap around the perimeter.
The bottom edge is a common leakage path. A suitable threshold, door-bottom seal or automatic drop seal may be required by the tested or engineered construction.
The frame must be correctly anchored, aligned and sealed to the supporting wall. An unsealed frame perimeter can bypass the intended acoustic construction.
Every opening through the leaf changes the local construction. Smart-lock cables, viewers, glazing and other cut-outs should be controlled against the tested design.
Excessive gaps, frame distortion, poor seal adjustment or on-site cutting can reduce installed sound isolation.
An STC 37 tested door assembly may be relevant to projects where speech privacy and corridor-to-room noise control are important. However, suitability cannot be determined from the door rating alone.
The project designer should also consider:
For hotel, apartment, office, school or healthcare projects, the door should be selected as one part of the complete room-separation strategy.
TOF DOOR’s TFTS-02 specimen achieved a calculated STC 37 under ASTM E90-23 and ASTM E413-22 laboratory testing.
We treat this as evidence for a defined door assembly—not as a generic claim for every rock-wool door or every steel door we manufacture.
For an acoustic project, TOF first reviews the required rating and opening configuration. We then compare the requested size, leaf, frame, seals, threshold, hardware and installation conditions with the tested construction before confirming the appropriate solution.
This evidence-based approach helps buyers avoid a common sourcing problem: receiving a door described as “soundproof” without a report that matches the product being supplied.
STC 37 is meaningful when it is connected to the correct specimen, test method and complete door construction.
The core contributes to acoustic design, but it does not own the rating. Door gaps, seals, frame, hardware, manufacturing and installation all matter.
Do not buy an STC number in isolation. Verify the tested assembly and control the installed opening.
STC 37 can represent a useful level of laboratory-tested airborne sound insulation for a door assembly. Whether it is sufficient depends on the project’s room use, surrounding construction, noise source, local requirements and installed-performance target.
Not as a constant value across all frequencies and conditions. STC is a single-number classification calculated from transmission-loss measurements over multiple frequency bands.
No. TOF has tested rock-wool door specimens with different STC results. The rating belongs to the tested assembly, not to the core name.
Not automatically. Flanking transmission, wall construction, frame-to-wall sealing, clearances, threshold adjustment and installation quality can reduce field performance.
These changes can affect sound transmission and may move the supplied door away from the tested construction. They should be reviewed before the rating is applied to a quotation.
No. Thickness alone does not define total mass, stiffness, core continuity, sealing or the complete frequency response.
