Krieger Specialty Products
Acoustical Questions
STC stands for Sound Transmission Class. An STC is a single number rating system derived from measured values of sound transmission loss in accordance with ASTM Classification E90 and E413. An STC rating provides a standard industry accepted method for comparing the sound reduction effectiveness of various sound doors and windows.

Some people will refer to a sound control door as a soundproof door because of the high quality of noise reduction it provides. But technically speaking, there is no such thing as a soundproof door. No door can stop 100% of the noise, however, you can control the amount of noise leakage by using special designs and materials. Krieger's acoustical doors employ these elements to create custom doors which come with an STC rating.

To receive a Sound Transmission Loss test report, a manufacturer must arrange for a testing session in an acoustical laboratory. The laboratory must be accredited by the United States Department of Commerce, National Institute of Standards and Technology (NIST) under the National Voluntary Laboratory Accreditation Program (NVLAP) for test procedure. A laboratory test assures that the manufacturer's door or window performs to a specified STC rating.

The laboratory report should be printed on the issuing laboratory's own stationary and be clearly dated. It should name the company requesting the test and assign a report number. There should be an introduction indicating which test method is being utilized and whether the laboratory is accredited.

There should be a description of the tested item which indicated the essential details of the product and a result of the test measurement. The report must be signed by the certifying technician and a laboratory official. Finally, the report should be accompanied by a graph indicating the STC contour.

Field Sound Transmission Class (FSTC) evaluates the sound isolation between two rooms and the performance of the partitions installed in the interior of a building. While, Sound Transmission Class (STC) represents optimum conditions of a laboratory that is rarely achieved in actual construction.

The difference between the FSTC and STC results is based on the receiving space may not be calibrated for sound absorption or from sound leaks and "flanking" paths. Flanking is sound that travels between two rooms along paths other than through the partition being tested. Because of this, partitions composed of multiple elements such as doors, windows and walls will tend to have an overall FSTC close to the lowest FSTC value of any component.

The results of the FSTC tested per ASTM E336 are usually lower than in E90 laboratory tests for the same specimen. The normal rule is specify an STC rating of five points higher than the field result required.

Laboratory STC certification is intended to test a specified construction and design, not every conceivable configuration. Once a design is certified at a specific STC rating, the size the customer requests retains that certification.

Based upon previous testing experience and laboratory reports, calculations can be made to accurately estimate the STC value of a door with various vision light sizes. For example, a laboratory tested STC 46 door can have up to 900 sq. in. of glass. Similar glass sizes can then be furnished based on calculations extrapolated from the tested door.

Currently there are no louver designs that provide optimum sound reduction quality therefore Krieger does not recommend them.

Pairs of acoustic sound doors require acoustical astragals at the meeting stile. This astragal should match the perimeter seals in design. Depending on the STC rating required, either a single or double astragal will apply.

ASTM E90 is a test method for laboratory measurement of airborne sound transmission loss of building partitions. The sound transmission loss is calculated from a basic relationship involving the sound levels, absorption levels, and the test specimen size. The transmission loss data is used in E413 to determine Sound Transmission Class (STC). Both specifications are important when specifying an acoustical door or window assembly.

The technical leader of the acoustical door industry since 1936, Krieger was the first door manufacturer to achieve an STC 51 and then STC 53 in a 1 3/4" thick door without a raised sill. Krieger was also the first to achieve a STC 47 on a 1 3/4" thick wood door. Requesting the KriegerSonic brand will assure you receive the highest quality product.

Investigate whether it comes from a manufacturer that specializes in acoustical doors and windows? Does the manufacturer's available literature illustrate current testing data from an accredited laboratory? Is the finished product developed in house from start to finish, or is it a collection of components from various manufacturers? Is the field performance guaranteed and backed up with ratings?

KriegerSonic doors are available with 20 minute, 60 minute, 90 minute, 3 hour or "S" Label fire ratings.

Krieger offers acoustical doors with ratings up to STC 55 and acoustical windows up to STC 56. Please note that the highest STC may not be the right solution for you. Our knowledgeable and experienced sales staff is available to discuss your requirements and help you identify the optimal STC rating for your project.

The complete assembly; door, frame, perimeter sound seal and door bottom are supplied as part of the tested assembly. Cam lift hinges and an aluminum threshold are included on doors rated STC 45 or higher.

Materials with similar Sound Transmission Class (STC) ratings can provide similar performance in many applications. However, the resonant frequency of different materials may change the STC ratings required. Whenever possible, use a consultant to advise you of the proper STC ratings to use when designing.

Yes, an appropriately fitted threshold is critical for achieving a good seal and an optimal acoustical barrier.

A Cam Lift Hinge lifts the door during its travel and seats the door bottom for a positive seal in the closed position.

Learn More about Cam Lift Hinges

Acoustical doors are typically heavy doors. KriegerSonic doors range from 7 lb/sq. ft. to 22.9 lb/sq.ft. depending on type.

Yes, in most conventional applications, however it is recommended you consult the factory.

Krieger offers various technical and field services such as installation crew training, turn key assembly, troubleshooting and field testing.

There is no limit to the size of door or window Krieger can manufacture.

Krieger designs and fabricates frames that meet the requirements of your walls.

Not a problem, ask about our slip-in design.

Learn More about the Slip In Frame

Krieger has branch sales offices and local representatives throughout the nation. To locate the branch office serving your area click here.

All Door and window models featured on this Website have downloadable Cad drawings and technical specifications. If you do not see a model that fits your needs, please contact your local sales representative to get customized Cad drawings and specs.

See our Pre-Engineered Models

Our standard lead-time is 6 weeks in production, however lead times can change depending on complexities and scope. Please contact your local representative to discuss your requirements.

Performance times are subject to revision on a weekly basis. If quick ship is critical, please contact your sales representative for expedited fabrication. (Subject to availability.)

Yes, Krieger products come with a guaranteed.

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