What You Need to Know About Sound Transmission Control Doors

July 30, 2024

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Today, more commercial building projects want effective sound control incorporated in their design and construction. By lowering noise transmission throughout a space, the comfort, privacy, and acoustics are all improved. Door assemblies that limit loud noise exposure lower the risk of hearing loss, tinnitus, and other health issues for the occupants.  

There’s no question that sound control steel doors add value to building projects, but how do you know if the design calls for one? And what type of door is the best fit? The hollow metal door and frame experts at HMMA are here to help. Learn what you need to know about sound transmission control doors, including when to consider using them.  

Your Guide to Sound Transmission Door Ratings

Not all sound transmission control doors are the same. Some manufacturers offer component solutions, but only a tested and certified door assembly consisting of the door(s), frame, acoustic perimeter seals, door bottom(s), threshold, and astragal (pairs) is a proven solution. There are different performance ratings they can achieve. Every rated door assembly provides value to commercial projects, but each application is unique. By understanding the different ratings, you’ll have better insight into which assembly is the best fit for each use on your project.  

As the STC value increases, the volume noise allowed to pass through it decreases. Here’s a breakdown of the Sound Transmission Classification (STC) ratings scale:  

  • STC 25-29: This is the rating that many standard steel doors with steel frames and commodity sound seals fall into. A conversation at normal speaking volume can be fully understood through this door.  

  • STC 30-34: At close proximity, normal conversation would be audible hard to hear through this door opening. 

  • STC 35-39: Loud conversation can be heard and understood. Doors at this rating or higher will need to be specified as special acoustic assemblies.  

  • STC 40-44: Normal speech can be heard, but some words or phrases may not be audible,  and louder conversations will sound slightly muffled. This is the lowest STC range you want when sound control is a priority for your project. Doors with these STC ratings are commonly used in applications where room-to-room sound needs to be minimized like a school classroom. If speech privacy is a concern, a higher rating is required.  

  • STC 45-49: Normal speech and phrases are mostly blocked with some words being possible to decipher. Extremely loud speech like yelling or screaming will still be heard through the door and this rating is not a guarantee of speech privacy. 

  • STC 50-54: Loud noises like musical instruments, speakers playing at high volume, and industrial equipment running will sound like distant background noise. Doors in this range of STC ratings may be thicker. This is typically the rating used when speech privacy is required.  

  • STC 55+: Doors with this high of a rating leverage soundproofing to cancel out most noises. To reach this level of noise reduction, these steel doors are at least two inches thick. For a point of reference, STC 55+ doors are often used in manufacturing, sound studios, band practice rooms, and testing facilities.  

When Should You Consider Using Sound Control Steel Doors

One of the best ways to determine if sound control door assemblies are a good fit for your commercial building project is by asking a few questions:   

  • What is the end use of the project? Could the space benefit from having some level of noise reduction?  

  • Is noise reduction and/or acoustics essential to the building occupants health and does it impact the buildings main use?  

  • Does speech privacy matter for the business or organization that will be primarily using the space?  

If you answered yes to any of these questions, sound control steel door assemblies would be beneficial to your project. 

Some buildings like concert halls or theaters require more specialized sound control methods, including robust door assemblies that reverberate sound. Steel door assemblies with tested and certified sound control and transmission capabilities help to create the right acoustic environment.  

Measuring the time it takes for sounds to travel throughout the space can help you decide on what STC rating you’ll need for these applications. The HMMA specification on Sound Control Hollow Metal Doors and Frames is also a valuable resource to reference. If sound control is a priority, then contracting the services of an acoustic engineering consultant is recommended.  

Explore More Hollow Metal Door and Frame Specifications 

If you want to learn more about the benefits sound transmission control and other specialized steel doors offer your projects, HMMA has resources to help. Head over to the HMMA website to explore our hollow metal doors and frames specifications.