Sound Blocking vs. Sound Absorption: What’s the Difference?

Sound absorption is not sound blocking

I often find myself explaining this question to my clients. Many people confuse these two terms, or do not understand their meaning.  Confusing information is also propagated on the Internet, an example is here.


In laymen terms, this is the short explanation of the terms:

Sound absorption is a process of reducing sound energy that is already in the room, reducing reverberation.

Soundproofing (also called sound blocking) is a method of preventing sound from getting into a room that should be quiet.

Where is sound absorption used?

Materials that create sound absorption in a room are called acoustic treatment. You can use them in spaces that need more pleasant or more functional ambiance.

Where is soundproofing used?

Process of soundproofing creates a barrier between the noise source and the quiet location. You use soundproofing to create quite spaces.                                   

Knowing the difference between sound absorption (acoustic treatment) and sound blocking (soundproofing) is crucial if you are selecting a desired treatment for your space.

About room treatment (sound absorption)

There are numerous products on the market designed for room treatment. The products are applied to walls and ceilings, or just hang in the space.  When correctly placed and installed, they reduce sound reverberation in the room.  This is done to make the space more pleasant or functional (restaurants, conference rooms, home theatres).  These products have only small effect on overall noise in the room and are ineffective for soundproofing.

Metric that characterizes a product’s ability to absorb sound is called Noise Reduction Coefficient (NRC).

About sound blocking (soundproofing)

Soundproofing products are assembled into wall, floor, or ceiling assemblies in a way to maximize the assembly’s ability to block sound.  Soundproofing products individually are not used, they only work in proper assemblies. Soundproofing products generally are ineffective for creating sound absorption in a room.

Metric that characterizes an assembly’s ability to block sound is called Sound Transmission Class (STC).  A related metric designed to characterize assembly’s ability to block impact noise (footsteps, dropped objects) is called Impact Insulation Class (IIC).

About using both soundproofing and sound absorption

For a complete room design, for example a home theatre, a proper soundproofing must be installed to prevent external noise interfering with use of the room, or to prevent noisy audio programs disturbing others in adjacent spaces.  To make the home theatre functional and the sound of the programs pleasant, room treatment (sound absorption) need to be included in the room design.  Both functions, soundproofing and room treatment, are separate parts of the overall room design.  Each has a different purpose and different effect on the functionality of the space.

Complexity of soundproofing and sound absorption

The above information is concise and simplified. Noise reduction (the effect of soundproofing) and sound absorption are highly dependent of frequency of sound. Sound normally consists of many frequencies simultaneously. The products require expertise to use properly.

Soundproofing is not a do-it-yourself project, unless you are prepared to study all aspects of the problem and understand how to make it work.  Repairing a botched soundproofing job usually requires ripping the incorrect assembly out and starting from scratch, paying for the job twice.

In most cases, it is best leaving the job to an expert. To contact a professional engineer for advice about soundproofing or room treatment, use the button below. To get a soundproofing estimate from a specialized contractor contact City Soundproofing.

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About the Author Ivan Koval

The author is the publisher of the Soundproofing.Expert website. He is a soundproofing and building acoustics consultant working in Toronto and GTA, Ontario, Canada. Telephone (416) 471-2130

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