I often find myself explaining this question to my clients. Unfortunately, many people need clarification on these two terms or help understand their meaning. Confusing information is also propagated on the Internet; an example is here.
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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) prevents sound from getting into a room that should be quiet.
Where is sound absorption used?
Materials that reduce sound reflections within a room are referred to as acoustic treatments. Unlike soundproofing materials, which block sound transmission between rooms, acoustic treatments are designed to absorb sound energy within the space itself.
They improve speech intelligibility, reduce echo and reverberation, and create a more pleasant and functional acoustic environment. Common examples include fabric-wrapped panels, acoustic ceiling tiles, bass traps, and diffusers.
Acoustic treatments are typically used in spaces such as home theaters, recording studios, offices, restaurants, classrooms, and other environments where clarity, comfort, and controlled sound quality are desired.
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Where is soundproofing used?
The process of soundproofing involves creating a barrier between the noise source and the space that requires quiet. The goal is to block or isolate sound transmission, preventing unwanted noise from entering or leaving a room.
Effective soundproofing relies on four key principles:
Mass – Heavier materials block more sound.
Decoupling – Separating structures prevents the transfer of vibration.
Damping – Specialized compounds reduce resonance and vibration.
Airtightness – Sealing all gaps and penetrations stops sound leakage.
Soundproofing is used when the objective is to create quiet, private, or acoustically isolated spaces, such as home theatres, recording studios, bedrooms near mechanical rooms, or offices requiring speech privacy.
Knowing the difference between sound absorption (acoustic treatment) and sound blocking (soundproofing) is crucial if you need to select 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 hung 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). Unfortunately, these products only slightly affect the overall noise in the room and are ineffective for soundproofing.
A 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 to maximize the assembly’s ability to block sound. Soundproofing products individually are not used; they only work in proper assemblies. As a result, soundproofing products generally are ineffective for creating sound absorption in a room.
A metric that characterizes an assembly’s ability to block sound is called Sound Transmission Class (STC). A related metric designed to describe an 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—such as a home theatre—proper soundproofing must be installed to prevent external noise from interfering with the use of the room, and to ensure that loud audio playback does not disturb adjacent spaces. Soundproofing provides the noise isolation necessary for privacy and acoustic control between rooms.
In addition to soundproofing, room acoustic treatment (sound absorption and diffusion) must be included to make the theatre functional and acoustically balanced. Acoustic treatment enhances the listening experience by controlling reflections, reverberation, and tonal balance within the space itself.
Both soundproofing and acoustic treatment are essential but distinct components of a successful acoustic design. Each serves a different purpose and contributes differently to the overall functionality and comfort of the space:
Soundproofing controls sound transmission between rooms.
Acoustic treatment controls sound behavior within the room.
A well-designed home theatre integrates both systems to achieve optimal performance, comfort, and usability.
Complexity of soundproofing and sound absorption
While the basic concepts of soundproofing and acoustic treatment can be simply described, their practical application is complex. Both noise reduction (soundproofing) and sound absorption (acoustic treatment) depend heavily on the frequency characteristics of the sound being reduced or absorbed.
Sound is rarely composed of a single frequency—it typically contains a broad spectrum ranging from low-frequency vibrations to high-frequency reflections. Materials and assemblies respond differently across this range; a product that performs well at mid or high frequencies may provide little attenuation at low frequencies. For this reason, specialized knowledge and experience are required to select, design, and install the appropriate materials and systems.
Although some soundproofing concepts may appear suitable for do-it-yourself application, successful implementation demands a comprehensive understanding of acoustic principles, construction methods, and material behaviour. Inadequate design or installation often results in poor performance, wasted expense, and client dissatisfaction.
In most cases, repairing an improperly executed soundproofing job necessitates removing the existing assembly and rebuilding it correctly from the framing outward—effectively doing the project twice. Engaging a qualified soundproofing specialist or acoustical consultant at the design stage can prevent these costly and disruptive errors.
In most cases, it is best to leave 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.
