As Summer begins to wane and attention begins to shift back to indoor living, we at Gravio wish to draw attention to the subject of sound transmission – and how Gravio is a “super material” at reducing sound transmission.
Earlier this month the BBC published a piece featuring the impact of sound and noise on sound-sensitive populations: https://bbc.com/future/article/20250804-inside-the-brains-of-noise-sensitive-people
The reporting notes that noise sensitivity can have long-term impact on both physical and emotional health. 10-40% of the population suffers from noise sensitivity. There is a link between noise and heart disease, diabetes and noise has mental health impacts. The offered solution is for better attention to sound within the built environment.
Which is where Gravio comes in as a superior solution. Since Gravio is created from volcanic ash that is “popped” in at a very high temperature, it has a great deal of trapped air. That trapped air does superbly at absorbing sound energy, thereby reducing sound transmission between walls. In fact, one layer of Gravio applied to a wall generates the same Sound Transmission Coefficient rating as double drywall.
The further advantage of Gravio is that it delivers this sound transmission reduction, while providing a beautiful aesthetic of modern tile or brick, and a Class A fireproof rating.
Below we provide a full primer on sound reduction and how Gravio shines in this regard.
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Physics of sound transmission
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Sound is energy that travels through air, activating atoms. When that sound energy encounters a wall, some is absorbed and bounced back into the room. This is referred to as sound absorption, and can cause effects like echoes. The rest of the energy travels through the wall, referred to as sound transmission. It is that sound which comes out the other side that we are concerned with, for it causes so much trouble with neighbors.
To reduce sound transmission through walls, one must consider the following:
A. Materials:
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- Mass – in general, the greater the mass, the less sound transmits. Lead is one of the best-known materials for reducing sound transmission, but it is not a feasible material to use
- Stiffness – again, in general, the stiffer the material, the more sound will transmit through the wall
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- Depth of air space. The more air space between the walls, the better the sound transmission
- Framing material. In general, steel studs will provide greater sound transmission than wood studs
- Insulation materials. The more insulating materials to slow the transmission of sound the better
- Fastening and Decoupling. Strong and tight fastening helps sound transmit through the wall structure. Decoupling materials (through adhesive or specialized strips) slows the transmission of sound
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What transmits through the wall can be measured as a Sound Transmission Coefficient (or STC) and its determination is governed by ASTM E-90. When these are measured, we have established the following for STCs.
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- STC 25-30: Speech can be easily understood through the partition. This rating is common in residential buildings with minimal soundproofing.
- STC 35-45: Loud speech is audible but less intelligible. This range is suitable for offices or moderately noisy environments.
- STC 50-55: Speech privacy is achieved at normal voice levels, but loud sounds are still audible through the wall. This rating passes the minimum building code requirements for shared walls in multi-family dwellings. This is also a minimum range for sound isolation between hotel rooms.
- STC 60-65: Loud sounds are barely audible. This range is ideal for spaces requiring high levels of privacy, such as luxury condominiums, conference rooms, or executive offices.
- STC 65+: Very high soundproofing, with most sounds virtually inaudible. This rating is used in specialized environments like recording studios or luxury apartments.
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It is generally accepted that an STC of 55 is sufficient for walls between units in a multifamily setting, though standards bodies and zoning commissions are beginning to rethink this in favor of a higher STC rating.
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Common methods for building walls for an increased STC rating include:
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From Japan, we introduce Gravio, a material made by Daiken in Japan from naturally recurring volcanic ash and steel slag (a byproduct of the steel-making process). Daiken places the volcanic ash into an oven, where it pops like popcorn into a much larger volume. The material is placed into a mold, and through a proprietary methodology, a panel emerges that has the appearance of brick or tile. The panels are interlocking with tongue and groove, and are sized 6 feet x 18 high. Installation can be handled by a carpenter.
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The Gravio panels were taken to Riverbank Acoustic Laboratories in Geneva, IL, to test Gravio’s sound transmission absorption capacities. We were amazed to learn that just one layer of Gravio over a standard wall installation provided an STC of 56 – the same as double dry wall on both sides. Gravio does this while delivering a Class A fireproof material that offers superior aesthetics.
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When Gravio was applied to both sides of the wall, we found an even more amazing result, an STC of 59.
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Gravio delivers these superior results, with an aesthetically beautiful finish that is simple to install, and provides the following benefits over gypsum board:
Gravio vs. type x gypsum for a STC 56
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