Modular Wall Tiles Sound Absorption Ratings David Hurtado Oct 22, 2026 Table of Contents When two modular wall tile submittals both list an NRC of 0.70, a specifier evaluating an open-plan claims office assumes the acoustic performance is interchangeable between them. The acoustic consultant’s reverberation time model says otherwise: once installed, one tile measurably outperforms the other in the low-frequency range that matters most for speech masking near workstations. The published number was correct. What differed was the test condition behind it. That same gap shows up again during a submittal review for a corporate reception build-out, where a manufacturer’s cut sheet for its modular wall tile collection lists two NRC values side by side for what looks like one product, 0.55 and 0.80, with no obvious explanation for why a single tile would carry two ratings. For a design team working against a reverberation time target set by code or by an owner’s acoustic consultant, picking the wrong number off that sheet can mean the difference between a space that measures correctly at commissioning and one that requires a change order. Both scenarios come down to the same root cause: NRC and SAA are not properties of a tile the way thickness or color are. They are the output of a specific laboratory test, run under a specific mounting condition, on a specific sample of the product. Reading a modular wall tile’s acoustic rating correctly means understanding what that test actually measured and under which conditions it was measured. NRC and SAA: Two Different Math Problems From the Same Test Data Before comparing two products’ absorption ratings, it helps to know that NRC and SAA come from the same underlying lab measurement, a set of sound absorption coefficients recorded at one-third-octave frequency bands, but they condense that data differently. Noise Reduction Coefficient (NRC) NRC averages the absorption coefficients measured at four frequency bands, 250, 500, 1,000 and 2,000 Hz, and rounds the result to the nearest 0.05. It has been the standard single-number rating for acoustic wall and ceiling products for decades, which is why most modular wall tile data sheets still lead with it. Its narrow four-band average is also its main limitation: a tile engineered to perform well specifically in those four bands can post a strong NRC while absorbing poorly below 250 Hz or above 2,000 Hz, ranges that matter for mechanical hum and higher-pitched office chatter respectively. Sound Absorption Average (SAA) SAA is calculated from twelve one-third-octave bands between 200 and 2,500 Hz and rounded to the nearest 0.01, giving a finer, wider-spectrum picture of the same tile’s performance. Two products can carry an identical NRC and still show a measurable SAA gap once the additional bands are factored in. Some manufacturers now publish both numbers on the same data sheet for exactly this reason, and a specifying team comparing several tile lines side by side should check that it is comparing NRC to NRC and SAA to SAA, not treating the two figures as interchangeable. Inside the ASTM C423 Reverberation Room Test What the Test Chamber Actually Measures Both NRC and SAA come from the same laboratory procedure. The lab measures how quickly broadband sound decays in an empty reverberation chamber, then installs the tile sample and measures the decay rate again. The difference between the two decay rates at each frequency band, converted to an absorption coefficient, is the tile’s contribution to the room’s total absorption. A faster decay with the specimen installed means the tile is absorbing more sound energy at that frequency. Specimen Size and Mounting Frame Prep The test method calls for a specimen large enough to behave like a continuous installed surface rather than a small isolated sample, commonly an array sized around eight by nine feet for flat modular products, mounted according to one of several standardized mounting conditions defined in a companion standard for specimen mounting. That mounting condition, not just the tile’s own material properties, is what the rest of this comparison depends on. How Perforation Percentage and Pattern Change the Measured Rating Open Area and Hole Diameter For a perforated modular wall tile, the percentage of open area and the diameter of each perforation largely set the frequency range where the tile absorbs best. A higher open-area percentage with smaller, closely spaced holes tends to push absorption higher across the mid and upper frequencies captured in the NRC calculation, while a lower open-area tile with larger holes shifts absorption toward lower frequencies but can reduce the coefficient at any single band. Two tiles that look visually similar from a few feet away can carry noticeably different NRC values once the open area and hole size behind the facing change. Pattern Layout and Hole Spacing Perforation pattern and spacing matter almost as much as percentage. A perforated wall board panel with holes clustered densely in one zone and sparse in another will not test the same as one with an even grid at the same nominal open-area percentage, because the reverberation chamber measures the sample as installed, pattern included, not as an averaged material property. When a submittal lists a single open-area percentage without naming the actual pattern tested, that percentage alone is not enough to predict the published rating. How Core Material and Backing Change the Measured Rating Fiber Density and Thickness Underneath the perforated or textured facing, the tile’s absorptive core does most of the acoustic work. A thicker, lower-density fiber core generally absorbs more low-frequency energy than a thin, dense one, which is why two tiles with identical facings and perforation patterns can still carry different published NRC figures if their cores differ. A vertical felt wall paneling product and an acoustical felt wall panel built on the same general concept can land at meaningfully different ratings once core thickness is factored in. Facing and Finish Layers A fabric scrim, a printed laminate, or a wood-grain finish sits between the perforations and open air, and each layer adds a small amount of flow resistance that changes high-frequency absorption slightly. A wood-look acoustic wall tile still relies on the same perforated-core mechanics underneath that finish layer, which is why its published rating should always be checked against the specific finish and core combination tested, not assumed to match a plain-faced version of the same core. Mounting Type: Why the Same Tile Tests Differently, Type A vs Type E Of all the variables behind a published rating, mounting type has the single largest effect on a modular wall tile’s low-frequency absorption, because it changes how much the panel itself can flex and how much air space sits behind it during the test. Type A: Direct Surface Mount Type A mounting places the test specimen directly against the hard reverberant test surface, with no air space behind it. This represents how a modular wall tile is installed when it is adhered or clipped flush to a solid substrate such as masonry or an existing finished surface. Direct mounting generally produces the lowest low-frequency absorption in a given tile’s test series, since there is no air cavity behind the panel to extend its effective absorption range downward. Type E: Mounted With an Air Space Type E mounting introduces a defined air space behind the specimen, commonly furred out on a specified depth of blocking or studs. The same tile tested under Type E mounting will typically show a meaningfully higher NRC than the identical tile tested under Type A, because the air cavity behind the panel extends useful absorption into lower frequencies the direct-mount condition cannot reach. A manufacturer’s data sheet showing two different NRC values for what looks like one product is very often reporting Type A and Type E results side by side rather than two different tiles. Reading and Comparing Published NRC Data Sheets None of this is useful to a specifier unless it changes how a data sheet gets read. The practical habit worth building into any submittal review is checking the mounting type footnote before comparing one tile’s NRC against another’s, since the two numbers are only comparable if both were tested the same way. The same discipline applies whether the product in question is a modular wall tile or any other acoustic wall and ceiling treatment the consultant has modeled into the room. Mounting ConditionInstallation Condition It RepresentsTypical Effect on Low-Frequency AbsorptionWhere It Shows Up on a Data Sheet Type A, direct mountTile adhered or clipped flush to a solid substrate with no air gapLowest of the mounting series for a given tileDefault or only value listed on most cut sheets Type E, mounted over an air spaceTile furred out over studs or blocking with a defined cavity behind itMeaningfully higher than the same tile under Type AListed as a second value, or footnoted as an alternate mounting No mounting type statedUnknown, cannot be assumedCannot be compared to a competitor’s stated-mounting valueShould be requested from the manufacturer before specifying The same discipline applies when a design team is referencing felt wall panels for commercial spaces and the acoustic consultant’s spec calls out a minimum NRC under a named mounting condition. Confirming that the manufacturer tested under that exact mounting type is the only way to know whether an installed modular wall tile system will hit the reverberation time target a consultant modeled, and that confirmation ultimately traces back to the lab report generated under ASTM C423, the reverberation room test method that produces every NRC and SAA figure on the market. Conclusion A modular wall tile’s published NRC or SAA is not a fixed property of the material. It is the result of a specific test, run under a specific mounting condition, on a specific sample. Checking which mounting type, which perforation pattern, and which core and facing combination a published number represents is what turns a cut sheet figure into something a project can actually be specified against with confidence. FAQ Is a higher NRC always better for a modular wall tile? Not necessarily on its own. NRC averages only four frequency bands, so a tile optimized to perform well in those specific bands can post a high NRC while offering little absorption outside them. Matching the rating to the frequency range of the actual noise problem in the space matters more than chasing the highest single number. Can a specifier request a specific mounting type’s test data from a manufacturer? Yes. Reputable manufacturers test their tiles under more than one mounting condition and can provide the underlying lab report, not just the summary NRC, on request. That report will state the exact mounting type used, which is the only way to confirm two products are being compared on equal terms. Is SAA replacing NRC in acoustic specifications? Not entirely. Some specifications and acoustic consultants have shifted to SAA because its twelve-band calculation gives a more complete picture, but NRC remains common enough that many modular wall tile data sheets still list it first, with SAA included as a secondary figure. Why do two products with the same published NRC behave differently once installed? The most common reason is mounting type. A tile tested under Type A direct mount and installed the same way should perform close to its published number, but if the installed condition actually includes an air gap behind the panel, or the published number came from Type E testing while the installation is direct-mounted, the real-world result will not match the data sheet.