SOUNDBLOX and SOUNDCELL ACMUs are practical solutions to suppress problem noise and improve the acoustical atmosphere

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SOUNDBLOX and Sound Cell ACMUs are Structural/Absorptive/Barriers. They positively improve sound quality of interior rooms and outdoor environments and provide structure for walls and buildings with inherent performance advantages.

Improve Sound Quality SOUNDBLOX and Sound Cell ACMUs are practical solutions to effectively suppress problem noise and thus improve the acoustical atmosphere for safe, affable, human occupation. ACMUs provide healthier acoustical environments via two means of treating unwanted noise:
1) reduce noise within an enclosed space through absorption and diffusion of sound energy within its core matrix, and
2) suppress noise transmission to an adjacent room or space by structuring a robust sound barrier.

Provide Structure
SOUNDBLOX and Sound Cell ACMUs are utilized to construct versatile structures. ACMUs provide permanent walls comprising system performance characteristics and benefits not found with other wall systems and acoustical improvement products:
1) Strong, load-bearing (ACMU walls can support tons of structural loads)
2) Structural stability (ACMU walls can provide rigid shear strength to withstand wind loads)
3) Fire resistant (Fire-resistive-ratings from 1 to 4 hours may be attained)
4) Tough, hard-wearing (wear & tear, abuse, and vandal resistant)
5) Minimal maintenance (only an occasional cleaning)
6) Durable (Last for the life of the structure or building)
SOUNDBLOX and Sound Cell – three-fold performance: Structure/Absorption/Barrier within a single component acoustical wall system.

Noise Reduction
Problem noise within a room or enclosed space
is primarily addressed by means of noise reduction through sound energy absorption. Various acoustical materials attempt to dampen sound annoyances, but thin, add-on, acoustical treatments typically do not have the depth of absorption required to capture noise at the low-end of the audible frequency bandwidth. A good means to achieve sound absorption at all frequencies is with Helmholtz resonators.

Helmholtz resonators consist of a rigid structure encompassing a volume of air that is connected to outside air via a small opening or slot. As air or noise flows between the coupled atmospheres through the aperture, it results in a resonance effect on the cavity. This Helmholtz effect can be seen when one blows air over the opening of a bottle thereby creating a resonant tone; or when a slightly opened sunroof in a fast-moving car causes the passenger compartment to acoustically resonate resulting in loud, vibrating noise. The Helmholtz resonator is the core of SOUNDBLOX and Sound Cell ACMUs. Configuration modifications and augmentations are made to enhance the effectiveness of these concrete acoustical resonators.

The Sound Cell and ACOUSTADE models work by forming slot-type, stacking, volume resonators. The SOUNDBLOX models work by forming slot-type, single cavity or sequential, box resonators. All models comprise fillers that are additive impedance modifications to improve absorption across broader Hz frequencies.

SOUNDBLOX and Sound Cell Helmholtz resonator ACMUs are designed to effectively capture and eliminate problem noise at all frequencies – including absorption efficiency at low bandwidth. (Example: the 12” Sound Cell and ACOUSTADE stacking, volume resonators offer and unmatched 100% absorption average absorption efficiency at the 100-125-160-200 Hz frequency bandwidth. This low frequency absorption is invaluable in supplying sound control that cannot be captured by carpets, surface treatments, acoustical tile, and related products.

Fibrous filler inserts are added to SOUNDBLOX and Sound Cell ACMUs to improve mid-range and upper-range frequency noise absorption. Metal septa are added to divide cavity spaces within SOUNDBLOX, which further increases sound absorption. Grout shield inserts are added to form a cavity space within 12” Sound Cell units for placing vertical steel reinforcement and grout. Galvanized steel septa inserts are added to the SOUNDBLOX type Q unit to improved low-range frequency absorption.

Fibrous Fillers

Semi-rigid, fibrous filler elements are utilized to increase SOUNDBLOX and Sound Cell noise reduction performance. They are placed within the ACMU’s cavities during factory manufacturing. The fillers are composed of incombustible fibrous glass material and are inorganic, which will not deteriorate, rot, or support mildew. SOUNDBLOX utilize black-colored fiber inserts, because of their visual proximity to the apertures; Sound Cell utilizes standard-yellow, noise attenuating fiber inserts due to their invisibility—away from the apertures. Both semi-rigid fibrous fillers will temporarily hold water within their pore structure if wetted, but moisture typically drains and evaporates rapidly once the filler elements are exposed to dry conditions.

Poly Encapsulation Wrap

In areas of repeated wetting, i.e. all outdoor applications, or of constant high humidity, e.g. natatoriums, water treatment facilities, etc. it is recommended to specify the fibrous fillers beencapsulated and sealed within 2 mil polyethylene plastic film. The poly wrap option does not reduce the sound absorption qualities of the filler elements.

Metal Foil Septa
Placing a metal septum within a SOUNDBLOX cavity divides the resonator hollow acoustically into two different sized resonators, which further increases sound absorption. Low frequency passes through the fiberglass filler, vibrating the foil septum and is absorbed by the mass of concrete in the sequential absorbing chamber. The metal foil septa are laminated to a single face of thesemi-rigid, fibrous fillers, which are installed as a unit into the ACMUs during factory manufacturing with the metal foil septa facing toward the rear of the SOUNDBLOX ACMUs. Because SoundCell ACMUs are stacking volume type resonators – with unmatched 100% average absorption efficiency at the 100-125-160-200 Hz frequency – they do not require metal foil septa to increase low frequency absorption.

Grout Shields

Grout shields are made of high-density, tempered hardboard and are utilized in 12" Sound Cell units where vertical wall reinforcement is required. They are placed in the AMCUs in the field by the masons during installation; only as often as vertical steel and grout is required, e.g. 2’-8” on-center, 4’-0” on-center, etc. When a grout shield is placed in the cavity space of a Sound Cell unit, it creates a rear chamber suitable for reinforcement and grout while maintaining the sound- absorbing characteristics of the front portion of the unit.

Galvanized Steel Septa

SOUNDBLOX Type “Q” units have narrow slots and uniquely comprise 28-gauge galvanized steel septa without fibrous fillers. These steel inserts are purposed to perform like the metal foil septa utilized by other SOUNDBLOX units, but offer greater low-frequency absorption. The Type Q units offer a peak 100% absorption of unwanted noise at the 125Hz frequency range.

Yes; there are acoustical advantages to using Stout-Face units.Read More Here

Acoustical Testing

Laboratory tests are performed on various building materials to determine their effectiveness at abating and partition attenuating airborne sound. ASTM C423 – 09a is a Standard Test Method for determining Sound Absorption and Sound Absorption Coefficients of material assemblies. Test results are provided listing the assembly’s noise reduction coefficients (NRC) and related sound absorption averages (SAA), which is a rating of their efficiency.

ASTM E90 - 09(2016) is a Standard Test Method used for measuring a building material’s ability to partition sound and prevent it from transmitting from one space to another. It measures the airborne sound transmission loss of building partitions such as walls of all kinds, floor-ceiling assemblies, doors, windows, and other space-dividing elements. Sound transmission loss ratings are provided listing the Sound Transmission Class (STC) of the materials tested.

Noise Reduction Coefficient – NRC Sound absorption tests measure the sound reduction capabilities of a material by how well it either absorbs or reflects sound energy. Noise Reduction Coefficient (NRC) are unit measures indicating a product’s sound absorption qualities. An NRC rating of 0.00 indicates zero sound absorption and 100% reflection; an NRC rating of 1.00 indicates 100% absorption with no refection occurrence. Ergo, the higher the NRC measurement, the more absorptive the material is.

The NRC is calculated by averaging four mid-range sound absorption coefficients at frequencies: 250 Hz, 500 Hz, 1000 Hz and 2000 Hz, rounded to the nearest 0.05 increment. These frequencies represent the general hearing acuity of human speech and thus the NRC provides a simplistic number of how well a material will absorb the human voice.

Specifications for acoustical materials typically include an NRC, but its practical use may be limited when assessing its effectiveness at controlling problem noises. A broader frequency range is required for most other sound attenuation, e.g. music, school and work-place noise. Additionally, concentrated problem noises are produced by amplified music and mechanical equipment, e.g. pumps, transformers, and generators having substantial low-frequency energy below the NRC targeted frequencies.


Sound Absorptive Average – SAA

A more useful single number rating obtained from ASTM C423 testing is the Sound Absorption Average (SAA). It is the average of the twelve sound absorption coefficients for the frequencies from 200 Hz to 2500 Hz, rounded to the nearest 0.01 increment. Superseding the NRC, the SAA provides a broader scope of a materials ability to absorb sound. As with the NRC value, the higher the SAA value, the better the material absorbs sound.

Sound Transmission Class – STC

Sound partitioning tests determine how well a building product or assembly performs as a barrier to airborne sound passing through it. This airborne sound reduction efficiency is expressed as Sound Transmission Class (STC). The STC is a "one-number" average derived from sound attenuation values tested at sixteen standard frequencies from 125 Hz to 4000 Hz and indicate the product's sound barrier qualities.


Utilizing dense, weighty, mass-laden materials are the most effective means to design and construct walls to prevent problem noise from transmitting from one space to another. Poured concrete and concrete block walls achieve significantly higher STC values than equally thick wood or metal framed walls.

Even though SOUNDBLOX ACMUs have slots in one face shell, they still have slightly better sound transmission loss than ordinary hollow CMUs of the same thickness and composition, because of theacoustical effects of the resonator mechanism and their heavier-than-normal, solid-top configuration. Although the primary function of SOUNDBLOX ACMUs is sound absorption, they can also be utilized as effective sound barrier.

Think of SOUNDBLOX and Sound Cell ACMUs as substitutions for the typical stretcher configuration of regular Concrete Masonry Units (CMUs); but with added built-in noise controlling features. If a concrete masonry wall is properly designed for structural stability comprising needed reinforced pilasters, columns, bond beams, etc., then the regular stretcher CMUs in the design may be substituted with SOUNDBLOX or Sound Cell units, as they will perform similarly in strength, shrinkage, absorption, etc. when made with identical cement/aggregate mix design.

Neither SOUNDBLOX nor Sound Cell ACMUs are available with finished outside corners; with solid bottoms for use at door heads or for bond-beams; nor are they made as half-long block, as steel-sash units, with bull-nose corners, etc.

Architectural finishes are optional on SOUNDBLOX units, including: scoring, burnished-face, split-face, and Decro-Face®. Because SOUNDBLOX are made with (2) partial interruptions of the face-shell plane, which slightly reduces the bedded area; yet are made in a solid-top configuration, which adds strength and stability, the units have been allowed 90% of the shear value of ordinary hollow concrete masonry units of the same thickness. International Conference of Building Officials Research Recommendation No. 2539 and Los Angeles Department of Building and Safety Report No. RR 23609

Sound Cell ACMUs have aperture reductions occurring in the cross webs instead of the face-shell plane and the bedded area is greater than required. As such, axial and flexural stresses are lower on the Sound Cell unit than on a standard stretcher configuration CMU, and is considered an equivalent structural masonry unit. Theoretical Stress Analysis white-paper explanation

Yes, SOUNDBLOX and Sound Cell ACMUs are load-bearing concrete masonry units and they may be utilized in most applications where regular CMUs are installed with the purpose of supporting building live and dead loads.

Extended White-Paper Explanation Yes, SOUNDBLOX, Sound Cell, and Acoustade AMUs meet, or more often exceed, the minimum requirements of ASTM C90 Standard Specification for Loadbearing Concrete Masonry Units. They are Structural, Load-Bearing CMUs and will provide comparable physical characteristics, i.e. density, absorption rating, and net area compressive strengths as standard hollow concrete masonry units made with identical materials, manufacturing process, and curing methods.

It is recommended to seek the assistance of acoustical design professionals to formulate the best solution for improving acoustics, but for simple noise reduction, consider the following: It is recommended to seek the assistance of acoustical design professionals to formulate the best solution for improving acoustics, but for simple noise reduction, consider the following: Start with examining the nature of the noise issue. Determine the anticipated sound pressure strength and frequency intensity levels of the sound source. If designing enclosures for pumps, generators, chillers, etc. the manufacturers of the equipment should have sound data available. If designing walls surrounding gymnasiums, cafeterias, auditoriums, worship centers, etc. generalized charts can be accessed on the internet.

Next, compare the noise source frequency levels you are trying to absorb to the noise reduction coefficient levels of the absorptive product to determine its effectiveness at reducing the noise frequencies generated. It is a mistake is to simply assume a product with the highest Noise Reduction Coefficient (NRC) number will be the best absorptive material to use to curtail a noise problem. As an example, even though an acoustical tile may attain a high NRC rating of .70 because it performs well from 250 – 2,000 Hz, it could be inadequate at capturing low-frequency noise if it has little or no absorption at 250 Hz and below.

If noise source level measurements indicate a pronounced peak at a specific frequency or range of frequencies, the unit with the highest sound absorption coefficient at those frequency is usually the best choice, but other application and use factors that should be considered:

Interior Walls

Good sound level absorption is achieved over a wide frequency range with the following ACMUs, which are appropriate for interior applications:

Sound Cell

Exterior Walls

ACMUs may be utilized for exterior applications. SOUNDBLOX ACMUs are manufactured in a solid-top configuration and are laid with the slots facing downward, so rain or snow entering the apertures will flow back out of the openings; what little may pool on the surface will eventually evaporate. Acoustade and Sound Cell units are hollow-cored, stacking resonators. Water entering these units will flow downward to the bottom supporting structure where flashing material should be installed to direct water back out.

When designing for outdoor applications, it is recommended, but not required, the ACMUs and the mortar to lay them, shall be treated with integral water repellent; and the fibrous filler inserts shall be encapsulated and sealed within 2 mil polyethylene plastic film. In areas of constant high humidity, such as a natatorium, the use of fibrous fillers sealed in 2 mil polyethylene bags is an available option and is recommended..

Sound Cell

Reinforced Masonry

These ACMUs provide straight-through cavities at the rear portion of the units, allowing them to be specified in applications requiring vertical reinforcing, or for providing accommodations forvertical conduits and/or pipes.

Acoustade – 12” with Grout Shield
SOUNDBLOX Type RSC/RF – 12”, 10”, 8”
Sound Cell – 12” with Grout Shield

Low-frequency Absorption

SOUNDBLOX Type A-1 units have narrow slots, unified cavities, and are installed without any fillers or septa. SOUNDBLOX Type Q units have narrow slots, unified cavities, and 28-gauge galvanized steel septa. Both the Type A-1 and Q units are designed for optimum absorption at the 125 Hz low-frequency range. Both Acoustade and Sound Cell ACMUs form stacking volume type resonators, which offer 100% average absorption efficiency at the 100-125-160-200 Hz frequency range.

Sound Cell


Style, texture, and relief can be achieved with Sound Cell’s visually attractive grid pattern; Acoustade ACMUs provide a striking vertical wave design; and various architectural finishes are optional on SOUNDBLOX units, including: scoring, burnished-face, split-face, and Decro-Face®.

Sound Cell

Diffusion / Flutter Echo / Standing Wave – Resonate Frequency

When designing spaces with hard surface walls, e.g. concrete, masonry, drywall, etc. the room can become reverberant, causing a significant build-up of noise. Introducing diffusion (the random reflection and dispersion of sound after striking irregular surfaces and reliefs) will improve sound quality. Square rooms with parallel surfaces support standing waves (notes and noises are sustained louder and longer), which fall primarily in the bass (low frequency) range. Walls constructed further apart than 30 feet may result in flutter echo (high frequency ringing or buzzing). These ACMUs are designed to alleviate these aforementioned noise concerns: Acoustade----Sound Cell----SOUNDBLOX Type RSR

How many SOUNDBLOX and Sound Cell ACMUs should one use?

Again, it is best to use the services of an acoustical consultant to appraise the unique conditions involved with any particular project. There are no absolute rules to determine coverage, but as simple as it sounds, the more ACMUs that are installed, the more sound will be absorbed. However, diminishing returns will be experienced as the coverage grows over a certain point. A basic rule of thumb is to calculate the cubic foot volume of the room and multiply this number by 3% to determine the square foot coverage of noise attenuating material needed for improved acoustics. E.g. a 40’ x 80’ room with a 20’ ceiling would require 1,920 sq.ft. of ACMUs.

For rooms with variable noise sources, e.g. gymnasiums, cafeterias, etc. or rooms with a central noise sources, e.g. pump and generator rooms, it doesn’t make much of a difference where the ACMUs are placed as long as they are spread out evenly around the room.

For auditoriums, theatres, etc. sound absorption is best placed on the rear wall along with combination diffusion/absorption ACMUs, i.e. Sound Cell and Acoustade being placed on the side walls.

For school classrooms, gymnasiums, and other public buildings, it is recommenced that SOUNDBLOX ACMUS be installed above door height, to prevent fingers from sticking into the apertures and injury occurring. With Sound Cell’s depressed aperture openings, this is not a concern.

Yes, both SOUNDBLOX and Sound Cell provide for vertical reinforcement. These ACMUs provide straight-through cavities at the rear portion of the units, allowing them to be specified in applications requiring vertical reinforcing; or for providing accommodations for vertical conduits and/or pipes.

The 8", 10", and 12" SOUNDBLOX Type RSC/RF units and SOUNDBLOX Type 12” RSC/RF4 have an integrally formed rear cavity spaces, while the Sound Cell and Acoustade ACMUs require field installed grout shields to be placed only as often as vertical steel and grout is required, e.g. 2’-8” on-center, 4’-0” on-center, etc. Sound Cell Wall Section - Reinforcing

The 12” RSC/RF comprises a 6” sound absorbing chamber with closed top in the front portion of the unit, with a 6” open cell space formed in the rear. It has an NRC of .85. This unit is the preferred unit for greater noise absorptions.

The 12” RSC/RF4 comprises a 4” sound absorbing chamber with closed top in the front portion of the unit, with an 8” open cell space formed in the rear.

It has an NRC of .80. This unit is used in states like CA and FL that have seismic and hurricane specifications requiring the larger 8” open cell space for the placement of reinforcing and grout. Both units are available with a split face on the exterior for single-wythe construction.

No, none of the SOUNDBLOX and Sound Cell styles are available in half-long block configurations.

Nor is it recommended to cut any of the SOUNDBLOX ACMUs in half to form half-long units. Although cutting a SOUNDBLOX unit will only result in a slight change in the sound absorbing properties, it may compromise the structural integrity of the unit and resulting wall. Sound Cell and Acoustade units may be cut to form half-long units without structural compromise.

YES. Both SOUNDBLOX and Sound Cell ACMUs may be painted with an interior latex paint without reduction of noise absorption characteristics. Utilizing a heavy block fill paint or heavy glazing on the sound absorbing face (aperture side) may reduce high-frequency absorption. Heavy masonry paint may be utilized – and is recommended – on the back, non-aperture side of the wall.

It is recommended that SOUNDBLOX ACMUs be painted with a roller, because if paint is sprayed it may enter the apertures and paint over the black acoustical filler inserts. With the acoustical inserts installed back-and-away from the aperture opening, both Sound Cell and Acoustade units may be spray painted without paint clogging their surface.

Yes, but with precautions. SOUNDBLOX Type A-1 and Type Q units, as well as Sound Cell and Acoustade ACMUs may be hosed down with water or steam-cleaned. Other SOUNDBLOX units incorporating fibrous filler insert immediately adjacent to the apertures should not be used in areas that are to be hosed or steam-cleaned due to the possibility of dislodging the filler from its precise placement in the unit.

The optional Spectra-Glaze® finish is readily cleaned as well. Dust and dirt may be vacuumed from the cavities if necessary. In areas of constant high humidity, such as a natatorium, the use of fibrous fillers sealed in 2 mil polyethylene bags is an available option and is recommended.

Fire resistance rating are determined by the aggregate mix-design utilized to manufacture the ACMUs and then calculated by using “FIRE RESISTANCE RATINGS OF CONCRETE MASONRY ASSEMBLIES NCMA –Tek Bulletin 7-1C.” SOUNDBLOX and Sound Cell ACMUs Fire Ratings

Yes, but only 12" SOUNDBLOX Type RSC/RF and Type RSC/RF4 units are available with a split-faced back for a decorative single-wythe application

The weight of the ACMUs is dependent on the concrete mix design that is specified and used to manufacture the units, e.g. lightweight, medium-weight, or normal weight. General unit weights are listed here: STC Ratings, Weights, & Fire Resistance Analysis

Please consult the SOUNDBLOX and Sound Cell distributor For Weights and Cost for your project for the specific weights of the ACMUs to be made:

The Stout-Face CMU is similar to the typically produced Horizontal Chamfer CMU, but the chamfered portion is cast solid. The unit is manufactured with 2” smaller-than-normal, off-set cores, which renders one face-shell having a width of 1-1/4” and the other face-shell a stout 3-1/4” in thickness. Stout-Face units are available in 12” widths (shown) and 8” widths for use with 12” and 8” ACMUs.soundcell

The Stout-Faced units are utilized as transitional coursing between regular CMUs and Sound Cell or Acoustade units in order to provide proper face-shell bearing alignment.
Either Stout-Faced Units, Solid Top Units, or filled Bond Beams will serve as transitional CMUs; and are laid as a masonry course immediately above and below a field of Sound Cell or Acoustade units. Stout-Faced CMUs are laid with the stout face shells towards the aperture opening side of the wall.


Yes; there are acoustical advantages to using Stout-Face units. When Solid Top and/or Bond Beam units are used beneath and above the field of Sound Cell and Acoustade units,
it effectively caps the length of the stacking resonators that these units form.


However, if the Stout-Face CMUs are utilized as bottom (shown) and top transitional CMUs, there is no termination of the stacking resonator. This means the resonator cavity space is notably enlarged by extending continuous vertical cores into the field of regular CMUs. This greater cavity configuration significantly increases the effective noise reduction characteristics of the wall at all frequencies; but especially low frequency absorption.

Need to insert Chart12” Sound Cell & Acoustade ACMUs - Noise Reduction and Sound Absorptive Average (SSA)

Stout-Face CMUs vertical cavity Stout-Face CMUs may also be utilized to allow for vertical reinforcing or vertical pipe chases within the wall cavity.

stout faced

The left-hand and right-hand units were initial solutions for providing a means to incorporate vertical steel reinforcement and grout into a SOUNDBLOX wall. With this system, three block configurations are required to form a wall if the units are laid in a running-bond pattern (see diagrams). The left-hand unit and right-hand unit configurations are yet, and only, available in the following Types

SOUNDBLOX Type A-1 – 8”; Type Q – 8”; Type RSC – 12”, 8”


A more economical and practical means of incorporating vertical reinforcement was developed with the introduction of SOUNDBLOX Type RSC/RF – 12”, 10”, 8” and Type RSC/RF 4units. Their design eliminated the necessity of requiring multiple units by forming the standard unit comprising two (2) straight-through cavities toward the rear, allowing either left-hand, right-hand, or both cores to be filled with reinforcement materials.

R-Value rating are determined by the aggregate mix-design utilized to manufacture the ACMUs, i.e. normal weight or Lightweight units and then computed using “NCMA & ASHRAE Approved Series Parallel R-Value Calculations.” STC ratings, Weights, Fire-resistance analysis; R-Value ratings




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