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Item # 4-A-1
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Soundblox type A1 units have narrow slots and unified cavities. These block are used without any fillers or septa. They are specially designed for low frequency absorption, optimum sound absorption is achieved at 125 hz.

Left-Hand and Right-Hand Units
For situations requiring a full core for vertical reinforcement, SOUNDBLOX units with open cavities on either the left- or right-hand side are available. When used in conjunction with standard SOUNDBLOX units, reinforcing bars and grout can be incorporated easily and efficiently. SOUNDBLOX left-hand and right-hand units have been approved for use in reinforced masonry construction and are allowed 90% of the shear value of ordinary hollow concrete block.

Solid Content & Equivalent Thickness(PDF, 20KB)


16" x 8" x 4"



Exposed Slots




Solid Content

66.2 %

Equivalent Thickness



Sound absorptive concrete masonry units shall be used to construct exterior and interior walls or partitions as shown on the plans and/or indicated in the Schedule of Finishes.


All sound absorptive masonry units shall be SOUNDBLOX made on standard block machines using molds furnished or approved by The Proudfoot Company, Inc., Monroe, Connecticut. They shall be made of carefully prepared aggregate and shall meet the current ASTM C-90 or ASTM C-129 requirements as appropriate. Carefully controlled use of the SOUNDBLOX molds shall be employed so all units have one end of the cavities tightly closed. Slots and edges shall be straight and clean. Where Types a RSC, RSC/RF or RSR SOUNDBLOX units are called for, filler elements as supplied by The Proudfoot Company, Inc., shall be installed in the cavities of the blocks at the block plant. The fillers shall be of specially fabricated incombustible fibrous material, cut accurately to size and installed as recommended. The fillers shall have metal septa laminated to one side of the fibrous material and shall be installed with the septa facing away from the slots. Where 8" Type Q units are called for, they shall have a bare (without fibrous material) metal septum as furnished by The Proudfoot Company, Inc., installed in each cavity in the recommended manner at the block plant.

Sizes and Types

SOUNDBLOX Type A-1 is available in 4" 6"and 8" thicknesses only.


SOUNDBLOX units shall be installed by the General Contractor (or Masonry Contractor) using only mechanics skilled in the laying of masonry blocks. All necessary cutting on the job site shall be performed with power tools in such a manner as to provide straight and true edges. No chipped or broken blocks shall be used. SOUNDBLOX units shall be laid in running bond (or stack bond) with the open ends of the cavities facing downward, and shall be seated in a full horizontal bed of mortar. The slots shall be exposed to the area where the sound absorption is desired as indicated on the plans. Care shall be taken to ensure that the slots are kept free of mortar or debris above the mortar joints. Lines shall be straight and true and the SOUNDBLOX workmanship shall otherwise conform to all requirements of the General Specifications for masonry work.


SOUNDBLOX units may be painted without significant reduction of sound absorption from the values shown which were determined after the faces had already been painted. Lightweight SOUNDBLOX units have substantially more sound absorption when unpainted but - except for split-rib units - few units are ever left unpainted. Walls of SOUNDBLOX units made of lightweight, porous aggregates must be heavily painted with cement base or other sealing type paint on the unslotted side to prevent porous sound trans mission where maximum sound transmission loss is desired. Such painting is also required on ordinary hollow concrete masonry units of lightweight, porous aggregates to prevent porous sound transmission.

Fire Endurance

Fire testing in accordance with ASTM E-119 requirements show fire endurance ratings of up to 3 hours plus for load-bearing walls built of SOUNDBLOX units. Specific details are available upon request.

Code Acceptance

SOUNDBLOX units are approved for use in rein forced masonry construction wherever ordinary hollow concrete masonry units are permitted. This applies to seismic zones as defined under the Uniform Building Code, with 90% of the shear value of ordinary hollow concrete masonry units allowed for the SOUNDBLOX units. (See City of Los Angeles Dept. of Building and Safety Research Report No. RR23609.)
SOUNDBLOX® Type A-1 have been specially designed for low frequency absorption. Optimum sound absorption is achieved in both of these units at 125 Hz. Narrow slots, unfiled cavities.
    Exposed Frequency - Hertz
Size Type Cavities 125 250 500 1000 2000 4000 NRC
4" A-1 2/2 0.12 0.85 0.36 0.36 0.42 0.45 0.5
6" A-1 2/2 0.62 0.84 0.36 0.43 0.27 0.5 0.5
8" A-1 2/2 0.97 0.44 0.38 0.39 0.5 0.6 0.45
The above sound absorption data was determined by tests conducted at Geiger and Hamme Acoustical Laboratory in strict compliance with ASTM C423 specifications. Actual installed performance may vary.
SOUNDBLOX® can be painted and are available in a variety of colors and architectural finishes, including:
  • Ground-Face
  • Burnished
  • Decro-Face®
  • Spectra-Glaze®
Check your local SOUNDBLOX® producer for available architectural finishes in your area.

Decro-Face is a trademark of E.P. Henry, Woodbury, NJ.
Spectra-Glaze® is a trademark of The Burns & Russell Co., Baltimore, MD.