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Acoustics for operable partitions and operable walls

Operable Partitions and acoustics (sound separation) go hand in hand. In fact many would say that  acoustic control is the number one customer consideration when selecting an operable partition supplier. And the way that virtually all partition suppliers attempt to prove to the customer  that their partition will minimize the transfer of sound is by the submission of a test showing an STC value – anywhere from the high 40’s to the mid 50’s. Subsequently the recipient looks at the number, compares it to other suppliers under consideration and assumes that the higher the number the better the ability of the wall to stop sound transference.

Wrong assumption!   There is much more to a sound test than a high number.



STC is determined by installing a test specimen in a “test assembly” with the typical partition dimensions being 14’ wide X 9’ high and which separates a room having a noise source from a receiving room. The sound transmission loss (STL – the difference between the sound level in the source room and the receiving room) - is measured at different sound frequencies (Hz) with the results plotted on a graph in order  to calculate the STC using a specific procedure and formula. The higher the calculated STC the more quiet it is in the receiving room. The procedure is named ASTM E-90. The E-90  test procedure is regularly reviewed and sometimes “changed” with the year the change takes place designated by a suffix: for example E-90-04 would indicate that the procedure was modified in 2004. The standard has been revised several times over the years but since it is definitely not reasonable to expect that  manufacturers  re-test their products every time a revision occurs, a generally accepted rule of thumb has evolved. That is that one can with confidence accept ASTM E-90 sound test results as being equal if the tests submitted are no more than 3 test procedures of each other in an upward progression with the earliest as the comparative choice. The latest E-90 test is E-90-09. The three previous are E-90-99, E-90-02 and E-90-04.  These 4 procedures would be considered as equals.

  1. STC testing  not conducted as per E-90-09, E-90-04, E-90-02 and E-90-99 should not be viewed as being acceptable as proof of acoustic quality. All Moderco sound tests were conducted using one of these procedures however other manufacturers are using much older test procedures such as 90 -70 (46 years old), 85 (31 years old) & 90 (26 years old).Moderco suggests that you review all sound test procedures as  to what year the test was conducted to ensure acceptable acoustic results in the field.
  2. Credible sound tests contain a description of the partition tested including materials, acoustic seals, closure method. Read the body of the sound test and compare the material description to what the supplier is proposing. Some manufacturers will have tested, for example, a steel skinned panel and propose to supply a gypsum board or MDF skinned panel. Not the same and not the same results in the field. Moderco will never change the composition of the panel tested as it relates to the STC sound test we submit: materials will be one and the same.
  3. Until recently the industry standard test opening size and number of panels tested has always been 14’ wide X 9’ high – 126 sq. feet. But the ASTM E-90 test procedure is weak in that it does not specify a minimum size, just a minimum dimension, for the partition with a  minimum of two panels.  One major manufacturers have recently tested their partitions using only two panels approximately 89” high by 48” wide totaling approximately 59 square feet or 2 panels and 67 square feet less than Moderco. This unorthodox procedure is to minimize the length and number of panel joints with the sole purpose being to artificially elevate the STC. Ensure that the partition you are considering has been tested in a conventional size opening (14’ X 9’) in order to acquire quality acoustic results in the field. All Moderco partitions have been tested in a 14’ X 9’ test opening.

Call Moderco so that we can visit with you to review our sound tests and if you wish compare them to others you may have. 1 800 363-3150

Thank you for considering Moderco as your operable partition supplier.