The acoustic resistance capability of an operable wall partition is most definitely one of the criteria of selection used in the field. The acoustic performance is most commonly measured using the STC rating.

WHAT IS A STC RATING?
STC stands for Sound Transmission Class and is a single number quantifier used to rate operable walls, as well as other partitions, windows, etc. The STC is based on calculating how effective the wall or window is on blocking sound.

The STC rating attributed to a specific operable wall partition is the result of a test which represents a best conformance to a set of standards which defines it. Independent to the test environment, the test attributes a number to the partition only, while the resonance and size of the room are taken into consideration.

Based on the frequencies of a person’s speech, the STC rating evaluates the way an operable wall is assembled, which will include all the sound paths of the wall partition.

STC RATING LEVELS OF PERFORMANCE
If a sentence can clearly be understood, than the STC rating is found between 20 and 22. If only individual words and occasional phrases are clearly heard and understood, the STC rating would be between 25 and 27. If a medium loud speech is audible and an occasional word is understood, the STC rating would be close to 35 and 37. At the extreme, in order to effectively block most air-borne sound sources, the STC rating should be over 65.

To give an idea of the impact of a variation in STC rating of an operable wall partition, here is a quick comparison. A variation of 1 is almost imperceptible, a variation of 5 is clearly noticeable and a variation of 10 is half, or twice as loud.

The STC rating of an operable wall partition evaluates air-borne sounds while not taking into full consideration low bass sounds such as noise from mechanical equipment, or any other noise that is heavier in low frequency than speech. The standard used is thus 125 Hz.

STC RATING STANDARDS
In order to reach the level of the laboratory STC sample, an operable wall partition must seal all leaks and flanking paths which carry out sound from one room to the next. The seal in between the panels of the partition, as well as the seal between the operable wall and its neighboring element such as floor or ceiling, must be tight.

However the STC rating of an operable wall partition does not take into consideration the noise filtered through the floor and ventilation systems. This why one must take into consideration the built quality of a room, as well as the performance of its operable walls in order to achieve maximum sound acoustic performance.

A few items are to watch in the making of an operable wall in order to evaluate the acoustic performance such as the insulation and whether the wall is staggered or doubled. For optimum STC, the stud of the wall partition should be metal and the resilient channel should be controlled.


WHAT ABOUT WEAK POINTS
Since sounds travel through the weak points such as doors windows and electrical outlets, the operable wall partition has an advantage as the seal between its doors or window like panels is controlled and tightly sealed using specific materials. Moreover, certain operable walls offer greater insulation and will be attributed a higher STC rating, as well as higher in room acoustic performance.

Aside from the insulation, having a space of air within the operable wall partition can also reduce the resonance factor of an operable wall without increasing the weight of the structure. Quality operable walls will often carry the optimal combination of methods in order to provide for comparable acoustics, while not necessarily increasing the weight and space needed of the wall partition.

Quality operable walls partitions with high STC ratings will have end seals, obstruction sensors, rigid insulation, honeycomb composite panels and strong bottom seals. You can get state of the art acoustics while conserving cutting edge design, ease of use and optimal storage space.

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