Zero Seal Systems

Our featured ‘SOUNDTRAP’ gasketing systems can satisfy a wide range of common commercial and industrial sound-control applications for single swinging doors – as well as providing privacy behind pairs of doors for typical office applications. These are proven acoustic solutions.

Sound Transmission Class (STC) ratings indicate the ability to prevent the transfer of sound from one area to another. For example, 305mm of reinforced concrete would be rated at 56 STC, while 6mm plate glass is 26 STC.

We are often asked what is the difference between STC ratings as used in the USA and SRI-Rw ratings as used in the UK.

Sound Reduction Index – Rw – (SRI-Rw) measures the value of the barrier by recording the sound pressure levels (dB decibel rating) in both source and receiving rooms at a specific frequency. This is measured across a weighted average of 16 frequencies from 100 – 3150 Hertz. The SRI-Rw level is recorded as the difference between the two values.

Sound Transmission Classification (STC) follows the same logic but is measured across a weighted average of 16 frequencies from 125-4000 Hertz. Again, the value is the difference in average values between source and receiving rooms. The higher the value, the better is the attenuating effect of the barrier.

In summary, STC and Rw measurements are very similar – the Rw range is 100 – 3150Hz whereas the STC frequency range is 125 – 4000Hz. In reality, the numerical value of the two ratings are very often the same.

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