Are you among those promised amazing soundproofing by DGU Glass and were left wide-eyed after hearing the prices? Are you looking for cost-effective alternatives?
In this blog, we will discuss what soundproofing is, how it is measured, what the soundproofing ratings are, and what they mean, and if you stick around till the end, we will demonstrate using calculations the difference between the soundproofing by different types of glass in real-world scenarios.
Our cofounder Amod completed his MS in Engineering Acoustics from the Technical University of Denmark and returned to India to start our company called Consonance Acoustics. We have soundproofed studios, home theatres, classrooms, and solved complex industrial noise problems.
We are here to bust the myth of the DGU.
If you have specific queries regarding soundproofing, post them in the comments below or contact us.
In our previous blogs, we touched upon how the sound propagates after coming in contact with a change in medium. It reflects, gets transmitted, and gets absorbed. When we discuss soundproofing, we are talking about reducing the sound that gets transmitted.
Soundproofing is measured by producing something called “pink noise” which sounds like this -
This sound is produced in the source room and the average sound pressure level in that room is recorded. The sound pressure level in the receiver room is recorded as well.
The difference between these levels and a small addition compensating for the influence of sound absorption in the receiver room is calculated. This is done either for one-third octave bands or for octave bands.
This gives what is called airborne sound insulation.
ISO 717-1:2013 outlines a way to find a single number that shows the acoustical insulation performance instead of the frequency-dependent values we found earlier.
The problem arises when people start to think this single number rating is the equivalent sound level reduction that will be achieved after installing a certain material.
Let me explain the process outlined in ISO 717.
For one-third octave bands, the standard outlines a reference curve that looks like this.
The sound insulation measurement data is compared to this reference curve.
The reference curve should now be shifted up or down in increments of 1 dB towards the measurement curve such that the sum of the measured data below the reference curve is as large as possible but less than 32 dB.
Another condition to this is that the difference between the measured data below the reference curve and the reference curve should be less than 8 dB at any one point.
Once this condition is achieved, the value of the reference curve at 500 Hz is taken as the single number rating that we call the Sound Transmission Class or STC.
Let’s take an example.
Look at this comparison here, this graph compares the reference curve and that of a DGU with 6mm glass and 12mm argon filled in between.
To get the STC, we will now have to bring down the reference curve by 1 dB.
As the curve comes down, the difference becomes 26 dB which is the maximum difference below 32 dB. At this point, all the individual differences are below 8 dB.
At this point, we take the value of the reference curve at 500 Hz, which is 35 dB.
Let’s do that again with another type of glass which is a monolithic construction, that is, a single pane of glass of 9.5mm.
As we repeat the procedure, we can observe that the difference is now below 32 dB. But the individual difference is 9 dB at 2 places.
Hence, we have to bring down the reference curve by another dB. Now the individual difference at the 2 places is 8 dB and the total difference is the highest below 32 dB.
As all the conditions are met, we take the value of the reference curve at 500 Hz, which is 34 dB.
According to the STC values, it appears that the 24mm DGU construction is slightly better than the 9.5mm single pane of glass. Yet we can observe that this is still a slight difference. But let’s put them head to head.
Looking at this graph, we can see that the single pane performs much better at certain frequencies when compared to the DGU.
What does that mean? Let’s put this to test in the real world. Here is a graph showing the traffic noise we measured at a site recently for a coaching class.
When you calculate, you can see that in reality, the single pane reduces the sound to 55 dB vs the DGU which reduces the sound to 58 dB. The single pane reduced more sound than the DGU. The single pane was better than DGU for an example of traffic noise.
But would the result be the same for all kinds of noise? Let us know what you think in the comments. For more of such information related to sound, acoustics, and more, subscribe to our blog. Hit the like button if you have saved some money after reading this blog and share it with others possibly going through the same problem.
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