YouTube offers a vast collection of advice videos on virtually any topic, including soundproofing. However, the quality of these videos varies widely — from unreliable or even absurd to genuinely informative — and it is often difficult to tell the difference.
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One of many soundproofing videos that I have come across is this one presented by a YouTube author:
NOTE: I WAS ASKED BY THE AUTHOR OF THE VIDEO TO REMOVE IT DUE TO "COPYRIGHT INFRINGEMENT". However, the video is still out there and the content of my article is unchanged.
The presenter covers many aspects of basement soundproofing reasonably well, but his explanations of the underlying physical principles are oversimplified and somewhat inaccurate [5:00]. Although he appears competent in practical terms, his instructions contain several omissions and errors. If a homeowner or contractor followed his advice, specific critical details might be executed incorrectly, reducing the overall effectiveness of the soundproofing.
Soundproofing errors
Here is a list of the errors or omissions in the presentation. Time reference in the video is shown in [square brackets].
[1:40] The Sound Transmission Class (STC) explanation is very inaccurate. The author recommends referring to Wikipedia, and he is right. Wikipedia description is accurate.
[3:21] The author suggests removing air ducts from the ceiling and using in-floor heating. This suggestion is not practical or necessary in most cases. Air conditioning still needs to be installed, even if the heating is in-floor. Noise transfer reduction through ducts can be successfully achieved and relatively cheaply if done at the same time as the rest of the renovations.
[6:15] The author states that fibreglass is much cheaper than rock wool insulation. Fibreglass insulation indeed is about half or a third of the cost of rock wool insulation, but any insulation is only a small fraction of a project's cost. His advice to use fibreglass makes sense only on low-budget projects done by a homeowner himself. In most cases, the additional cost of rock wool is quite small and worth the improved acoustical performance.
[6:40] The author's explanation of Green Glue function is completely incorrect. This noise-reducing compound, in fact, creates adamping effect in drywall, reducing vibration transfer.
[7:22] The author claims that no insulation in the ceiling, with two layers of drywall with Green Glue, provides good sound insulation. This is incorrect; it only provides about 6 STC points better sound transmission than one layer of drywall. In my opinion, it is not worth the cost and effort, especially in new construction, as is demonstrated.
[8:56] The author inserts one layer of 3-inch insulation into the ceiling cavity. That is fine as a minimum. He does not tell you that doubling the insulation thickness can add 2 to 3 STC points to sound attenuation.
[14:40] The author suggests using one or two tubes for every sheet of drywall. This is incorrect. The instructions for Green Glue clearly state that you should use two tubes per sheet for optimal effectiveness.
[17:10] The author talks about “decoupling wall” when he talks about the double wall system. This is somewhat misleading, because decoupling usually refers to resilient channels or resilient clips.
[19:20] The author illustrates a wall assembly with a layer of drywall inside, between two walls. It is entirely wrong. The inside drywall should be removed. Leaving it reduces the wall's sound attenuation by 5 to 10 STC points. This means that his 65 STC actually becomes 55.
[20:50) The author left a gap in the wall, saying that it does not matter. However, deficiencies are cumulative, and each one matters. It does not take much effort to caulk the gap or fill it in with drywall compound.
[26:20] The author also leaves out another important point. Especially if you build a double wall, you need to resiliently attach the base plate and the top plate. Then leave a ¼-inch gap around the perimeter of the drywall and caulk the gap with acoustical sealant.
Conclusion
Overall, the demonstration is quite good, and the author appears to know what he is doing. He achieves a better result than a typical contractor who claims to offer soundproofing services. However, his approach contains many technical inaccuracies, and the outcome is less effective than it could be. Obtaining proper advice and hiring a qualified expert would not cost much more, yet would ensure a significantly better result than relying on a self-proclaimed soundproofing specialist.
