[johnwoitalla]

How detrimental is dry wall to the spectral decay of a room? Do room treatments do any good in helping remedy this?

[AllanS]

Drywall is reflective but the ultimate answer to whether treatments are THE answer depends on a lot of other factors. No two rooms and systems are created equal so there aren’t any cookie cutter answers to how a room should be treated.
These a few of many helpful videos that you might start with.
https://acousticgeometry.com/videos/#how-acoustics-work
https://www.youtube.com/watch?v=DrPvXt5Anz4
https://www.youtube.com/watch?v=1PbhQaLrSbI
https://www.youtube.com/watch?v=lVfxxUEhmnQ

[marcos overload brazil]

How detrimental is dry wall to the spectral decay of a room? Do room treatments do any good in helping remedy this?

ABOUT INSULATION

technical study on the subject (in Brazilian Portuguese) - images help.

 here: https://normadedesempenho.com.br/wp-content/uploads/2022/10/Manual-de-Desempenho-Acustico-em-Sistemas-Drywall.pdf

o here    https://blog.artesana.com.br/manual-pratico-acustica/

em ingles  >   https://www.emseal.com/article/sound-attenuation-expansion-joints/

my experience: if you have 2 rooms separated by a wall, you can further isolate both by creating a wall with drywall,
in my case: I did not let the acoustic structure made, metal profile, touch the wall that separated the rooms.

The metal profile only touched the floor and ceiling through a 3mm rubber (although they were screwed)
 to the slab and floor. But under no circumstances did I let the new drywall wall touch the existing wall.
I placed a rock wool blanket between the new drywall wall and the masonry wall (brick).

https://www.isopur.com.br/la-de-rocha/la-de-rocha-sem-revestimento.html

The insulation was almost maximum. You could hit the plaster wall with a hammer and in the side
 environment NOTHING was heard.


ABOUT REFLECTIONS

In Brazil, there are specific panels to reduce and minimize reflections. In the US, since DRY walls
are used more, such panels should also exist. See the photos in Portuguese

https://www.aecweb.com.br/empresa/gypsum-drywall/8000/conteudo/chapas-para-absorcao-e-controle-de-reflexao-sonora/14186

I have noticed that some restaurants do not have this treatment on the ceiling, as a result the noise
 of people talking is quite annoying. In places equipped with these specific panels, the noise is much
greater and makes the environment more comfortable.


Absorption
When we need to eliminate reverberation, that is, sound reflections, known as ECHO, we should
use acoustic foam coverings, which are lightweight and have great absorption power, depending
on the thickness, because the thicker they are, the more they will absorb the sound.

If the place has smooth walls or the floor is made of porcelain, for example, the sound reflects and
 generates an echo. Imagine an empty apartment or house to buy, without furniture, and inside this
place your voice reflects off the walls, ceiling and floor, and without absorption, it generates an
 echo, the voice becomes full-bodied and difficult to understand; this is an example of reverberation.

Sofas, carpets, curtains and similar materials also help to reduce reverberation (ECHO); the more
 of these materials are present in the room, the lower the reverberation will be.


source of information

https://acusticaemfoco.com.br/artigo/isolamento-vs-absorcao-qual-a-diferenca/

[tomlinmgt]

Drywall is an acoustically reflective surface, so it will create a long decay time if there's nothing in the room to reduce the energy of the reflections.  As you start adding furnishings and decor items that help break up or absorb the reflections, the decay time will be reduced.  But that's not really a very reliable method for achieving favorable decay times if your objective is to optimize the fidelity of two-channel recorded music playback.  If that is your objective, then you want to control decay times across the spectral range rather than only some of the frquencies and not others (e.g. curtains and carpet only absorb high frequencies, leaving mid range and low frequency energy uncontrolled, thereby maintaining long decay time in the low-mid spectral range while reducing it in the highs).  The most common and effective method for achieving a favorable decay/reverb profile for recorded music playback is to use broadband absorption, meaning an absorption device (panel) that can absorb energy across the spectral range evenly.  For a panel made from rigid fiberglass or rockwool, this means it needs to be 6" in thickness and, ideally, provided the same amount of airspace between the panel and the wall as the thickness of the panel (6" panel gets a 6" air gap between itself and the wall).  This will provide effective absorption in the 125-20kHz range and several will be needed to achieve a favorable decay time.  Where they are located and how many is determined by the size of the room and how you want to control the primary reflections of sonic energy created between the speakers and boundaries close to the speakers (side walls, ceiling, floor).  There are tutorials all over YouTube that explain primary/early/first reflections and how to identify where they are ("mirror method").  Some like to use diffusion or a mix of diffusion and absorption at primary reflection locations, but that's a whole 'nuther topic.  Just know that it's a lot less expensive and effective to get reverb/decay under control with absorption.  For the very low frequencies (below 125 Hz), you'll need to use purpose built bass traps.  This gets a little more complicated and, usually, expensive.  The bottom line is you'll need to do a little homework and, ideally, get equipped so you can measure the acoustic behavior of your room.  Again, there are plenty of tutorials on YouTube and various websites (GIK acoustics has lots of info on their website). Ron from the New Record Day YouTube channel has a fantastic multi-part presentation on the construction and finish out of a dedicated listening space that uses drywall interior walls and he walks you through the entire process of optimizing the space for recorded music playback by using acoustic treatments.