# Sound isolation capacity of an idealized wall construction

• sigertdejean
In summary, the conversation is about estimating the sound isolation capacity of a wall structure and the complexity that comes with increasing detail. The impedance of the wall is important and there are two fundamental aspects that affect its sound isolating qualities: mass and rigidity. The equation presented involves calculating the wall impedance using different variables such as frequency, thickness, Young's modulus, Poisson ratio, mass, and speed of sound. The person has some questions about their calculations and is wondering what the next step would be in determining the sound isolation quality of the wall.

#### sigertdejean

I'm looking to understand how to estimate the sound isolation capacity of a wall structure. With rising degree of detail will probably come an exponantial increase in complexity. I'm looking to start of, euhm,... gently. :shy:
What I've gathered so far:
-The impedance of the wall seems to take center stage
-There's atleast two fundamental aspects of the wall that govern its sound isolating qualities: mass and rigidity, each dominant over the other in a different frequency range

I've posted one of the equations I've tried to solve, hoping someone can shine a light.
A plane wave of single frequency 200Hz traveling through air at 344m/s is obstructed by a single leaf gypsum board wall, 25mm thick, with infinite X and Y dimensions (some wall eh).

Frequency f = 200Hz
Thickness h = 0.025 m
Young’s modulus E = 2,3*10^9 N/m²
Poisson ratio V = 0,33
Mass M = 25 Kg/m²
Speed of sound c = 344 m/s
Angle of incidence φ = Perpendicular to boundary = 1/2π

w = f * 2π
= 200Hz * 2π
= 400π

Rigidity D = (E*h³)/(12*(1-V²))
= (2,3*10^9*0.025³)/(12*(1-0.33²))
= 3360,78

Z = M*w² (wall impedance as a result of its Mass)
= 25*(400π)²
= 39478417,6
=> 20*LOG(39478417,6) = 151,93 dB

Z = D*((w / c)*sinφ)^4 (wall impedance as a result of its Rigidity)
= 3360,78*((200Hz*2π / 344)*sin (1/2π))^4
= 3360,78*(400π / 344)^4
= 598474,66
=> 20*LOG(598474,66) = 115,54 dB

My questions:
1) Are my numbers really off, or is it just me?
2) Assuming I get the impedance right, what would be the next step in determining the sound isolation quality of this idealized wall structure?

Last edited:
*bump*

Another forum perhaps?

## 1. What is sound isolation capacity and why is it important in wall construction?

Sound isolation capacity refers to a material or structure's ability to reduce the transmission of sound from one side to the other. In wall construction, this is important because it helps create a quieter and more comfortable environment by blocking out unwanted noise from outside or other rooms.

## 2. How is the sound isolation capacity of a wall construction measured?

The sound isolation capacity of a wall construction is typically measured using a sound transmission class (STC) rating. This rating is determined by measuring the sound transmission loss (STL) of the wall at various frequencies. A higher STC rating indicates a better sound isolation capacity.

## 3. What factors affect the sound isolation capacity of a wall construction?

The sound isolation capacity of a wall construction can be affected by several factors including the thickness and density of the materials used, the presence of air gaps or leaks, and the overall design and construction of the wall. Other factors such as room acoustics and external noise sources can also impact the sound isolation capacity.

## 4. Can an idealized wall construction achieve complete sound isolation?

No, even an idealized wall construction cannot achieve complete sound isolation. Sound can still travel through solid materials, and the higher the frequency of the sound, the easier it is to transmit. However, an idealized wall construction can greatly reduce sound transmission and create a more peaceful environment.

## 5. How can I improve the sound isolation capacity of an existing wall construction?

If you want to improve the sound isolation capacity of an existing wall construction, you can try adding additional layers of sound-absorbing materials such as acoustic insulation, mass-loaded vinyl, or acoustic panels. Sealing any air gaps or leaks can also help improve sound isolation. Consulting with a professional acoustical engineer can also provide tailored solutions for your specific situation.