# Acoustic transmission through walls

I am looking to understand the equation and physics of audio transmission through walls. I wish to model the indoors transmission of sound between rooms and I wish for any academic (not tutorials) material on the transition of the wave, as well as, physical approximations of physical parameters such as different materials transition coefficient approximations.

Also, any example implementation would be most welcome.

Any recommendations for such materials?

• Walls act like low pass filters to sound, so you could start by looking into the basic concepts of those. Commented Jul 23, 2020 at 14:03

I'm not really sure if this can help you because I don't know about your background, but for a first approach to the topic I recommend Kinsler's "Fundamentals of Acoustics". It even has a chapter dedicated to reflection and transmision of waves, and although it mainly focuses on fluid media, it also have a section about solid walls.

• Agree with @pablo Lemos. Kinsler is a good text and deals with transmission, reflection, and absorption in detail. Commented Jul 25, 2020 at 6:04
• While very helpful, the modeling extraction here is problematic. I could not find anything here on the wall's role as an LPF. Commented Jul 26, 2020 at 7:28
• Check also chapters 12 and 13 if you haven't, those are focused on architectural acoustics Commented Jul 27, 2020 at 13:59

When one hears sound from a wall, that means that the wall moves. There are two mechanisms: contact sound (when some neighbour in the building is drilling etc) or sound transmitted from the air on the other side of the wall. The questions was about transmitted sound.

An interior wall acts like a massive membrane with stiffness. The stiffness couples the oscillations of different parts of this surface. Averaging of the forces over an area makes that only long wavelengths in the air on the other side will sett a panel in motion. The forces from shorter wavelengths will cancel out. That is also a reason why such a wall is a low-pass filter.

Heavy walls are more difficult to set in motion, so that would reduce transmission.

I have not considered thickness, internal structure or damping. This is just theory. In reality, most of the sound may be transmitted by leaks. I do not know.

• I need books or paper references on the subject and equations that may help me simulate this. A literal explanation does not answer my question. Commented Jul 27, 2020 at 13:57
• @havakok Was that a reason for you to downvote? I thought you were looking to understand the physics. I have an acoustics book somewhere but maybe you should ask building engineers instead.
– user137289
Commented Jul 27, 2020 at 14:13
• Well, it is written quite clearly at the question. Commented Jul 27, 2020 at 15:30