Volume through walls of speakers with rear bass drivers

[Ultrasonic]

well, personaly I have hear all kind of crazy stuff with room modes when I walk trough my AP while music is playing in my cave.

Does AP mean apartment here?

When walking about in other rooms, and from a neighbours perspective, it's important to note that standing waves/resonance absolutely are still important, just not the same ones as those relevent inside the listenng room. Now the geometry of the neighbouring room and it's relationship with the listening room become much more important. This can mean that sound at some very low frequencies in particular can actually end up sounding louder in a neighbours room than in the listening room.

 

[dasdoing]

Does AP mean apartment here?

yes

When walking about in other rooms, and from a neighbours perspective, it's important to note that standing waves/resonance absolutely are still important, just not the same ones as those relevent inside the listenng room. Now the geometry of the neighbouring room and it's relationship with the listening room become much more important. This can mean that sound at some very low frequencies in particular can actually end up sounding louder in a neighbours room than in the listening room.

note that it is very comon to find exactly the same dimensions on the other side of the wall. in that case a room mode in your room, can actualy exite the same mode on the other side.

 

[Ultrasonic]

note that it is very comon to find exactly the same dimensions on the other side of the wall. in that case a room mode in your room, can actualy exite the same mode on the other side.

Sure but importantly the combined dimensions are also important.

 

[dasdoing]

another important frequency we forgot is the resonant frequency of the wall. if you hit that one it will be sure anoying on the other side

 

[Frgirard]

another important frequency we forgot is the resonant frequency of the wall. if you hit that one it will be sure anoying on the other side

it's the major problem. Lower the resonant frequency is, harder is to treat.

 

[kyle_neuron]

I’m on my phone right now, but I’ll try to share some stuff to address the ‘armchair acoustics’ properly later. Let’s just say that it’s a pretty complex problem in practice, but considering each ‘wall’ as either a constrained or unconstrained set of mass-damped plates to calculate the relevant specific acoustic and radiation impedances is the fundamental principle.

That means doing some calculus to solve the second Rayleigh integral and Green’s functions. You can also use some measured Sound Transmission Index values, but those will need to be adapted since you can generally guarantee your room isn’t using the same makeups or mountings

The room itself will additionally have some natural frequencies or Eigenmodes, and the cabinet’s total radiation impedances combined with the physical placement to different surfaces will also have a contribution.

If you want something cool, that would also help address the problem then check this out.

It is a marketing video, but the principle of turning your room into a plane wave tube at sub frequencies with an ‘anechoic’ termination at the opposite end is acoustically almost ideal.

You just need to create a very solid (e.g. concrete) infinite baffle with sources mounted 1/4 wavelength apart at one end. Then, if possible, do the same thing at the opposite end but delay and invert it to create an equal-impedance absorber.

For slightly less madness, you could use custom tuned limp mass composite absorbers at the ‘anechoic’ end.


You know you want this now

 

[abdo123]

Walls in the US are not wildly different from those in the UK going by your last post by the way.

Really? As far as i know we have very few forests left (In Europe) and whatever we have left is very very protected. Making brick and concrete houses more affordable. we also don't move (far) as much for work and thus we invest long term in our houses.

While Wood frame walls (drywall) is very common in the US, making most properties obselate in 20 or 30 years.

 

[Doodski]

While Wood frame doors and drywall are very common in the US, making most properties obselate in 20 or 30 years.

I have seen entire neighborhoods where the houses where built in the 1920s or earlier and are wood frame construction. People gut the houses, install all new wiring, plumbing and gyproc and have a like new house. They keep replacing the asphalt shingle roofs every 20-40 years dependent on the quality of shingles and prevalence of hail that the roof has endured. It is becoming more common at the inner cities to tear down the old houses and replace them with duplex or triplex buildings and then there is no yard to speak of. That's progress. It seems the municipality encourages the duplex/triplex trend because it makes for a more taxes collected for the same space. The urban sprawl is costing a fortune for mechanical services like water supply, sewage systems and treatment plants, electricity distribution and such and so tri-plex/duplex is a great way to go.

 

[Ultrasonic]

Really? As far as i know we have very few forests left (In Europe) and whatever we have left is very very protected. Making brick and concrete houses more affordable. we also don't move (far) as much for work and thus we invest long term in our houses.

While Wood frame walls (drywall) is very common in the US, making most properties obselate in 20 or 30 years.

The post I quoted referred to walls between rooms, not external walls. Yes, the overwhelming majority of UK houses have solid (brick etc) external walls, however all but necessarily load-bearing internal walls are typically made from plasterboard/drywall.

Which is not to say that external wall construction won't have an impact on acoustics too but this wasn't what was being discussed.

 

[617]

I think everyone is overthinking this. The reality is, both partition and structural walls do very little to block bass. I really don't think dipole radiation will do much of anything for you and I doubt anyone has actually measured it.

The STC system for rating the sound transmission of different wall assemblies has a curve which it fits to the measured performance of a wall. So a wall with an STC rating of 56 will reduce sound above 500hz by 60db, but at 125hz (the lowest point on the curve) the wall assembly is only good for 40db. At 80hz you're looking at 30db of reduction if you're lucky, and at 40 and 20hz you might be looking at under 10db. 10db isn't nothing but when you consider that an STC of 20 permits 'soft conversation' to be heard between rooms, you realize it isn't ideal.

If you research this topic a lot you see some people trying to increase dampening at LF, which is expensive and fraught with problems, but transmission? There's essentially nothing a typical apartment dweller can do to reasonably reduce the level of loud bass coming through a wall. Any improvements to STC rating have to be done inside the wall, so it's not practical to 'add' anything to the wall such as mass loaded rubber or more gyp.

Generally high mass masonry walls do well for STC at bass frequencies, but as many have pointed out, these are generally not the assembly used for apartment parti walls, which depending on where you are, may just be a thicker partition wall, maybe with RC channel or more air space for plumbing. This depends on where you live, of course, and in England I know that interior masonry walls are more common. In high COL areas, a lot of innovation has been applied to making thinner walls with better STC ratings, since an apartment building with many parti walls can increase square footage by reducing 10 walls by even an inch. The cost of specialized rubber sheets and RC installation becomes justified. Incidentally, metal studs tend to do better than wood.

However, a good walls are only part of the problem. Bass will radiate out of your windows and into the windows of your neighbors. It will go through your door and through their door. It will go through any shared ducts. It will go through cutouts for electrical boxes. STC ratings in the real world are almost always significantly worse than specified because it is so difficult to model all the factors which contribute to sound ingress, but common points of failure are air gaps between walls and ceilings/floors, nearby windows, and subtleties in construction such as contractors not knowing how exactly to install resilient channel and floating baseboards. Resilient channel walls flex all over, and this goes against the instincts of any builder who wants to make things 'solid'.

Anyway, the moral of the story is that nothing works, which is why headphones are so popular - the ultimate nearfield solution. A subwoofer located near the listener might get you some dB of improvement but bass tones are many many times the size of any domestic space so as always, the room dominates.

If you want to listen to simulations of what different transmission classes sound like, I did a little piece on it that you can read here. It has some simulated sound samples which show what different types of environmental noise sound like when filtered by a nominal wall assembly. In some respects, sound actually gets more annoying when a wall is introduced, because the treble is filtered out, leaving only the booming bass tones.