Acoustic Windows (noise reduction)

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Tim Robbins

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We live on a cul de sac and can have 8 - 10 kids and 4 or 5 of their parents right outside for hours and hours especially on a nice summer day.
Noise can be really annoying as since its a modern estate, the driveway is tiny and so the front rooms of our house downstairs and upstairs are right beside at all the noise.
So plan is to get really good triple glazed windows - some people saying get double glazed with acoustic glass is better.
Anyone got any tips?
Appreciated.
 
Either will make a big difference assuming you don’t have in room vents or wooden floorboards with vents low to the front. Or indeed poor insulation. Attic soffit's can let in noise also. If you have any of these it may not make the difference you hope for. We are on a relatively busy road and planed triple glazing but after a mix up ended up with double. We didn’t bother sorting it out as the vent noise makes it not worth making windows more sound proof, we also have internal insulation, which deadens any noise through the walls.
 
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My experience is that double glazing on its own does indeed reduce noise.

Fitting of the windows makes a huge difference and if done wrong there is not much impact.

Trickle vents also allow noise in.

Ventilation shafts let in more noise than you might think and these remain.
 
Ok so an update. Our current windows are High Performance PVC

The acoustic spec on them is -30DB. Now, if you were to get a new tripe glaze window, the spec if about -35dB.
However, if you stay with double but upgrade the glass and so one glass is 6mm and the other is acoustic you can get -39dB. And if you get a new triple glaze and ask for one of the glass panes to be acoustic it's -41dB.

So, in our house a few of our windows are already triple glaze and -35dB. You can still hear the shouting and all the noise through it but not as much. So, think if this sort of thing is really bothering you need to go all in and get the triple with an acoustic glass. I don't have prices yet, in the process of getting that.

Lastly there's another option called secondary glaze. It's when you put in second interior window unit. They get some great acoustic performance but then you have to open and close two windows. So that's the last option really.
 
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Also I agree the vents let in a huge amount of noise and not much you can do hear. I got some products on amazon and will post to let you know how I get on. The idea is they absorb sound waves as sound comes in - so reduce sound but not air flow.
 
Tim Robbins said:
Also I agree the vents let in a huge amount of noise and not much you can do hear. I got some products on amazon and will post to let you know how I get on. The idea is they absorb sound waves as sound comes in - so reduce sound but not air flow.
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Be interested to hear how you get on, I’ve tried various attenuator options, the best ones basically just block the vents with thick foam which there is no future in.

-30 to -35 is a big jump, in theory very 3dB or so is halving the sound let in, so -30 to -35 is a big jump, however that’s why most of the sound comes through vents as they are attenuating at 0dB while windows are doing -30dB.

In reality although sound ‘power’ is halved ever 3dB we perceive loudness differently so to our ears it could take say 10dB for us to perceive the loudness ‘halved’.
 
Tim Robbins said:
Lastly there's another option called secondary glaze. It's when you put in second interior window unit. They get some great acoustic performance but then you have to open and close two windows. So that's the last option really.
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We had this in our old house, which was on a main road, and it worked a treat. The gap was substantial, about 10 cms between the outer and inner window. We seldom opened them except to clean the windows!
 
I would say, with fact free opinion, you're wasting you money by upgrading double glazed windows to a higher spec. We have new triple glazed windows, top spec insulation. Old house, thick walls. The vents let the noise in. It's not noticeably quieter than before we did our refurb, when we had 25 year old double glazed.
 
Thanks for all the replies. Our vent's are 150mm diameter so think the builder over spec'd. I am going to reduce them to 100mm diameter which reduces the area for air by more than half. They are small rooms, that currently also have trickle so going to reduce to 100mm by placing 100mm duct piping in the middle and wrapping it with rockwool.

I will use hydrometer's than to measure relative humidity and leave at 100mm. I also got some products which claims to reduce sound flow in a duct piping so going to try them out. They work by absorbing the sound wave so hence reduce sound but leave air flow.
 
Just an update on this. I designed something to reduce the sound coming through vents.

I bought 101 mm perforated metal tubes like these ones here: https://pickeringperforatedproducts.co.uk/perforated-product/perforated-metal-tubes/

I wrapped the tubes with insect netting on the exterior and then I stuffed in lots of rockwool in the 25 mm gap between the existing 150mm waven duct and the and 101mm perforated metal. The insect netting was stop bits of rockwill falling into the the inner tube.

So why did I use the perforated steel as opposed to 100mm waven ducting? Because, when the sounds waves come into the 101 mm tube, most of them eventually hit a hole and get absorbed by the rockwool. Whereas if I used waven duct piping they wouldn't.

On the inside of the 101mm perforated metal tube, I put some open cell foam. This won't block air flow but it's just another mechanism to absorb the sound.

Lastly, to close off the rockwool at the end of the vent, I used acoustic plasterboard. I cut out an annular shape to fit around the 101mm and inside the 150mm This won't absorb any sound instead it reflects it but it reflects it back into the rockwool.

Sound reduction, very good. Air flow still happens.
 
Interesting idea. Why would you need the metal tube at all? Wouldn’t just the 25mm of rock wool lining around the edge give the same or better result?
 
If you get the hole diameter right, the holes will attenuate the most prevalent frequency range. The downside is they will amplify others so it's not fool proof. Perforated tubes like this are used to tune car exhaust sound, to attenuate higher frequencies and enhance lower for example.

An absorbent lining of the bigger opening should in theory be a lot more effective, and you can buy acoustic foam in self-adhesive sheets.
 
@Setforlife the perforated metal tube is to give it structure and confidence that you have a sturdy airflow that will look the same when you check it in a few years time.

@Leo I am not sure how it would amplify any bass sound. Think what is happening in the car exhaust scenario is that it's filtering out high so you are left with bass. Also bear in mind there is no rockwool in the car exhaust sound.

In the annular, I only have 25mm to absorb the sound so obviously I am not going to be able to get the low frequencies. But in my scenario I don't care about car noise - it's mainly voices from adults talking very loudly I am trying to filter.
 
Tim Robbins said:
@Leo I am not sure how it would amplify any bass sound. Think what is happening in the car exhaust scenario is that it's filtering out high so you are left with bass. Also bear in mind there is no rockwool in the car exhaust sound.
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It can be amplified through resonance. Think about how wind instruments work, or how the internal chamber of a guitar amplifies the string sound.

Car exhausts deliberately use a solid backer behind the perforations as this has a greater effect on attenuation.
 
Tim Robbins said:
Also I agree the vents let in a huge amount of noise and not much you can do hear. I got some products on amazon and will post to let you know how I get on. The idea is they absorb sound waves as sound comes in - so reduce sound but not air flow.
Click to expand...
Can you link these?
Ah just read your other post with the vented tubes so presuming it's them.
 
@Leo great points. On the paper you reference it says: "The upper bound of this bandgap is determined by the dimensions and separation of the perforations.". Really key point. They are tuned to resonate at that real low bass noise you get from certain cars.
Funnily enough, I don't care about car noise. It's mainly adults talking very loudly followed by kids shouting and screaming.

Now voice is very interesting. The strongest frequency can be quite low. But there's lots of harmonics and over tonnes which are much higher. So you if filter them out you muffle the sound. So it's like the way you might be able to hear someone talking in another room but you can't hear what they are saying because the stud partitioning muffles the sound.

My DIY project is muffle and attenuate the adults talking loudly as much as possible. The kids aren't as loud. And I don't care about car noises.
 
Tim Robbins said:
Funnily enough, I don't care about car noise. It's mainly adults talking very loudly followed by kids shouting and screaming.
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And that's the challenge here, you might not care about car noises per say, but you are likely interested in attenuating some of the same frequency range that car exhausts do.

Essentially the point that if using a perforated tube, the science would suggest a solid backing that can introduce disruptive elements is a plus. In reality though, I'm guessing you're not really measuring the sound levels across the spectrum and tuning the dimensions of the tubes and holes sizes to the specific range you're most concerned with. You seem happy with your solution and so that's all that really matters to you. I just wanted to caution others that they might not find the method so effective with any random perforated tube.
 
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