Wood acoustic diffusers have become a decorative item - loved the idea!

[goat76]

The diffusers are beautiful at the start of the thread, but most are ineffective according to a calculator I found. With a depth of only 5 centimeters (2 inches), they are only effective from 3400 Hz and up. If we want the diffusers to be effective from 600 Hz and up, they must have a depth of 28 centimeters (11 inches).

This is the calculator I use: http://www.mh-audio.nl/Acoustics/DiffusorCalculator.asp

 

[sarumbear]

The diffusers are beautiful at the start of the thread, but most are ineffective according to a calculator I found. With a depth of only 5 centimeters (2 inches), they are only effective from 3400 Hz and up. If we want the diffusers to be effective from 600 Hz and up, they must have a depth of 28 centimeters (11 inches).

This is the calculator I use: http://www.mh-audio.nl/Acoustics/DiffusorCalculator.asp

If you look at various charts you will see that the effectiveness curve is not steep. As there’s only one element at work the curve is 6dB/octave I.E. it is 50% effective at half the frequency you calculated and 30% at a third.

Think of this as the FR of a small bookshelf speaker with an f3 of 100Hz producing bass frequencies half that.

However, 5cm is very small for a diffuser. There are picture frames deeper than that! if you use 10cm at least you should expect effectiveness at half of the audible range. Go another 5cm and you cover 2/3rd.

 

[Berwhale]

Do the diffusers with angled facets (usually 45 degrees the in images i've seen) work differently from the ones with facets that are perpendicular to the wall? Does the former change the vector of the reflected sound and the latter change the timing?

 

[Tom C]

Surely angled facets would give greater diffusion, right? The greater the number of individual facets, and the greater the differences in their angles, the greater the diffusing effectiveness, I would expect (intuitively).

 

[sarumbear]

Do the diffusers with angled facets (usually 45 degrees the in images i've seen) work differently from the ones with facets that are perpendicular to the wall? Does the former change the vector of the reflected sound and the latter change the timing?

As I said a few times above, there are different diffuser types. Each works to a different concept and formula. They all do one thing though, diffuse the reflected sound. They achieve this using different geometry and at different efficiency.

However, a diffuser will not change the speed of the sound as it operates in the same volume of air.

I don’t see an ASR forum thread suitable to further discuss the math behind each type. I suggest reading the papers on the subject if you have a basic understanding of math.

 

[sarumbear]

Surely angled facets would give greater diffusion, right? The greater the number of individual facets, and the greater the differences in their angles, the greater the diffusing effectiveness, I would expect (intuitively).

Nope. There’s no intuitiveness. It’s all about the math.

 

[Doodski]

I am hence pleasantly surprised when I stumbled upon these on Etsy!

Wood Sound Diffuser - Etsy UK

Check out our wood sound diffuser selection for the very best in unique or custom, handmade pieces from our wall decor shops.

www.etsy.com

I've done a ton of woodwork when I was younger and worked construction building houses and after looking at the labor intensive construction of those diffusers I can easily say the prices are good for what a person is getting. I like them!

According to a seller on Etsy who sells a pair of panels, covering an area of 108cm x 61cm and 15cm deep weighs 27kg. Do you think that is very heavy?

27kg is the nature of the construction. It's freight intensive but it's the real deal.

 

[Tom C]

Well, OK then, based on what the physics profs have taught me about wave propagation, the angle of reflection is equal to the angle of incidence, wrt a normal line perpendicular to the reflective surface. If the object is to break up the wavefront into smaller bits and send them off in different directions in order to reduce their perceivability (did I just make up a word?) at the listener’s ear, then perhaps what I wrote previously would hold. Or perhaps not. I hear you saying not necessarily,, read the papers, so I suppose the answer is in there.

 

[Tom C]

Yeah, 50 plus pounds sounds significant. A person would want to be sure to have a solid mounting point on the wall, and may need a friend to lend a hand during installation. A lighter product, if feasible, would be easier to handle.

 

[Berwhale]

21 examples of DIY diffusers here: https://weekendbuilds.com/diy-sound-diffuser/

 

[sarumbear]

Well, OK then, based on what the physics profs have taught me about wave propagation, the angle of reflection is equal to the angle of incidence, wrt a normal line perpendicular to the reflective surface. If the object is to break up the wavefront into smaller bits and send them off in different directions in order to reduce their perceivability (did I just make up a word?) at the listener’s ear, then perhaps what I wrote previously would hold. Or perhaps not. I hear you saying not necessarily,, read the papers, so I suppose the answer is in there.

What you are saying is correct but it is a simplification as it only explains reflection in a single direction. There are not many different angles on an angled diffuser. On a 2D diffuser (quadratic or skyline) N number of different reflections occur. The convolution of those create the diffusion.

Imagine if an angled diffuser you mention is made of mirror pieces. You will see the reflection of yourself as fragments, not recognisable but it will look like a person. The light is diffused but not much. Now imagine a skyline diffuser made of mirrors. It will be impossible to recognise yourself (from a distance larger than the size of each block).

 

[Berwhale]

The

read the papers, so I suppose the answer is in there.

BBC paper referenced in the Wikipedia article looks like a good place to start... http://downloads.bbc.co.uk/rd/pubs/reports/1990-15.pdf

 

[MCH]

Very interesting @sarumbear thanks for starting this thread.
I would really like to learn a bit more and maybe end up building something, however I prefer to stay away from wood. Are you aware of any cost effective "Lego like" solution that you can buy the "building blocks" and assemble and reassemble at your convenience or needs?

 

[Berwhale]

And this looks interesting too...

Metadiffusers: Deep-subwavelength sound diffusers - Scientific Reports

We present deep-subwavelength diffusing surfaces based on acoustic metamaterials, namely metadiffusers. These sound diffusers are rigidly backed slotted panels, with each slit being loaded by an array of Helmholtz resonators. Strong dispersion is produced in the slits and slow sound conditions...

www.nature.com

 

[sarumbear]

The

BBC paper referenced in the Wikipedia article looks like a good place to start... http://downloads.bbc.co.uk/rd/pubs/reports/1990-15.pdf

Excellent. It was published 32 yrs ago! You can always trust the BBC, which is celebrating its centenary…

 

[sarumbear]

Very interesting @sarumbear thanks for starting this thread.
I would really like to learn a bit more and maybe end up building something, however I prefer to stay away from wood. Are you aware of any cost effective "Lego like" solution that you can buy the "building blocks" and assemble and reassemble at your convenience or needs?

I’m afraid no. However, if you are willing to assemble, ordering pre-cut wooden blocks shouldn’t be a problem. All you need then is to glue them together.

 

[DanielT]

If you feel like DIY, you can buy a few different types of shapes, for example:

https://www.amazon.com/dp/B01ATW8ETW/ref=sspa_dk_detail_0?pd_rd_i=B01ATW8ETW&pd_rd_w=RnHrO&content-id=amzn1.sym.46bad5f6-1f0a-4167-9a8b-c8a82fa48a54&pf_rd_p=46bad5f6-1f0a-4167-9a8b-c8a82fa48a54&pf_rd_r=DJS11KNS11V3GV9B3TYT&pd_rd_wg=rKtnb&pd_rd_r=2fb79f7f-5536-4e38-9eb6-98b202310640&s=arts-crafts&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw&smid=A1DAYYSW7X7ON2&th=1

Maybe also together with:

+

And then put something together. An advantage is perhaps if you are a bit artistic, if you want to paint and create something that resembles a work of art, that is.

Having said that, if the sound is going to be good with DIY wood ("acoustic") diffusers it might not be the easiest, if I understood correctly what Sarumbear wrote in the thread. In any case, thanks for the tips and advice Sarumbear.

 

[Berwhale]

I could only find one example of someone selling a DIY key for a Skyline diffuser (and they don't appear to be selling them anymore)...

DIY Acoustic Diffuser Kit | Reverb UK

The DIY Diffuser kit gives you all the necessary tools in order to complete the job. Build your own beautiful diffuser, all the hard work has already been taken out!Each kit includes all of the necessary materials and a guide as to how to go about assembling your kit. A detailed diagram is also i...

reverb.com

 

[Doodski]

I saw a artsy panel made from pine cones. They come up to ~10 or 12 inches in length (30cm) but the average length for larger ones is maybe 6 inches (15cm). One can collect them from under trees or buy the monster sized ones online from peeps that collect them and sell them online for art projects. Imagine a 1m x 3m panel of pine cones glued to a panel so they stick out towards the viewer. It would be lightweight compared to solid wood construction. Just a idea.

 

[sarumbear]

And this looks interesting too...

Metadiffusers: Deep-subwavelength sound diffusers - Scientific Reports

We present deep-subwavelength diffusing surfaces based on acoustic metamaterials, namely metadiffusers. These sound diffusers are rigidly backed slotted panels, with each slit being loaded by an array of Helmholtz resonators. Strong dispersion is produced in the slits and slow sound conditions...

www.nature.com

Indeed it is. Never heard of it before. Thank you posting.

I like it especially because it uses my favourite acoustic tool Helmholtz resonator