Noise level numbers Piggott design

[Dutch John]

Dear list,

I am in the midst of building a Hugh Piggott 10' windturbine. City hall of our town gave me a building license, but want to pull it back (yes, they can), because I urgently need to provide them with noise level numbers. My neighbours live 250 meters away, but rules are rules is the official comment.

So, are there "offficial" noise level numbers of a Piggott style windturbine? Or at least something that looks official and could impress a civil servant?

Regards,
DJ

[David HK]

An interesting post.

You do not say if anyone is objecting to your plan, but, if they are, you should make your local Government treat the case fairly.

By this i mean anyone complaining should obtain and submit some sort of medical certificate to establish the hearing level of such persons and produce this in support of their objection or claim and make a copy available to you

Its unfair to claim against your supposed noise levels if you do not know what the objectors hearing level is.They themselves might not even know.

I have not described this well because I am not a Doctory specialising in ear matters but i hope you understand what i am getting at.


David HK

[Dutch John]

Hello David,

I understand you. But unfortunately this is not how it works in this overorganised country (Netherlands). It is not about anyone complaining, not even about anyone not complaning, it is about rules. I need to prove in advance that the noise level is low enough. I could proceed building and have the noise level checked afterwards by a big-bucks specialized company, but that will cost more than the entire setup together. My wallet does not allow that and it also takes away the fun and good feeling.

Either way, they want to see numbers. Ideologic motives do not work in this country. On behalf of green energy we a developing country.

It was funny that my conversation with the calling offical was several times interrupted by loud passing tractors and jet fighters. Perhaps I should not have made a cynical remark on behalf of that...

Regards,
DJ

[Vanhook2]

It sounds like you are in a catch 22 postion.
What i mean is, how can you give them an accurate level since it is not built?
On the other hand, they will not allow to build it without the level.
All you can do is give them your best guess.
Even if someone has measured the dB level of the one they built, yours will have a different level.
The reasons are, blade difference, skill of fabrication & installation, location of installation, Etc.

Take you best guess (what you think) to them.

Here is a link to some common dB levels:

 http://noiselimiters.co.uk/buy/noise-levels-what-is-noise.php

[ghurd]

What is the limit it must be below?
And the distance at the noise level, if that is relative.

If there are trees around, and the blades have a sharp trailing edge, the wind in the trees will generally drown out the blade noise.
My best blades are 0.6 meter diameter.  At over 1500RPM, about 1.7 meter above the road, on a causeway in the middle of a lake, I could not hear them at all from 2 meters away.

If you need a solid number, whatever "wind in the trees" is would be about the same number?

It may be helpful to know the number it must be below.
It would be easier to prove "Below X" than "Exactly XX.XXX".

If anyone knows a solid number, it would probably be Hugh.  It could be a while before he sees this post.
I suggest emailing him directly.
G-

[Bruce S]

Dutch John;
 It might be a good quick idea to jump over to Hugh's website and drop him an email. He's really good about getting back to emails.
He checks into here a lot as well, but an email might get a quicker response.
An old test I once read about had it lower than 90dba but I could be mistaken.

Best of luck
Bruce S 

[DanB]

Actual numbers would vary, depending on how you build it - and how you load it.  Little details on blade carving could make a difference.  Hopefully Hugh gets back on this - I know he's travelling right now  in the US (he just left here 2 days ago).

I cannot speak for Hughs machine, but it's very close to what we build.  Mick Sagrill ran/tested one of ours for about 6 months and said it was the quietest wind turbine he'd ever had on his tower.

If it were me, and they want 'numbers' (pulled out of somewhere)...  I would go look at some of the quieter 'manufactured' machines out there, and pick the lowest number you can find - odds are it will be better than that.

[DanG]

One solid background data point they may be looking for may be the "profile family" of the blade airfoil you are proposing.

I found this publication six years ago and printed out the airfoil cross sections but it appears they've stripped those graphics out on copyright grounds a few years back, a little leg work to get the profiles to lend some graphics and key vocabulary points for explaining what elements (mentioned in this report) your blades have or don't have etc. might help support your cause.

Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines

[Dutch John]

DanG,

Thanks for the report. I guess it is a bit too detailed, since governments usually use dB(A) numbers instead of dB-frequency relation.

DanB,

I know that many other factors should be taken into account for a decent measurement. Lets not make them wiser. Any decent number on an official looking paper, together with circumstances like windspeed, direction, distance will do. The only thing important is that the turbine is Piggott-style.

BruceS, Ghurd,

I'll contact Hugh personally. 90 dB(A) is rather high, or be it measured in very short distance.

Regards,
DJ

[David HK]

A couple of web sites here may be of some help to you.

http://www.ceere.org/rerl/publications/whitepapers/Wind_Turbine_Acoustic_Noise_Rev2006.pdf

http://www.wind-works.org/articles/noisesummary.html

http://www.bksv.com/doc/ba0705.pdf
(Nederlands site)

David in HK

[David HK]

Spend some time going through this web site in depth because it contains much useful data on small wind turbines, noise, tests, charts and much else.

http://www.wind-works.org/articles/Noiseair403.html

David in HK

[ghurd]

I thought another post should be mentioned in this post,
read it to the end,
http://fieldlines.com/board/index.php/topic,144253.0.html

G-

[Dutch John]

Update.
Hugh had no ready answere either. All in all the probably non-issue of noise gives me the courage to proceed and measure afterwards. I'll give the blades extra attention. Once it runs I will make some dB(A) measurements myself and put the results on this forum. Hope that the numbers are low that these and a visit on-site will convince the officials. Otherwise a solution could be to temporary adjust the air gap to stalling? A stalling turbine is less noisy?

Regards,
DJ

[Photon]

The council or EPA regulations will have an allowance over backround noise level. Let's say the backround level at night time is 45db(A), you may be allowed 5dbA over this.
Therefore the noise level needs to be logged over night at the reciever [neighbours] , then work out noise generated at 250m.

I would ask this of planning because if it's not measured (backround) they can assume any level and it might not pass. Get the allowance first , measured or assumed and it will be easier to make turbine noise data comply. Modify blades etc.

Hope this help
Ross   

[Dutch John]

Bless common sense. Our town gave me allowance, without demanding measurements. They took the allowed noise level at the homes of our neighbours, calculated the corresponding level at the turbine (87 dB(A)) and compared this number with known numbers of turbines with blades 10 times my size (100 dB(A)). "Only" 13 dB(A) difference. Let's not talk about logarithmic scale....

Regards,
DJ

[DamonHD]

For once a lack of science training in the ruling class may have worked in your favour!  B^>

Rgds

Damon