Any noise specialists?
Discussion
We have a potential noise problem at a site we are developing, and we have had a 'noise specialist' confirm that the noise level from our air source heating pumps is too high against the level set by the local authority.
The long and short of it is, I don't believe their findings.
In brief, there are 3 ASHP's totalling 55dB(A) SPL, 33.000m away from the nearest dwelling.
The ASHP's are located on the roof over the second floor of our building, and the receptor building is a bungalow....the figure they are quoting at the bungalow is 40dB(A)......
With the location of the pumps allowing the noise to disperse in all directions, I fail to see how the level of 40 is reached at the house?! Seems high to me.
If anyone has any thoughts, please let me know........this is scuppering the whole scheme at the minute.
The long and short of it is, I don't believe their findings.
In brief, there are 3 ASHP's totalling 55dB(A) SPL, 33.000m away from the nearest dwelling.
The ASHP's are located on the roof over the second floor of our building, and the receptor building is a bungalow....the figure they are quoting at the bungalow is 40dB(A)......
With the location of the pumps allowing the noise to disperse in all directions, I fail to see how the level of 40 is reached at the house?! Seems high to me.
If anyone has any thoughts, please let me know........this is scuppering the whole scheme at the minute.
davido140 said:
If all else fails get some greenie propoganda and tell them they are killing baby seals if they dont let you use the ASHP...
I'm assuming these are estimated/guessed/carefully calculated figures?
Carefully calculated by someone we've paid to tell us that the noise level will be fine....grrr!I'm assuming these are estimated/guessed/carefully calculated figures?
I'm not a noise specialist but this doesn't sound right to me.
I've had noise surveys done on a few projects that I have worked on and they provide a graph of a range of dBA readings over a range of frequencies.
From memory ambient noise (wind, distant traffic etc) is usually in the 50dBA area. I cant imagine where they have got 23dBA from.
If you are working to calculated figures I would forget them and get some readings taken at the property with and without your equipment running.
I've had noise surveys done on a few projects that I have worked on and they provide a graph of a range of dBA readings over a range of frequencies.
From memory ambient noise (wind, distant traffic etc) is usually in the 50dBA area. I cant imagine where they have got 23dBA from.
If you are working to calculated figures I would forget them and get some readings taken at the property with and without your equipment running.
Measuring the intrusiveness of sound in dB never was/will be adequate. Hence the legal definition of a noise nuisance is a "nuisance or prejudicial to health". Authorities come up with arbitrary limits, purely because it can be measured. But with the db(A)filter particularly, Low Frequency Noise(LFN) is actually attenuated (filtered out) in the reading. Power in dB is only partly related to perceived volume, being subjective anyway. I suspect the problem with your pumps is LFN, some people will be severly distressed at the threshold of audibility whilst others will not even hear it. LFN is hardly attenuated by distance, indeed it can appear amplified and louder than the source at remote locations! This is a quality of life destroying issue which has only recently become understood.
I can't offer a solution, but perhaps you can research it more and find one.
I can't offer a solution, but perhaps you can research it more and find one.
Edited by Mr GrimNasty on Thursday 28th October 10:41
The 23dB(A) rating set by the LA comes from the British Standard sound test that was undertaken on the site. The average level came out at 28dB(A), and with a 5dB penalty, we're allowed only 23dB!
We are going to try and push this up to 30dB....but we're still a way off!
Just to clarify - this is a pre-commencement condition, we haven't put a spade in the ground yet!
We are going to try and push this up to 30dB....but we're still a way off!
Just to clarify - this is a pre-commencement condition, we haven't put a spade in the ground yet!
I realise this is a potential problem, but I wanted to show you it is a very real potential problem with serious consequences for the people that are going to have to live with it.
If you Google for air conditioning unit regs. in Australia for example, you might find some suggestions on siting and acoustic barriers (Google that too). Don't the acoustic consultants have any suggestions?
The best solution is to render the units inaudible - to do that there will have to be no line of sight, no potential reflective surfaces, and a well-engineered acoustic fence or a mass partition i.e. masonry between the pumps and anyone that might be affected. A parapet wall to the roof? Or a L or C shaped wall or acoustic barrier around the pumps? But will that affect their efficiency.....
If you Google for air conditioning unit regs. in Australia for example, you might find some suggestions on siting and acoustic barriers (Google that too). Don't the acoustic consultants have any suggestions?
The best solution is to render the units inaudible - to do that there will have to be no line of sight, no potential reflective surfaces, and a well-engineered acoustic fence or a mass partition i.e. masonry between the pumps and anyone that might be affected. A parapet wall to the roof? Or a L or C shaped wall or acoustic barrier around the pumps? But will that affect their efficiency.....
40dB does sound realistic, given the figures you have quoted. Sound pressure levels drop inversely proportional to the distance - remember dB is a logarithmic scale.
The change in SPL with distance is given by the following formula:
Change = 20xLog(R/r)
Where, r is the original distance, and R is the distance you want to know the level at.
Using your figures:
Change = 20xLog(33/6)
Change = 14.8 dB
So if the initial spl at 6m is 55 dB, then at 33m it is going to be 40.2 dB, inline with the figure you were given.
The change in SPL with distance is given by the following formula:
Change = 20xLog(R/r)
Where, r is the original distance, and R is the distance you want to know the level at.
Using your figures:
Change = 20xLog(33/6)
Change = 14.8 dB
So if the initial spl at 6m is 55 dB, then at 33m it is going to be 40.2 dB, inline with the figure you were given.
These guys might be able to help!
http://www.adrianjamesacoustics.co.uk/
I recently used them (to good effect) where the project was a Motor bike Racing Dyno testing station with a recorded level of 124!
As it was in an industrial unit it had to be brought down to circa 40.
Bit of clever engineering, job done!
http://www.adrianjamesacoustics.co.uk/
I recently used them (to good effect) where the project was a Motor bike Racing Dyno testing station with a recorded level of 124!
As it was in an industrial unit it had to be brought down to circa 40.
Bit of clever engineering, job done!
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