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Night and noise levels

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1214982.  Wed Dec 07, 2016 8:02 am Reply with quote

Sandi stated that 87 (I'm sure she meant to add dB!) was a maximum noise level in the Night episode when talking about how birdsong noise levels increase in noisy environments. Its actually an average reading over 8 hours. If a bird is singing at 135dB (measured instantaneously) it is singing at the maximum level allowed by law. This all assumes that the birds actions are covered by health and safety - which they ain't! But if they were, under health and safety legislation, an omniscient being - or whoever is the birds employer - should have started considering the provision of hearing protection to those exposed to the tyranny of twittering for 8 hours or more each day......maybe on the eighth day god created pillows. Read on for the dry stuff!

For dB please read dB(A)

In Health and Safety legislation there are action levels at 80dB and 85dB and a limit of 87dB but, crucially, these are daily or weekly averages. So noise levels can vary considerably over a measurement period . After the average is calculated the following actions may be needed ( )
The lower exposure action value is a daily or weekly average noise exposure level of 80 dB, at which the employer has to provide information and training and make hearing protection available.
The upper exposure action value is set at a daily or weekly average noise exposure of 85 dB, above which the employer is required to take reasonably practicable measures to reduce noise exposure, such as engineering controls or other technical measures. The use of hearing protection is also mandatory if the noise cannot be controlled by these measures, or while these measures are being planned or carried out.
Finally there is an exposure limit value of 87 dB, above which no worker can be exposed (taking hearing protection into account).
In other guidance it also lays out the peak sound pressure level, a very large number, which is a single measurement not an average.
All measurements should be taken at the ear, so if hearing protection is worn the measurement should take into account the attenuation provided. The maximum noise levels however are absolute and measured ignoring any hearing protection
What are exposure action values?
The Noise Regulations require an employer to take specific action at certain action values. These are the daily noise exposure level or the peak sound pressure level which, if exceeded, for an employee, action will need to be taken to reduce the risk.
These relate to:
The levels of exposure to noise of your employees averaged over a working day or week; and
The maximum noises (peak sound pressure) to which employees are exposed in a working day.
The values are:
lower exposure action values:
daily or weekly exposure of 80 dB;
peak sound pressure of 135 dB;
upper exposure action values:
daily or weekly exposure of 85 dB;
peak sound pressure of 137 dB.

Last edited by Johnzw on Wed Dec 07, 2016 9:55 am; edited 1 time in total

1214987.  Wed Dec 07, 2016 8:13 am Reply with quote

Am I right in assuming these are (a) received sound pressure levels at the "point of annoyance", so moving the source further away would be acceptable mitigation, and (b) values on the dBA weighted scale - or are they dBr(n) measurements relative to some other reference noise floor?


1215000.  Wed Dec 07, 2016 8:58 am Reply with quote

Thanks for the response!

yes, received sound pressure levels. In practical terms it's probably more about attenuating at source or excluding people from the risk area. Large plant making lots of noise is not normally too mobile!

But increasing the distance or interposing obstacles would help.

The measurements are dB(A)

Mr Red
1215661.  Fri Dec 09, 2016 8:08 am Reply with quote

soft yellow earplugs are good at attenuating higher frequencies, and soft enough to sleep in. The kind of sound that a nightingale would produce. But I have to say, on the rare occasions at a (say) festival that Mr Nightingale visits, he is louder than the leakage from venues. Thankfully.
Without him - its earplugs all the night.


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