Environmental noise: measurement interval

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nos.peter@gmail.com - 25 Jul 2008 15:16 GMT

Hello,

I'd like to know if there is a way (or some kind of guide) to define
the duration of environmental noise measurement (how long to measure)
as a funciton of noise parameters such as: LAeq, SPL, L99, L90, L10,
L1...?

I know that percentile levels can provide an indication of the degree
of fluctuation in noise readings, but how to use this parameters and
define criteria for measurement interval.

Thank you, Peter

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Savant - 25 Jul 2008 19:36 GMT

On Jul 25, 9:16 am, nos.pe...@gmail.com wrote:

> Hello,
>
[quoted text clipped - 8 lines]
>
> Thank you, Peter

If it's not explicitly defined in the measurement section of, e.g., an
applicable noise regulation, measurement duration is a function of the
temporal nature of the noise source. See ANSI S12.18, or equivalent.

Savant

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nos.peter@gmail.com - 25 Jul 2008 23:15 GMT

> On Jul 25, 9:16 am, nos.pe...@gmail.com wrote:
>
[quoted text clipped - 16 lines]
>
> Savant

Well our regulation refers to ISO 1996-1,2 which probably are
something like ANSI S12.18 (I'm not familiar with that document). In
ISO 1996-1,2 there is some information about measurement duration, but
nothing exact. I need defined criteria for measurement duration, e.g.
if the difference between Leq and L99 is less than 3 dB, than that
means that it is enough to measure for five minutes and perform three
repeats. The reason why I need this is that an accreditation body gave
me a non conformance and some useful information would be very
helpful.

Thanks

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Peter Davis - 26 Jul 2008 19:21 GMT

nos.peter@gmail.com wrote in news:1f1462da-28a7-415b-b16b-653cde7d2274
@s21g2000prm.googlegroups.com:

> Hello,
>
[quoted text clipped - 8 lines]
>
> Thank you, Peter

It is dependent on the applicable noise regulation. Here in Alberta the
nighttime period (2200-0700) has a permissible sound level (PSL)10 dBA
below the daytime permissible. The PSL varies from area to area and is
dependent on factors such as population density, proximity to
transportation (heavily travelled roads, railways, aircraft corridors).
PSLs of more remote or 'pristine' areas are sometimes set by conducting a
24 hour ambient or background sound survey and setting the daytime PSL
5dBA higher. This is very dependent on the season in which survey is
taken.
For extended environmental sound measurements I log for the nighttime
period. The parameters logged simultaneously are 1 minute:
LAeq (Local noise regs look at the LAeq10hr)
LCeq (Handy to help evaluate low frequency contribitions and LCeq-LAeq)
L10 (The level exceeded for 10% of each logged minute-short term events)
L90 (The level exceeded 90% of each logged minute-indication of
background, i.e; frogs, industrial contribution, etc.)
The measurement interval of practically anything depends on the source to
be measured. For machinery that operates constantly, an LAeq measurement
of 20-30 seconds is usually sufficient. For machinery that cycles, like a
pump one needs to measure the entire cycle. For environmental noise one
looks first to applicable local regulations, and then must use common
sense and experience to decide if the interval captured is representative
of the soundscape -bearing in mind that such measurements are at best
'snapshots' of the soundscape and are highly influenced by weather, time
of day, season, and local activity.
Peter Davis
FDI Acoustics Inc.
www.fdiacoustics.com

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Savant - 28 Jul 2008 17:45 GMT

> nos.pe...@gmail.com wrote in news:1f1462da-28a7-415b-b16b-653cde7d2274
> @s21g2000prm.googlegroups.com:
[quoted text clipped - 39 lines]
> Peter Davis
> FDI Acoustics Inc.www.fdiacoustics.com

I agree with Peter.

Standards are general guidelines. When you get into specific details
of specific sources in specific circumstances, the best approach to
take often comes down to experience.

Savant

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Natural Science Forum / Physics / Acoustics / July 2008

Environmental noise: measurement interval