Hi Mike,
I sent the following email to Eric Benjamin, and hoping you might be
able to help out with the figures I have now given? i.e. how would
they translate into dB for noise regulation purposes?
(I am feeling somewhat shell-shocked today after the past 10 days of
these bikes riding in circles, 2-strokes and 4-strokes and various
old cars as well. :-(
best wishes,
Vicki
Hi Eric,
Thanks very much for your response. It is very hard to find the
specific information I want re noise and dB, but my legal angle so
far is that excessive noise from neighbours is definitely regarded as
a legal nuisance. I reckon I can support my case by claiming that
the bikes in question are motocross bikes (Honda CR85) designed for
racing and unable to ever be registered because the noise is way
above the registerable vehicle limit (which is Australia seems to be
95-100 max). I only found 1 reference (Wiki Answers) to the CR85
having output of 130 dB, altho I think it is probably true. It would
be good if I could actually demonstrate how noisy the bikes are.
Today (now that the bikes have gone home) I received my Digital Sound
Level Meter. With it, I checked my car horn at 100 metres in still
conditions at max. 74.6 dB. The same horn recorded at 100 metres
measures -23 dB on my LS10 (low sensitivity, vol. 10, no low cut).
In comparison, the racing bikes at a distance of 100 metres, as
recorded on LS10 same settings, is from -15 dB to 0 dB.
Quieter 4-stroke bikes at 100 metres seem to be about -22 dB on LS10.
(I am measuring the dB via Izotope RX, rather than on the recorder
itself).
I am hopeless at maths and in understanding how dB works, and I was
rather hoping you might be able to tell me what dB you think the
noisy bikes might be, as might be measured on a sound level meter?
I'd be very grateful if you could help out Eric,
best wishes,
Vicki
On 30/09/2012, at 1:50 AM, Mike Rooke wrote:
> Hi,
> I contacted Vicki off list with some estimates based on the
> measured sensitivity of the capsules (since I supplied and measured
> them before shipping) - given some error in the measurements
> related to the boundary they are mounted on, plus temperature &
> distance effects. Using a fiddle factor I gave a couple of
> estimates for the SPL based on low sensitivity and gain 10 of the
> LS10. -Rough estimates at that.
>
> Using phones as SPL meters works providing you have a decent
> calibrator and can calibrate the (external) capsule, ignoring the
> response differences compared to a flat mic, the iphone manages
> down to around 20dBA with the EM172. Or used to Ive not checked or
> used it in a while for SPL measurement. Signal Scope pro for ios
> works well...
>
> -Mike.
>
>
>
>
>
>
>
> --- In "mipartitus"
> <> wrote:
>>
>> Hi Vicki,
>>
>> Good sound level measurement is a science in itself, but just to
>> get an idea you can in principle use a recording like you made, as
>> long as your recording chain has somehow been calibrated. I did
>> this for an Olympus LS-5 and EM-172 capsules (in free field, no
>> boundary rig), for all recording levels. I wanted to upload the
>> resulting graph, but it seems there is no room left for new files
>> in our Files directory.
>>
>> So here are the raw numbers: to get the sound pressure in Pascal
>> from the recorded wave file (assuming numbers range from -1.0 to
>> 1.0, which is standard in most editing/analysis programs) one has
>> to multiply the value in the recording with: 27.22, 7.18, 3.57,
>> 2.32, 1.68, 1.09, 0.80, 0.55, 0.43, 0.41 for recording levels 1-10
>> MIC Sense LOW, and 3.22, 0.70, 0.36, 0.24, 0.17, 0.13, 0.09, 0.06,
>> 0.05, 0.05 for recording levels 1-10 MIC Sense HIGH.
>>
>> There may well be a difference between the LS-5 and LS-10, and of
>> course the boundary rig has an effect too, so there probably is
>> little point in using these multiplication factors for this
>> specific recording. But if you have loose EM-172's and an LS-5 you
>> could give it a try (with the obvious benefit that you can make
>> unattended long-term recordings, and then later measure the noisy
>> parts).
>>
>> If the info above is not helpful in your case, in may be of
>> interest to people who use the LS-5/EM-172 combination, and who
>> want to get an estimate of, or reproduce, the absolute sound
>> levels of the auditory scenes they recorded.
>>
>> Best, Gabriel
>>
>> --- In vickipowys <vickipowys@>
>> wrote:
>>>
>>> All,
>>>
>>> Its spring in Australia, the birds are singing, but school holidays
>>> have just started and kids on motor bikes are doing constant
>>> circuits
>>> on the property next door. One new 2-stroke bike is particularly
>>> annoying. There is a 1-minute recording of it on SoundCloud here:
>>>
>>> http://snd.sc/VGh7DW
>>>
>>> I would like to be able to get a rough estimate of its noise level
>>> for legal reasons. Does anyone know how I can estimate a decibel
>>> reading from this recording? Details of equipment are on
>>> SoundCloud.
>>>
>>> My legal advice is that I have 'an entitlement to the quiet
>>> enjoyment
>>> of my property' and that the 2-stroke motorbike noise constitutes 'a
>>> legal nuisance'.
>>>
>>> Being able to measure the actual noise level would be a bonus.
>>>
>>> Thanks in advance,
>>>
>>> Vicki Powys
>>> Australia
>>>
>>
>
>
>
>
> ------------------------------------
>
> "While a picture is worth a thousand words, a
> sound is worth a thousand pictures." R. Murray Schafer via Bernie
> Krause.
>
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