Hi Vicky,
Based on your measurements, the sound level of the bikes would be approxima=
tely 74dB - 15dB + 23dB =3D 82 dB at that distance. Under ideal conditions,=
the sound level drops by 6 dB on each doubling of the distance. This would=
result in the following sound levels at closer distances:
at 100 m : 82 dB
at 50 m: 88 dB
at 25 m: 94 dB
at 12.5 m : 100 dB
at 6.2 m : 106 dB
at 3.1 m : 112 dB
at 1.5 m : 118 dB
at 1.0 m : about 121 dB SPL
The sound propagation over larger distances near the ground is however quit=
e complex (depending on vegetation, temperature of both the ground and the =
air, wind speed, wind direction, =85). So, the estimated sound level of 121=
dB SPL at 1 m is just a very rough estimate.
I guess that the number of 130 dB that you found for that bike model applie=
s to a distance of 1 meter, which seems to match your own measurements quit=
e well.
Regards,
Raimund
--- In vickipowys <> wrote:
>
> 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,
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
------------------------------------------------------------------------
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/naturerecordists/
<*> Your email settings:
Digest Email | Traditional
<*> To change settings online go to:
http://groups.yahoo.com/group/naturerecordists/join
(Yahoo! ID required)
<*> To change settings via email:
<*> To unsubscribe from this group, send an email to:
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
------------------------------------------------------------------------
|