Thanks for that Raimund.
I was thinking the bikes might be even louder at 1.0m, than your
suggested 121 dB. The car horn measured with Digital Sound Level
Meter at 1.0m was 99.5 dB. The car horn was MUCH quieter than the
bikes at 100 m.
Wiki answers (see earlier email) suggested the Honda bike could be
114 dB at 100 metres.
Vicki
On 02/10/2012, at 7:23 PM, Raimund wrote:
> Hi Vicky,
>
> Based on your measurements, the sound level of the bikes would be
> approximately 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 quite 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 applies to a distance of 1 meter, which seems to match your
> own measurements quite 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.
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