[Spridgets] 1275 with headers exhaust?

[GUY DAY]

 On Sat, Jun 30, 2018 at 2:42 PM, derf <derf247 at gmail.com> wrote:

104dB is 4x as loud as 98dB.
On Sat, Jun 30, 2018, 12:37 AM Billy Zoom via Spridgets <spridgets at autox.team.net> wrote:

> UK Noise limits vary but 98 to 103, and occasionally 105 are typical.


Assuming these are db ratings, at what distance from the car is it measured?
The sound pressure drops by half each time the distance is doubled.
104db would be twice as loud as 98db, so it seems there’s quite a range.
I’ve had much experience with ill-trained security guards misusing sound pressure meters, so I’m naturally skeptical of such regulations.

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For UK Motor Sport (governed by the RACMSA) the sound levels are outlined in the PDF, 
 https://www.msauk.org/.../144-155commonregulationsforcompetitorsvehiclesj-2.pdf
The paragraphs at 5.17 and 5.18 refer in combination with the drawing at 5.18 ( page 11 of the PDF and page 154 of the 'Blue Book') with the drawing being the most readily understandable depiction.  I fully endorse Billy Zoom's comments about sound level measuring being open to variations in the manner levels are taken and even a child shouting/crying 100 metres away or being level with a noise reflecting building can cause meter level reading anomaly.  In civil practise, that is normal use on public roads, it is illegal to modify the exhaust system to make a vehicle noisier after it has been ‘type approved’ (checked by manufacturer so it meets environmental and safety standards).The police can also take action if your vehicle’s silencer does not work in the way it was designed or if you’re driving in a way that creates too much noise.
Hope it helps,
Guy R Day
   
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