Fast weighting ready to drive sound

[jakem]

Greetings,

The FSAE rule EV4.14.3 states, "The sound level must be a minimum of 70dBA, fast weighting, in a radius of 2m around the car." What is meant by "fast weighting?"

[MCoach]

I think I should start a new rule...
If I search for something and it is on the first page of Google search, you owe me a beer.

I searched 'fast weighting' in Google. This was the first link:

http://www.noisemeters.com/hel...q/time-weighting.asp (http://www.noisemeters.com/help/faq/time-weighting.asp)

Time Weightings - Fast, Slow or Impulse?

Sound level measurements using any grade of sound level meter can be Fast, Slow, or Impulse time weighted. These weightings date back to the time when sound level meters had analogue meters and defined the speed at which the meter moved. Under Fast the needle would move fast to show quickly varying noise and under Slow the needle would be damped to smooth the noise out to be easier to read.
The Impulse time weighting is about four times faster than Fast, with a short rising time constant but a slow falling one. It is little used in most countries these days and so can usually be ignored.
Fast corresponds to a 125 ms time constant. Slow corresponds to a 1 second time constant. Impulse has a time constant of 35 ms.
As these time constants were set in standards, they have continued in digital meters, now being calculated or simulated before being displayed, stored or used to calculate other acoustic parameters that need the time weighting.
The following terms are used to express the sound level, clearly indicating the time weighting as well as the frequency weighting:

LAS Slow, A-weighted Sound Level
LAF Fast, A-weighted Sound Level
LCS Slow, C-weighted Sound Level
LCF Fast, C-weighted Sound Level

TL;DR Fast corresponds to a 125 ms time constant.

[TMichaels]

I think I should start a new rule...
If I search for something and it is on the first page of Google search, you owe me a beer.

+1

Though that would make some people in this forum an alcoholic right away http://fsae.com/groupee_common/emoticons/icon_smile.gif

[jlangholzj]

Originally posted by TMichaels:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I think I should start a new rule...
If I search for something and it is on the first page of Google search, you owe me a beer.

+1

Though that would make some people in this forum an alcoholic right away http://fsae.com/groupee_common/emoticons/icon_smile.gif </div></BLOCKQUOTE>

Tobias you should remember that we're all already alky's anyway http://fsae.com/groupee_common/emoticons/icon_razz.gif

[TMichaels]

I am fine with that as long as you are able to stay dry during the event. We actually test that at FSG during the driver briefings http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Tilman]

Originally posted by jakem:
Greetings,

The FSAE rule EV4.14.3 states, "The sound level must be a minimum of 70dBA, fast weighting, in a radius of 2m around the car." What is meant by "fast weighting?"

If your ready to drive sound is significantly louder than a normal conversation in a distance of 2 metres around the car you will most likely pass this test.

[Steve Works]

If your ready to drive sound is significantly louder than a normal conversation in a distance of 2 metres around the car you will most likely pass this test.
Ha ha...never heard of this "test" before...but yeah...I guess it sums it up.
_________________________________
Steve Works
decibel meter (http://www.dalimar.ca/en/product/sound-level-meters)