SpeedyManiac
Member
- Aug 8, 2000
- 2,378
- 0
Hi guys,
As most of you know, I'm in Mechanical Engineering at the University of Alberta. Well, in my vibrations class we are also covering sound. Today in class, we talked about sound pressure levels, sound power levels and the different scales used to correct for frequency range. The idea of the scale correction is to account for the ear's ability to pick up frequencies around 3100Hz better than other frequencies. In essence, it is a perceived loudness correction.
There are four correction scales used today: A, B, C and D. A is the most common, widely accepted scale. C is still used a little bit and B and D are close to extinct, though they still exist. I don't have the graph handy (I'll ask my professor for a copy) but in essence, the 'A' scale reduces the sound rating of lower frequency sounds. Sometimes by as much as 20dB. The 'C' scale weights all frequencies close to the same. Guess which scale the AMA uses.
That's right, the AMA uses the dB(A) scale, which underrates low frequency noise. What frequencies do four-strokes make noise at? Anyone? That's right, lower frequencies. So, while a two-stroke and four-stroke might 'test' the same on a 'A' scale measurement system, in essence, the four-stroke is actually louder in absolute sound pressure level. No wonder there is noise complaints. What a bunch of idiots the AMA is.
I want to know if they actually consulted any professionals in the sound industry, or if they did any research? I have a grasp of this stuff after two 50 minute lectures on the material. Someone who's livelihood depends on this stuff should know what's going on. What a bunch of idiots... :bang:
As most of you know, I'm in Mechanical Engineering at the University of Alberta. Well, in my vibrations class we are also covering sound. Today in class, we talked about sound pressure levels, sound power levels and the different scales used to correct for frequency range. The idea of the scale correction is to account for the ear's ability to pick up frequencies around 3100Hz better than other frequencies. In essence, it is a perceived loudness correction.
There are four correction scales used today: A, B, C and D. A is the most common, widely accepted scale. C is still used a little bit and B and D are close to extinct, though they still exist. I don't have the graph handy (I'll ask my professor for a copy) but in essence, the 'A' scale reduces the sound rating of lower frequency sounds. Sometimes by as much as 20dB. The 'C' scale weights all frequencies close to the same. Guess which scale the AMA uses.
That's right, the AMA uses the dB(A) scale, which underrates low frequency noise. What frequencies do four-strokes make noise at? Anyone? That's right, lower frequencies. So, while a two-stroke and four-stroke might 'test' the same on a 'A' scale measurement system, in essence, the four-stroke is actually louder in absolute sound pressure level. No wonder there is noise complaints. What a bunch of idiots the AMA is.
I want to know if they actually consulted any professionals in the sound industry, or if they did any research? I have a grasp of this stuff after two 50 minute lectures on the material. Someone who's livelihood depends on this stuff should know what's going on. What a bunch of idiots... :bang: