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Post by tkw251070 on Jun 15, 2009 16:05:03 GMT -4
Seems Jarrah thinks that a 140 dB jet engine is twice as loud as a 70 dB guitar. Seems he is not aware that dBs are measured on a log scale. As pointed out by a couple of people... yet, he criticises the science of someone else in the same sentence. www.youtube.com/watch?v=je2YOJMEQ98&feature=channel_page |
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Bob B.
Bob the Excel Guru?
Posts: 3,072
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Post by Bob B. on Jun 15, 2009 17:28:16 GMT -4
Seems he is not aware that dBs are measured on a log scale. Does he know what a log scale is? |
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Post by Ginnie on Jun 15, 2009 17:51:09 GMT -4
Can't wait to see his reply - if indeed he does...
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Post by tkw251070 on Jun 15, 2009 18:23:26 GMT -4
Does he know what a log scale is? He probably thinks it is the build-up of calcium carbonate on the outside of trees. Let's see him back pedal from this one. The point he does not seem to understand is that he makes these errors and when they are picked up he can't understand why anyone with two brain cells to rub together does not take him seriously. How can anyone who shows such bumbling incompetence and lack of knowledge for the most basic scientific definitions be believed when handling systems that are time evolving, complex in geometry and tend to have statistical distributions (space radiation being the prime example). My expertise is solid state physics and radiation. While I think I can see faults with his lego model in a box experiment, is there anyone on here who is better qualified to explain why it is so wrong. The whole photography and albedo argument is probably not my best area. Learning, but it's just not as interesting as radiation. Sorry  |
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Post by HeadLikeARock (was postbaguk) on Jun 17, 2009 13:22:26 GMT -4
My expertise is solid state physics and radiation. While I think I can see faults with his lego model in a box experiment, is there anyone on here who is better qualified to explain why it is so wrong. The whole photography and albedo argument is probably not my best area. Learning, but it's just not as interesting as radiation. Sorry The most obvious thing to me is the fact that he is eliminating much of the reflected light from the surface with the sides of the box (in his experiment there is very little surface available to light reflected from the ground behind and to the sides of the Lego astronaut). Another is that he is trying to compare his photos to Apollo photos that have been processed to increase the contrast. He hasn't factored in the difference in reflectivity of the material of the model and lego figure compared to the LM (how much of a difference this would make I don't know, but he's just ignored it). Problems with comparing the albedo of tarmac to the albedo of the moon are covered in this article:- jeff.medkeff.com/astro/lunar/obs_tech/albedo.htmThose are the problems that struck me, with the box itself being the biggest. When I pointed it out to him, he asked if I wanted him to use a bigger box.  |
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Post by tkw251070 on Jun 17, 2009 15:17:44 GMT -4
My expertise is solid state physics and radiation. While I think I can see faults with his lego model in a box experiment, is there anyone on here who is better qualified to explain why it is so wrong. The whole photography and albedo argument is probably not my best area. Learning, but it's just not as interesting as radiation. Sorry The most obvious thing to me is the fact that he is eliminating much of the reflected light from the surface with the sides of the box (in his experiment there is very little surface available to light reflected from the ground behind and to the sides of the Lego astronaut). Another is that he is trying to compare his photos to Apollo photos that have been processed to increase the contrast. He hasn't factored in the difference in reflectivity of the material of the model and lego figure compared to the LM (how much of a difference this would make I don't know, but he's just ignored it). Problems with comparing the albedo of tarmac to the albedo of the moon are covered in this article:- jeff.medkeff.com/astro/lunar/obs_tech/albedo.htmThose are the problems that struck me, with the box itself being the biggest. When I pointed it out to him, he asked if I wanted him to use a bigger box. Maybe I should have more confidence in my physics, but I was thinking along those lines too. Just didn't want to post on here and find that I wrong and later have it screen captured by a CTer. Yes, he blocked out the scattered light. I'd also like know how much light the metal LM on the moon would reflect compared to his plastic lego model. Thanks for link on comparing tarmac and the moon. I'll have a jolly good read of that and educate myself some more. |
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Post by Ginnie on Jun 17, 2009 21:57:16 GMT -4
I tried to test this a couple of years ago...  |
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Post by brotherofthemoon on Jun 17, 2009 22:29:31 GMT -4
Allow me to propose a simple experiment for Mr. Jarrah:
1. Sit in front row of James Taylor concert. Record Db level.
2. Sit in front row of ManoWar concert. Record Db level.
3. Compare results.
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Post by gwiz on Jun 18, 2009 16:39:21 GMT -4
I tried to test this a couple of years ago... Of course it makes a big difference if you set your exposure for the shaded side of the object, which is generally what the astronauts did for their LM shadow pictures, but there are also pictures with a normal surface exposure where the shadow side of the LM is very dark. |
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Post by laurel on Jun 18, 2009 16:54:40 GMT -4
Forgive the off-topic question, but are those salt and pepper shakers Vietnamese ceramic from Ten Thousand Villages? That blue and white lotus pattern looks very familiar.
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Post by Ginnie on Jun 18, 2009 17:06:52 GMT -4
Forgive the off-topic question, but are those salt and pepper shakers Vietnamese ceramic from Ten Thousand Villages? That blue and white lotus pattern looks very familiar. They could be, laurel. They sit in a basket that came with them. We've shopped at Ten Thousand Villages a few times. |
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Post by Ginnie on Jun 18, 2009 17:07:53 GMT -4
I tried to test this a couple of years ago... Of course it makes a big difference if you set your exposure for the shaded side of the object, which is generally what the astronauts did for their LM shadow pictures, but there are also pictures with a normal surface exposure where the shadow side of the LM is very dark.  My cheap digital doesn't have exposure settings... |
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Post by tedward on Jun 19, 2009 4:29:34 GMT -4
Thought this was basic skool stuff? At least I remember my physics and maths from yonks ago,
But, just like the other video's, you don't have to go far for a reason as to why he has not made any main stream challenges.
Thing about the box, and the rest of it, it is made to fit his particular way of trying to win an argument or at least present it as a done deal. If someone was to look through and not realise the gaffe (whether intended or not) then they might accept it without looking at what the environment is like. The albedo argument is all up the spout, I found out a bit about it a few years ago and there are issues with argument. Going back a few video's the dish capabilities were woefully inaccurate. Theme continued I am afraid.
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Post by Obviousman on Jun 19, 2009 9:39:21 GMT -4
Jarrah has never been one for facts...
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Post by dumbtechie on Jul 4, 2009 0:24:12 GMT -4
Even when he acknowledges that decibels are a logarithmic unit he manages to get it wrong, claiming that halving sound pressure corresponds to a change of -3 dB.
What SPL measurements are actually based on is the intensity of the sound field, measured in W/m2. As it happens, intensity varies as the square of the sound pressure, so a change in RMS sound pressure from 1 Pa to 2 Pa is a change of approximately 6.02 dB.
The intensity of sound can be found by taking the square of the sound pressure and dividing it by the characteristic acoustic impedance of the medium. The characteristic impedance of air at STP is approximately 420 acoustic ohms, (sometimes called "Rayls" after Lord Rayleigh), so a sound pressure of 20 uPa RMS (the 0 dB SPL reference pressure) corresponds to a sound intensity of approximately 9.52 x 10-13 W/m2- very close to the "0 dB SPL= 1 x 10-12" used by sound system designers.
If you work it out for yourself, it turns out that 1 Pa RMS =2.381 x 10-3 W/m2 = 94 dB SPL and 2 Pa RMS = 9.52 x 10-3 W/m2 = 100 dB SPL.
As for the subjective human perception of loudness, the usual rule of thumb is that most listeners will describe a change in SPL of 10 dB as "twice (or half) as loud".
This is all stuff that those of us who work in the technical side of the audio industry can whip out from memory. I guess you can't expect someone who is Googling or Wikiing for all their information to understand what they're reading.
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My cheap digital doesn't have exposure settings...