David Josephs Posted January 18, 2012 Share Posted January 18, 2012 Probably done before yet It always bothered me that it was claimed that hulls and a bolt action was heard AFTER THE FIRST SHOT I say no way... and then two more shots? They couldn't have heard very much of anything DJ http://www.elcaudio.com/tablesforweb.pdf A blast of the type produced from the MC would exceed 150 decibels... These men were no more than 10-20 feet from the muzzle These three guys wouldn't have been able to hear each other after the first shot with the ringing in their ears, let alone hulls hitting the floor OR the action of the bolt.... add to this their story of deciding to run up to the 5th floor at 12:20-12:25, taking the back entrance... to get to the shooting zone JUST IN TIME to testify hearing hulls dropping http://www.elcaudio.com/decibel.htm Fortunately, even the quietest rifle shots were loud enough at 50 ft. to be much louder than the ambient, or background, noise The effects of hearing loss as a result of blasts (such as those produced by firearms) isn't as well documented as occupational hearing loss. There are individuals who have suffered permanent hearing loss as a result of shooting, but the effects of single, loud-noise events varies from person to person. One common complaint shooters have isn't hearing loss, but tinnitus (a "ringing in the ear"). It should be noted that tinnitus frequently accompanies hearing loss resulting from noise exposure. The most well-known aftereffect of exposure to high-intensity sound is the change in auditory sensitivity. If an individual’s auditory threshold (hearing sensitivity) is measured before and after an exposure, the difference in hearing threshold levels is, by definition, the threshold shift (TS). If the threshold shift later disappears, then it is called a temporary threshold shift (TTS). If the shift does not disappear, the final measured threshold shift is called a permanent threshold shift (PTS). The most undesirable aftereffect of exposure to high-intensity sound is a PTS. Sound-induced PTS is commonly divided into two categories depending on whether the loss was produced by a single, short exposure at a very high intensity (acoustic trauma) or by repeated longer exposures to noise at more moderate sound pressure levels. It is clear from animal studies that in acoustic trauma the inner ear has been subjected to such stress that its mechanical (or elastic) limit has been exceeded. Various structures of the organ of Corti, including hair cells (the individual receptor cells within the inner ear), may become partly or wholly detached. Additionally, one or more of the several membranes in the cochlea may be ruptured, allowing an intermixture of fluids of different composition, thereby poisoning hairs cells that survived the mechanical stress. The end consequence is a pronounced loss of hearing sensitivity at the frequencies correlated with the locus of this destruction. In addition to studies showing that high-intensity impulse noise affects the cochlea differently than does continuous noise, there are logical reasons why the equivalent energy theorem can’t always predict risk for hearing damage. Logically, we know there are levels associated with impulses that are dangerous with just one exposure. But at lower levels, individuals can withstand almost an infinite number of the same “signature” impulses (same waveform, but at a lower intensity) without harm. Also, most of the data supporting the equivalent energy theorem have been large-scale demographic studies. Controlled laboratory studies using animals (e.g., ref. 9) have shown that hearing loss resulting from exposure to impulse noise of equal energy increases with peak level. To iterate: The danger of hearing loss resulting from a single exposure to high-intensity impulse noise is at least as great as what we would predict using Figures 1 or 2. Link to comment Share on other sites More sharing options...
Karl Kinaski Posted January 20, 2012 Share Posted January 20, 2012 (edited) Probably done before yet It always bothered me that it was claimed that hulls and a bolt action was heard AFTER THE FIRST SHOT I say no way... and then two more shots? They couldn't have heard very much of anything DJ http://www.elcaudio.com/tablesforweb.pdf A blast of the type produced from the MC would exceed 150 decibels... These men were no more than 10-20 feet from the muzzle These three guys wouldn't have been able to hear each other after the first shot with the ringing in their ears, let alone hulls hitting the floor OR the action of the bolt.... add to this their story of deciding to run up to the 5th floor at 12:20-12:25, taking the back entrance... to get to the shooting zone JUST IN TIME to testify hearing hulls dropping http://www.elcaudio.com/decibel.htm Fortunately, even the quietest rifle shots were loud enough at 50 ft. to be much louder than the ambient, or background, noise The effects of hearing loss as a result of blasts (such as those produced by firearms) isn't as well documented as occupational hearing loss. There are individuals who have suffered permanent hearing loss as a result of shooting, but the effects of single, loud-noise events varies from person to person. One common complaint shooters have isn't hearing loss, but tinnitus (a "ringing in the ear"). It should be noted that tinnitus frequently accompanies hearing loss resulting from noise exposure. The most well-known aftereffect of exposure to high-intensity sound is the change in auditory sensitivity. If an individual’s auditory threshold (hearing sensitivity) is measured before and after an exposure, the difference in hearing threshold levels is, by definition, the threshold shift (TS). If the threshold shift later disappears, then it is called a temporary threshold shift (TTS). If the shift does not disappear, the final measured threshold shift is called a permanent threshold shift (PTS). The most undesirable aftereffect of exposure to high-intensity sound is a PTS. Sound-induced PTS is commonly divided into two categories depending on whether the loss was produced by a single, short exposure at a very high intensity (acoustic trauma) or by repeated longer exposures to noise at more moderate sound pressure levels. It is clear from animal studies that in acoustic trauma the inner ear has been subjected to such stress that its mechanical (or elastic) limit has been exceeded. Various structures of the organ of Corti, including hair cells (the individual receptor cells within the inner ear), may become partly or wholly detached. Additionally, one or more of the several membranes in the cochlea may be ruptured, allowing an intermixture of fluids of different composition, thereby poisoning hairs cells that survived the mechanical stress. The end consequence is a pronounced loss of hearing sensitivity at the frequencies correlated with the locus of this destruction. In addition to studies showing that high-intensity impulse noise affects the cochlea differently than does continuous noise, there are logical reasons why the equivalent energy theorem can’t always predict risk for hearing damage. Logically, we know there are levels associated with impulses that are dangerous with just one exposure. But at lower levels, individuals can withstand almost an infinite number of the same “signature” impulses (same waveform, but at a lower intensity) without harm. Also, most of the data supporting the equivalent energy theorem have been large-scale demographic studies. Controlled laboratory studies using animals (e.g., ref. 9) have shown that hearing loss resulting from exposure to impulse noise of equal energy increases with peak level. To iterate: The danger of hearing loss resulting from a single exposure to high-intensity impulse noise is at least as great as what we would predict using Figures 1 or 2. One of them (Yarmann, Normann, or Williams?)said, he located the first bumm down the street, and thought it was backfire...the first bumm was indeed caused by a sort of fire cracker... Quote. Mr. Liebeler. So, you were standing directly in front of the Texas School Book Depository Building and on the same side of Elm Street that the Texas School Book Depository is located? Mrs. Baker. Yes. Mr. Liebeler. Tell me what you saw? Mrs. Baker. Well, after he passed us, then we heard a noise and I thought it was firecrackers, because I saw a shot or something hit the pavement. () Mr. Liebeler. As you went down Elm Street that you saw this thing hit the street--what did it look like when you saw it? Mrs. Baker. Well, as I said, I thought it was a firecracker. It looked just like you could see the sparks from it and I just thought it was a firecracker and I was thinking that there was somebody was fixing to get in a lot of trouble and we thought the kids or whoever threw it were down below or standing near the underpass or back up here by the sign. close quote IMO...the first bang was indeed caused by a firecracker, hitting the pavement behind the "Queen Mary"... Jarman, Norman and Williams heart only two shots directly above them...whoever the SBDB shooter was, he fired TWO shots... KK I should add this firecracker bang occurred about Zappi frame 200 Edited January 20, 2012 by Karl Kinaski Link to comment Share on other sites More sharing options...
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