Blast Sounds Research Articles

Impact of Single Blast Exposure on Neuronal Damage and Protein Levels in the Rat Brain at Varying Pressures

Abstract Introduction Brain injuries from blasts are increasingly common in both civilian and war settings. The impact of blast injuries at different pressure levels remains unclear, and their long-term effects are not well understood. This study investigates how varying blast pressures affect the rat brain over time. Materials and Methods Forty adult Sprague-Dawley rats were randomized into four groups of 10. Three groups were exposed to blasts, while one served as a control and was only subjected to blast sounds. Each group received a single blast at different pressures, followed by neuropsychological tests. After 28 and 84 days, the rats were sacrificed to measure tau protein and acetylcholine esterase levels and to conduct histological examinations of brain tissues. Results A single blast exposure did not significantly impact visuospatial memory or recall. Despite the lack of noticeable cognitive deficits, histopathological and biochemical analyses revealed reduced tau protein levels, indicating ongoing neuronal damage. Conclusion While a single blast did not significantly impair visuospatial memory or recall in this rat model, there were decreases in tau protein and acetylcholine esterase levels, along with histological signs of neuronal damage.

Recording anechoic gunshot waveforms of several firearms at 500 kilohertz sampling rate

Acoustic gunshot signals consist of a high amplitude and short duration impulsive sound known as the muzzle blast. This experiment involved documenting gunshot muzzle blast sounds produced by eight commonly used firearms. An elevated bracket (3 m above the ground) was built to achieve a quasi-anechoic environment for the duration of the muzzle blast. Twelve microphones (GRAS 46DP) were mounted on the bracket in a semi-circular arc to observe the azimuthal variation of the muzzle blast. Signals were recorded using LabVIEW. Similarities and differences among waveforms are presented.

Blast noise classification with common sound level meter metrics

A common set of signal features measurable by a basic sound level meter are analyzed, and the quality of information carried in subsets of these features are examined for their ability to discriminate military blast and non-blast sounds. The analysis is based on over 120 000 human classified signals compiled from seven different datasets. The study implements linear and Gaussian radial basis function (RBF) support vector machines (SVM) to classify blast sounds. Using the orthogonal centroid dimension reduction technique, intuition is developed about the distribution of blast and non-blast feature vectors in high dimensional space. Recursive feature elimination (SVM-RFE) is then used to eliminate features containing redundant information and rank features according to their ability to separate blasts from non-blasts. Finally, the accuracy of the linear and RBF SVM classifiers is listed for each of the experiments in the dataset, and the weights are given for the linear SVM classifier.

Factors Affecting Blast Traumatic Brain Injury

The overlapping pathologies and functional outcomes of blast-induced TBI (bTBI) and stress-related neurobehavioral disorders like post-traumatic stress disorder (PTSD) are significant military health issues. Soldiers are exposed to multiple stressors with or without suffering bTBI, making diagnosis and treatment as well as experimental modeling of bTBI a challenge. In this study we compared anxiety levels of Naïve rats to ones that were exposed to each of the following conditions daily for 4 consecutive days: C I: transportation alone; C II: transportation and anesthesia; C III: transportation, anesthesia, and blast sounds; Injured: all three variables plus mild blast overpressure. Following behavioral testing we analyzed sera and select brain regions for protein markers and cellular changes. C I, C II, and C III animals exhibited increased anxiety, but serum corticosterone levels were only significantly elevated in C III and Injured rats. C III and Injured animals also had elevated interferon-γ (IFN-γ) and interleukin-6 (IL-6) levels in the amygdala (AD) and ventral hippocampus (VHC). Glial fibrillary acidic protein (GFAP) levels were only significantly elevated in the VHC, prefrontal cortex (PFC), and AD of Injured animals; they showed an apparent increase in ionized calcium-binding adapter molecule (Iba1) and GFAP immunoreactivity, as well as increased numbers of TUNEL-positive cells in the VHC. Our findings demonstrate that experimental conditions, particularly the exposure to blast acoustics, can increase anxiety and trigger specific behavioral and molecular changes without injury. These findings should be taken into consideration when designing bTBI studies, to better understand the role of stressors in the development of post-traumatic symptoms, and to establish a differential diagnosis for PTSD and bTBI.

Multi-Evaluation of Blast Sound Propagation Attenuation by using Digital Simulation for Both Frequency and Time Weighting

Multi-Evaluation of Blast Sound Propagation Attenuation by using Digital Simulation for Both Frequency and Time Weighting

Basic results from full-scale tests at Fort Drum

This paper summarizes the principal results from two sets of full-scale tests of high-energy blast sound-absorbing surfaces. Test I involved two 3.66-m-square pits over which charges of military C-4 explosive were detonated. Pit 1 had a top layer of coarse gravel, a middle layer of pea gravel, and a bottom layer of coarse sand; Pit 2 had a homogeneous layer of pea gravel. Data from pressure gages at a distance of 2.6-m indicated that Pit 2 absorbed the sound of the blasts relative to the blast sounds measured over a grassy Reference Site, while Pit 1 was not absorptive at this distance. At a distance of 15 m, the opposite was true. The same trend that was evident at the 15-m distance was also evident at the 250-m distance, to a lesser extent. Test II involved plowing the ground in a region extending from a blast site. The plowed ground attenuated the blast sound at all frequencies of interest at distances up to 100 m. At distances greater than 100 m, the sound exposure level of the blast waves was attenuated for frequencies greater than 100 Hz but increased for frequencies less than 100 Hz. Some of the low-frequency data from both Tests seemed to implicate ground elasticity effects. Overall these tests indicate that the reduction of blast sound by local sound-absorbing surfaces is feasible and should receive further development.

Prediction of shock waves over a sound-absorbing area

High-energy impulsive sounds from firing large weapons or demolition charges are of particular interest because the high sound pressure levels and the low-frequency content of the spectrum mean the sounds are readily heard at long distances. The rules of linear acoustics do not apply for high-energy impulsive sounds impinging on reflecting or absorbing surfaces close to the source. Reflections of blast sounds from a reflecting surface, e.g., the ground, can contribute substantially to the sound perceived at locations in communities surrounding the blast site. This paper describes predictions of blast sound-pressure waveforms, determined by the previously described Flux-Corrected-Transport computer code, and corresponding measured waveforms of blast sounds produced by charges ofC-4 explosives mounted on a pole above a 3.66-m-square gravel-filled pit. Gravel was chosen as the sound absorber because it withstands the high pressures and high temperatures that are present near such explosive sources. It is shown that the predictions agreed well with the measurements. An analytical study showed that increasing the size of the pit to a 9-m radius would yield significant additional reductions in blast sound pressures.

Prediction of the difference between CSEL and ASEL of blast sound for correlation purposes with annoyance

ISO-TC43/SC1/WG45 plans to have three categories of impulsive sound sources for purposes of noise ratings. Each category, ‘‘ordinary impulsive’’ (adjustment 5 dB), ‘‘highly impulsive’’ (12 dB), and ‘‘high-energy impulsive’’ (significantly more than 12 dB to ASEL) sound, will receive the indicated adjustment to its measured SEL. But these adjustments based on categories of sources do not take into account the change of ‘‘impulsiveness’’ with propagation. This omission raises uncertainties—especially for high-energy blast sounds. Recently published proposals by Buchta and Vos use the differences between CSEL and ASEL at the receiver to determine impulse adjustments that correlate with annoyance. However, this level difference is not reliably obtained by measurement because the spectrum is influenced by local properties of the ground due to superposition, and because the A-weighted levels are close to the background noise level at typical receiver distances. For blasts from explosive sources (e.g., demolitions, weapon firing), this paper presents a theoretical approach to predict CSEL-ASEL using an energy concept forthe sound spectrum. This approach yields an expected value for the dif-ference between C- and A-levels that depends on the acoustical energy of the sound at the source and on the frequency-dependent attenuation along the propagation path.

A comparative study of human response, indoors, to blast noise and sonic booms

Abstract : For the past two decades, blast sounds and sonic booms have been assessed in a like manner in the United States using a C-weighted day-night level. Recently, a new method which replaces the C-weighted day-night level had been recommended (Schomer, Nov. 1994), and reviewed and recommended (NRC, 1996). In this new method, as in the old, blast sounds and boom sounds are once again assessed in a like manner. However, while available evidence suggested that in an indoor setting, blast sounds and sonic booms could be treated similarly, evidence in the form of a side-by-side comparison was lacking. The purpose of the study reported herein was to provide the lacking side-by-side data. The study tested if subjects indoors responded in a like manner to both blast and boom sounds. This study also tested if the response of subjects to sonic booms followed the new method suggested in Schomer (Nov. 1994).

Human and community response to military sounds: Results from field-laboratory tests of small-arms, tracked-vehicle, and blast sounds

Human and community response to military sounds: Results from field-laboratory tests of small-arms, tracked-vehicle, and blast sounds

Properties and Measurement of Blast Sound due to Blasting

Properties and Measurement of Blast Sound due to Blasting

Indoor human response to blast sounds that generate rattles.

The two major noise sources that cause environmental problems for the U. S. Army are helicopters and large weapons such as artillery, tanks, and demolition. These large weapons produce blast sounds that contain little energy above 200 Hz and that are particularly troublesome to deal with because they excite rattles in structures. The purpose of this study was to systematically test subjective response to the presence or absence of rattles in otherwise similar blast sound environments. A second purpose of the study was to test if there were structural changes that could reduce annoyance within the indoor blast sound environment. This study was done using a specially constructed test house and highly repeatable shake table to generate the blast sounds. The data clearly show that no commonly used environmental noise measure adequately describes the indoor environment when the blast excites rattles. Although the indoor blast ASEL changes by only about a decibel or so (and the indoor blast CSEL changes by even less), the subjective response changes by up to 13 dB. At low blast levels, the increase in human annoyance response is largest, and this annoyance response offset decreases to about 6 dB when the outside, flat-weighted peak sound-pressure level of the blast increases from 112 to 122 dB.