David M. Jenkins

The effects of continuous application of the TASER X26 waveform on Sus scrofa.

This study investigated and evaluated the safety margins of the continuous long duration (up to 30 min) effect of the TASER X26 waveform, using a Sus scrofa model. Long duration continuous stimulus has not been evaluated on humans or human surrogates prior to this study. Swine were used as models due to similarities with humans in their skin and cardiovascular systems. Very long duration was used to determine both exposure dose and possible adverse physiological effects of dose. The trial began with an application of 10 min, and subsequent animals received increasing exposure time up to a survived maximum duration of 30 min. At the onset of this work, it was hypothesized that there would be a time limit after which most animals would not survive consistent with increased dose response. However, this hypothesis was not supported by the experimental results. All animals (10 of 10) survived up to 3 min. Seven of the 10 animals survived up to a 10‐min exposure and 3 of 5 animals with a 30‐min target exposure survived the full exposure. Surviving animals were recovered and observed for 24 h, with no postrecovery deaths. This suggests that swine (based on physiology) will not experience a fatal event when exposed to the TASER X26 for a continuous 3 min. Conclusions regarding longer duration (10–30 min) are not as certain due to the small sample sizes at these time intervals.

Feasibility of a high-powered carbon nanotube thin-film loudspeaker

The thermophone, conceived in 1917 by Arnold and Crandall, was a unique thermoacoustic loudspeaker. The high heat capacity per unit area (HCPUA) of thin-film materials at that time limited the usefulness of thermophones. Recently, researchers of carbon nanotubes (CNTs) have developed techniques to create a super-aligned thin-film of multi-walled CNTs, possessing extremely low HCPUA. This paper will discuss CNT thin-film loudspeaker theory as well as some initial investigations into the feasibility of a high-powered audio CNT speaker. The advantages of such a loudspeaker include: Ultra-lightweight, compact, no moving parts, low cost, and independence from expensive rare-earth materials.

An investigation of induction motor zeroth-order magnetic stresses, vibration, and sound radiation

A computational approach is undertaken to better understand what can be one of the primary contributors to sound radiation from induction motors-the n=0 magnetic stresses. An electromagnetic finite-element model, a structural dynamic finite-element model, and an acoustic boundary-element model of an induction motor are used to illustrate some sources of n=0 electromagnetic stresses, and how their resultant vibration field on the stator can be enhanced by boundary conditions, such as stator supports, to result in peaks in the radiated noise spectrum.

Human electromuscular incapacitation devices characterization: a comparative study on stress and the physiological effects on swine.

Werner, JR, Jenkins, DM, Murray, WB, Hughes, EL, Bienus, DA, and Kennett, MJ. Human electromuscular incapacitation devices characterization: A comparative study on stress and the physiological effects on swine. J Strength Cond Res 26(3): 804–810, 2012—Human electromuscular incapacitation devices or electromuscular disruption (EMD) devices are increasingly used in police and military applications. Most individuals who experience electromuscular incapacitation are in a stress-filled state, and the effects of prolonged or repeated exposures are not well understood. Three different commercially available EMD devices were tested randomly on 6 anesthetized pigs each for a total of 18 pigs. Each animal was exposed to an initial 60-second application of the EMD device as an initial stressor. The animals were then allowed to rest under anesthesia for 60 minutes followed immediately by a 180-second application of the same device. Arterial blood gases and serum samples were collected throughout the experiment to measure catecholamines (epinephrine, norepinephrine, and dopamine) and cortisol. All the devices produced some level of muscle tetany as a result of the electrical delivery to the animal. All the pigs showed a mixed metabolic and respiratory acidosis. Cortisol tended to decrease after the initial exposure and slightly increased over the rest period. The extreme muscular work caused by the electrical stimulation resulting in muscle contractions did not result in a strong stress response but did result in an immediate sympathetic response during both applications of the device leading to the conclusion that initial stressor followed by rest and prolonged EMD device application did not exhaust the sympathetic system. For healthy adult animals, despite the prolonged muscular exertion and physiological stress caused by EMD devices, the body should be able to mount an appropriate sympathetic response and recover normally.

Advancements toward a high-power, carbon nanotube, thin-film loudspeaker

The carbon nanotube (CNT) thermophone has been explored as a novel loudspeaker. Potential advantages of this technology in the audio industry include ultra-lightweight, low production cost, compact size, and independence from rare-earth materials. In this paper, progress toward a practical CNT loudspeaker is presented. Large, high quality CNT thin-film assemblies are designed and built. Design guidance for these types of assemblies is provided. Maximum sound output level, total harmonic distortion, and power efficiency tests are performed. A maximum source level of 111 dBA at 1 m is achieved at 2 kHz with the new sources. The main hurdle to this technology remains power efficiency. Several paths forward are discussed as this technology continues to advance to a position where it may be able to compete with current state-of-the-art, moving-coil loudspeakers.

Scale Time Offset Robust Modulation for code division multiaccess

This paper introduces and analyzes Scale-Time Offset Robust Modulation (STORM) for use in code division multiaccess (CDMA) systems using spread quadrature phase shift keying (QPSK) to increase the capacity of a CDMA network. Since current commercial CDMA systems have dedicated spectrum, the capacity is primarily limited by the interference of other CDMA users; thus, power control and multiuser interference mitigation are the focus of CDMA capacity enhancements. Although extensive research in these areas continues, significant, robust, practical capacity enhancements have been difficult to realize for existing commercial CDMA systems such as Wideband-CDMA (WCDMA). STORM offers potential to practically enhance the capacity of CDMA systems by robustly realizing more rapid power control and more efficient multiuser interference mitigation.

Effects of Human Electro-Muscular Incapacitation (HEMI) Devices on Cardiovascular Changes in Anesthetized Swine as Measured by Transesophageal Echocardiography (TEE)

The abundance of, and reliance upon, human electro‐muscular incapacitation (HEMI) devices, especially in law enforcement, has generated scrutiny and examination of these technologies. The purpose of this study was to examine cardiovascular effects resulting from typical (5 sec) and longer activation (20 sec) HEMI applications studying myocardial function and peripheral vascular system using a combination of invasive cardiovascular catheters and transesophageal echocardiography (TEE). Six healthy swine (Sus scrofa) 3–5 months in age and weighing between 60 and 86 kg were anesthetized and exposed to the TASER Model X26 waveform while transesophageal echocardiography was performed. Stroke volume was shown to statistically decrease during HEMI application indicating an increase in systemic vascular resistance, but HEMI application did not result in myocardial dysfunction (“cardiac stunning”).

Removing Unwanted Noise from Operational Modal Analysis Data

Operational modal analysis data includes the measurement of dynamic signals such as structural vibration data and the corresponding excitation force or pressure. In addition to the desired information, measured structural vibration data can include unwanted electrical noise and vibration energy from adjacent structures. Measured dynamic pressures can contain unwanted signals such as acoustic and vibration induced pressures. In this paper, a noise removal technique is presented in which an unlimited number of unwanted correlated signals can be removed from a set of measured data. In its simplest form, this technique is related to coherent output power (COP). However, unlike COP noise removal, multiple signals can be removed from measured data while retaining the magnitude and phase of the original data required for modal analysis processing. This technique is demonstrated using vibration data and dynamic wall pressure measurements from a thin-walled aluminum cylinder filled with water flowing at 20 ft/s.

Beam steering for a long range Acoustic Hail and Warning Device for maritime applications

A new means for steering the beam of a phased line array, electromechanical steering, is described and applied to a long range Acoustic Hail and Warning Device (AHWD) developed for maritime applications. In electromechanical steering, the array elements pivot individually resulting in elements being off-set and rotated in the desired steered beam/sound projection direction. A digital signal processor is used to align the phase fronts of the elements due to the mechanical offsets. Electromechanical steering has several advantages over the purely electronic steering of the array. The electromechanically steered beams are not subject to the individual element aperture function attenuation that reduces the sound pressure level (SPL) that commonly occurs for electronically only steered beams at large steering angles. Also, the primary lobe distortion and (lower frequency) onset of grating lobes that occur when a beam is steered electronically is absent with electromechanical steering. In short, with electromechanical steering, the SPL and directivity from the AHWD is entirely equivalent to that obtained by rotating the AHWD to the desired angle with a conventional pan and tilt mount but requires much less space and provides for more flexible mounting options including improved system stealth. In addition, a novel type of line array phase shading is presented which allows the AHWD to be electronically switched from directional mode (typical beam steering highly focused mode) to non-directional wide field of regard for applications that require simultaneous ensonification of targets over large lateral angles. ©2011 Institute of Noise Control Engineering

Development of a long range acoustic hail and warning device for maritime applications

An Acoustic Hail and Warning Device (AHWD), intended to project intelligible voice warning messages to listeners at 500 yards (457 m) where at least 80% of the words in an unknown message are intelligible, was designed, fabricated and tested. Design was facilitated by a methodology developed to help ensure long range intelligibility in different listener environments. Two intelligibility goals, i.e. listener environments, were evaluated: I) an outdoor listener at a distance of 457 m over water and in the presence of 89 dBA background noise levels, and II) a listener inside a closed watercraft enclosure at 457 m and in the presence of 63 dBA background levels. The 457 m distance corresponds to the radius of the protection zone surrounding U.S. Naval vessels and the background noise levels are representative of those encountered in maritime scenarios. Component testing and analyses indicated that a uniformly phased horizontal line array of 8 horn-loaded compression drivers would satisfy both goals I and II. The array was then fabricated and its voice warning message spectrum was measured. The measured spectrum and subsequent prediction showed that the 8 horn/driver array satisfies both goals I and II with 89% and 94% of the words in an unknown voice warning message being intelligible in those respective scenarios assuming homogeneous, quiescent atmospheric conditions. ©2009 Institute of Noise Control Engineering