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About this book

This book examines the human auditory effects of exposure to beams of high-power microwave pulses, which research results have shown can cause a cascade of health events when aimed at a human subject or the subject’s head. The book details multidisciplinary investigations using physical theories and models, physiological events and phenomena, and computer analysis and simulation. Coverage includes brain anatomy and physiology, dosimetry of microwave power deposition, microwave auditory effect, interaction mechanisms, shock/pressure wave induction, and Application in Microwave Thermoacoustic Tomography. The book will be welcomed by scientists, academics, health professionals, and practicing engineers as an important contribution to the continuing study of the effects of microwave pulse absorption on humans.

Table of Contents

Frontmatter

Chapter 1. Introduction

Abstract
This beginning chapter sets the stage for the materials covered in this book. It provides brief introductions to microwaves as a component of the electromagnetic radiation spectrum. It lists representative microwave technology and their typical applications. It gives a brief historical background on the auditory effect from pulsed microwave exposure and summarizes the cascade of events that take place when a beam of microwave pulses is aimed at a human or animal subject’s head. The chapter describes the involvement of microwave auditory effect in some recent diplomatic situations and ends with an account of the organizing principles for the book.
James C. Lin

Chapter 2. Principles of Microwave and RF Exposure

Abstract
Understanding the interaction of microwave and RF radiation with biological systems is facilitated through knowledge of the actions and characteristics of microwave and RF radiation in space and time. The chapter begins with the pertinent physical laws that govern the interaction of microwave radiation with biological systems. It provides the basic information on antenna radiation characteristics and microwave reflection and transmission at biological interfaces, and also describes RF electromagnetic fields in the near- and far-zone of radiating antennas. It shows that the interactions are functions of the source frequency and configuration, shape and size of the exposed subjects, and orientation and location of the subject with respect to the source, among others.
James C. Lin

Chapter 3. Brain Anatomy and Auditory Physiology

Abstract
Knowledge of human and mammalian brain anatomy and auditory physiology is important to understanding the various behavioral and neurophysiological investigations aimed at gaining better insights into the distinctive features of the microwave auditory effect. The materials presented are essential elements of the auditory system and their functions, including the external, middle, and inner ears; cochlear mechanical to electrical transduction; action potentials of the auditory nerve; central auditory nuclei and pathways; perception of sound and pressure; loudness and pitch or frequency, sound localization, and masking.
James C. Lin

Chapter 4. Microwave Property of Biological Materials

Abstract
The interaction of microwave radiation with biological systems is influenced by the electromagnetic property of tissue media, specifically, dielectric permittivity and magnetic permeability. The frequency-dependent characteristics of the dielectric properties of biological materials may be described by the relaxation processes, displaying a time-dependent response to sudden excitation. This chapter describes the dielectric relaxation processes and presents summaries of the measured tissue dielectric permittivity data for dielectric constants and conductivities as functions of frequency and temperature. Since water is a major constituent of biological materials, tissues may be classified into three major groups according to their water content.
James C. Lin

Chapter 5. Dosimetry and Microwave Absorption

Abstract
Microwaves must be coupled into the biological body and energy must be transferred, deposited, and absorbed by tissues in the body for the system to respond in some manner. The exposure may produce highly complicated distributions of RF and microwave energy within the subject, regardless of the uniformity of external exposure. Dosimetry is defined as the quantification of RF and microwave energy distribution and absorption in biological bodies. This chapter discusses the dosimetry of RF and microwaves in planar, spheroidal, and anatomical models of biological bodies. These topics are complex functions of not only the exposure sources and scenario but also the shape, size, composition, and structures of the exposed subjects, as well as orientation and position of the subject with respect to the source.
James C. Lin

Chapter 6. The Microwave Auditory Effect

Abstract
The microwave auditory effect has been widely recognized as one of the most interesting and significant biological phenomena from microwave exposure. The hearing of pulsed microwaves is a unique exception to the airborne or bone-conducted sound energy, normally encountered in human auditory perception. This chapter describes the research studies leading to scientific documentation that absorption of a single microwave pulse impinging on the head may be perceived as an acoustic zip, click, or knocking sound, depending on the incident microwave power. A train of microwave pulses to the head may be sensed as an audible buzz, chirp, or tone by humans. It discusses the neurophysiological, psychophysical, and behavioral observations from laboratory studies involving humans and animals as subjects. The objective is to present what is scientifically known about the microwave auditory effect.
James C. Lin

Chapter 7. Mechanisms for Microwave to Acoustic Energy Conversion

Abstract
Research have shown that a cascade of events takes place when a beam of microwave pulses is aimed at a human or animal subject’s head. Absorption of pulsed microwave energy creates a rapid expansion of brain matter and launches an elastic wave of pressure that travels inside the head to the inner ear. There, it activates the nerve cells in the cochlea and the neural signals are then relayed through the central auditory system to the cerebral cortex for sound perception. The microwave thermoelastic theory is widely recognized as the mechanism of interaction for the microwave auditory effect. This chapter discusses the mechanisms that have been suggested whereby auditory responses might be induced by pulse-modulated microwave radiation and is followed by detailed description of the thermoelastic theory.
James C. Lin

Chapter 8. Thermoelastic Pressure Waves in Canonical Head Models

Abstract
This chapter presents rigorous multidisciplinary, mathematical analyses of the thermoelastic pressure wave generated in spherical human and animal heads exposed to pulsed microwave radiation. The results include dependence of induced sound pressure frequency and strength on microwave pulse characteristics. It provides information on the attributes of sound wave generated in the head as perceived by humans. It summarizes the first mathematical models for analyzing the sound pressure waves inside the head due to a microwave pulse and generalizations of the methodology to arbitrary SAR patterns of spherical symmetry. It also includes comparisons of predicted and measured response characteristics in human and animal heads.
James C. Lin

Chapter 9. Computer Simulation of Pressure Waves in Anatomic Models

Abstract
This chapter presents computer simulations of the thermoelastic pressure waves generated in anatomical human heads and whole-body models exposed to pulsed RF and microwave radiation by applying the numerical FDTD formulation. More precise descriptions of specific features and accurate information on the acoustic pressure waves generated inside the head and sound perceived by human observers are obtained. Computational simulations are examined for thermoelastic pressure waves generated in anatomic models exposed to near-zone sources and far-zone plane waves ranging in RF and microwave frequencies from 40 MHz to 3 GHz. It also includes anatomic head models exposed to localized 300- and 400-MHz magnetic resonance imaging (MRI) coil antennas driven by rectangular RF pulses.
James C. Lin

Chapter 10. Applied Aspects and Applications

Abstract
This chapter explores where and how the microwave auditory effect or microwave induced thermoelastic wave phenomenon may be applied for practical purposes in life science, medicine, and other realms of human endeavors. An interesting and potentially significant diagnostic imaging applications of the microwave thermoelastic pressure wave interaction and some applied aspects of the microwave auditory effects are described. They include a discussion on early and current investigations of microwave thermoacoustic tomography (MTT) imaging and some applied aspects of the microwave auditory effects such as the recently reported covert personnel attacks at some diplomatic missions and the startle reaction from a sudden unexpected microwave auditory stimulus potentially causing the aircraft pilot to experience spatial disorientation during flight.
James C. Lin

Backmatter

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