Session: 07-01-02: Injury Sensing and Mitigation

Paper Number: 173972

Characterization of Acoustic Wave Transmission in Biologically Relevant Soft Materials 

As directed energy-related injury becomes increasingly prevalent in modern environments, the need for effective protective measures against sonic and ultrasonic waves has become a critical concern in recent decades. This concern spans both industrial and defense sectors, where engineers are tasked with developing solutions to mitigate these often-invisible threats. In principle, sound-induced injury occurs when intense acoustic energy transmits inside the human body and damages interior tissues, particularly the ears and brain. Based on the existing studies, prolonged exposure to sounds above 85 dB can lead to hearing loss, while impulses above 140 dB may rupture the eardrum or damage cochlear hair cells. At higher levels (160–190 dB), such as during blasts, sound waves can cause traumatic brain injury (TBI) by transmitting pressure waves through the skull, disrupting neural and vascular structures. These injuries may result in various conditions such as hearing loss, cognitive dysfunction, dizziness, or long-term neurological deficits, even without visible external trauma. Vulnerability increases with proximity and the duration of exposure. As such, a systematic approach to defining acoustic shielding requirements is in high demand and relevant to current threat scenarios. We aim to help build this understanding by determining the zero-transmission threshold, below which the transmission of sound becomes nearly zero, based on material selection and exposed frequency. Using the Stratasys 850, which enables the use of materials with varying stiffnesses and viscoelastic properties (such as Agilus30), multiple specimens can be manufactured with different materials and incremental thicknesses, allowing for the exploration of various options for energy dissipation and acoustic wave scattering. With this, we can construct a parametric experiment used to determine the zero-transmission threshold of various materials and geometries, to relate the results, and to predict this threshold for future specimens. The testing method employed is the through-transmission substitution technique, which utilizes a water-filled tank with a transducer and a receiver to generate and detect ultrasonic waves. Sound transmission loss (STL) is determined by first measuring the signal with no sample as a control, followed by repeating the measurement with the sample inserted. From these measurements, the frequency-dependent attenuation coefficient of each material can be calculated and used to derive the zero-transmission threshold. Once characterized, these thresholds can guide future material selection and structural design, enhancing our ability to tailor protection against a wide range of acoustic frequencies. We believe this study will advance our understanding of how sound-induced injury aids in preventing hearing loss, improve protective gear, guide treatment, and reduce brain trauma from blasts or high-intensity noise exposure.

Presenting Author: Vi Pham University of Texas at Arlington

Presenting Author Biography: Vi Pham is a graduate student in Mechanical and Aerospace Engineering Department at UTA

Authors:

Ethan Cross University of Texas at Arlington
Vi Pham University of Texas at Arlington
Ashfaq Adnan University of Texas at Arlington