Measurements of Infrasound Signatures From Grenade Blast During Training

Area of Science:

• Military medicine
• Acoustics
• Neuroscience

Background:

• Military personnel experience repeated low-level blast overpressure during training and operations.
• These exposures can cause transient neurological effects, even without concussion.
• Impulsive acoustic sources, like those in military training, contain infrasound frequencies.

Purpose of the Study:

• To investigate the presence and characteristics of infrasound energy in acoustic signals from grenade training.
• To determine if infrasound contributes to reported neurological symptoms in military personnel.

Main Methods:

• Acoustic data collected using traditional and specialized infrasound microphones during grenade training.
• Time and time-frequency analysis performed on collected signals.
• Identification of infrasound energy levels and specific frequency components.

Main Results:

• Peak sound pressure levels (SPLs) between 140-160 dB recorded during explosions.
• High-intensity infrasound detected, particularly below 3 Hz.
• Three distinct infrasound tones (1.987, 2.296, 2.528 Hz) observed during blast waves.

Conclusions:

• Reported symptoms in military personnel may be linked to acoustic loading from infrasound.
• Future studies on blast exposure effects should incorporate acoustic measurements.
• Understanding infrasound's role is crucial for military health and safety protocols.