A recently published article in the Chinese Journal of Traumatology provided a narrative review of injuries of sonic weapons to the human body. [1]
Below are my notes from this article, which has free full access available for your reading.
Ultrasound: frequencies higher than 20kHZ. Inaudible to the human ear. Directional and can penetrate the body.
Sound frequencies categories
Low- frequency (<400 Hz)
Mid-frequency (0.4-1 kHz)
High-frequency (> 1 kHz)
*The human auditory system has a higher tolerance for low-frequency noise, even at high sound pressure levels (SPLs), resulting only in temporary threshold shifts (TTS) rather than permanent threshold shifts (PTS).
Low Frequency Noise
(150-155 dB) – Chest wall vibration, slight nausea, dizziness
(154-171 dB) – Increased heart rate, flushing of skin, swallowing, pain, visual impairment, subcostal discomfort, coughing, sternum compression, breathing difficulties.
Mid Frequency Noise
(120 dB) – Can resonate with the nasal cavity or sinus and enhance tactile sensations.
(>142 dB) – Can stimulate vestibular system
(165 dB) – Can cause itching
High Frequency Noise
(80-120 dB) – Temporary or permanent threshold shifts can be caused by sound pressure levels.
(120 dB) – Tactile sensations or itchiness
(125 dB) – Vestibular reactions
(140 dB) – Balance problems
(160 dB) – Thermal effects
Sound intensity x exposure time = level of damage
Example:
135 dB x 7 minutes
140 dB x 40seconds
145 dB x 4 seconds
150 dB x 0.4 seconds
160 dB
= perforation of eardrum
Acoustic Power: Amount of sound passing through a specified area per unit of time.
When measured in energy = sound intensity (W/m²)
When measured in pressure = sound pressure levels (Pa)
*Acoustic power is directly proportional to the square of sound velocity, sound frequency, and amplitude.
Therefore,
Ultrasound = high acoustic power
Explosions = high acoustic power secondary to high amplitudes
High-intensity sound:
(>120 dB) – ear discomfort and potential hearing loss
(140 dB/200 Pa) – painful to human ear
(>160 dB/2 kPa) – eardrum rupture
(173 dB/9 kPa) – lung rupture
*Infrasound and audible sound propagate at the same speed. 300-340 m/s in the atmosphere and 1480 m/s in water.
*The penetrating power of sound waves is inversely proportional to the sound frequency.
7 Hz infrasound – penetrates through reinforced concrete walls several meters thick, steel plates, seawater, and soil layers.
7 kHz audible sound – cannot penetrate a piece of paper
Sonic Weapons
- Types:
- Sonic cannons
- Sonic bullets
- Sonic guns (The Chinese Academy of Sciences has developed a sonic gun with a frequency < 20 Hz)
Infrasonic Weapons
Five Categories:
- Burst Type – Compressed gas, high-pressure steam or high-pressure gas is released in a pulse to excite the medium and generate sonic waves.
Advantages: small size, low frequency, easy control.
Disadvantages: low sonic intensity, short range effect.
- Explosive Type – Infrasonic waves generated by explosions. Approximately 50% explosive energy converts shockwaves, then decay to produce infrasonic waves.
- Tube Type – Infrasonic waves generated when air inside the tube vibrates at the same frequency of the tube itself.
- Speaker Type – Similar to a speak. Special diaphragms are used to generate infrasonic waves through vibration.
- Beat-frequency Type – Two sound wave generators with different frequencies are used simultaneously to generate infrasonic waves based on the different frequencies.
*It was reported that infrasound attacks on the Bosnian Serb Army caused a large number of soldiers to faint and vomit within seconds, resulting in loss of combat effectiveness.
*The U.S. suspects infrasonic weapon attacks in Havana and Guagzhou on embassy personnel.
*The main characteristic of infrasonic weapons’ harm to the human body is organ resonance. When the frequency of infrasonic waves is close to the inherent frequency of human organs, the organs can absorb sonic energy at the maximum extent, thus causing damage through resonance.
*Infrasound can convert mechanical energy into thermal, biochemical, and bioelectricity energy, thereby damaging the molecular structure of cells.
Infrasonic Weapons:
- Neurological Type
- Organ Type
Neurological Infrasonic Weapons:
Frequency: 8-12 Hz (same inherent frequency of the head)
Symptoms: dizziness, numbness in limbs, confusion, abnormal behavior.
Studies show brain wave activity in animals can be significantly suppressed by infrasonic waves.
Organ Infrasonic Weapons:
Frequency: 4-18 Hz (Torso: 7-13 Hz, Heart: 5 Hz, Chest cavity: 4-6 Hz, Abdominal cavity: 6-9 Hz, Abdominal wall: 10 Hz, Pelvic cavity: 6 Hz)
Symptoms: tinnitus, palpitations, muscle spasms, difficulty breathing, rupture of blood vessels and organ damage.
*When the frequency of infrasonic waves is < 2 Hz the human body responds as a whole rather than at the organ level.
*Infrasonic injury is dependent on power, frequency, and duration of exposure.
When power is equal…
Frequency determines type of damage.
Duration determines degree of injury.
*Humans and animals have different inherent frequencies.
Study: males aged 20-25 years. Exposed to 10 Hz/136 dB infrasound for 15 minutes. Resulted in headaches, dry mouth, difficulty swallowing, sweaty palms, and extreme fatigue.
Infrasound of 1-30 Hz/125 dB can cause ear pressure sensations and a decrease in task performance.
95-110 dB for 20 minutes can make people drowsy.
16 Hz/95 dB for 30 minutes can increase diastolic BP and HR.
*Due to fast propagation, being inaudible, long operating distance, and strong penetration capabilities it is difficult to determine the attack source and diagnose quickly.
It is difficult to protect against sonic weapons.
Key protection strategies:
- Minimize infrasonic intensity
- Shorten exposure duration
*Due to the strong penetration capabilities of infrasound, the equipment made of ordinary materials cannot provide effective protection.
– The Chinese have anti-infrasound earplugs
– High-intensity music can mask infrasonic waves and provide some relief for certain symptoms
– Low-intensity infrasonic waves can alleviate the damage caused by high-intensity sonic waves. (potential to use as a pre-stimulating method to increase tolerance)
Infrasound can activate the body’s oxidative system, generate a large number of free radicals, and further exacerbate lipid peroxidation reactions therefore damaging biological membranes.
- Alpha-tocopherol
- Vitamin C
- 2.3-dimethyl-2-sulfopropionate sodium
- Imidazole derivatives
- Free radical scavengers
Have therapeutic effects on infrasonic weapon damage.
*Glutamate receptor antagonists can effectively reduce the number of damaged neurons affected by infrasonic waves.
Intense Sound Weapons
Long Range Acoustic Device (LRAD)
- Emits a high-frequency (1-2.5 kHz or 2-4 Hz) directional sound beam
- SPL is 165 dB at 1m, 140 dB at 300m
- Range of 8-9 km
- Permanent hearing loss can be caused within 15m
*Impulse noise causes greater injury to the human body than steady-state noise.
*Usually impulse noise of small arms ranges from 130 – 175 dB. Suppressors can reduce the impulse noise to 15-25 dB.
*The human ear is most sensitive to impulse noise in the frequency range of 2-4 kHz or 2-5 kHz therefore sonic weapons often select this sensitive frequency range.
Low-frequency noise:
90-120 dB for 1 minute = irritability and restlessness
110-130 dB = intestinal pain and nausea
140-150 dB = severe tissue damage
170 dB = injury similar to blast injury
Mid-frequency noise:
Can cause resonance in body cavities.
High-frequency noise:
Can cause extreme increases in body temperature, leading to tissue burns and dehydration.
*The extent of damage depends on acoustic power, frequency, and operating distance of the weapon.
*The human tolerance to a noise level of 140 dB should not exceed 1 second.
Biological Effects of Intense Sound Weapons
Auditory Effects: sonic damage to the sound conduction pathway and resulting tympanic membrane rupture, ossicles fracture, injury of vestibular sensory organs and inner ear hair cells. Symptoms: conductive, sensorineural or mixed hearing loss, dizziness, tinnitus.
Non-auditory Effects: systems of sympathetic nervous, neuroendocrine, gastrointestinal, and immune stimulation by strong sound. Symptoms: headache, dizziness, nausea, vomiting, increased HR and BP.
Equipment Protection
- Earmuffs and earplugs can attenuate noise >500 Hz by about 15-45 dB
- Earmuffs are not as effective as earplugs for protecting against noise below 250 Hz.
- Foam earplugs can attenuate low-frequency noise by 35 dB and reduce the occurrence rate of acute acoustic trauma by about 15 times.
- Earmuffs + earplugs can protect against impulsive noise >160 dB
- Earmuffs + earplugs + sound absorbing helmets can attenuate impulsive noise of 800-7000 Hz by 30-50 dB.
*Protective equipment made with sound-absorbing materials is more effective in protecting against high-frequency noise than low-frequency noise.
Ultrasonic Weapons
- The hand-held ultrasonic weapon can emit ultrasound waves ranging from 15-30 kHz, with a maximum SPL of 130 dB or 145 dB and an effective range of 6m.
- The ultrasonic bullet can transmit highly directional ultrasonic waves that can attack enemies in confined spaces such as caves.
- Ultrasound has stronger directional propagation compared to infrasound.
- Absorptive attenuation of ultrasound is small when propagating in liquids or solids, thus allowing them to penetrate through rocks, bricks, metal, and concrete walls up to 15m thick.
- Ultrasonic waves reflect with different material interfaces, where they can be absorbed and converted into thermal energy so increasing the interface temperatures and becoming more significant with higher frequencies.
*Injuries of ultrasonic weapons are similar to infrasonic weapons.
– visual blurring
– itching
– ear pain
– skin heating
– nausea
– vomiting
– abdominal pain
– skin burns
– increased body temperature at 160 dB
*Ultrasonic waves can cause bone fracture through resonance with the skeleton.
Reference:
- Li, Y., Yang, G., Zhao, Y., & Li, B. (2025). Injury of sonic weapons to human body: A narrative review. Chinese Journal of Traumatology.