Erfan Adeshi

Professor Cassidy Picken

ENG 100

4th December 2018

 

How inaudible sounds affect us?

 

It all starts from the day we are born, the day we hear the first screams, our own screams. Ever since that day we’ve been exposed to millions of sounds, every single day of our life. Some make us calm while others make us aggressive, hyped or sad. It’s amazing how a wave signal is capable of having such a huge impact on our brain. While most people think that sounds end at what we can hear, there are waves around us that we can’t hear at all. These waves can go as high as 125kHz and as low as 5Hz. One might wonder what’s the use of a sound we cannot hear? While it’s obvious that sounds that we hear are capable of harming us but, can inaudible sounds affect us or potentially be harmful to us and how does it affect our day to day life.

 

It’s been proven that humans cannot hear sounds in the frequency range above 20 kHz and below 20 Hz. However, whether the existence of such “inaudible” high-frequency components may affect the way we hear sounds is a mystery. In a study done by Tsutomu Oohashi on 28 Japanese volunteers in the year 2000, using noninvasive physiological measurements of brain responses to high-frequency waves above 20kHz, they found out that these waves significantly impact the brain. After putting the subject through the test, the came to find that high-frequency waves caused a spike in alpha-EEG waves in the brain. Alpha bands are responsible for our learning abilities. “Alpha-band oscillations are the dominant oscillations in the human brain and recent evidence suggests that they have an inhibitory function”. (Klimesch) However that was not the only increase they found, they also saw an increase in brains rCBF or the regional cerebral blood flow. “In conclusion, our findings that showed an increase in alpha-EEG potentials, activation of deep-seated brain structures”.(Oohashi et al.) However, the “Psychological evaluation indicated that the subjects felt the sound containing an HFC to be more pleasant than the same sound lacking an HFC” (Oohashi et al.), which is known as the “hypersonic effect”. The hypersonic effect is a term used by Tsutomu Oohashi in his studies which describes the effect of inaudible ultrasounds a measurable effect on their physiological and psychological reactions. People prefer sounds that have high-frequency noises even though they absolutely can not hear them.

 

Low-frequency waves, i.e anything below 250Hz, also have an impact on our brain and hearing system. A study done by Markus Drexl in the year 2016 shows that “intense, LF (Low-Frequency) sound causes cyclic changes of indicators of inner ear function after LF stimulus offset”. Most people believe that the low-frequency sound does not affect their hearing system just cause human hearing cannot really perceive anything under 250Hz. While high-frequency sounds may cause an immediate distraction, low-frequency noise does not usually pose an immediate effect. Low-frequency sounds are only noticeable when they start or stop all of a sudden. Walking into a room that a low-frequency wave exists makes it really hard to notice the existence of the wave until it stops and we feel the relief.  “A common reaction to low-frequency noise, and especially steady-state noise such as ventilation noise, is a feeling of relief when the noise ceases, even when the exposed persons have not been aware that the noise was present”. (Drexl et al.) LF noise affects our performance is in many ways, causing us to suffer from fatigue, concentration problems, and irritation. The reason LF noises cause us these problems “can be interpreted as the result of an information processing overload. As there are some indications that low-frequency noise may be more difficult to habituate to” (Waye) making it more difficult for our brains to process it and understand it.

 

So how can inaudible frequency impact our day-to-day lives? Inaudible frequencies play a major role in our media nowadays, especially when it comes to horror movies and science fiction genres. “One of the most popular examples comes from the French crime film Irreversible. For the first thirty minutes, the film barrages its audience with “infrasound.” Infrasound falls below the audible range of human hearing. It can create anxiety and fear in the listener.” (Stuebs) The film’s viewers report feeling dread, nausea, and paranoia after watching this movie. Infrasound is so powerful that it can and have been weaponized by governments many times. According to the BBC, in 2016, U.S. embassy employees in Havana, Cuba “began suffering cognitive impairment and headaches related to swelling in the brain. They were later diagnosed with brain damage and, in some cases, permanent hearing loss”. (“What Is A Covert Sonic Weapon?”) Ultrasounds do also come to help the humankind. The best example that comes to mind is a young couple anxiously awaiting to make sure their unborn child is doing fine. ultrasounds are applied to the uterus in order to get an image of the unborn baby. A transducer emits the high-frequency wave and then records the echoes as the sound waves bounce back using the speed of sound to determine the size, shape, and consistency of the organs.

 

In conclusion, both inaudible high-frequency and low-frequency noises can be harmful to human beings. High-frequency sounds are capable of causing an immediate distraction, while low-frequency noise does not usually pose an immediate effect. Low-frequency sounds are only noticeable when they start or stop all of a sudden. While HF noises might sound pleasant to some people even though we can’t hear them, LF noises cause distraction and loss of concentration. These noises can be weaponized and have a major impact on peoples health. However, if used with a positive purpose, both these waves can change lives and help us progress as human beings.

 

Work cited



Drexl, Markus et al. “Responses Of The Human Inner Ear To Low-Frequency Sound“.   Advances In Experimental Medicine And Biology, 2016, pp. 275-284. Springer International Publishing, doi:10.1007/978-3-319-25474-6_29.

Klimesch, Wolfgang. “Alpha-Band Oscillations, Attention, And Controlled Access To Stored Information”. Trends In Cognitive Sciences, vol 16, no. 12, 2012, pp. 606-617. Elsevier BV, doi:10.1016/j.tics.2012.10.007.

Oohashi, Tsutomu et al. “Inaudible High-Frequency Sounds Affect Brain Activity: Hypersonic Effect”. Journal Of Neurophysiology, vol 83, no. 6, 2000, pp. 3548-3558. American Physiological Society, doi:10.1152/jn.2000.83.6.3548.

“Sound And Ultrasound“. Bbc.Com, https://www.bbc.com/bitesize/guides/zwf92nb/revision/2.

 

Stuebs, Jessy Lee. “Inaudible Frequency: The Misuse Of A Valuable Tool – US Represented“. US Represented, 2017, https://www.usrepresented.com/2017/11/16/inaudible-sound-the-medical-misuse/.

Waye, K.P. “Effects Of Low Frequency Noise And Vibrations: Environmental And Occupational Perspectives”. Encyclopedia Of Environmental Health, 2011, pp. 240-253. Elsevier, doi:10.1016/b978-0-444-52272-6.00245-2.

 

“What Is A Covert Sonic Weapon?“. BBC News, 2017, https://www.bbc.com/news/world-us-canada-41047721.

Williams, Sarah C. P. “Sounds You Can’t Hear Can Still Hurt Your Ears”. Science Mag, 2014, https://www.sciencemag.org/news/2014/09/sounds-you-cant-hear-can-still-hurt-your-ears.