Preface

This project is mainly inspired by the book "Musical Illusions and Phantom Words" by Diana Deutsch.


We generally rely more on visual perception in our daily lives, but we sometimes have a misunderstanding of what we see. In fact, there are so many examples of optical illusions that we can find them on the internet very easily, while there are relatively very few examples of auditory illusions. Especially, when we don’t know how auditory illusions happen, it is even more difficult to notice the "misunderstanding" of what we hear. As I was at work a year ago, I noticed that human auditory perception is very fluctuating and is easily disturbed by the environment noise. Even the perceptions at different moments in a day are somewhat different. The perception is closely related to our physical and mental state at a certain moment. That is to say, our auditory perception will be affected by the inside and outside factors of ourselves, so I doubt whether our auditory perception is really as sensitive as we think.


Compared to visual perception, is human auditory perception really as sensitive as we think? Probably not. Each human eye contains 126,000,000 photoreceptors, but there are 15,500 hair cells in each ear and only 3,500 of them actually transmit sound signals to the brain [1]. This can probably explain why there are much more examples of optical illusions than auditory illusions. Although the theories of visual and auditory perceptions have lots in common, with one is to perceive images and the other is to perceive sound, the most significant difference between auditory and visual perception is that we can choose to open or close our eyes to see or not, while we cannot shut our ears. Even when we are asleep, our ears are still working. Perhaps we always take our auditory perception too much for granted.


Return to the issue of auditory sensitivity. Even musicians who have been trained in hearing, they won't totally turn to relying on hearing or give up visual perception in their daily lives. I talked to Zoe Lin. As a composer, although she knows how to use her hearing ability to make her daily life more comfortable than other people, she agrees that the sensitivity of auditory perception has its limits with the fact that there are so few hair cells in the ears. It is important to know that it is not the ears of musicians that are trained, but their brains!




Everything takes place in the brain


How to define auditory illusions? When we analyze a sound signal and find it inconsistent with the situation we feel, we can suspect there exists an illusion. Human brain is so complicated that we don't even understand what it is doing. The brain is like a complex system. A sound signal enters the complex system (brain) from ears (input) for processing and then perceived (output) by us.





Our brains help us "pre-process" everything all the time. For example, we can recognize an acquaintance among strangers. Under the circumstances of encountering an acquaintance in the crowd, we "discover" this familiar face without the need to look at every detail of each stranger’s face. This is evidence of the brain’s "pre-processing". It unconsciously helps us extract what to focus on.[2] Therefore, we cannot assume that the brain presents the actual sounds to us, nor assume that everybody’s brain processes in the same way. There might be differences in individual perceptions. It can even be said to be a very personal matter.




The hearing experiment


First of all, I invite you to participate in auditory experiments.

Please click the link here:

https://forms.gle/EGFwTkiBmDE6RpsB8


There are some examples and principles of auditory illusions, which will be shared with you on this website while the project is undergoing.





[1] Deutsch, Diana. Musical Illusions and Phantom Words (p. 2). Oxford University Press. (2019)

[2] Owen, Adrian. Into the Gray Zone: A Neuroscientist Explores the Border Between Life and Death, Ch.2. Faber & Faber. (2017)


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