Among all our external body parts, the shape of our ears is pretty unique, isn’t it? The shape of the curves in our ear cartilage is indeed peculiar. They are similar in every ear and no deviation is experienced in case of most people. So, does the shape of our ears affect our hearing? Let’s have a look at what researchers have to say about this.
Researchers used a dome of loudspeakers to test how people determine where a sound is coming from. Credit : Régis Trapeau
Our brain can easily detect the direction from where a sound is reaching us. This is explainable from the fact that the sound, either from left or right, reaches one ear later than the other. Thus, the neurons can send signals to the brain to determine where the sound is coming from. However, what bothered our researchers more was: What about the sounds from the top or bottom of our ears? Does the shape of the outer ear have any role to play in differentiating sounds from above and below?
Régis Trapeau, a neuroscientist at the University of Montreal and author of the new paper, said that the determination involves the way the sound waves bounce off the outer parts of your ear.
Curious to know how our brain processes the information about sound from height or depth, the researchers set up a series of experiments.
Pieces of equipment required-
- a dome of speakers
- ear molds made of silicone
- a fMRI machine
The volunteers were first made to hear a number of sounds using the dome of speakers and asked to indicate from where they thought the sound was coming. Consequently, ear molds were fitted in their ears and the experiment was repeated. A clear observation was that the results are different in both the sessions.
Observation and Conclusion
A piece of silicone was fitted into participants’ ears, changing how they perceived where a noise was coming from. Credit : Valérie Aubrais
To understand this, the fMRI scanner was used to see how the brain responded in the sessions. It was concluded that the shape of the ears indeed help us in hearing. With slight modifications in the ears, the brain is unable to determine the sound properly. Nevertheless, with time it gets adapted to the new modification in the shape of the ears.
The team discovered that as sounds originate from higher locations, the neurons respond less and less. This implies that the neurons are likely to be representing height by the magnitude of their response.
Additionally, when the volunteers first began wearing the ear molds and their test scores took a dive, their auditory neurons were firing in a much more disorganized manner.
The observations suggest that locating a sound in space will require our brain to incorporate not just the sound waves themselves, but our own grasp, however non-deliberate, of how our ears modify that sound.
The researchers are interested in finding out more about how a sound’s height is perceived in the brain, especially sounds coming from behind. Such research could lead to better hearing devices, and also improve our understanding of how the ear contributes to our ability to understand the world around us.
Anatomy of the Human Ear
Video Courtesy – ” SMC468 Graphic Design for Education “
Reference Paper – http://www.jneurosci.org/content/early/2018/03/05/JNEUROSCI.2530-17.2018