Hearing is 3 Dimensional
The human auditory system is made up of two ears and the brain. Hearing with both ears is called binaural hearing. This anatomical layout allows the brain to compare sounds coming from the left and right ears. Sounds will reach one ear fractionally faster and louder than the other – and your brain registers these subtle differences. Sound reaching the left ear first will travel around the human head (mass) before reaching the right ear. This results in time delay between both ears.
As the sound travels around the head, the loudness also decreases.These natural differences in time and loudness of sound between both ears allow the brain to organise and determine the location of different sound sources in the listening environment. This is a natural spatial organisational process of the human cognitive system.We are constantly bombarded with many different sound sources. The partnership between the brain and the ears gives humans the remarkable ability to deconstruct this complex world of sound, spatially separate multiple sound sources and place them where they belong in the environment.
This ability of knowing where sounds are coming from is called localisation.
Localisation – The ability to place sounds in space
Experiencing sound in this natural arrangement gives us access to spatial cues in our environment so that we can intuitively locate, separate and focus on the information we want to hear and ignore the information not important to us.It should therefore come as no surprise to learn that the brain works harder than our ears, especially in noisy environments, such as in a busy restaurant. It can be very exhausting trying to follow conversation in these environments sometimes even for people with normal hearing.
The ability to place sounds in space is important because:
It gives sound meaning.
Sounds do not happen in isolation. It happens in context.
We live in a 3 dimensional world, and the sounds that occur in that world occur in 3D too.
Organise Select Follow
Hearing provides us with information that is natural and complete and the brain is able to easily sort through all the information you apply your attention to through a cognitive process – organise, select, follow.
Organise
When entering an environment with many sound sources, the brain automatically tries to separate sounds of interest from competing sounds and noise.
Select
When the soundscape is organised, the brain is able to select a particular sound source and ignore intrusive background noise. This ability is crucial; as well as allowing us to direct our attention to a particular person it enables us to switch our attention from one person to another effortlessly; something we always do when interacting in a group.
Follow
When listening, the auditory system instinctively tunes into the individual characteristics of the voice of interest. We are able to focus and follow the voice over time.Hearing loss distorts sounds, disrupting this natural process. Localisation is compromised and the information delivered to the brain is incomplete and disorganised.
Acoustic Chaos
Hearing loss distorts sounds, disrupting this natural process. Localisation is compromised and the information delivered to the brain is incomplete and disorganised.Trying to make sense of the listening environment often leaves the person with hearing loss feeling exhausted, especially after visiting a noisy venue. What should be an organised world of sound presents as acoustic chaos for the individual with hearing loss.