Two Ears, One Brain
Two Ears, One Brain
Having two ears is better than one when it comes to listening and communicating with the world around us. There are a number of perceptual benefits to binaural hearing (both ears) that help us function better in our daily interactions and experiences.
For the brain to make sense of the sounds in the environment, the auditory system needs to analyze the input coming from both ears. Input from both ears provides the auditory system with a slight boost in volume (binaural summation) which, in general, makes things easier to hear.
Another interesting concept is how our brain uses the information from both ears to determine where a sound is coming from. This is called localization. Here, the input signals from both ears are compared against each other to determine slight timing and volume differences between the left and right input signals. A sound will be louder and will reach the ear faster on the side where the sound came from. For example, if you hear a loud crash, for safety reasons it is important to understand where it came from. Your brain will quickly analyze the signals coming from both ears to determine whether the crash occurred on your right or left. If the input from the left ear was slightly louder and arrived quicker, the brain can deduce that the crash came from the left.
When an individual has a unilateral or asymmetrical hearing loss, these timing and volume cues from both ears become distorted and often the brain is unable to make proper use of them.
Speech in Noise
When we are in a noisy environment, let’s say a loud restaurant, we typically want to be face-to-face with our friends. Not only is this polite, the visual cues from the talker’s lips and facial expressions help us to fill in the blanks that are missed or misheard due to the noisy environment. In addition to the visual cues, the brain uses the information from both ears in noisy situations to help differentiate what is important (speech) and what is not (background noise). Using the signals from both ears allows the brain to fill in the blanks in complex listening environments compared to listening with just one ear. For example, imagine you are at a bar talking with a friend and there is a large, noisy party sitting to the right of you. The information from the right ear may be messy/distorted from the noisy party while the information from the left ear will be clearer. Using the information from both ears the brain is better able to detect and focus on the speech you want to hear in the noisy environment. If you were in the exact same situation but had left unilateral hearing loss (you can only hear from your right ear) you would have a very difficult time communicating with your friend as the “good ear” would be facing the direction of the noisy party. The brain would have a much harder time segregating your friend’s voice from the background party noise when listening with only one ear.
Increased Listening Effort
After reading about some of the binaural cues that improve our perception and understanding of what we are hearing it would make sense that is it generally EASIER to hear and listen when both ears are working properly. And this is absolutely the case! Binaural listening decreases the effort required to listen and understand. People with unilateral hearing loss must work harder to hear and comprehend their environments, especially in noise. For many, a quiet environment does not create a hearing challenge because there is no competing sound for the brain to distinguish from but as soon as background noise is present, individuals with unilateral hearing loss are at an extra disadvantage and must work harder to hear their friends and family.
Take Home Message
In summary, having two ears allows us to make better sense of our environments, hear speech more clearly, distinguish between speech and noise in complex environments, and make it easier to hear and communicate with the people around us.
Understanding the perceptual and functional benefits of binaural hearing is important for individuals with unilateral hearing loss to understand that they, maybe unknowingly, are working much harder to communicate and interact with the world around them.