Think about how your brain is able to focus on certain sounds in loud environments like a crowded food court (before the pandemic of course!). All of the incoming sounds are being funneled through your ears to your brain and are able to prioritize the sounds you choose to pay attention to, like your friend talking at your table and ignoring the other loud sounds of people talking or machines in the background. Known as auditory spatial awareness, your brain performs this task by locating sound sources. While you’re in loud environments, spatial awareness helps you to efficiently identify and locate sound sources.
Try to imagine now, not being able to determine the location of where sound is coming from in your surroundings. Would you hear the direction a fire alarm is ringing? Or the direction of traffic? By distorting sounds, hearing loss can significantly reduce spatial awareness. For this particular reason, it explains why a common problem with hearing loss is not being able to understand conversation in noisy surroundings.
Sound waves interact with the ears, head and body and are directionally dependent, creating a three-dimensional sense of space - this is referred to as ‘acoustic cues’. For a better understanding of spatial hearing, imagine this: the difference between watching a movie on your cell phone or tablet using only one speaker, as opposed to watching the same movie in a theater with magnificent surround sound. The speakers in the movie theater truly enrich your auditory experience. Much the same, your listening experience with spatial awareness helps to paint a sonic picture of your surroundings.
Visually locating objects is not nearly as complex as localizing sound sources. Individuals as early as three months of age have the ability to visually locate objects. It has been discovered by researchers that infants are able to visually pick out and process information from their surroundings. In fact, babies can correctly differentiate and select a red car amidst multiple green cars. Since visual localization primarily depends on which part of the retina is stimulated, localizing sound sources are much more complex. The brain is required to use a higher processing level to select the various locations that sound cues come from. In turn, the brain processes those cues into understandable information.
Hearing aids have the ability to alter acoustic cues that indicate sound direction, thereby significantly improving spatial hearing - most specifically, the intensity of sound waves and the difference in when sound arrives to each ear. The cues differ considerably depending on the particular type of hearing aid being worn. For example, hearing aids that rest behind the ear provide quite different direction-dependent changes than the hearing aids that fit on the inside of the ear.
It has been researched in detail how hearing aids change spatial cues so that the wearer of the hearing aid has the ability to maximize spatial awareness. A significant amount of attention to detail and time is spent evaluating complex sound wave interactions as well as the location dependent differences of the acoustic signal. Extensive analysis has been done on different styles of hearing aids and how they differently change auditory cues. This research has led to the optimization of microphone location, the shape and size of hearing aids, and strategies of signal processing designed to create a smooth and a consistent listening pleasure for all those who wear hearing aids.
What does all of this mean for you? The brains of normal hearing individuals constantly and effortlessly perform spatial awareness. Hearing aid wearers can be positive that researchers are considering this aspect of hearing very diligently. They are continuing to develop new products with improvements to spatial awareness capability along with audibility and speech comprehension.