Considering the fact that verbal communication is how most people interact with others, being able to do so is essential. However, people can often conflate hearing and understanding. While undoubtedly interconnected, they are two distinct functions. Understanding the difference can help to improve outcomes and satisfaction with hearing instruments.
Audibility vs. Clarity
Audibility refers to the ability to detect that a sound is present. The brain simply does or does not acknowledge that an auditory stimulus is present. A person with normal hearing would be able to hear a certain sound at a volume that would be imperceptible to one with hearing loss. Clarity refers to the ability to assign meaning to a sound. Even if a sound is audible to a person, their brain may not be able to understand what that sound is supposed to convey. Take a car radio, for instance. Driving through the city, the songs can easily be heard and understood. In a remote location, though, the transmission could still be heard, but the clarity would be fuzzy and distorted enough as to make it incomprehensible.
Audibility and clarity are determined by two different mechanisms in the human auditory system. When a soundwave reaches the ear, it is funneled down the ear canal to the eardrum. This sets off a chain reaction wherein the eardrum, middle ear bones and fluid inside the cochlea (organ of hearing) vibrate in a specific pattern based on the stimulus. These vibrations are coded as electrical signals which are sent to the brain. With hearing loss, impedance occurs within the middle or inner ear, causing the signal that reaches the nerve to be weakened. A weaker signal means that the stimulus has to have a much higher intensity (louder) for the brain to notice.
Clarity is determined by filters within the auditory system. Imagine trying to create a personal budget for the year. The total sum of the prior year’s expenses is known, but that in itself is not too helpful. Budgeting requires knowing how that money was spent, meaning it needs to be categorized. Speech is categorized in the same way. Incoming soundwaves are filtered so that “s” is a separate category from “m,” and so on. When the cochlea sustains enough damage, those filters become broader and less specific, so that “m” and “s” could end up overlapping. Thus, the brain can hear the person talking, but cannot understand what is said as it is receiving the equivalent of a fuzzy radio signal.
Hearing aids are recommended for hearing losses which have become significant enough to affect communication. Hearing aids increase audibility by magnifying frequencies the ears have trouble hearing on their own. How does this help communication? Many consonant sounds, which give words their meaning, are rather soft and high-pitched (e.g., “f” and “s”). Incidentally, the majority of people suffer the most hearing loss in the high-pitch range. This means that, given the context of the situation, many consonant sounds are not audible to that person, making it difficult to understand others. The increased audibility provided by the hearing aids improves their access to these sounds.
The above scenario works well for an individual with good clarity. Unfortunately, other individuals may only have 50% clarity. In this situation, hearing aids are still a valuable resource in aiding communication. But they may not be enough in and of themselves. This is because while the hearing aids can be programmed to provide as clear and audible a signal as possible, the brain is still required to interpret that signal correctly. If the auditory system can only provide 50% clarity, a person may still struggle to understand at times, even if they are still doing better overall with the hearing aids. In these cases, assistive accessories that work in conjunction with the hearing aids and the use of good communication strategies can greatly improve an individual’s outcomes. For more severe cases, the literature shows that a cochlear implant is a safe and effective solution for significantly increasing clarity and improving communication.
There are many forms of managing hearing loss. A hearing care professional can help guide you to the best solution. Understanding the issue can help to properly address it. QCBN
By Jeff Lane, Au.D.
Trinity Hearing Center is located at 1330 N. Rim Dr., Suite B in Flagstaff. For more information, visit TrinityHearing.net.
Jeff Lane, Au.D., is a doctor of audiology with a passion for improving the lives of others. Dr. Lane may be reached at 928-522-0500 or at firstname.lastname@example.org.