Are Words Blurry? Or, "I Can Hear But I Can't Understand"
Many hearing aid users come into our office with the complaint of "I can hear but I can't understand." Does this sound familiar to you? There are a few reasons why a person using hearing aids may not understand speech as clearly as they would like.
Firstly, the hearing aids may simply not be adjusted appropriately for the person's hearing loss. Unless verification of the amplification levels has been done, there is no way to know if the hearing aid is delivering the precise levels of gain needed at every frequency. Unfortunately, patients sometimes come in to The Center for Audiology with hearing aids that were fitted elsewhere that were simply not providing the necessary gain needed for their hearing loss. I have also encountered patients with hearing aids that were set too loudly at certain frequencies, putting the hearing aid user at risk of further hearing damage. Sometimes simple programming adjustments can make a significant difference in the user's ability to understand and distinguish speech sounds. At The Center for Audiology, every hearing aid fitting is followed by probe microphone measurements performed in the ear canal with the hearing aid in the ear, to verify that the user is getting the most precise fitting possible.
Secondly, sometimes, even with the best hearing aid technology, and the most precise fitting, the hearing aid user may still experience a "clarity gap", i.e., they do not hear speech with the clarity they would like. Sometimes this is isolated to very challenging listening environments with loud background noise, but sometimes speech may sound distorted even in quiet environments with good acoustics. This is one of the most frustrating and challenging situations that we encounter as audiologists.
Poor word recognition stemming from a breakdown of the nerve endings in the inner ear may be the culprit. The sensory cells in the inner ear have a remarkable ability to make extremely fine distinctions among sounds, for example, "f" and "th". When these sensory cells, or the nerve endings connected to these cells start deteriorating, it can cause some blurring of speech sounds, leading to distortion. This is more common with more severe degrees of hearing loss. Even with the best hearing aids, these patients may not ever achieve the quality of speech distinction they may have once enjoyed with normal hearing, and expectations of realistic hearing aid performance may have to be adjusted.
Thirdly, there is evidence that our "auditory processing" skills decline as we age. The higher levels of the brain play a large role in our ability to hear and understand speech in complex environments, such as those with background noise. Once sounds pass through the ear and reach the auditory cortex (a process which may already be compromised with sensorineural hearing loss), the brain must then assign meaning to what it has received and, in complex environments, sort out the signal of interest from the other unwanted noise. This is an extremely complex operation that requires rapid processing of signals and the use of various interconnections among different regions of the brain.
Is this cause for pessimism? I think not. Despite all the challenges we audiologists sometimes face in providing help to those with impaired auditory systems, there is still reason to be hopeful. With the use of well-fit, appropriately adjusted hearing aid technology, assistive listening devices, the right counseling and setting of expectations, and other rehabilitative therapies (e.g., the LACE auditory training program), we can still significantly improve the quality of life for the majority of those with hearing loss. And that's why I love what I do.