As I’ve gotten older, I’ve noticed that conversation in noise has become an increasingly difficult task. I find that I quickly become tired from the effort of trying to understand what one person is saying when there are a lot of other people talking, especially in the evening hours when I’m tired. When the effort becomes too great, I start tuning out the conversation, sometimes missing important information. I’m an audiologist, so I probably have my hearing tested more often than most people.
Despite my struggles to hear in noise, however, the typical audiological evaluation – thresholds for tones and speech understanding scores – has always indicated normal hearing. My experiences are not unique – the audiogram is not a good predictor of the ability to hear in challenging listening environments. One of my biggest frustrations as a clinician has been my inability to predict how well my patients will hear in noise based on audiometric test results, even with high-end digital hearing aids. Two people with identical hearing losses may report vastly different hearing experiences in real-world listening environments.
These experiences led me to make a dramatic career change. After working as a clinical audiologist for more than two decades, I decided to pursue a Ph.D. degree to study hearing problems in older adults. Because I knew that the typical audiological test battery failed to provide an adequate explanation for these difficulties, I was motivated to investigate the neurobiological basis of hearing problems in older adulthood. This desire led me to Nina Kraus’ Auditory Neuroscience Laboratory at Northwestern University. For several decades Dr. Kraus has pioneered the use of electrophysiologic (EEG) responses to speech syllables to examine the brain’s response to speech in individuals from different age groups or with different clinical impairments. As the oldest lab member (by a few decades!), I frequently volunteered myself for preliminary testing of protocols designed to evaluate the effects of aging on the brain’s responses to speech in noise. The first time I participated in one of these experiments, the colleague who was testing me was reluctant to show me my results because my brain’s responses to speech presented in noise were so degraded compared to those of younger lab members. Rather than being dismayed, however, I was excited to have the first objective confirmation of the hearing difficulties I already know I have.
While in the Kraus Lab, I published the results of several EEG experiments that have verified the effects of aging on the brain’s response to speech and the importance of accurate neural encoding of speech factors for being able to understand speech in noise. One important finding is that older adults have delayed or slower neural processing of speech, especially for the segments of speech that change rapidly, such as transitions from consonants to vowels (Anderson et al., Journal of Neuroscience, 2012). When the brain can’t keep up with these rapid changes, we naturally have trouble distinguishing between similar-sounding words, especially in noisy environments. These results have been consistent with the work of Drs. Sandra Gordon-Salant (University of Maryland) and Peter Fitzgibbons (formerly at Gallaudet University and now affiliated with University of Maryland). One of their key findings was that older adults have more trouble understanding sentences that have been time-compressed (spoken more rapidly) than do younger adults, even when hearing is matched between the groups (Gordon-Salant & Fitzgibbons, Journal of Speech and Hearing Research, 1993). So, talking louder doesn’t always help – we need people to slow down and speak more distinctly.
If you’re like me, you don’t like being told that your problems are “normal” for your age and that you just have to learn to live with them. If I can do something that at least partially reverses the effects of aging, then I’m motivated to do it. Furthermore, as a clinician, I’d like to go beyond mere identification of the problem – I’d like to offer my patients a real solution. Therefore, I was motivated to evaluate whether auditory training would improve the brain’s responses to speech, especially the brain’s ability to rapidly encode the rapidly changing segments of speech.