Auditory training can be defined as formal listening activities whose goal is to optimize the activity of speech perception (Dr. Arthur Boothroyd). It is based on an assumption that listeners often need help in dealing with the speech perception deficits that remain after auditory function has been optimized through an appropriate hearing aid selection process. This point cannot be overemphasized: engaging in auditory training without first being assured that the hearing aids are doing exactly what they should be doing is a waste of time for both the clinician and the consumer.
Note that the definition above includes the words “formal listening activities.” This serves to distinguish auditory training from the auditory learning that takes place whenever hearing aid users, particularly new users, are simply listening to speech. The amplified signals often sound a bit different to them, a bit strange. Hearing aid dispensers, from time immemorial, have always counseled new hearing aid users that it may take some time for them to “get used” to the new sounds the hearing aids are providing to their ears and their brains. It is an observation well grounded in years of experience.
In fact, a great deal of informal “auditory training” does take place during this initial hearing aid (and cochlear implant) adjustment phase. Hearing-impaired people are constantly trying to make sense of speech signals that are distorted in some fashion. Listening to speech is always a bit of a guessing game for them, in which they use their knowledge of the language and the context to fill in the acoustic gaps and distortions of the incoming speech signals. People do get better at this, over time. A formal listening program of auditory training assumes that hearing aid users have completed this initial adjustment stage, i.e., that they have reached a plateau in their listening skills and are now ready to attempt to further improve their performance through explicit training.
While auditory training has always theoretically been included within the scope of practice of Communication Disorders professionals, it was rarely used clinically – for several reasons. One was that, unlike speechreading (the other procedure which basically defined aural rehabilitation years ago), auditory training does not lend itself to group lessons; it must be practiced on a one-to-one basis. The other reason was that convincing research evidence attesting to its value was relatively sparse and did not appear to justify the time and expense that the activity required. But this view of auditory training has been changing in the last decade or so, thanks to developments in three areas.
The advent of the cochlear implant (CI) several decades ago was the first of these developments. The auditory sensations that the first generation of CI users received was so different from what they had been used to that they needed help in adjusting to, and learning to comprehend, these new and strange sound sensations. This is akin to orthopedic patients who routinely receive physical therapy after some sort of surgery (hip, knee, shoulder, etc.). In other words, if physical therapy helped people with post-surgical physical issues, why wouldn’t auditory therapy (training) be similarly helpful for people with hearing problems? And why limit therapy only to CI users, why not people wearing hearing aids as well? While the practice of auditory training had been with us for years, it seems not entirely coincidental that, since the advent of the CI, auditory training has been seeing a revival for both hearing aid and CI implant users.
The second of these developments was the emerging appreciation that mature neural systems – once viewed as immutable – are now beginning to be seen as malleable and subject to modification. Neuroscientists, using such procedures as magnetic resonance imaging (MRI), have quantified neural plasticity in adult human subjects. It appears that structural and physiological changes in the central nervous system can take place as a consequence of therapeutic intervention, such as repeated exposure to meaningful auditory stimuli in a training situation. Furthermore, there is evidence that these changes can be measured in the way the cortex responds to sound. In short, it seems that old dogs can learn new tricks.
The third development that has encouraged a new look at auditory training is the widespread use and familiarity with the personal computer and the Internet. Before this, it simply was not economically practical for clinicians to offer this service. To be effective, therapy has to be conducted frequently and over a relatively long period of time; any agency, including non-profit ones, concerned with the bottom line simply couldn’t afford to offer it as a routine clinical procedure. With personal computers and/or online training, however, it is now possible for people to conduct frequent training sessions at home, at a great savings in cost and personal convenience. The most effective model, in my opinion, is a blend of clinical and home activity, where the professionals can interact with the clients to monitor and provide assistance when needed.
Traditionally, auditory training can be separated into the analytic and synthetic approaches. In the analytic technique, the focus is on the elements of speech, to improve a person’s ability to identify the various sounds of speech, specifically those with which the person has difficulty. Thus in training vowel identification, a person may be required to distinguish between such words as /beet/ and /boot/, which have two vowels that considerably differ acoustically. From there, a person may be challenged to distinguish finer and finer vowel differences. In analytic consonant training, the vowel remains the same, but now the target consonant is changed. This training also proceeds from large to finer acoustic distinctions. Analytic training is termed a “bottoms up” approach because the intent is to improve overall speech comprehension by focusing on the acoustic “building blocks” of speech messages. The reasoning is that if someone can reliably distinguish the acoustic elements of speech, then he or she should be better able to comprehend the larger units, such as sentences and paragraphs.
A synthetic training approach, on the other hand, employs meaningful sentences as training stimuli. Most often the sentences are presented to the listeners in the presence of noise, thus mimicking the situation in which most people with hearing loss have the greatest difficulty. The task of the listener is to focus on comprehending the sentence meaning without attending to specific acoustic elements. Modern techniques use a presentation method in which the noise level is either increased or decreased automatically, depending upon whether or not the sentence was correctly understood. The intent is to ensure that listeners are continually challenged during the training session. The goal is for a listener to be able to comprehend speech in increasing levels of noise. As opposed to the “bottoms up” approach of the analytic technique, synthetic training is termed “top down,” as it requires listeners to employ their knowledge of language and context to fill in the acoustic/perceptual gaps in the message. In my judgment, both techniques have a place and both should be employed.
But now the central question of this article: Can auditory training assist hearing aid and cochlear implant users to improve their listening skills beyond that seen when people “get used to” the devices they are wearing? The short answer is “Yes,” provided the program is appropriate and sufficiently intensive. A few years ago, Sweetow and Palmer reviewed all the studies they could find that might even remotely be related to auditory training. They found 213 of them, but only six met the inclusion criteria that they employed (i.e., whether the study was “on topic” and met various research requirements). The results of these six studies, dating from 1970 through 1996, suggested that auditory training can improve speech recognition skills to some extent, especially if it used a synthetic training approach. The best results were obtained with the more intensive programs (longer duration and more sessions per week).
Recent research on auditory training has focused on home-based training programs, with results that are less ambiguous than the early studies. Currently, the most popular such program is termed LACE (for “Listening and Communication Enhancement”). This program can be completed at home, with or without the online guidance of a professional. In addition to the usual task incorporated in an auditory training program (recognizing speech in noise), LACE includes other relevant listening dimensions, such as comprehending rapid speech, and improving working auditory memory and processing speed. In a study published a few years ago, Sweetow and Henderson-Sabes found that their subjects made significant improvements in all the listening and cognitive dimensions for which they received specific training. It is reasonable to assume that these gains would positively impact on a person’s ability to communicate in the real-world. Furthermore, the study demonstrated significant improvement with listening tests for which the subjects had not been directly trained, demonstrating generalization beyond the training material. But it does take a sincere commitment by the user: five days a week, for at least thirty minutes per session, for a minimum of a month (see neurtone.com).
A new entry into the home-based auditory training market is termed “ReadMyQuips.” This is an audio-visual training program in which the subject both sees and hears the quips (sentences) being spoken. (Disclosure: I consulted on this program during some stages of its development.) It is an adaptive program in which the audio signal is alternately raised or lowered depending upon whether or not the answer was correct. The response format is that of a crossword puzzle, with each box containing a word not a letter. The entire quip (taken from such luminaries as Groucho Marx and Winston Churchill) is spoken and the listener fills in all the boxes that he or she can. The format is meant to be entertaining and to engage a subject’s interest for a long period of time. Two studies were carried out with this program; both showed that the majority of subjects significantly improved their performance. Further, the analysis showed that improvements were directly related to the duration of time that a subject worked on it (see sensesynergy.com).
While cochlear implants have been extensively studied, relatively little formal research has been carried out specifically on the effectiveness of auditory training. At the House Ear Institute, Dr. Qian-Je Fu and his colleagues have conducted much of the available research and have employed both analytic and synthetic approaches. For analytic training and testing, they developed a program termed CAST, or Computer Assisted Speech Training. A version of this (called Sound and Way Beyond) is now available commercially through the Cochlear Corp. Ten experienced cochlear implant (CI) users tried the program at home for about one hour a day, five days a week, for one month or more. The average results demonstrated significant improvements in the subjects’ vowel and consonant scores after training. Other studies, conducted at the House Institute and elsewhere, required identifying sentences under noisy conditions. The results of these studies also showed significant improvements in sentence recognition after training. Overall, it seems that both bottoms up and top down training can produce gains in the speech perception skills of CI users. For the interested person, listening activities can be found on all three cochlear implant websites (advancedbionics.com, med-el.com, cochlear.com). Practiced sufficiently assiduously, I have no doubt that individuals can improve their performance using these resources.
A number of authors have cautioned us that in order to be effective, a formal auditory training program must meet certain criteria:
- One, very pertinent for this day and age, is that it must be cost effective.
- It must be sufficiently engaging to sustain participation, not too easy and not too difficult.
- It must be practical and easily accessible (home-based is best).
- It should provide immediate feedback regarding responses.
- Optimally, it should incorporate elements of both bottoms up and top down processing.
- Optimally, too, it should include the active collaboration of a knowledgeable professional.
From my perspective, it does appear that auditory training is being resurrected from the dormant state it has been in since after WW II. Current developments, particularly in computers and the Internet, permit activities we could only dream about years ago. While professionals have a responsibility of making this option (home-based programs) known to their clients, it is still their clients – the person with a hearing loss – who often has to take the initiative. When it comes to hearing better, passivity is not an option.