Auditory training includes a collection of activities, the goal of which is to change auditory function, auditory behaviors, or the ways in which individuals approach auditory tasks. Auditory training most commonly is associated with the rehabilitation of individuals with hearing loss, but it has been used with other populations that have presumed difficulties with auditory processing, such as children with specific language impairment, phonologic disorder, dyslexia, and autism (Wharry, Kirkpatrick, and Stokes, 1987; Bettison, 1996; Merzenich et al., 1996; Habib et al., 1999). Auditory training has been applied to children diagnosed with central auditory processing and to adults learning a second language (Solma and Adepoju, 1995; Musiek, 1999). It also has been used experimentally to assess the plasticity of speech perceptual categories and to determine the neurological substrates of speech perception learning and organization (Werker and Tees, 1984; Bradlow et al., 1997; Tremblay et al., 1997, 1998, 2001; Wang et al., 1999).

Most auditory training programs are organized around three parameters: auditory processing approach, auditory skill, and stimulus difficulty level (Erber and Hirsh, 1978; Erber, 1982; Tye-Murray, 1998). When implementing an auditory training program, the first decision is whether to use a top-down (synthetic) or a bottom-up (analytic) processing approach or a combination of both. Most normal-hearing adults tend to rely primarily on top-down processing when listening to ongoing speech, but if the goal for a patient is to learn or relearn an auditory skill, a more bottom-up processing approach may be warranted. The skill to be learned or relearned (e.g., detection, discrimination, identification, and comprehension) and the complexity of the stimuli are largely dictated by the status of the patient's auditory skills and the goals of auditory training. The stimulus difficulty can be manipulated by changing such factors as set size, acoustic similarity, speed, linguistic complexity, lexical familiarity, visual cues, contextual support, and environmental acoustics. It also can be adjusted by digitally manipulating specific acoustic parameters such as formant transition duration, f₁ intensity, or noise burst spectra. Typically, the training starts with skill and stimulus levels at which the patient just exhibits difficulty. Then the skill and stimulus difficulty are systematically increased as performance improves until the training goal is attained. For example, the final goal might be that the patient will reduce fricative place confusions to 25% in connected discourse. In a bottom-up approach, the patient might work on fricative place discrimination in CV syllables with the same vowel, then with different vowels, words, phrasal and sentence structures, and finally at the discourse level. Speaking rate, vocal intensity, environmental acoustics, and contextual cues can be adjusted at each level to increase the listening demands. At the discourse level, the conversational demands also can be increased systematically. As with most skills, learning likely is facilitated by cycling across a number of difficulty levels and stimuli, having frequent training sessions, and varying the duration and location of the training.

In a more top-down approach, the patient might start at the discourse level and work on evaluating and using context to predict topic and word choices. The focus is less on hearing the place cues and more on increasing the awareness of various contextual cues that can be used to predict the topic flow within discourse. Initially, familiar topics and speakers may be used in quiet conditions with visual cues provided, and then the discourse material can be increased in complexity, unfamiliar and multiple speakers can be introduced, as well as noise and visual distractions. As a result, the patient becomes better able to fill information gaps when individual sound segments or even entire words and phrases are misperceived. With this type of training approach, patients usually receive counseling on how to manipulate context so that they reduce listening difficulty, and how to recover if a predictive or perceptual error results in a communication breakdown.

Auditory training is not routinely used with all adults with hearing loss but tends to be reserved for individuals who have sustained a recent change in auditory status or a substantive increase in auditory demands. For example, adults with sudden deafness, recent cochlear implant recipients, people switching to dramatically different hearing aids with different signal-processing schemes, students entering college, or individuals who are beginning a new job that is auditorily demanding might benefit from auditory training (see cochlear implants; evaluation of cochlear implant candidacy in adults; auditory brainstem implant). Patients who do not make expected improvements in audition and speech after the fitting of a hearing aid or sensory implant also are reasonable candidates for auditory training (see speech perception indices). The fact that most adults do not elect to receive auditory training and typically are not referred for auditory training may be a consequence of the limited data documenting the effectiveness and efficacy of auditory training programs. Only a small number of studies have been published that have assessed auditory training outcomes in adults with hearing loss. Rubenstein and Boothroyd (1987) found only modest benefit with sentence-and syllable-level auditory training with adults who had been successful hearing aid wearers, but they did observe maintenance of gains that were obtained. Walden et al. (1981) found that adults newly fitted with hearing aids benefited significantly from systematic consonant discrimination training, while Kricos and Holmes (1996) found that older adults with previous hearing aid experience did not benefit from consonant and vowel discrimination training but did benefit from active listening training. Auditory training usually focuses on speech and language stimuli, but music perceptual training programs have been developed for cochlear implant recipients and appear to be effective (Gfeller et al., 1999). In addition, auditory training is more strongly advocated for infants and children with hearing loss than for adults, but even fewer interpretable studies have been reported to support its application in children and infants.

Although supporting literature is limited with respect to auditory training of hearing-impaired populations, perceptual training studies with normal-hearing individuals suggest that the impact of auditory training on perception may be underestimated. For example, normal-hearing adults and children have been trained to perceive non-native speech contrasts (Werker and Tees, 1984; Bradlow et al., 1997; Wang et al., 1999). Although not all speech contrasts can be learned equally well, and adults usually fail to reach native speaker performance levels, the effects of training are retained over months and show generalization within and across sound categories (McClaskey, Pisoni, and Carrell, 1983; Lively et al., 1994; Tremblay et al., 1997). Digitally manipulating specific acoustic parameters of speech does not always improve speech perception in expected ways, but shaping speech perception by gradually adjusting more difficult acoustic properties is under investigation in various disordered populations and may prove fruitful in the future for persons with hearing loss (Bradlow et al., 1999; Habib et al., 1999; Merzenich et al., 1996; Thibodeau, Friel-Patti, and Britt, 2001). Furthermore, Kraus and colleagues (Kraus et al., 1995; Tremblay et al., 1997) have argued that auditory training impacts the physiology of the central auditory system and might result in cortical and subcortical reorganization. If neural reorganization occurs after the fitting of a hearing aid or cochlear implant, then it is likely that these types of patients would be sensitive to intensive auditory training during the reorganization period (Kraus, 2001; Purdy, Kelly, and Thorne, 2001).

See also auditory brainstem implant; speech disorders secondary to hearing impairment acquired in adulthood; speech tracking; speechreading training and visual tracking.