Advanced Communication Systems for Hearing Impairment
Enhancing Communication for Deaf Individuals
The PC System: Visualizing Speech
The PC system is a visual aid for speechreading, designed to eliminate potential confusion points that may arise due to similar articulation. For instance, distinct phonemes like /m/, /p/, and /b/ have the same articulation point and are therefore perceived as identical through lip-reading alone. Furthermore, some phonemes are “invisible” (e.g., velar phonemes /k/, /g/, /x/).
The PC system allows phonemes that appear similar at the oral production level to be distinguished by hand position. The visual unit of representation is the syllable, and the emission rate is coupled with oral broadcasting. It is not a signed method; rather, it is an oral reading system that complements lip-reading.
The information obtained through hand positions is not sufficient on its own; simultaneity with mouth movements is required. Research, such as that by Nicholls and Ling, suggests that the PC system can significantly improve spoken language comprehension in deaf children, with 100% of test subjects in their experiment achieving correct answers. This indicates it is a complementary system, highly useful for understanding oral language and for facilitating access to reading.
The Bimodal System: Integrating Manual and Oral Language
The Bimodal System involves the simultaneous expression of manual and oral language within the deaf community. It utilizes the manual vocabulary of sign language prevalent in their community. It is crucial to understand that this system does not involve two separate languages (sign language and oral language); instead, it is the emission of a single language accompanied by signs.
While oral and manual information are complementary, they are not always simultaneous in their processing; the message is expressed in two forms at once. The primary reason for creating the bimodal system is to leverage the broadcast modality to “make visible” oral language for the deaf, intending this system as an approach to bridge with sign language.
Objectives for Communication System Choice
- The deaf child should acquire a language with which they can effectively communicate with their environment.
- This language should primarily facilitate the conveyance of oral language to familiar listeners.
The two fundamental functions of oral language are communication and learning.
Understanding Communication Pathways and Processes
Modes of Communication (MOC) Pathways
These pathways represent resources that facilitate the entry, processing, and departure of information.
Input: Resources for Information Entry
- The PC system.
- Hearing aids for amplification.
- Equipment and signal modification.
- Design of cognitively transparent materials.
Processing Information (PI): Cognitive Resources
- Procedures.
- Strategies.
- Tasks.
- Electronic resources.
Output: Resources for Information Departure
- Speech.
- Reading.
- Writing.
Complex Processes: Language and Thought
Understanding communication involves intricate language and cognitive processes.
Language
- Speech comprehension.
- Speech perception.
- Speech production.
Cognition
- Problem-solving.
- Concepts.
- Basic processes: memory, perception, and attention.
Mental Representation and Learning
- Mental representation.
- Learning.
Attention and Spatial Perception
- Spatial perception.
- Selectivity (e.g., selective attention).
Linguistic Levels
- Phonetic-phonological level.
- Semantic level.
- Morphosyntactic level.
- Pragmatic level.
Information Units
- Bit: Phonology and semantics.
- Chunk: Simultaneous/successive processing and morphosyntax.
- Script: Organization of information, mental models, etc.
Reading and writing are considered the via regia (royal road) for independent learning.
Discontinuity in Speech Perception
Discontinuity, or variations in frequency and intensity over time, plays a significant role in speech perception.
- Discontinuity in low frequencies tends to be better received by individuals with hearing impairment.
- The addition of a discontinuous high-frequency band can significantly increase comprehension.
- Both people with hearing impairment and normal-hearing listeners can better understand speech through a discontinuous transmission that includes a specific frequency band.
- Discontinuity, which appears to eliminate intermediate-frequency parts, can promote discrimination.
Impact of Discontinuity on Discrimination (Examples)
The following examples illustrate how the removal of certain frequency bands (a form of discontinuity) can negatively impact word discrimination:
- -18% word discrimination for normal-hearing individuals when speech is passed only between 480-660 Hz.
- -25% when speech is passed only between 1800-2400 Hz.
- -70% when speech is passed through both bands simultaneously (implying only these narrow bands are present, leading to significant loss).
This demonstrates that while certain types of discontinuity can be beneficial or inherent to perception, the removal of crucial frequency information through discontinuity can severely hinder understanding.