How Can Deaf and Hard of Hearing Children Benefit from Hearing Aids?

A child with a profound hearing loss cannot hear sounds without amplification. The overwhelming majority of children with profound hearing loss do have some residual (remaining hearing) that with amplification, allows them to develop spoken language communication.

In the auditory-verbal approach, comprehensive audiological management is integral in ensuring the maximal use of residual hearing, which, in turn, is crucial for the development of spoken language. The Central Speech and Hearing Clinic recognizes the vital link between audiological management and auditory-verbal therapy. Optimal amplification allows the child to benefit from therapy sessions as well as auditory input during all waking hours. Intensive therapy develops the child's listening skills and contributes behavioural information regarding the child's auditory skills allowing for more complete audiological information at a younger age. The active participation of the parent in both audiological assessment and therapy and home teaching ensures ongoing assessment and evaluation of the benefit of amplification at home by the parents. Each child involved in the program at the CSHC undergoes comprehensive evaluation to ensure they obtain maximal benefit from their hearing aids. This process is both diagnostic and ongoing.

The Central Speech and Hearing Clinic is equipped to provide comprehensive services in the following areas:

Hearing Assessments
Evaluations in soundfield (through loudspeakers) or earphones are provided according to protocol established by Auditory-Verbal International. Children with fluctuating or progressive hearing loss are monitored every three months or sooner if parental or other concerns dictate. Impedance audiometry is conducted to determine the status of the child's middle ear system and may include other special tests as deemed appropriate.

Oral Hearing Aid Amplification

Hearing aid evaluations are conducted to ensure the child has optimal amplification. Electroacoustic analysis of hearing aids are performed routinely as well as at the request of parents to ensure satisfactory hearing aid performance at all times. Children enrolling in the program are initially provided with loaner hearing aids to allow for extensive evaluation for the 'best fit' while ensuring the child is provided with access to hearing as soon as they are diagnosed. The electroacoustic characteristics of a child's hearing aids are determined through the use of the Desired Sensation Level [DSL i/o], a fitting protocol specifically designed for children. The Clinic conducts measures consistent with this fitting protocol (Real ear to coupler measures) in order to account for differences in fitting children versus adults. Hearing aids are unlike eyeglasses- they do not correct hearing (ie. 20/20 hearing). Only with therapy can children with significant degrees of hearing loss maximize the information provided by the hearing aids and in turn learn
to speak.

Types of Hearing Aids

1. Behind-the Ear
2. In-the Ear*
3. In-the Canal*
4. Body Aids
5. Frequency Transposition Hearing Aids
6. Tactile Devices 

*In-The-Ear/In-The-Canal: rarely appropriate for children because of:
- growth
- lack of flexibility
- not powerful enough for severe to profound hearing loss
- hard casing
- not easily coupled to an FM system
- difficult to secure in small ears

Major Components of Hearing Aids

1. Microphone
2. Amplifier
3. Receiver
4. Battery
5. Earmold- feedback (don't turn down volume)
6. Switches/trimpots or coupling for programming 

Earmolds

Earmolds are critical in the fitting of hearing aids because the ear molds are what deliver the acoustic energy provided by the hearing aids to the child's ear.

FM Systems and Auditory Trainers

An FM System consists of a receiver (worn by the hearing aid user) and a transmitter with a microphone (worn by the speaker). The FM system allows the signal presented by the speaker to reach the listener as if the person speaking were 4-6 inches away from them. These systems allow for delivery of the signal to the listener from distances as far as 300 feet. The system assists in combating the detrimental effects of noise, distance and reverberation (sounds bouncing off hard surfaces)--all of which are problematic for individuals using hearing aids. All children can benefit from a personal FM system--as young as when they begin to walk. In the pre-school years, parents can use the system with their child to improve the listening environment and to keep their child within 'earshot' even when they are not. Once a child enters a nursery school or day-care, the FM system assists the child in hearing the teacher over the pitter patter of the other children. In the classroom, the FM system is critical in ensuring the child has access to the information provided by the teacher. The Central Speech and Hearing Clinic fits and monitors the systems used by the children. In addition, the Clinic offers in-services and workshops to teachers, educational assistants and parents to ensure their effective use.

An Auditory Trainer is a hearing aid and FM system in one. These systems have important applications, particularly in fitting babies with profound hearing loss where their tiny ears are not able to support ear level hearing aids.

Different types of hearing aids

Traditionally, hearing aids have been mini amplifiers. These devices are referred to as analog hearing aids. The microphone in these systems receives the signal and converts it into electrical energy. The amplifier increases the strength of the electrical signal to the proper loudness to compensate for the individual's hearing loss. The receiver then converts the electrical energy back into sound energy, and delivers it to the ear. In an analog system, the electrical signal replicates the sound signal.

With advances in technology, hearing aids now include digital devices which are capable of complex signal processing. Unlike analog hearing aids, these devices encode the signal into a sequence of numbers which do not resemble the original signal at all. In a digital hearing aid, the electrical output of the microphone is converted in an analog to digital converter. Key parameters in this process are the sampling rate and quantization. In the conversion, a binary number system is applied, creating a stream of bits. This stream runs through the processor which makes calculations and modifies it accordingly. The net result of these manipulations emerges after reconversion in the digital-to-analog converter and presents an analog signal to the receiver. The receiver finally transforms the signal to sound.

Among the analog and digital hearing aids, there are an array of products which include programmable and digitally programmable hearing aids -- some of these being analog and some digital. The literature describing these devices can sometimes be confusing and it is important that you discuss the different types of hearing aids and different signal processing options with your audiologist when deciding on hearing aids for your child.