The use of NAL FM amplification systems for improving classroom communication by hearing-impaired Aboriginal & Torres Strait Islander children

Robyn Massie, Denis Byrne, Deborah Theodorus (U.Qld), Joseph Smaldino (U.Northern Iowa), Brad McPherson (U.Hong Kong)

National Acoustic Laboratories Annual Report 1996/1997 

Background

The high prevalence of middle ear disease and consequent hearing problems amongst Aboriginal and Torres Strait Islander school children means there are numerous classrooms where a high percentage of children have chronic or fluctuating hearing levels at any given time. Mainstream classrooms are environments in which instruction is presented through the speech of the teacher with the assumption that students can hear and attend to spoken communication. A major problem in the typical classroom is that background noise levels tend to be similar throughout the room, but the teacher's speech level at the student's ear becomes weaker as the distance between teacher and student increases. Therefore, in some locations, the speech signal may be so poor at the student's ear that speech sounds become masked by the noise. Sound field FM amplification consists of FM transmission from the teacher to a single stationery receiver, followed by amplification of the signal over several loudspeakers positioned around the classroom. It is meant to enhance accessibility to teacher instruction for all children, and therefore is an intervention strategy which is designed to assist school children with their classroom communication. Research overseas has indicated that this approach may overcome the listening difficulties experienced by the many school children with slight or mild hearing losses, without making voices too loud for the normal hearing children in the class.

Previous R & D reports have described the NAL designed classroom amplification system. There are over 200 systems operational in Australian rural Aboriginal and Torres Strait Islander communities, with many more expected to be installed in the relatively near future. Although teachers and audiologists are subjectively providing positive feedback, and report anecdotally that the systems are an efficient and effective amplification option, there has been no objective evaluation of the efficacy of the systems within Australia. There is a clear need for formal Australian-based research in the area of classroom amplification, and the present study aims to provide this.

Research Questions

1. What are the effects of sound field FM amplification intervention on the classroom interactions of Aboriginal and Torres Strait Islander primary school children in two rural Queensland communities?

2. What is the current hearing status of the same population of children?

3. What are the acoustic characteristics of the listening environment of typical Aboriginal and Torres Strait Islander community classrooms?

Research Procedures

An initial step in answering the first question was to develop an evaluation procedure to record and measure the interactions occurring naturally between the teachers and students in the classroom. An observational assessment tool was developed and refined by conducting a pilot study at a local school, with the observations being carried out by two of the investigators. The main part of the study followed, and involved the conduction of an eight week field trial of FM amplification in two classrooms on two rural Queensland communities. For each locality, the amplification is alternated every two weeks for a period of eight weeks. One classroom begins the trial with the amplification system on for two weeks, off two weeks, on two weeks, off two weeks, whilst the other starts with the amplification off for two weeks, then on for two weeks, two weeks off, and two weeks on. Data are collected by trained observers sitting in each classroom every second week of each field trial. The measurement tool examines the flow of verbal and non-verbal interactions between each child, the teacher, and the other children. As well as examining "whole classroom interactions" with and without amplification, data are being obtained on individual children in the two listening conditions. Teachers are also asked to complete questionnaires at the beginning and end of the trials. In addition, each child is audiologically evaluated at the beginning and end of the field trials. A variety of acoustic measurements (reverberation times, ambient noise levels, signal to noise ratios with and without amplification) are also recorded for each of the four classrooms participating in the study.

Progress

The first field trial has been completed at Cherbourg, 7 kms from the town of Murgon, north-west of Brisbane. The second field trial is presently being conducted at the North Queensland community of Yarrabah, south from Cairns.

Significance

Despite the growing literature regarding the benefits of sound field FM amplification with paediatric populations, particularly in the United States of America, (Crandell, Smaldino & Flexer, 1995) little is known of the benefits of this technology with a disadvantaged group of children, many of whom have mild hearing impairment. The findings will provide insight into the communication problems faced by Aboriginal and Torres Strait Islander children in typical classroom listening conditions. Furthermore, as no other research into amplification has attempted to quantify ratings of behaviour occurring naturally in the classroom, the coding system utilised in this study may lend itself to the development of a behavioural rating of communication that audiologists and teachers "in the field" can use to demonstrate changes occurring with the introduction of classroom amplification. Such information will not only optimise Australian Hearing services to hearing impaired Aboriginal and Torres Strait Islander children, but also to other paediatric populations.

References
Crandell, C.C., Smaldino, J.J., & Flexer, C. 1995. Sound-field FM Amplification: Theory and Practical Applications, Singular Publishing, San Diego.