Frequency Modulation System and speech perception in the classroom: a systematic literature review

Abstracts

PURPOSE:

This review aimed at presenting the benefits regarding the speech perception in noise shown by children who wear hearing aid devices and/or cochlear implants with the Frequency Modulation (FM) System at school.

RESEARCH STRATEGY:

A bibliographic survey was conducted in an electronic database with standardized search until the year 2012, and a manual search was performed by using specific keywords.

SELECTION CRITERIA:

For the selection and evaluation of the scientific studies chosen in the search, criteria were established covering the following aspects: type of study, participants, adopted intervention, and evaluation of results.

DATA ANALYSIS:

The FM system was verified to improve speech perception and speech threshold in noise in all studies.

RESULTS:

Regarding the performance as to type, the best results were obtained when children used the personal FM system, followed by the table and the sound field systems.

CONCLUSION:

After extensive review of national and international literature, it was concluded that the studies indicate the need for further research concerning mainly the impact of the FM system on the school performance of children who have sensory devices coupled to the FM system. Findings in the literature with relation to the publications focused on speech perception in noise did not relate educational and auditory aspects.

Keywords
Hearing Loss; Hearing Aids; Cochlear Implantation; Self-Help Devices; Noise; Child; Faculty; Learning

OBJETIVO:

Esta revisão teve como objetivo apresentar os benefícios, em relação à percepção de fala no ruído, que crianças usuárias de aparelho de amplificação sonora individual e/ou implante coclear demonstram com o Sistema de Frequência Modulada (FM) na escola.

ESTRATÉGIA DE PESQUISA:

Foi realizado levantamento bibliográfico conduzido em base eletrônica de dados com busca padronizada até o ano de 2012 e busca manual, utilizando palavras-chave específicas.

CRITÉRIOS DE SELEÇÃO:

Para a seleção e avaliação dos estudos científicos levantados na busca, foram estabelecidos critérios contemplando os aspectos: tipo de estudo, participantes, intervenção adotada e avaliação dos resultados.

ANÁLISE DOS DADOS:

Foi possível verificar que o Sistema de FM melhora a percepção de fala e o limiar de fala no ruído, sendo esses resultados encontrados em todos os estudos.

RESULTADOS:

Em relação ao desempenho quanto ao tipo, os melhores resultados foram obtidos quando as crianças utilizavam o Sistema de FM pessoal, seguido pelo de mesa e o campo livre.

CONCLUSÃO:

Após a extensa revisão da literatura nacional e internacional, foi possível concluir que os estudos indicam a necessidade de pesquisas voltadas principalmente ao impacto do Sistema de FM no desempenho escolar de crianças usuárias de dispositivos sensoriais acoplados ao Sistema de FM. O que foi encontrado na literatura específica quanto às publicações voltadas à questão da percepção de fala no ruído não relacionaram os aspectos educacionais e auditivos.

Descritores
Perda Auditiva; Auxiliares de Audição; Implante Coclear; Equipamentos de Autoajuda; Ruído; Criança; Docentes; Aprendizagem

INTRODUCTION

Recent progress in the treatment of children with hearing impairment has enabled the access to the auditory perception of speech sounds for individuals with sensorineural hearing loss, thus providing valuable benefits for communication and quality of life of these people.

Such progress can mostly be seen in sensory devices applied to hearing impairment. Among them, hearing aid devices and cochlear implant (CI) stand out, as well as the Frequency Modulation (FM) systems.

With early diagnosis and the activation of the National Policy of Hearing Health Care^{( 1 )}, implemented in September 2004, many children with hearing impairment gained free access to sensory devices such as the hearing aids and the CI; so, they could go to school and use these devices, which favors the learning process in the school context^{( 2 )}. Currently, we are living in a new historical moment, with the implementation of the program "Viver sem Limites"^{( 3 )}, which is organized in four principles: access to education, social inclusion, health care, and accessibility of people with disabilities in a vulnerable situation, as well as to promote initiatives with the Union, state, and city. According to the National Policy on Special Education^{( 4 )}, the integration between education and school refers to the process of educating - teaching the child both with and without impairment, in the same group, part or full time at school.

When the child has a disability, it is important to ensure access to education. The FM system is seen as an alternative among all support resources used by students with hearing impairment, aiming at assisting the integration between education and school. For some authors, the FM system is the most important and essential educational tool that has ever been developed for people with hearing impairment; regardless of type (personal, self-contained, and free-field), it is the most effective means that favors signal-to-noise ratio, especially in an education environment^{( 5 - 7 )}.

The benefit regarding speech perception in the school environment of children with hearing impairment wearing sensory devices (hearing aid and CI) together with the FM system is important in school and in studies of the Audiology field.

The current hearing health reality in public services provides better conditions for the development of the auditory function and language among children who received an early diagnosis of hearing impairment; therefore, they have more access to specialized treatment. However, even if these children show good functional performance in terms of hearing and oral language, during their development and when attending school they are faced with many obstacles, such as noise in the classroom, distance between the teacher and the child (speaker-listener), and reverberation in the classroom. These adverse conditions are mostly owed to the large number of students in the same classroom and classrooms with little or no acoustic treatment; besides, teachers in general have little or no prior knowledge regarding hearing impairment. It is estimated that guidance on management and necessary conditions to value the use of sensory devices is also scarce.

These adverse conditions lead to difficulties acquiring academic content, and, in more severe cases, the educational performance is totally harmed.

In this sense, the FM system is an electronic device used for the accessibility of people with hearing impairment, especially in the educational setting. It enables children with hearing impairment who wear sensory devices to perceive the voice of the teacher in the classroom, regardless of distance and noise that is usually generated in classrooms. Therefore, it is considered to be an assistive instrument that is part of the treatment for hearing impairment. This resource is used in school, regardless of age; however, it is potentially addressed to children.

In Brazil, sensory devices (hearing aid and CI) are already made available by the Unified Health System (SUS), and the use of the FM system was an important step toward the academic accessibility of children with hearing impairment since it was included in Recommendation n. 1,274, from June 25, 2013, in the table of Procedures, Medications, Orthoses, Prostheses and Special Materials of SUS^{( 8 )}.

OBJECTIVE

As the essential principle of a study based on evidence, the question of this study's investigation was: does the child with hearing impairment who wears sensory devices (hearing aid and CI) have benefits regarding speech perception in school environment when using the FM system in the classroom?

RESEARCH STRATEGY

The search strategy used in the literature review was oriented by the combination of nine descriptors indexed in the Health Sciences Descriptors (DeCS), in Portuguese and in English; besides, keywords that are not considered to be health sciences descriptors were also used, however, they were used to help the bibliographic survey in the databases. All of the descriptors were used in groups with, at least, two keywords (Chart 1).

Chart 1.
Searching strategies to consult the databases

The scientific databases chosen for the study were the following: LILACS, MEDLINE, SciELO, Cochrane Library, PubMed, EMBASE, Institute for Scientific Information (ISI), and Science Direct. The manual search was also conducted, with the objective of finding bibliographic references when they were not present in the electronic bases.

SELECTION CRITERIA

This study considered publications produced from 2000 to 2012, and the last search was made in the electronic databases in October 2012.

The selection of articles followed the inclusion criteria based on the agreement of the limits of the topics and the objectives of this study. The adopted criteria were as follows:

• participants: children wearing sensory devices (hearing aids and/or CI) who attended elementary school and high school;

• intervention: studies were selected in case the intervention had been performed by standardized tests, aiming at assessing speech perception of the child wearing hearing aid devices and/or CI together with the FM system;

• measured outcomes: according to categories of interest - results are expressed as percentage of hits in tests of perception and speech intelligibility, by the classification of scales related to the development of hearing skills and description of academic status;

• period: published in the past 12 years (2000-2012);

• language: studies in Portuguese, English, and Spanish; and

• types of study: published in indexed journals with level of evidence 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B, and 4, according to the classification from the Oxford Centre for Evidence-Based Medicine ^{( 9 )} (Table 1).

Table 1.
Levels of scientific evidence according to the classification from the Oxford Centre for Evidence-Based Medicine

Levels of evidence	Treatment/prevention - etiology
1A	Systematic review (with homogeneity) of controlled and randomized clinical trials
1B	Controlled and randomized clinical trials with narrow confidence interval
1C	Therapeutic results such as “it is all or nothing”
2A	Systematic review (with homogeneity) of cohort studies
2B	Cohort study (including randomized clinical trials with lower quality)
2C	Observation of therapeutic results (outcomes research)/ecological study
3A	Systematic review (with homogeneity) of case-control studies
3B	Case-control study
4	Case reports (including cohort or case-control of lower quality)
5	Opinion without critical evaluation or based on basic subjects (physiological study or study with animals)

DATA ANALYSIS

Studies were selected in three stages, and this process was oriented by the aforementioned criteria. First, three reviewers analyzed all of the studies identified by the combination of the descriptors in all of the proposed databases, by verifying the study title and selecting the ones that presented the predetermined eligibility criteria.

In that stage, it was possible to conduct a manual search of the articles that were not in the electronic databases (first stage). Afterwards, in the stage of text selection, abstracts were analyzed regarding the information available about the use of any assessment instrument on the speech perception of children enrolled in the elementary school and high school with the FM system. The full texts were analyzed when the title or the abstract left doubts (second stage). The main data from each selected paper were collected in detail in a standard file used for this study. Articles were fully read (third stage).

The descriptive analysis of the selected publications was performed according to the objectives of the review.

RESULTS

In total, 2,241 papers were identified in all of the electronic databases and in manual searches (Table 2). When these texts were preselected, based on the titles and the abstracts of all of the studies located in the electronic search, 2,233 were excluded; therefore, eight papers were fully read (Table 3).

Table 3.
Reasons to exclude the papers found in each analyzed database and number of papers selected for reading

	PubMed (n=635)	Science Direct (n=952)	LILACS (n=7)	MEDLINE (n=95)	SciELO (n=6)	Cochrane Library (n=4)	EMBASE (n=408)	Institute for Scientific Information (n=108)	Manual search  (n=26)	Total
Repeated ones	91	224	1	30	1	0	177	35	0	559
Theme	457	310	6	51	5	4	146	65	9	1.053
Language	0	0	0	6	0	0	12	5	0	23
Literature review	7	3	0	5	0	0	41	3	10	69
Comment	1	0	0	1	0	0	0	0	0	2
Incomplete abstracts	58	407	0	0	0	0	32	0	0	497
Age	12	3	0	0	0	0	0	0	2	17
Case study	4	5	0	2	0	0	0	0	1	12
Recommendation	0	0	0	0	0	0	0	0	1	1
Selected for reading	5	0	0	0	0	0	0	0	3	8

Table 2.
Number of articles identified in the databases and in the manual search

	PubMed	SciELO	Cochrane Library	LILACS	MEDLINE	Science Direct	EMBASE	Institute for Scientific Information	Manual Search	Total
Hearing Loss X Child X Hearing Aids X Education	187	0	0	2	26	177	158	21	–	571
Hearing Loss X Child X Cochlear Implant X Education	190	0	1	2	19	230	93	43	–	578
Child X Hearing Aids X Education X Assistive Technology	11	0	0	0	2	5	8	2	–	28
Child X Cochlear Implant X Education X Assistive Technology	1	0	0	0	0	3	2	1	–	7
Hearing Loss X Child X Hearing Aids X Education X Noise	12	0	0	0	3	56	12	0	–	83
Hearing Loss X Child X Cochlear Implant X Education X Noise	12	0	0	0	1	92	6	2	–	113
Child X FM Amplification	6	1	0	0	2	14	10	8	–	41
Child X FM Amplification X Hearing Aids	0	1	0	0	0	12	9	5	–	27
Child X FM Amplification X Cochlear Implant	0	0	0	0	0	7	4	2	–	13
Child X FM System	1	3	0	0	5	47	0	0	–	56
Child X FM System X Hearing Aids	6	0	0	0	5	28	27	8	–	74
Child X FM System X Cochlear Implant	4	0	0	0	0	32	15	5	–	56
Hearing Loss X Hearing Aids X Education X Rehabilitation of Hearing Impaired	99	1	2	2	18	67	17	5	–	211
Hearing Loss X Cochlear Implant X Education X Rehabilitation of Hearing Impaired	0	0	0	0	0	3	7	3	–	13
Hearing Loss X Hearing Aids X Education X Hearing Impaired Persons	48	0	1	1	12	24	18	1	–	105
Hearing Loss X Cochlear Implant X Education X Hearing Impaired Persons	33	0	0	0	1	34	8	2	–	78
Hearing Loss X Child X Hearing Aids X Education X Faculty	13	0	0	0	1	42	10	0	–	66
Hearing Loss X Child X Cochlear Implant X Education X Faculty	12	0	0	0	0	79	4	0	–	94
Manual Search	0	0	0	0	0	0	0	0	27	26
Total	635	6	4	7	95	952	408	108	26	2.241

In Figure 1, it is possible to see a summary of the survey conducted in the electronic databases and in the manual search.

Figure 1.
Exclusion criteria of the identified studies

Finally, eight papers met the inclusion criteria. From the articles included in the review, seven studies were classified as being cross-sectional, 2B level of evidence, and one was characterized as a systematic review, classified as level 2A, according to the Oxford Centre for Evidence-Based Medicine classification^{( 9 )} (Table 1).

The systematic review was described in Chart 2 as to the name of authors, title, name of the journal, year of publication, objective of the study, study method and participants, levels of scientific evidence in each study, results, and conclusion.

Chart 2.
Summary file of the studies included in the systematic review

SUMMARY OF FINDINGS

On the basis of the analysis of the studies, it was possible to identify the reasons for the exclusion of articles; they were not fully analyzed for being repeated, or for presenting nonrelated themes, for not including the studied age group, for being in another language, among others. Out of the eight studies that were selected for the systematic review, three included only the population wearing CI: studies number 1, 2, and 6. Study number 1 investigated speech perception in noise among children wearing CI together with the FM system, and study number 2 investigated speech perception, noise, and reverberation with a single FM system (free field) in two situations that were acoustically different in the school environment (ideal and poor acoustics). In study number 6, through a systematic review and a meta-analysis, the authors verified if the three types of FM system provide better speech recognition in noise than the CI alone.

The analysis of the selected articles showed that study number 3 investigated speech perception, noise, and reverberation only among children wearing hearing aid devices, by using three types of technology (infrared, desktop FM, and personal FM).

Two other articles analyzed both users of hearing aid devices and CI. Study number 4 investigated speech perception among users of CI and/or hearing aid devices exposed in acoustically poor and ideal rooms, using three types of technology from the FM system (infrared, desktop FM, and personal FM). Study number 5 assessed the improvement in speech perception in noise provided by the three types of stimulation (bilateral, bimodal, and monaural) among users of hearing aid devices and/or CI together with the FM system. Studies number 7 and 8 only assessed children wearing hearing aid devices.

Regarding the evaluations performed in the studies in relation to speech perception in noise, it was possible to observe that six of them evaluated speech perception in noise (studies number 1, 3, 5, 6, 7, and 8) and two of them compared the speech perception in acoustically different environments: one that was acoustically poor and the other that was acoustically ideal (studies number 2 and 4).

From the articles that were fully analyzed, studies number 1, 5, 7, and 8 only assessed the performance with the personal FM system, and the other studies analyzed the following three types of FM: free field, desktop FM, and personal FM, comparing their results.

The analysis of the papers regarding the type and level of evidence of each of them showed that only study number 6 was considered to be a systematic review and a meta-analysis with 2A level of evidence, and the rest of the studies were considered to be cohort, with 2B level of evidence, according to the classification from the Oxford Centre for Evidence-Based Medicine ⁽⁹⁾ (Table 1).

CONCLUSION

It was possible to verify that the FM system improves speech perception and speech threshold in noise, and these results were found in all of the papers. Concerning the performance with relation to the type of FM system, the best results were obtained when children were wearing personal FM system, followed by desktop FM system and free field.

After a national and an international literature review, it was possible to conclude that studies indicate the need for analyses addressed to the impact of FM system on school performance of children who wear sensory devices together with the FM system because the findings in the eight papers analyzed in this study were addressed to the matter of speech perception in noise.

ACKNOWLEDGMENTS

I thank all of the researchers participating in the study "Proposta de Formação de Profissionais da Área da Educação sobre Deficiência de Audição e uso do Sistema de FM em Âmbito Nacional" (Multicenter Study: Cooperation Report N. 15850/FNDE).

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• Study carried out at the Speech Language and Audiology Department, Dental School of Bauru, Universidade de São Paulo - USP - Bauru (SP), Brazil.
• *
  ALLB and RTSJ were in charge of the project, search and analysis of the studies included in the review, and the elaboration of the article; RTSJ, ACP, MM, MANM, MCB, SAB, and ALMM were responsible for the general orientation of the stages of execution and elaboration of the manuscript.

Publication Dates

• Publication in this collection
  May-Jun 2015

History

• Received
  02 June 2014
• Accepted
  29 Oct 2014