Portuguese Version

Year:  2000  Vol. 66   Ed. 5 - (3º)

Artigos Originais

Pages: 439 to 442

Low Intelligibility in Noisy Environment in Young People with Normal Audiometry.

Author(s): Ari de Paula*,
José A. P. Oliveira**,
Natália M. Godoy***.

Keywords: audiometric threslhold, word recognition, noise induced hearing loss, back noise, intelligibility, hearing

Abstract:
Introduction: Six patients between 14 and 35 years old (on avarage of 27,8) with normal audiologic level were studied. They declared that their quality in audition was not good, even though their conventional audiological level was a normal and the intelligibility 100%. Material and methods: We used a methodology developed to evaluate the audiologic level in silence and in the presence of a competitive noise (white noise) in an audiometric cabin without earphone where we could observe the increasing difficulty in discriminating monosyllables according to the rise of white noise into the cabin. Results: It has been showed, comparing the results found in the study with 14 normal patients with any complaint, that the six studied patients in fact, have a comprehension of the words far short of the normal ones in a competitive environment although they showed a 100% of discrimination in silence. Conclusion: The current study proves that a normal result of a conventional audiogram not always shows the reality so that we should use this kind of evaluation to a more accurate definition of an individual's audition condition.

INTRODUCTION

The complaint of hearing difficulties is among the most commonly reported in the daily routine of otorhinolaryngologic practice; basic audiological exam is always conducted in order to confirm or exclude the existence of such a complaint. In such situations, pure tone air and bone conduction are performed, in addition to impedanciometry, complemented by index of speech recognition for monosyllables and disyllables (Costa, Cruz and Oliveira, 1994; Lopes Filho, 1994). There are situations, however, in which patients complain of difficulties in understanding speech in noise; despite the fact that results of exams are within normal ranges. This is also a relatively common complaint in patients who have a certain degree of hearing loss, especially if it is a sensorineural loss (Simonton, 1953; Anianson, 1979; Dubno, 1984); however, we rarely consider the same complaints when they are made by young patients who have normal audiometric results. Actually, the exam is conducted in a sound proof booth, and therefore, we do not test patients' hearing skills in noise, and we can not confirm that there is nothing wrong with these patients. Cooper (1971) stated that audiologists should perform both measures of discrimination, in quiet and in noise, in order to understand the problems of subjects who have such kind of complaints. Jokinen (1973) studied 120 patients of various age ranges and concluded that from the 5th decade of life significant difficulties of discrimination were common when in noise; however, Middelweerd (1990) did not confirm such a fact in his studies, because he tried to investigate young subjects who complained of difficulties to understand words in noise and he found 15 subjects who had a reduction of word recognition index in noise not compatible with their ages. Elbaz (1992) also showed this type of patient in his studits: In order to assess the presence of central auditory dysfunction in children, Pereira and Schochat (1997) addressed this type of test that compares speech recognition in quiet and in competitive noise and they measured the function performance-intensity for monosyllable words and sentences.

OBJECTIVES

To evaluate comprehension of monosyllable words in noise in a group of six patients with complaints of hearing difficulties, despite the normal result in conventional audiometric assessment.

To propose the inclusion of tests that assess speech recognition in noise in the basic audiologic routine.

MATERIAL AND METHOD

Using the methodology developed by De Paulo and Oliveira (1998) especially designed to study the speech recognition index in quiet and in noise using a audiometric booth and normal audiometers, we assessed 6 patients aged between 14 and 35 years (mean age of 27.8 years), without history of use of ototoxic medication or chemicals, exposure to industrial noise, repetitive otitis in childhood and no past or present history of otological disease and normal otoscopy, but with complaint of difficulty to understand words in noise, despite the normal results in both pure tone air and bone thresholds, and impedanciometry and word recognition index within normal ranges. The patients underwent an assessment with the lists of monosyllables by Geraldo de Sá (1952), in an environment with progressively increasing white noise (buzzing), but constant signal level - 40dB above the mean of 500 to 2000Hz thresholds at conventional audiometry. Therefore, speech recognition index would decrease until it reached the level of zero, and the results produced a graph (Graph 1) to be compared to results of normal groups previously determined by the study conducted by De Paula and Oliveira (1998). We started the exam with 50 dB noise and at the end of each column of words, we incremented 5dB in noise, mainitaining the same signal. Therefore, after each column of monosyllables, noise increased and hearing discrimination worsened.

RESULTS

Graph 1 shows the position of patients of experimental group (simple lines) comparing to the normal subjects (straight line, N); in the horizontal line we observe the difference in dB between the produced signal of monosyllables and the noise produced in the environment. In the vertical, there is the percentage of recognition index found in each situation of the exam. We observed that all studied patients, normal or not, had values for speech recognition within normal ranges in quiet, reaching the index of 100%. However, when submitted to this kind of test, we noticed the difference in performance, and the patients in the experimental group performed worse in word understanding than normal subjects of the same age range. For the comprehension of 50% of monosyllable words, the normal groups needed 10 to 15dB S/N ratio (that is, 10 to 15dB more of signal than of noise), whereas the experimental group reached the same level at 0 to 5dB in average of S/N ratio. For the group of normal subjects to reach the level of understanding no words, a S/N ratio of 25 to 30dB was required, whereas for the same situation the experimental group would not understand any word when the noise was 15 dB higher than the signal. Therefore, the difficulty in understanding words in noise was more marked in studied patients than in normal subjects.

In the vertical axis there is the percentage of speech recognition index, whereas the horizontal axis shows the difference between signal (40 dB above the mean of 500 to 2.000 Hz found in the conventional audiogram of each patient) and environment noise produced in the booth, incremented by 5 dB each time we came to an end of a column of monosyllables in Geraldo de Sá (1952) tables. The straight line (N) represents the middle line of normal patients and the printed region represents the normal range for these patients (De Paula and Oliveira - 1998), without complaints of hearing difficulties, and with conventional tests results within normal ranges. The remaining lines represent the six studied patients who had normal audiogram but insisted in reporting hearing complaints. It was clearly seen that the higher the noise in the audiometric booth, the lower the index of speech recognition found for all patients; however, the curves of the 6 studied patients were much worse than those of normal subjects, despite the fact that they had had a recognition index of 100% before the introduction of noise in the exam.
Graph 1. Hearing discrimination in competitive noise.

DISCUSSION

It is part of the daily lives of people today to be in noisy environments. It is seldom damaging to the extend of resulting in Corti's organ lesion, but it .may somewhat affect understanding of words. These alterations have been clearly demonstrated in the elderly population (Dirks, 1982; Dubno, 1984; De Paula and Oliveira, 1998); however, few have addressed the topic in young people with normal audiometric results. On the other hand, existing routine audiological assessment does not take this fact into consideration, because the tests are conducted in quiet environments without competitive noise, and the more the booth is sound proof, the better the quality of the exams. However, in the routine of otorhinolaryngologic practice, there are some patients, usually young ones; who complain of hearing difficulties, even in the presence of normal audiometry. Middelweerd (1990) and Elbaz (1992), studying groups of audiologically normal subjects, found impairment of speech recognition index in competitive noise. The present study confirms the concerns of the authors, because it clearly shows that a group of patients with normal audiograms performed worse in identification of monosyllables in noise than the group of normal subjects at the same age range. Therefore, according to Jokinen (1973), "the use of masking in a sound proof booth to assess the index of speech recognition in noise is complex if compared to the battery of audiometric tests we routinely conduct; however, in the future it will be necessary to review its definite diagnostic value for some groups of patients".

CONCLUSION

1. Speech recognition index in quiet does not reflect the speech recognition index in competitive noise.

2. In addition to existing audiological tests, we should include an audiological test in noise to determine more precisely the difficulties patients have in discriminating words.

3. We should be attentive during the anamnesis for patients' report about hearing difficulties not compatible with the audiometry found in the conventional exam; if possible, we should submit patients to a more detailed assessment, such as the one presented here.

REFERENCES

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* Preceptor of Medical Residence at Santa Casa and Hospital Irmãos Penteado, in Campinas.
** Ph.D. Professor and Head of the Department of Otorhinolaryngology at Universidade de São Paulo - Ribeirão Preto /SP.
*** Speech and Hearing Pathologist with the Department of Otorhinolaryngology at Santa Casa and Hospital Irmãos Penteado, in Campinas.

Affiliation: Departamento de Otorrinolaringologia da Irmandade de Misericórdia de Campinas: Santa Casa a Hospital Irmãos Penteado.
Address for correspondence: Ari de Paula - Avenida Júlio de Mesquita, 960 - 18° andar - Cambuí - 13025-061 Campinas /SP.
Tel: (55 19) 236-8972 - Fax: (55 19) 232-4478.
Article submitted on March 20, 2000. Article accepted on August 31, 2000.

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