Effects of a noise-induced audiometric notch on tinnitus distress

Emre Gürses 1 Hacettepe University Sıhhıye, Ankara, 06100, Turkey

Esma Akış 2 University of Southampton University Road, Southampton, SO17 1BJ, United Kingdom

ABSTRACT

Noise-induced hearing loss (NIHL) is a widely known occupational health problem. Two initial characteristics of NIHL are audiometric notch and tinnitus. Many studies focus on the relationship between NIHL and either audiometric notch or tinnitus. However, an investigation on the link between audiometric notch and tinnitus is still missing. The objective of the current study is to evaluate tinnitus distress in individuals with a noise-induced audiometric notch. A group of 11 individuals with a history of noise exposure and sensorineural hearing loss was included. Tinnitus mapping, including location, loudness, pitch, and minimal masking level; residual inhibition (RI), tinnitus handicap inventory (THI), and Mini-Tinnitus Questionnaire (TQ 12-T) were performed. Audiometric notch was observed at 4 kHz, being in line with previous studies, in 54% of the participants. However, a significant number of participants (46%) had an audiometric notch at 6 kHz. THI and TQ 12-T results showed that noise-induced audiometric notch was associated with moderate tinnitus distress. Additionally, tinnitus pitch was closely correlated to the notch frequency and efficiently inhibited by the sound.

Keywords: Audiometric notch, Tinnitus, Tinnitus handicap inventory, Tinnitus questionnaire, Noise- induced hearing loss

1. INTRODUCTION

Noise remains an inevitable pollutant in many areas of life, especially in the workplace. It is widely known that immoderate noise exposure induces degeneration in hair cells of the inner ear and irreversible sensorineural hearing loss [1, 2]. Nearly one-third of all hearing loss cases have been reported to be attributed to noise exposure, and occupational noise exposure is the most common cause of noise-induced hearing loss [3].

An audiometric notch is a sharp threshold dip that occurs at a certain frequency, usually in an ear exposed to noise or a sudden explosion. Among the characteristics of noise-induced hearing loss, the first sign is defined as an audiometric notch at high frequencies of 3, 4, or 6 kHz with recuperation at 8 kHz [4]. However, noise-induced audiometric notch is not the only impairment caused by noise exposure.

Tinnitus, the perception of sound in the head or ears that arise in the absence of a physical origin [5], is another common consequence of noise exposure [6]. Additionally, tinnitus is one of the first warning symptoms of noise-induced hearing loss besides audiometric notch [7]. It has been reported that significantly higher lifetime noise exposure is associated with tinnitus, although there is no deterioration in hearing thresholds [8]. Nevertheless, tinnitus and noise-induced sensorineural hearing loss are generally connected to each other [9]. According to comprehensive national British survey

1 gursess.emre@gmail.com 2 E.Akis@soton.ac.uk

results, the prevalence of hearing loss and tinnitus increases with the duration of occupational exposure to noise [10].

The objectives of this study were to investigate individuals suffering from tinnitus with an audiometric notch as a result of exposure to noise and to better understand the link between tinnitus characteristics and audiometric notches.

2. MATERIALS AND METHOD

2.1.Participants

The current study included 11 (Mean: 37.45 ± 12.62 years) individuals with a history of occupational noise exposure, sensorineural hearing loss (audiometric notch at a frequency), and tinnitus. All individuals completed the evaluation forms, including age, sex, location, and tinnitus duration. Inclusion criteria were determined as age between 18 and 65 years, tinnitus experienced for at least three months, and no apparent communication impairment. A short interview was also performed to determine the history of noise exposure, previous hearing tests and treatments, and physical examination of bruxism and neck movements. Almost all of the study’s data collection methodology was also part of a clinical routine, including pure tone and speech audiometry, immittance measurement, tone decay, reflex decay testing, and tinnitus mapping. More than 15 dB difference at one frequency compared to other frequencies was accepted as an audiometric notch in pure tone evaluation. For determining the tinnitus location, participants were asked where they heard their tinnitus.

2.2.Audiological Evaluation and Tinnitus Mapping

Following otolaryngologic examination, air (0.25 to 8 kHz) and bone (0.5 to 4 kHz) thresholds were measured in both ears in a double-walled sound-isolated booth. The tests were carried out according to a modified Hughson–Westlake procedure using a GSI 61 clinical audiometer (Grason- Stadler, Eden Prairie, MN) and TDH-39 supra-aural earphones (Telephonics, Farmingdale, NY) and a bone vibrator (Radioear Corp, New Eagle, PA). Hearing loss degree was determined according to the classification of Clark JG [11] with mean frequencies of 0.5, 1, 2, and 4 kHz. Immitancemetry was done only using a 226-Hz probe tone emitted by a GSI Tympstar tympanometer (Grason-Stadler, Eden Prairie, MN). Tinnitus-matching tones were delivered to the contralateral and ipsilateral ear for unilateral and bilateral tinnitus, respectively. The clinician provided instructions verbally and presented two stimuli to the subject using manual control. Each participant was asked to identify a similar frequency with their tinnitus. The identical frequency was determined gradually through two different stimuli selections. Residual inhibition was assessed via exposure to 1 minute of a similar frequency at a 10 dB higher tinnitus masking level.

2.3.Tinnitus Questionnaire Short Form (TQ 12)

Unlike the TQ, the Mini TQ is brief and short, with 12 items selected from TQ subscales (emotional distress; 1, 2, 5, 6, 7, 9, 12; cognitive distress: 3, 10, 11; sleep disturbance: 8). Individuals mark their distress level as “True,” “Partly True,” or “Not True.” Scores of the three-point Likert Scale are calculated as 0 points (Not True), 1 point (Partly True), and 2 points (True). The total score is from 0 to 24 points. The grading system, according to an overall score for the TQ 12, is shown in Table 1.

Table 1: Grading system for the TQ-12.

Total Score Classification Grade

0-7 No clinically relevant distress due to tinnitus Distress Level I

8-12 Moderately distressed Distress Level II

13-18 Severely distressed Distress Level III

19-24 Most Severely distressed Distress Level IV

TQ 12=Tinnitus Questionnaire Short Form

2.4.Tinnitus Handicap Inventory (THI)

The THI is a well-known self-assessment tool to assess tinnitus distress in clinical practice. The THI has 25 items and three subscales, which are functional, emotional, and catastrophic. Individuals mark their distress level as “Yes,” “No,” and “Sometimes,” and respective scores such as 4, 0, and 2 are given. THI grading system is shown in Table 2. Good reliability and validity have been reported for the total score of the original and all adapted versions in different languages [12-14].

Table 2: Grading system for the Tinnitus Handicap Inventory.

Total Score Classification Grade

0-16 Slight 1

18-36 Mild 2

38-56 Moderate 3

58-76 Severe 4

78-100 Catastrophic 5

2.5.Statistical Analysis

IBM SPSS Statistics software version 23 (IBM© Corp., Armonk, NY) was used for the statistical analyses. Descriptive values are presented using mean and standard deviation.

3. RESULTS

Descriptive results of 11 individuals (6 F + 5 M: Mean Age: 37.45 ± 12.62 years), such as tinnitus duration, location, loudness, pitch, hearing loss degree, and notch frequency, are shown in Table 3. The mean tinnitus duration of the participants was 2.18 ±1.88 years. According to the pure-tone average, 1 participant had slight, 5 participants had mild, and 5 participants had moderate sensorineural hearing loss.

Table 3: Descriptive properties of the participants.

Hearing Loss Degree

Notch Frequency

Tinnitus Location

Tinnitus Pitch

N (%)

N (%)

N (%)

N (%) Slight: 1 (9%) Mild: 5 (45%) Moderate: 5 (45%)

Right: 1 (9%)

4 kHz: 6 (54%)

4 kHz: 6 (54.54%)

Left: 7 (63%)

6 kHz: 5 (46%)

6 kHz: 4 (36.36 %)

Both Ears: 3 (27%)

12 kHz: 1 (9.09%)

The tinnitus pitch (mean:5.45 ± 2.38) was closely correlated to the notch frequency. The average tinnitus loudness value was 35.45 ± 14.74. Minimal masking levels ranged between 20 and 60 dB (42.27 ± 14.72). Residual inhibition results showed that 54.54 % of the participants had total inhibition, and 36.36 % had partial inhibition. Only one participant showed no change from the inhibition assessment.

The mean THI score was 50 ± 18.41, corresponding to 3rd grade. The average of the TQ 12-T results was 12.09 ± 4.03, and it was in the range of distress level II. According to THI and TQ 12-T results, the noise-induced audiometric notch was found to be associated with moderate tinnitus distress.

4. DISCUSSION Various studies have shown that audiometric notches result from exposure to noise, particularly occupational, and the first manifestations of noise-induced hearing loss [4, 15-17]. Tinnitus is another symptom that indicates noise-induced hearing loss, which has been demonstrated in many studies to be a common consequence of exposure to occupational noise [18-20]. Our present study aimed to analyze the association between noise-induced audiometric notch and tinnitus severity in people exposed to occupational noise.

In our study, the notches were identified by audiometry as an audiometric scan has been shown to identify notches associated with the pitch of tinnitus in a previous study [21]. As a result of tinnitus mapping, our results support the literature [22-25] by showing that tinnitus pitch is significantly correlated with audiometric notches.

Although the primary cause of subjective tinnitus is a dysfunction of the auditory system, the degree of distress tinnitus causes depends on the patient’s psychological status [26]. The THI and TQ 12 are well-established assessment tools that include questioning the psychological aspects to evaluate tinnitus distress level. Although tinnitus mapping gives valuable information about the properties, these self-assessment inventories are essential to understanding patients’ tinnitus perception [12]. In our study, moderate tinnitus distress was observed due to both TQ 12 and THI in patients with an audiometric notch.

Noise is one of the main factors underlying audiometric notches and tinnitus. Our results partially confirm the findings of others by showing a strong bond between noise-induced hearing loss and tinnitus distress [27, 28].

5. CONCLUSION

This study shows that noise exposure appears to provoke a high-frequency audiometric notch in either one or both ears and the link between noise-induced audiometric notch and moderate tinnitus distress. A substantial perception of the participants presented with an audiometric notch at 4 kHz. However, a 6 kHz notch was also recorded, which is compatible with the literature [15, 29]. The descriptive aspects of tinnitus are strongly correlated with hearing loss, as demonstrated by pure-tone audiometry. Tinnitus pitch correlates strictly with the notch frequency and is easily inhibited by sound. Audiometric notch and tinnitus are considerably important indications for early detection of noise damage.

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