Background: Loudness Discomfort Level (LDL), a test used in the hearing aid fitting process, has also been recommended to evaluate patients with tinnitus and/or suspect of hyperacusis.
Aim: To determine LDL reference values for normal hearing individuals and to correlate the LDL to the Acoustic Reflex Threshold (ART).
Method: LDL was investigated in 64 normal hearing subjects, with ages between 18 and 25 years (53.1% female), in the frequency threshold of 0.5 to 8KHz and for speech (non-recorded, non-standardized connected discourse). Pulsate pure tones were presented for two seconds, with a one-second interval between each presentation. The initial stimulus intensity was at 50dB and was followed by ascending presentations, of 5dB each, until the subject referred initial discomfort with loudness. The testing procedure was performed separately in each ear, and was immediately repeated at the end of the test (test and retest situation). The choice of the ear that would start the testing procedure was alternated for each subject. After that contralateral acoustic reflexes ART were measured. The presence of the ART was indicated by a minimal needle deflection (larger than 0.05ml) on the emittance equipment.
Results: Median varied from 86 to 98dBHL, with no statistically significant differences between gender (p > 0.11), between ears (p > 0.36) and between the test-retest situation (p > 0.34). The determination coefficients (r2) of the linear regression model revealed absence of correlation between log(LDL) and log(ART).
Conclusion: Normal hearing individuals have LDL between 86 and 98dBHL for all of the tested stimuli. Inter-subject differences and the good reproductivity suggest that the interpretation of the test should be cautious and analyzed considering the patient's history. The test can be an useful instrument go follow-up patients. No correlation was found between LDL and ART.