Question
Is there a link between the UCL and the stapedius reflex threshold?
Answer
Beginning in the 1970s, studies have been conducted to determine if the Acoustic Reflex Threshold (ART) could predict Uncomfortable Loudness Level (UCL, also known as Loudness Discomfort Level, LDL). If we could accurately predict UCL given ART, useful hearing aid fitting information could be obtained for difficult to test patients. The ability to predict UCL based on ART depends on the relationship between these two measures.
Both ART and UCL are affected by degree of hearing loss. Average ARTs are about the same for people with normal hearing and sensorineural hearing loss when the pure tone threshold is below 45-50 dBHL (Gelfand et al., 1990). As hearing threshold increases above this point, ART increases. UCL varies with hearing loss in a similar way. Average UCL is similar for people with normal hearing or sensorineural hearing loss with thresholds below about 50 dBHL, with a gradual increase in UCL as hearing threshold increases (Kamm et al., 1978). Thus, it would seem logical that as ART increases, UCL also increases; however, there have been conflicting reports in the literature regarding the strength of this relationship. Charuhas et al. (1979) investigated the relationship among UCL, ART, and hearing loss in 80 subjects with normal hearing or noise induced hearing loss. They found a high correlation between hearing threshold and UCL (-.99) and between hearing threshold and ART (-.98); however they found the ART to UCL relationship varied based on degree of hearing loss.
Dirks and Morgan (1983) provided a brief literature review on the UCL to ART relationship from studies conducted in the 1970s. Some of the studies indicated a wide intersubject variability for both ART and UCL and a low rank order correlation between the two measures. Dirks and Morgan concluded, "the variables affecting the LDL and the absence of a predictable relationship between LDL and ART make prediction of one measure from the other clinically inappropriate." More recently, Olsen (1999) conducted a meta-analysis of 11 studies of the relationship between ART, UCL, and HTL (pure-tone hearing threshold). He found no significant correlation between mean ART and mean UCL for people with normal hearing but a significant correlation between mean ART and mean UCL (.88), mean ART and mean HTL (.77), and mean UCL and mean HTL (.66) for people with hearing loss. Since this was a meta-analysis, he was not able to study individual participant data. Olsen suggested methodological issues including inconsistent instructions to the listeners, sound pressure level in the ear, subject selection criteria, and so forth, influenced the conflicting nature of the results from previous studies. He recommended further study of the relationship between UCL and ART in both normal and impaired ears using standardized instructions and more careful control of subject selection criterion.
In summary, early studies have suggested the absence of a strong relationship between individual ART and UCL measures, but a recent meta analysis found a significant correlation between mean UCL and mean ART for people with hearing loss, but not for people with normal hearing. More research, with careful control of study methodology, is needed to further explore the individual relationship between UCL and ART for people with normal hearing and hearing loss.
Charuhas, P.A., Chung, D.Y., & Barry (1979). Relationship between uncomfortable loudness level and acoustic reflex threshold as a function of hearing loss. The Journal of Auditory Research, 19, 237-242.
Dirks, D.D. & Morgan, D.E. (1983). Measures of discomformt and most comfortable loudness, pp 203-229. In D.F. Konkle & W.F. Rintelmann (Eds.), Principles of Speech Audiometry. Baltimore: University Park Press.
Gelfand, S.A., Schwander, T., & Silman, S. (1990). Acoustic reflex thresholds in normal and cochlear-impaired ears: Effects of no-response rates on 90th percentiles in a large sample. Journal of Speech and Hearing Disorders, 55, 198-205.
Olsen, S.O. (1999). The relationship between the uncomfortable loudness level and the acoustic reflex threshold for pure tones in normally-hearing and impaired listeners - A meta analysis. Audiology, 38, 61-68.
Kamm, C., Dirks, D., & Mickey, R. (1978). Effect of sensorineural hearing loss on loudness discomfort level for speech. Journal of Speech and Hearing Research, 11, 497-508.
Dr. Diana Emanuel has been a faculty member at Towson University for 9 years. She is currently the Audiology Graduate Program Director for the Au.D. Program at Towson University. She can be reached at demanuel@towson.edu.