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The optimal masking level during speech audiometry is one that falls above the minimum and below the maximum masking levels. The goal is to select a masking level that falls at the middle of the masking plateau. This article presents a simplified approach to selecting an appropriate level of contralateral masking during suprathreshold speech audiometry. The underlying theoretical
concepts and prerequisite conditions are reviewed. The advantages of insert earphones when using the simplified approach are discussed.
Key Words: clinical masking, speech audiometry, acoustic masking procedures, midplateau masking procedure, insert earphones
More than 25 years ago, Sanders (1972) wrote the following introduction to his book chapter on clinical masking:
Of all the clinical procedures used in auditory assessment, masking is probably the most often misused and the least understood. For many clinicians the approach to masking is a haphazard, hit-or-miss bit of guesswork with no basis in any set of principles. (p. 111)
Unfortunately, this statement probably still holds true today. Martin, Armstrong, and Champlin (1994) stated that "despite the large body of research regarding clinical masking, many audiologists use improper determinations for the need to mask and/or fail to mask using a logical method" (p. 26).
A strong foundation in the underlying theoretical and experimental bases of clinical masking serves a twofold purpose. First, it allows the clinician to make a well-informed decision when selecting a specific approach to clinical masking. Second, it allows the clinician to apply and modify a clinical masking procedure appropriately. A lack of understanding of the underlying theoretical concepts of masking, however, can lead to misuse of clinical procedures.
This article presents a simplified approach to clinical masking in suprathreshold speech audiometry. Stated simply, whenever it is determined that contralateral masking is required, an effective masking level is used that is equal to the presentation level of the speech signal at the test ear minus 20 dB. According to the results of a recent survey of audiometric practices in the United States, many audiologists "base their masking level for wordrecognition testing on the stimulus level presented to the test ear and subtract a set amount, such as 20 dB" (Martin, Champlin, & Chambers, 1998, p. 100). This "shortcut" approach to selecting an appropriate level of masking during...