One way to classify the degree of hearing loss is to apply the _____________ to the categories that define severity.

The correct approach to classifying the degree of hearing loss involves applying the Pure Tone Average (PTA) to the categories that define severity. PTA is a measure calculated by averaging the hearing thresholds at specific frequencies, typically 500 Hz, 1000 Hz, and 2000 Hz. This average provides an effective representation of an individual's overall hearing ability and is crucial for determining the degree of hearing loss, whether it be mild, moderate, severe, or profound.

In contrast, Speech Reception Threshold (SRT) evaluates the lowest level at which an individual can detect and repeat back words; while useful for assessing speech understanding, it does not directly classify the severity of hearing loss. Word Recognition Score (WRS) assesses how well a person can recognize spoken words at a comfortable loudness level, which, like SRT, does not classify overall hearing loss severity. Sound Awareness Threshold (SAT) measures the lowest intensity level at which a person can detect sound, but again, it is specifically focused on sound detection rather than providing a comprehensive classification of hearing loss severity.

Thus, PTA is the most appropriate measure for determining the degree of hearing loss, making it the key tool in this context.