The configuration of the hearing loss is determined by _________ .

The configuration of hearing loss is primarily determined by the air conduction (AC) thresholds. This is because the AC thresholds provide a comprehensive overview of how hearing abilities vary across different frequencies. By plotting these thresholds on an audiogram, one can visualize the degree and pattern of hearing loss, which is essential for identifying the specific type of hearing loss a patient may have. Different patterns, such as flat, sloping, or peaked configurations, emerge based on the relationship of these thresholds at various frequencies.

While other factors, such as the bone conduction (BC) thresholds, three-frequency pure tone average (PTA), and air-bone gap, provide important information about the type and severity of hearing loss, they don't define the configuration by themselves. The air-bone gap, for instance, helps indicate whether the hearing loss is conductive, sensorineural, or mixed, but it does not detail the pattern of hearing sensitivity across frequencies. Thus, AC thresholds are the primary means of determining the shape or configuration of the hearing loss as represented graphically on an audiogram.