Define the term "hearing threshold level" (HTL).

The term "hearing threshold level" (HTL) refers specifically to the softest sound that an individual can hear at least 50% of the time. This measurement is crucial in audiology, as it helps establish a baseline for an individual's hearing ability across different frequencies. By determining the HTL, audiologists can assess hearing loss and the effectiveness of hearing aids or other interventions.

To arrive at this measurement, thresholds are tested at various frequencies, and the lowest intensity of sound that can reliably be detected by a listener is identified. This approach is fundamental for diagnosing hearing impairments and planning appropriate care. In the context of the other options, the loudest sound a person can tolerate relates to discomfort and potential hearing damage rather than threshold sensitivity. The frequency at which sound is most clearly heard and the average hearing ability across all frequencies do not adequately define HTL, since those concepts address specific aspects of hearing rather than the threshold itself.