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How does an electric audiometer measure hearing thresholds?

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An electric audiometer measures hearing thresholds through a process known as pure-tone audiometry, which determines the lowest intensity level at which a listener can detect a specific tone at least 50 percent of the time.12

The device consists of a signal generator, an amplifier, an attenuator to control intensity, and an earphone or loudspeaker. During the test, the audiologist presents tones at discrete frequencies (typically 500 Hz to 8,000 Hz) using the "method of limits," where signals are presented in ascending or descending runs of intensity. The listener provides a response, such as a hand signal, whenever they detect a tone.21

Key aspects of this measurement include:
* Audiometric Zero: The baseline representing normal hearing for young adults.12
* Threshold Determination: The lowest intensity level at which the tone is perceived 50 percent of the time is recorded as the hearing threshold for that frequency.12
* Masking: If a signal is intense enough to cross the skull and be heard by the opposite ear, masking noise is used in the nontest ear to ensure accurate results.12
* Bone Conduction: A vibrator may be used to measure hearing via bone conduction, helping distinguish between conductive and sensorineural hearing loss.2