Speech audiometry is a specialized diagnostic tool used by audiologists to assess how well an individual can detect and comprehend spoken language. Unlike pure-tone hearing tests, which measure the softest sounds a person can hear, this evaluation uses speech as the stimulus. It provides a more comprehensive picture of hearing function and is a fundamental component of a complete audiological assessment. Speech audiometry helps determine the functional impact of hearing loss on daily communication.
Core Purpose of Speech Audiometry
While pure-tone audiometry measures hearing sensitivity across different pitches, it offers a limited prediction of a person’s ability to understand speech in real-world situations. Two individuals with identical pure-tone thresholds can have vastly different experiences following a conversation. The core purpose of speech audiometry is to quantify this difference—the clarity and processing of speech—which is often the primary complaint for those with hearing loss.
Hearing loss commonly affects the ability to clearly process the complex acoustic signals of human speech, particularly high-frequency consonant sounds. This testing determines the lowest level at which a person can hear and understand speech, and their maximum ability to understand words at a comfortable volume. The results are used for differentiating between various types of hearing loss and for planning effective rehabilitation. For instance, the data guides the selection and programming of amplification devices, such as setting appropriate gain and output levels for hearing aids.
Key Measurements and Procedures
The process of speech audiometry involves several specific measurements, each designed to isolate a different aspect of speech perception. These tests are typically conducted in a sound-treated booth using recorded or live-voice speech presented through headphones or speakers. The patient’s task is usually to repeat the words they hear.
Speech Detection Threshold (SDT)
The Speech Detection Threshold (SDT), also called the Speech Awareness Threshold, identifies the softest sound level at which a patient can simply perceive the presence of speech. The patient only needs to indicate they hear a sound, not that they understand it. This measurement is often used for individuals who cannot repeat words, such as young children or those with cognitive impairments.
Speech Recognition Threshold (SRT)
The Speech Recognition Threshold (SRT) determines the lowest sound level at which a patient can correctly repeat 50% of the speech material presented. Spondee words, which are two-syllable compound words with equal stress on each syllable (e.g., “hotdog” or “baseball”), are commonly used for this test. The audiologist presents these words at decreasing intensity levels until the 50% recognition level is reliably established.
Word Recognition Score (WRS)
The Word Recognition Score (WRS) measures the clarity of hearing when the volume is not an issue. For this measurement, a list of single-syllable, phonetically balanced words (such as the NU-6 or CID-W22 lists) is presented at a comfortable listening level, typically 20 to 40 decibels above the SRT. The final score is reported as a percentage of words the patient correctly repeats, indicating their ability to clearly understand speech when it is loud enough.
Interpreting the Test Results
The scores from speech audiometry are translated into functional terms to guide diagnosis and treatment strategies. The Speech Recognition Threshold is a valuable measurement because it should align closely with the Pure-Tone Average (PTA)—the average of a patient’s pure-tone thresholds at 500, 1000, and 2000 Hertz. A close correlation between the SRT and PTA provides a crucial internal cross-check, confirming the reliability of the pure-tone test results.
The Word Recognition Score is the most informative result, as it directly relates to real-world communication difficulties. A high WRS (e.g., 90-100%) suggests good clarity when speech is loud enough, often seen in cases of purely conductive hearing loss. A significantly reduced WRS (e.g., 50-70%) at a comfortable volume is characteristic of sensorineural hearing loss, indicating damage to the inner ear or auditory nerve where clarity is affected.
This percentage score helps the audiologist explain how much benefit the patient can realistically expect from hearing aids. For example, a patient with a severe hearing loss but a WRS of 96% is likely to adapt well to amplification. Conversely, a patient with a similar loss but a WRS of 60% may continue to struggle with clarity, even with well-fitted devices. If the WRS is unexpectedly poor compared to the pure-tone results, it can suggest a disorder beyond the inner ear, such as a retrocochlear pathology, prompting further medical evaluation.