After reading this guide, you will understand:
- What speech audiometry is.
- The importance of speech audiometry.
- Common types of speech audiometric tests.
- How to read speech audiometry results.
- What is speech in noise testing.
- Word recognition testing and it’s use in hearing aid fitting.
- When to mask during speech audiometry.
What is Speech Audiometry?
Speech audiometry refers to a set of hearing tests that measure an individual’s ability to detect, recognize, and repeat spoken words. This is done under various conditions, including quiet environments and backgrounds of competing noise, to simulate real-life listening situations. Speech audiometry is often used in conjunction with pure tone audiometry, but it provides additional information on a patient’s speech understanding ability.
Importance of Speech Audiometry
- Can detect hearing issues that pure tone testing might miss, especially certain auditory disorders.
- Provides a more accurate picture of real-world communication abilities compared to pure tone tests.
- Testing at conversational speech levels can show good understanding for those with normal or near-normal hearing. Reduced speech comprehension for individuals with hearing loss.
- Speech tests are sometimes easier for some groups to respond to, such as children and adults with cognitive decline.
Types of Speech Audiometry Tests
Speech Recognition Threshold (SRT)
The Speech Recognition Threshold (SRT) is the lowest level at which a person can correctly repeat 50% of presented speech. Typically, two-syllable words or spondee words are used as test material. The SRT score should correlate closely with the patient’s pure tone average (PTA), the average of an individual's hearing thresholds at specific key frequencies—typically 500, 1000, and 2000 Hz
Speech Detection Threshold (SDT)
The Speech Detection Threshold (SDT), also known as the Speech Awareness Threshold (SAT) is the minimum hearing level for speech which an individual can just discern the presence of speech stimuli 50% of the time.
For SDT, the patient only needs to detect the presence of speech, while in Speech Recognition Threshold (SRT), they must correctly repeat the words heard. Unlike SRT, SDT stimuli are not standardized and may include phrases like "bup, bup, bup" or "uh oh." SDT is less commonly used and is typically reserved for cases where word repetition isn’t possible, such as with children or individuals with special needs. SRT is usually measured about 10 dB higher than SDT.
Word Recognition Testing
Word recognition testing evaluates a person's ability to hear and correctly repeat spoken words. It uses monosyllabic words presented at a comfortable or suprathreshold volume to measure how well a person can understand speech when it is audible. The results are expressed as a word recognition score (WRS), given as a percentage. This test helps determine how clearly speech is perceived, especially for those with hearing loss.
Word Recognition Score Word Lists
In word recognition testing, standardized phonetically balanced word lists are used to ensure that speech sounds occur proportionally to their occurrence in spoken English are represented equally. These words help assess the patient’s ability to recognize subtle acoustic cues in speech.
Well-known lists of phonetically balanced monosyllabic words include CID W-22 lists and PBK-PBK-50 lists. Also, the NU-6 list is a commonly used list of consonant-nucleus-consonant (CNC) monosyllabic words that are not phonetically balanced.
To learn more about word recognition best practices, including appropriate presentation levels, please refer to: Am I Doing it Right? Word Recognition Test Edition.
WRS Word List & Clinical Use
- NU-6 lists contain more difficult words, making them suitable for adults.
- W-22 lists are easier, ideal for younger individuals or those with special needs.
- PBK-50 lists are designed for kindergarten-aged children but are also useful for children and those with special needs.
Purpose of Word Recognition Testing
The main goal of word recognition testing is to find the patient’s maximum speech understanding for one-syllable words, known as their maximum word recognition score.
To achieve this, word recognition is tested at various intensities above the hearing threshold, a process called performance intensity (PI) function. Word recognition improves as intensity increases, but only up to a point. The maximum score, called PB Max, is reached when further increases in intensity no longer improve the score.
PI function is useful in detecting retrocochlear pathology, which affects areas beyond the cochlea. PI rollover occurs when increasing intensity actually decreases word recognition, indicating a potential problem.
WRS and Fitting Hearing Aids
- Word recognition testing at a conversational level helps assess the need for amplification.
- Testing can be repeated with hearing aids in place to demonstrate improvement in speech understanding.
- Using the MCL level for testing is beneficial, as hearing aids are typically used at this level, giving a more accurate prediction of the patient’s performance with amplification.
It’s important to note that that while word recognition testing may help predict a patient’s performance with hearing aids, it has its limitations. A high WRS generally suggests that the patient may benefit more from hearing aids, as they can recognize speech well when it is audible.
However, a low WRS, especially in cases of severe sensorineural hearing loss, indicates that even with amplification, the patient may struggle with speech understanding due to damage in the auditory system. While useful, WRS in quiet doesn’t fully account for real-world conditions like background noise, where additional tests may be needed.
Speech-in-Noise Testing
A speech-in-noise (SIN) test assesses how well someone can understand speech with background noise, such as in a crowded restaurant. This test helps evaluate how well a person can "hear in noise," a common issue for those with hearing loss. The most common SIN is the Quick Speech in Noise (QuickSIN) test.
How to Read Speech Audiometry Results
Understanding speech audiometry results involves looking at several key indicators that give insight into a person’s hearing ability. Here’s how to interpret them:
Pure Tone Audiometry: Pure tone thresholds are typically measured alongside speech audiometry to determine the degree and type of hearing loss. This is crucial because the pure tone average (PTA)—the average of thresholds at 500, 1000, and 2000 Hz—should align with the SRT for accurate results.
Speech Recognition Threshold (SRT): The SRT is typically expressed in decibels (dB). The SRT should be within +10 dB of the patients PTA for SRT to be considered reliable.
Word Recognition Score (WRS): The WRS is expressed as a percentage, representing how many words a person can correctly repeat at a certain intensity level. Some clinicians also use verbal descriptors, which some find useful in report writing.
Be cautious with verbal descriptors, as they may not accurately reflect real-world communication abilities. Word recognition testing in quiet often shows similar performance across different levels of sensorineural hearing loss, making it a less sensitive measure.
When to Mask for Speech Audiometry
Masking in audiometry refers to the process of introducing noise into the non-test ear to ensure it does not "help" the test ear. When performing speech audiometry, masking is necessary under specific conditions to obtain accurate results.
When to Mask:
1. Significant difference between ears: If one ear hears much better than the other, the better ear may pick up speech signals meant for the poorer ear, leading to inaccurate results. Masking ensures only the test ear is assessed.
2. Interaural attenuation: This refers to the reduction of sound as it crosses from one ear to the other. The amount of attenuation depends on the earphones used. Insert earphones typically offer higher attenuation (around 60 dB), while supra-aural headphones provide less (around 40 dB). If the test signal exceeds the attenuation, masking is needed.
By evaluating how well an individual can detect, recognize, and understand speech, audiologists can gain valuable insights into their hearing abilities. Whether through SRT, WRS, or SIN testing, these assessments help in forming a comprehensive picture of a patient’s hearing.
Other Good Reads: Understanding Tympanometry: A Comprehensive Guide
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