Articulation index

The Articulation Index (AI) is a tool used by audiologists to predict the amount of speech that is audible to a patient with a specific hearing loss. The AI reading for a given patient can range from zero to 1.0, representing the proportion of the average speech signal that is audible. The closer the AI is to 1.0, or 100 percent, the better the person should be able to hear speech.

The AI is often used as a counseling tool since it presents an individual’s hearing loss in terms of percentage of speech missed during a typical one-on-one conversation. The AI can also be used to measure the effectiveness of hearing aids and other forms of amplification devices.

Since the creation of the AI, there have been several proposed ways to simplify and increase its use in the field of audiology. In 1990, Gustav Mueller and Mead Killion proposed an AI calculation involving one hundred dots on an audiogram, each of which represented an important speech frequency; the number of dots audible to the listener, multipled by .01, represented the patient's AI. Unfortunately, not all areas on the audiogram (taking into account frequencies and intensity levels) are equally weighted. According to this procedure, the highest density of the audiogram dots is concentrated in the frequency region of 1-3 kHz, which means that this is the region containing the most speech information.