Articulation Index

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In audiology, the Articulation Index (AI) is a tool used 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 one, representing the proportion of the average speech signal that is audible. The closer the AI is to one, 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 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 proportion of dots audible to the listener estimates 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, since this is the region containing the most speech information.

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Amlani, A., Punch, J., & Ching, T. (2002). Methods and Applications of the Audibility Index in Hearing Aid Selection and Fitting. Trends in Amplification, 6(3), 81-129.

Mueller, G. & Killion, M. (1992). An Easy Method for Calculating the Articulation Index. The Hearing Journal, 45(9), 14-17.

French, N.R. and Steinberg, J.C. Factors governing the intelligibility of speech Sounds. J Acoust Soc Am 1990-119, 1949.

Kryter, K.D. Methods for the calculation and use of the Articulation Index. J Acoust Soc Am 34(11): 1689-1697, 1962.

Kryter, K.D. Validation of the Articultion Index. J Acoust Soc Am 34(11): 1698-1702, 1962.