Articulation index

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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. “In general, the AI is an expression of the proportion of the average speech signal that is audible to a given patient, and therefore, it can vary from 0 to 1.0” (Mueller and Killion, 1992, p. 14). 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 original inception 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 a modified AI calculation procedure based on placing 100 dots across an audiogram to represent important speech frequencies. “To calculate an AI using this procedure, therefore, one need only to count the number of dots audible to the listener (the number of dots falling physically below, or touching, the threshold curve) and multiply by 0.01” (Amlani et al., 2002, p. 89). In other words, AI is calculated by counting the amount of dots that fall above an individual’s hearing threshold. The closer the AI is to 1.0 or 100%, the better the person should be able to hear speech. Unfortunately not all areas (frequencies and intensity levels) on the audiogram are weighted equally. According to this AI calculation procedure, the highest density of dots on an audiogram is concentrated in the frequency region of 1-3 kHz (Mueller & Killion). This means that the frequency region of 1-3 kHz contains the most speech information.


[edit] References

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.

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