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Speech intelligibility

By
Floris Hollander
5/12/2022
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Speech intelligibility measures how understandable speech is, or the extent to which speech can be understood. This is influenced by clarity, expressiveness, transparency, comprehensibility, clarity, and accuracy.

Speech intelligibility (STI): the extent to which speech can be understood

The intelligibility of speech is influenced by background (disturbing) noise and reverb. Speech intelligibility and reverberation time are often related to each other. The greater the reverberation time, the worse speech intelligibility usually becomes.

What determines speech intelligibility?

Speech intelligibility is determined by:

• Frequency transmission. The extent to which high and low notes are reproduced and the distortion that occurs.

• Reverberation and reflections. On the one hand, this is about the strength ratio between the sound that the listener sends directly and indirectly (i.e. via reflection). On the other hand, it concerns the runtime differences between direct and indirect sound. In other words, the extent to which the reflected sound reaches the listener.

• Noise level, or sound pressure, compared to other sounds present. This is therefore about the question of how much the speech is louder than any noise present.

Can speech intelligibility be improved?

Speech intelligibility in a room can definitely be improved. By choosing the right materials for the layout of a room, speech intelligibility can improve enormously.

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