Noise Levels
For satiable communication, the average speech level should exceed that of an interfering noise by 6dB; lower sound:noise ratios are rarely acceptable (Moore, 1997). Manifesting in a wide frequency range, speech is quite resistant to many types of masking frequency cut-off—Moore reports, for example, that a band of frequencies from 1000 Hz to 2000 Hz is sufficient (sentence articulation score of about 90%).
| Quantity to be measured | Unit of measurement | Good values |
|---|---|---|
| STI | Intelligibility (international known) | > 0.6 |
| CIS | Intelligibility (international known) | > 0.78 |
| %Alcons | Articulation loss (popular in USA) | < 10% |
| C50 | Clarity index (widespread in Germany) | > 3 dB |
| RASTI (obsolete) | Intelligibility (international known) | > 0.6 |
Word articulation remains high even when only 1–2% of the wave is unaffected by distortion:
Read more about this topic: Intelligibility (communication)
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