STI to CIS
Convert a positive Speech Transmission Index to Common Intelligibility Scale using CIS = 1 + log10(STI).
Description
Common Intelligibility Scale is a logarithmic transform of positive STI.
Common Intelligibility Scale is a logarithmic transform of positive STI. It does not independently measure speech transmission.1
Convert a positive Speech Transmission Index to Common Intelligibility Scale using CIS = 1 + log10(STI).
When to use STI to CIS
Use this tool to convert a positive Speech Transmission Index to Common Intelligibility Scale using CIS = 1 + log10(STI).
Choose a supported reference topic, run an input-free reference with an empty object, or prepare the measured values and caller-supplied test records requested. Keep acoustic metrics, frequency, units and test conditions consistent.
How to use STI to CIS and understand its results
- Choose a supported reference topic, run an input-free reference with an empty object, or prepare the measured values and caller-supplied test records requested. Keep acoustic metrics, frequency, units and test conditions consistent.
- Enter speechTransmissionIndex using the field table and calculation rules, then run the tool.
- Read commonIntelligibilityScale. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| speechTransmissionIndex | Speech Transmission Index | number; minimum: 0; maximum: 1 | Required |
Enter STI strictly above zero and at most one; return CIS.
CIS=1+log10(STI) Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| commonIntelligibilityScale | Common Intelligibility Scale | number; maximum: 1 |
{
"input": {
"speechTransmissionIndex": 0.5
},
"output": {
"commonIntelligibilityScale": 0.6989700043360187
}
}Limitations and assumptions
Small STI can give negative CIS. Zero is rejected; no standardized STI measurement or classification is performed.
Numeric inputs, where present, must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.
Alternative or Complementary methods
Use Speech Transmission Index Method Reference: Summarize the scope and limitations of the standardized STI method. For a complementary task, use Speech SNR Screen: Calculate speech-to-noise level difference and compare it with an explicit caller-supplied minimum.
References
-
STI to CIS — tool.io
Similar or alternative tools
- Speech Transmission Index Method Reference
Summarize the scope and limitations of the standardized STI method.
- Speech SNR Screen
Calculate speech-to-noise level difference and compare it with an explicit caller-supplied minimum.