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Speech Intelligibility and Speech Privacy Testing – STI & CIS

Field measurement of speech intelligibility and speech privacy using STI and CIS metrics for secure facilities, emergency communication systems and occupied spaces.

On-Site Acoustic Testing performs speech intelligibility measurements for applications ranging from secure-facility speech privacy to verification of emergency notification and public-address systems.

STI, STIPA and CIS Speech Intelligibility Measurements

Speech Transmission Index (STI) and Common Intelligibility Scale (CIS) provide objective measures related to how intelligibly speech is transmitted or reproduced in a space. Depending on the application, measurements can be used either to demonstrate adequate intelligibility or to evaluate speech privacy where intelligible speech transmission is undesirable.

For public-address, voice-alarm, and emergency communication systems, STIPA measurements provide a standardized field method for determining STI using an appropriate test signal and the installed sound system.

Secure Facilities and Speech Privacy

For SCIF, SAPF and other secure environments, CIS measurements can be used as part of evaluating speech privacy and the effectiveness of sound-masking systems. Measurements may be performed within the protected space and at relevant adjacent locations according to the applicable project requirements.

CIS speech intelligibility test results for speech privacy testing

Emergency Communication and Occupied Spaces

STI measurements can be used to evaluate speech intelligibility for emergency communication and evacuation systems, public-address systems, conference rooms, classrooms, auditoriums and other spaces where spoken information must be understood reliably.

STI speech intelligibility test result showing a measured STI of 0.07

NTi TalkBox Speech Test Source

OSAT uses dedicated NTi Audio instrumentation for speech intelligibility testing, including the NTi TalkBox acoustic test source. The TalkBox provides the standardized acoustic source used for STI measurements and allows the test signal to be introduced into the space through a controlled loudspeaker source.

NTi Audio TalkBox used for speech intelligibility testing
NTi Audio TalkBox speech intelligibility test source

Discuss Your Speech Intelligibility or Privacy Testing

Contact On-Site Acoustic Testing to discuss the facility, system, applicable criteria and measurement objective.

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