3M DL, SE Speech Intelligibility, STI-PA testing, Zones, Selecting STI scale or CIS scale

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Speech Intelligibility

STI-PA testing

Speech Intelligibility

Another available add-on feature is Speech Transmission Index (STI) used to evaluate and classify speech intelligibility dependent of background noise level. STI is the standardized measurement in the IEC 60268-16:1998 standard.

STI-PA testing

STI refers to the amount of modulation preserved in the broadcasting of an artificial speech signal through an alarm system. The intelligibility measurement is a single value between zero and one, which factors in corruption of speech, with modulating speech frequencies over octave bands between 125Hz to 8kHz.

STI-PA is measured using seven octave bands and 2 modulation indices per octave band simultaneously allowing a 15 second measurement. In essence, any noise which masks (or corrupts) the talker-to-listener path is evaluated and a recommended measurement is computed at the end of an intelligibility test. The following sections briefly address points to consider when setting up a STI-PA test.

Zones

Where do I measure speech intelligibility?” A building or stadium can be broken into “zones”. Each “zone” has a room with one alarm system. In some situations, one room may have more than one alarm system or may have a change in ceiling height (such as an atrium or a balcony seating versus lower level seating). In those instances, each section would be considered a zone and each zone would be tested.

After determining the “zones” in your building, it is recommended to design a map of the key zones/rooms. Generally, a zone is a 20X20 area. If the room is larger than 20X20, it is recommended to take another measurement in this section.

Selecting STI scale or CIS scale

With the SoundPro, you have two measurement options which will determine the intelligibility of your building which are the STI scale and the CIS scale (explained below.)

Models SE and DL