Electronic speech intelligibility testing involves introducing a test signal into the room, and analyzing the signal at the listening position with an electronic measurement instrument. Here's how to measure speech intelligibility using the Rapid Speech Transmission Index (RaSTI).
First, apply a test signal to the system. Then connect an amplified speaker to a CD player, and insert the RaSTI test signal CD. The location of the speaker is the “talker” location.Set up the measurement microphone at the “listener” position. Use a stand, if possible.Using the SPL meter function, set the level of the test signal to the “nominal” listening level. In most cases, this will be 75 dB to 85 dB SPL.Select the RaSTI function on the measurement device.Begin the test, and wait for the test cycle to be completed.Read the RaSTI value on the measurement device.