Speech Transmission Index for PA system (STIPA) and optimization of Electro-Acoustic and acoustic of building (Part I)

【Writer/ Hunk Huang】

In PA system, how to make sure the system can transmit the sound message clearly in order to achieve the “public message broadcast” target? In the past, we would use different way to measure. To the acoustic of building, we would measure the reverberation time, RT60 (60dB reduction), RT30(30dB reduction); To Electro-acoustic, we would measure the frequency response and sound pressure level (SPL). But the above values haven’t been straight explained to let audience to understand due to the below factors:
the speech level via background noise
frequency response of the channel
non-linear distortions
background noise level against the cover of the broadcast content
quality of the sound reproduction equipment
The power of amplifier to the audience go through straightly or not?
echos(reflections with delay> 100ms)
the reverberation time (interaction of absorb the sound in space)
psycho-acoustic effects (masking effects)
Comprehension of listening words to construct the sentence by ear
High sound pressure because the tired to affect comprehension by ear
Feature of sound compare to noise (human has more comprehensive on first language than others)

Thus, a method called STIPA is developed for measure “public message broadcast”.