AFMG Network Forum

Sven · Member

Hi

If RaSTI is defined as a single figure value and is also calculated by examining the MTFs to the 500Hz and 2kHz octave bands why does EASE force us to map 3 separate values at 500Hz, 1kHz and 2kHz? Is there a method of viewing a single figure (obviously depending on position of interest in the mapped areas).

Having read the pdf help file I see reference to information that the different octave bands have varying contributions to the overall intelligibility but no explanation as to why we are presented the aforementioned data or how to read the single figure value.

Maybe I'm missing something fundamental here in the use of the program. I understand that seeing the detailed octave band data can help in identifying frequency dependence of problem locations.

Does EASE actually calculate the full 98 MTFs and then only present the 3 octave band data at 500Hz, 1kHz and 2kHz? Or is the 1kHz information an interpolation of some sort?

Sven

Sven · Member

A little digging through the posts here has provided some insight to my question. The reply to 'Time to Replace RaSTI' titled 'STI calcualtion in statistic mode' has highlighted the part of the manual that I read, but did not process. The Farrell Becker approximation is the key.

thanks to Paul for his detailed explanation.

Sven

PaulMalpas · Member

No problems Sven. EASE may call it RaSTI, in factr it is an STI as RaSTI is a measurement method for STI (now discredtitted).

Interstingly, if you did the farrellBecker conversion on %Alcons calculated for each octave band 125hz to 8k and treated each results as an MTI, then combined these according to the STI method, the answer would probably be close.

Paul