HP RM500SL manual FastFacts 16.7 SII calculation in Insertion gain

16.7 SII calculation in Insertion gain

The RM500SL calculates a Speech Intelligibility Index (SII) value (in %) for unaided speech at 70 dB SPL (REUR), the target REIG and for each aided test. The calculations use the 1/3 octave band method of ANSI S3.5 –1997 without the 160 Hz band and without masking effects. Level distortion effects are included but no hearing loss desensitization is applied. An idealized speech region of LTASS +/- 15 dB is used.

The speech recognition associated with a given SII is a function of the test material and the cognitive abilities of the listener. There is considerable individual variability in relating the SII to speech recognition, especially amongst impaired listeners. The following shows expected nominal recognition scores vs SII for normals on the Connected Speech Test (Sherbecoe and Studebaker 2003).

SII (%)	Score (%)
10	1
15	8
20	20
25	45
30	60
35	74
40	84
45	90
50	94
55	96
60	98
70	99
80	100
90	100

FastFacts 16.7: SII calculation in Insertion gain

0611 RM500SL User’s Guide Version 2.8 Page 69