# sii: Compute ANSI S3.5-1997 Speech Intelligibility Index (SII) In SII: Calculate ANSI S3.5-1997 Speech Intelligibility Index

## Description

Compute the Speech Intelligibility Index (SII) described by ANSI specification S3.5-1997, including extensions for conductive hearing loss. Optionally apply interpolation obtain values for the required frequencies.

## Usage

 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13``` ```sii(speech = c("normal", "raised", "loud", "shout"), noise, threshold, loss, freq, method = c("critical", "equal-contributing", "one-third octave", "octave"), importance = c("SII", "NNS", "CID22", "NU6", "DRT", "ShortPassage", "SPIN", "CST"), interpolate=FALSE) ## S3 method for class 'SII' print(x, digits=3, ...) ## S3 method for class 'SII' plot(x, ...) ## S3 method for class 'SII' summary(object, digits=2, ...) ```

## Arguments

 `speech` Either a numeric vector providing E'[i], the equivalent speech spectrum level (in dB) at each frequency, or a character string indicating the stated vocal effort corresponding to one of the standard standard speech spectrum levels ("normal", "raised", "loud", "shout"). Defaults to `speech="normal"` correspoding to the normal level of stated vocal effort. `noise` A numeric vector providing N'[i], the equivalent noise spectrum level (in dB) at each frequency. If missing, defaults to -50 dB for each frequency. `threshold` A numeric vector providing T'[i], the equivalent hearing threshold level (in dB) at each frequency. If missing, defaults to 0 dB for each frequency. `loss` A numeric vector providing J'[i], the conductive hearing loss level (in dB) at each frequency. If missing, defaults to 0 dB for each frequency. `freq` Vector of frequencies for which `speech`, `noise`, `threshold`, and/or `loss` are specified. If `interpolate=TRUE`, `freq` must be specified. Otherwise, it must either match the required value for SII calculation method given by argument `method`, or be missing, in which case it will default to the values required for the specified method. `method` A character string specifying the SII calculation method ("critical", "one-third octave", "equal-contributing", "octave") `importance` Either a numeric vector providing F[i], the transfer function (importance weights) at each frequency, or a character string indicating which transfer function to employ ("SII", "NNS", "CID22", "NU6", "DRT", "ShortPassage", "SPIN", "CST"). Defaults to the standard SII transfer function, `importance="SII"`. `interpolate` Logical flag indicating whether to interpolate from the provide measurement values and frequencies to those required by the specified method via linear interpolation on the log scale. `object,x` SII object `digits` Number of digits to display `...` Optional arguments to `print`, `summary`, and `plot` methods

## Details

American National Standard ANSI S3.5-1997 ("Methods for Calculation of the Speech Intelligibility Index") defines a method for computing a physical measure that is highly correlated with the intelligibility of speech as evaluated by speech perception tests given a group of talkers and listeners. This measure is called the Speech Intelligibility Index, or SII. The SII is calculated from acoustical measurements of speech and noise.

The `sii` function implements ANSI S3.5-1997 as described in the standard, without any attempt to optimize the performance. The implementation does, however, include the extension for handling conductive hearing loss from Annex A (utilizing the optional `loss` argument), and for utilizing alternative band weights (i.e. transfer function) appropriate for differing message contents (e.g. types of speech) as described in Annex B or user-specified band weights (utilizing the optional argument `importance`).

Further, this implementation provides a mechanism for interpolating/extrapolating available measurements to those required for the specified calculation procedure. When `interpolate=TRUE`, required values for `speech`, `noise`, `threshold`, and `loss` will be computed using linear interpolation (of the log-scaled data). In this case, missing values may be provided and will be appropriately interpolated.

## Value

The return value is an object of class SII, containing the following components:

 `call` Function call used to generate the SII object `orig` List containing original (pre-extrapolation) values for `freq`, `speech`, `noise`, `threshold`, and `loss`. `speech, noise, threshold, loss, and freq` Values used in calculations (extrapolated if necessary) `table` SII calculation worksheet, containing columns corresponding to both Table C.1 and C.2 in Annex C of the standard. Table columns are FiCenter frequency of SII band, Hz E'iSpectrum level of equivalent speech, dB N'iSpectrum level of equivalent noise, dB T'iEquivalent hearing threshold level, dB ViSpectrum level for self-speech masking, dB BiLarger of the specrum levels for equivalent noise and self-speech masking, dB CiSlope per octave (doubling of frequency) of the upward spread of masking, dB/octave ZiSpectrum level for equivalent masking, dB XiSpectrum level of internal noise, dB X'iSpectrum level of equivalent internal noise, dB DiSpectrum level for equivalent disturbance, dB UiSpectrum level of standard speech for normal vocal effort, dB JiEquivalent hearing threshold due to conductive hearing loss, dB LiSpeech level distortion factor, dB KiTemporary variable used in the calculation of the band auditability function AiBand auditability function IiBand importance function IiAiProduct of the band importance function (Ii), and band auditability function(Ai) `sii` Calculated SII value

## Author(s)

Gregory R. Warnes [email protected]

## References

ANSI S3.5-1997, "American National Standard Methods for Calculation of the Speech Intelligibility Index" American National Standards Institute, New York.

Other software programs for calculating SII are available from http://www.sii.to/html/programs.html.

SII Constants: `critical`, and `sic.critical`
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60``` ```## Example C.1 from ANSI S3.5-1997 Annex C sii.C1 <- sii( speech = c(50.0, 40.0, 40.0, 30.0, 20.0, 0.0), noise = c(70.0, 65.0, 45.0, 25.0, 1.0,-15.0), threshold= c( 0.0, 0.0, 0.0, 0.0, 0.0, 0.0), method="octave" ) sii.C1 # rounded to 2 digits by default print(sii.C1\$sii, digits=20) # full precision summary(sii.C1) # full details plot(sii.C1) # plot ## The value given in the Standard is \$0.504\$. ## Same calculation, but manually specify the frequencies ## and importance function, and use default for threshold sii.C1 <- sii( speech = c(50.0, 40.0, 40.0, 30.0, 20.0, 0.0), noise = c(70.0, 65.0, 45.0, 25.0, 1.0,-15.0), method="octave", freq=c(250, 500, 1000, 2000, 4000, 8000), importance=c(0.0617, 0.1671, 0.2373, 0.2648, 0.2142, 0.0549) ) sii.C1 ## Now perform the calculation using frequency weights for the Connected ## Speech Test (CST) sii.CST <- sii( speech = c(50.0, 40.0, 40.0, 30.0, 20.0, 0.0), noise = c(70.0, 65.0, 45.0, 25.0, 1.0,-15.0), method="octave", importance="CST" ) round(sii.CST\$table[,-c(5:7,13)],2) sii.CST\$sii ## Example C.2 from ANSI S3.5-1997 Annex C sii.C2 <- sii( speech = rep(54.0, 18), noise = c(40.0, 30.0, 20.0, rep(0, 18-3) ), threshold= rep(0.0, 18), method="one-third" ) sii.C2\$table[1:3,1:8] sii.C2 ## Interpolation example, for 8 frequencies using NU6 importance ## weight, default values for noise. sii.left <- sii( speech="raised", threshold=c(25,25,30,35,45,45,55,60), freq=c(250, 500, 1000, 2000, 3000, 4000, 6000, 8000), method="critical", importance="NU6", interpolate=TRUE ) sii.left ```