| Step |
|
Modulation
frequency
$f_m$ (Hz) |
Frequency $f_k$ (Hz) |
Note |
| 125 |
250 |
500 |
1k |
2k |
4k |
8k |
| 1 |
$L_k$ – Combined speech and noise level (dB) |
50 |
42 |
35 |
32 |
30 |
28 |
26 |
Measure the speech levels (background noise included) in a real space under the circumstances where the artifical noise which has the frequency response of male's voice shown in Table A.4 is exposed. The exposed noise should be equalized and adjusted with Normal: 60 dB or Raised: 66 dB A-weighted levels at 1 meter far from a source point
|
| 2 |
$L_{N,k}$ – Background noise level (dB) |
48 |
40 |
34 |
30 |
27 |
25 |
23 |
Measure the background (ambient) noise levels |
| 3 |
$m_{k,\,f_m}$ – Modulation transfer fuction (MTF) calculated from impulse response |
0.63 |
0.997 69 |
0.996 51 |
0.997 12 |
0.997 02 |
0.997 30 |
0.997 17 |
0.994 28 |
| Compute MTF from octave-filtered impulse response $\small{h_k(t)}$ and modulation frequency $\small{f_m}$.
\[
m_{k,\,f_m} = \frac{\left| \int \limits^{\infty}_{0} h^\textsf{2}_k (t)\,\exp (-j\textsf{2} \pi f_m t)\,\textsf{d}t \right|}{\int\limits^{\infty}_{\textsf{0}}h^\textsf{2}_k (t)\,\textsf{d}t}
\]
|
|
| 0.8 |
0.996 31 |
0.994 44 |
0.995 40 |
0.995 26 |
0.995 69 |
0.995 49 |
0.990 88 |
| 1 |
0.994 32 |
0.991 44 |
0.992 94 |
0.992 71 |
0.993 39 |
0.993 07 |
0.985 99 |
| 1.25 |
0.991 34 |
0.986 94 |
0.989 25 |
0.988 90 |
0.989 94 |
0.989 45 |
0.978 65 |
| 1.6 |
0.986 38 |
0.979 45 |
0.983 15 |
0.982 61 |
0.984 25 |
0.983 49 |
0.966 50 |
| 2 |
0.979 83 |
0.969 66 |
0.975 24 |
0.974 43 |
0.976 88 |
0.975 75 |
0.950 66 |
| 2.5 |
0.970 78 |
0.956 39 |
0.964 61 |
0.963 46 |
0.967 01 |
0.965 36 |
0.929 27 |
| 3.15 |
0.958 28 |
0.938 96 |
0.950 71 |
0.949 20 |
0.954 16 |
0.951 77 |
0.901 09 |
| 4 |
0.941 77 |
0.918 28 |
0.933 92 |
0.932 52 |
0.938 89 |
0.935 40 |
0.866 92 |
| 5 |
0.923 57 |
0.899 27 |
0.917 20 |
0.917 52 |
0.924 39 |
0.919 53 |
0.833 30 |
| 5.3 |
0.903 34 |
0.884 22 |
0.900 28 |
0.905 59 |
0.911 23 |
0.905 03 |
0.800 53 |
| 8 |
0.882 69 |
0.878 28 |
0.885 35 |
0.898 58 |
0.901 35 |
0.895 21 |
0.773 08 |
| 10 |
0.868 97 |
0.877 88 |
0.877 15 |
0.895 38 |
0.897 01 |
0.891 48 |
0.759 21 |
| 12.5 |
0.868 75 |
0.866 70 |
0.878 97 |
0.894 79 |
0.900 34 |
0.890 17 |
0.758 89 |
| 4 |
$L_{S,k}$ – Signal Level (dB) |
45.670 77 |
37.670 77 |
28.131 75 |
27.670 77 |
26.979 38 |
24.979 38 |
22.979 38 |
Compute $\small{L_{S,k}}$ from $\small{L_k}$ and $\small{L_{N,k}}$.
\[
L_{S,k} = \textsf{10} \log _{\textsf{10}}\left[\textsf{10}^{(L_{k}/\textsf{10})}- \textsf{10}^{(L_{N,k}/\textsf{10})}\right]
\]
|
| 5 |
$\rho_k$ – Ratio of signal to background noise level (dB) |
-2.329 23 |
-2.329 23 |
-5.868 25 |
-2.329 23 |
-0.020 62 |
-0.020 62 |
-0.020 62 |
\[ \rho_k = L_{S,k} - L_{N,k} \] |
| 6 |
Correction factor for background (ambient) noise |
0.369 04 |
0.369 04 |
0.205 67 |
0.369 04 |
0.498 81 |
0.498 81 |
0.498 81 |
\[
\left[ \textsf{1}+\textsf{10}^{-\rho_k /\textsf{10}} \right]^{-\textsf{1}} = \frac{I_{S,k}}{I_{S,k}+I_{N,k}} = \frac{I_{S,k}}{I_{k}}
\]
|
| 7 |
$m^{\prime}_{k,\,f_m}$ – Ajusted MTF with background noise |
0.63 |
0.368 19 |
0.367 76 |
0.205 08 |
0.367 94 |
0.497 46 |
0.497 40 |
0.495 96 |
\begin{align*}
m^{\prime}_{k,\,f_m} &= m_{k,\,f_m} \cdot\left[ \textsf{1}+\textsf{10}^{-\rho_k /\textsf{10}} \right]^{-\textsf{1}} \\
&= m_{k,\,f_m} \times \frac{I_{S,k}}{I_{S,k}+I_{N,k}}
\end{align*}
|
| 0.8 |
0.367 68 |
0.366 99 |
0.204 73 |
0.367 29 |
0.496 66 |
0.496 56 |
0.494 26 |
| 1 |
0.366 95 |
0.365 88 |
0.204 22 |
0.366 35 |
0.495 51 |
0.495 36 |
0.491 82 |
| 1.25 |
0.365 85 |
0.364 22 |
0.203 46 |
0.364 95 |
0.493 79 |
0.493 55 |
0.488 16 |
| 1.6 |
0.364 01 |
0.361 46 |
0.202 21 |
0.362 62 |
0.490 96 |
0.490 58 |
0.482 10 |
| 2 |
0.361 60 |
0.357 84 |
0.200 58 |
0.359 61 |
0.487 28 |
0.486 72 |
0.474 20 |
| 2.5 |
0.358 26 |
0.352 95 |
0.198 39 |
0.355 56 |
0.482 36 |
0.481 53 |
0.463 53 |
| 3.15 |
0.353 65 |
0.346 52 |
0.195 53 |
0.350 30 |
0.475 95 |
0.474 75 |
0.449 47 |
| 4 |
0.347 55 |
0.338 88 |
0.192 08 |
0.344 14 |
0.468 33 |
0.466 59 |
0.432 43 |
| 5 |
0.340 84 |
0.331 87 |
0.188 64 |
0.338 60 |
0.461 10 |
0.458 67 |
0.415 66 |
| 5.3 |
0.333 37 |
0.326 32 |
0.185 16 |
0.334 20 |
0.454 53 |
0.451 44 |
0.399 31 |
| 8 |
0.325 75 |
0.324 12 |
0.182 09 |
0.331 62 |
0.449 60 |
0.446 54 |
0.385 62 |
| 10 |
0.320 69 |
0.323 98 |
0.180 41 |
0.330 44 |
0.447 44 |
0.444 68 |
0.378 70 |
| 12.5 |
0.320 61 |
0.319 85 |
0.180 78 |
0.330 22 |
0.449 10 |
0.444 03 |
0.378 54 |
| 8 |
$I_k$ - Intensity of speech and noise |
100 000 |
15 849 |
3 162 |
1 585 |
1 000 |
631 |
398 |
\[
I_k = \textsf{10}^{(L_k/\textsf{10})}
\]
|
| 9 |
$L_{a,k}$ - Levels of auditory masking factor (dB) |
- |
-40 |
-44 |
-47.5 |
-49 |
-50 |
-51 |
Determine the values of $\small{L_{a,k}}$ from Table A.3 without 125 Hz |
| 10 |
$a_k$ – Auditory masking factor |
- |
0.000 10 |
0.000 04 |
0.000 02 |
0.000 01 |
0.000 01 |
0.000 01 |
Ommit 125 Hz.
\[
a_{k} = \textsf{10}^{(L_{a,k}/\textsf{10})}
\]
|
| 11 |
$I_{am,k}$ – Auditory masking Intensity |
0 |
10 |
0.6309573 |
0.0562341 |
0.0199526 |
0.010 |
0.0050 |
The value of 125 Hz determines zero.
\[
I_{am,k} = a_k \times I_{k-\textsf{1}}
\]
|
|
$A_k$ – Level of the absolute reception threshold (dB) |
46 |
27 |
12 |
6.5 |
7.5 |
8 |
12 |
Refer Table A.2. |
| 12 |
$I_{\textsf{rt},k}$ - Intensity of the absolute reception threshold |
39810.72 |
501.19 |
15.85 |
4.47 |
5.62 |
6.31 |
15.85 |
\[
I_{\textsf{rt},k} = \textsf{10}^{(A_k/\textsf{10})}
\]
|
| 13 |
Intensity ratio correction factor $C_k$ |
0.715 25 |
0.968 75 |
0.994 82 |
0.997 15 |
0.994 39 |
0.990 08 |
0.961 70 |
\[
C_k = \frac{I_k}{I_k+I_{am,k}+I_{\textsf{rt},k}}
\]
|
| 14 |
$m^{\prime\prime}_{k,\,f_m}$ – Adjusted MTF with masking factor |
0.63 |
0.263 35 |
0.356 27 |
0.204 02 |
0.366 90 |
0.494 67 |
0.492 47 |
0.476 96 |
\[
m^{\prime\prime}_{k,\,f_m} = m^{\prime}_{k,\,f_m} \times C_k
\]
|
| 0.8 |
0.262 98 |
0.355 52 |
0.203 66 |
0.366 25 |
0.493 88 |
0.491 64 |
0.475 33 |
| 1 |
0.262 46 |
0.354 45 |
0.203 16 |
0.365 31 |
0.492 73 |
0.490 44 |
0.472 99 |
| 1.25 |
0.261 67 |
0.352 84 |
0.202 41 |
0.363 91 |
0.491 02 |
0.488 66 |
0.469 47 |
| 1.6 |
0.260 36 |
0.350 17 |
0.201 16 |
0.361 59 |
0.488 20 |
0.485 71 |
0.463 64 |
| 2 |
0.258 64 |
0.346 66 |
0.199 54 |
0.358 58 |
0.484 55 |
0.481 89 |
0.456 04 |
| 2.5 |
0.256 25 |
0.341 92 |
0.197 37 |
0.354 55 |
0.479 65 |
0.476 76 |
0.445 78 |
| 3.15 |
0.252 95 |
0.335 69 |
0.194 52 |
0.349 30 |
0.473 28 |
0.470 05 |
0.432 26 |
| 4 |
0.248 59 |
0.328 29 |
0.191 09 |
0.343 16 |
0.465 70 |
0.461 96 |
0.415 87 |
| 5 |
0.243 78 |
0.321 50 |
0.187 66 |
0.337 64 |
0.458 51 |
0.454 12 |
0.399 74 |
| 5.3 |
0.238 45 |
0.316 12 |
0.184 20 |
0.333 25 |
0.451 98 |
0.446 96 |
0.384 02 |
| 8 |
0.233 00 |
0.314 00 |
0.181 15 |
0.330 67 |
0.447 08 |
0.442 12 |
0.370 85 |
| 10 |
0.229 37 |
0.313 85 |
0.179 47 |
0.329 49 |
0.444 93 |
0.440 27 |
0.364 20 |
| 12.5 |
0.229 32 |
0.309 86 |
0.179 84 |
0.329 28 |
0.446 58 |
0.439 63 |
0.364 04 |
| 15 |
$\rho_{\textsf{eff}_ {k,\,f_m}}$ – Convert MTF values into effective SNRs (dB) |
0.63 |
-4.467 33 |
-2.569 34 |
-5.912 42 |
-2.369 29 |
-0.092 54 |
-0.130 86 |
-0.400 46 |
-15 ≤ $\small{\rho_{\textsf{eff}_{k,\,f_m}}}$ ≤ +15
\[
\rho_{\textbf{eff}\,_{k,\,f_m}}=\textsf{10} \log_{\textsf{10}}\left( \frac{m^{\prime\prime}_{k,\,f_m}}{\textsf{1}-m^{\prime\prime}_{k,\,f_m}} \right)
\]
|
| 0.8 |
-4.475 47 |
-2.583 41 |
-5.921 80 |
-2.381 46 |
-0.106 36 |
-0.145 29 |
-0.428 84 |
| 1 |
-4.487 22 |
-2.603 73 |
-5.935 31 |
-2.398 99 |
-0.126 24 |
-0.166 04 |
-0.469 72 |
| 1.25 |
-4.504 89 |
-2.634 32 |
-5.955 59 |
-2.425 27 |
-0.155 96 |
-0.197 07 |
-0.531 06 |
| 1.6 |
-4.534 40 |
-2.685 30 |
-5.989 22 |
-2.468 80 |
-0.205 00 |
-0.248 30 |
-0.632 81 |
| 2 |
-4.573 44 |
-2.752 29 |
-6.033 11 |
-2.525 50 |
-0.268 55 |
-0.314 76 |
-0.765 65 |
| 2.5 |
-4.627 70 |
-2.843 53 |
-6.092 47 |
-2.601 93 |
-0.353 73 |
-0.404 03 |
-0.945 64 |
| 3.15 |
-4.703 23 |
-2.964 34 |
-6.170 89 |
-2.701 84 |
-0.464 69 |
-0.520 98 |
-1.184 03 |
| 4 |
-4.803 98 |
-3.109 15 |
-6.266 76 |
-2.819 60 |
-0.596 77 |
-0.662 04 |
-1.475 50 |
| 5 |
-4.916 38 |
-3.243 67 |
-6.363 53 |
-2.926 43 |
-0.722 38 |
-0.799 19 |
-1.765 60 |
| 5.3 |
-5.043 12 |
-3.351 30 |
-6.462 87 |
-3.011 95 |
-0.836 75 |
-0.924 84 |
-2.052 13 |
| 8 |
-5.174 51 |
-3.394 02 |
-6.551 74 |
-3.062 41 |
-0.922 77 |
-1.010 09 |
-2.295 50 |
| 10 |
-5.263 01 |
-3.396 89 |
-6.601 02 |
-3.085 54 |
-0.960 55 |
-1.042 55 |
-2.419 82 |
| 12.5 |
-5.264 44 |
-3.477 82 |
-6.590 05 |
-3.089 81 |
-0.931 56 |
-1.053 95 |
-2.422 71 |
| 16 |
$TI_{k,\,f_m}$ – Convert trancateed $\rho$ values into transmission indices |
0.63 |
0.351 09 |
0.414 36 |
0.302 92 |
0.421 02 |
0.496 92 |
0.495 64 |
0.486 65 |
0 ≤ TI ≤ +1
\[
TI_{k,\,f_m} = \frac{\rho_{\textbf{eff}\,_{k,\,f_m}}+\textsf{15}}{\textsf{30}}
\]
|
| 0.8 |
0.350 82 |
0.413 89 |
0.302 61 |
0.420 62 |
0.496 45 |
0.495 16 |
0.485 71 |
| 1 |
0.350 43 |
0.413 21 |
0.302 16 |
0.420 03 |
0.495 79 |
0.494 47 |
0.484 34 |
| 1.25 |
0.349 84 |
0.412 19 |
0.301 48 |
0.419 16 |
0.494 80 |
0.493 43 |
0.482 30 |
| 1.6 |
0.348 85 |
0.410 49 |
0.300 36 |
0.417 71 |
0.493 17 |
0.491 72 |
0.478 91 |
| 2 |
0.347 55 |
0.408 26 |
0.298 90 |
0.415 82 |
0.491 05 |
0.489 51 |
0.474 48 |
| 2.5 |
0.345 74 |
0.405 22 |
0.296 92 |
0.413 27 |
0.488 21 |
0.486 53 |
0.468 48 |
| 3.15 |
0.343 23 |
0.401 19 |
0.294 30 |
0.409 94 |
0.484 51 |
0.482 63 |
0.460 53 |
| 4 |
0.339 87 |
0.396 36 |
0.291 11 |
0.406 01 |
0.480 11 |
0.477 93 |
0.450 82 |
| 5 |
0.336 12 |
0.391 88 |
0.287 88 |
0.402 45 |
0.475 92 |
0.473 36 |
0.441 15 |
| 5.3 |
0.331 90 |
0.388 29 |
0.284 57 |
0.399 60 |
0.472 11 |
0.469 17 |
0.431 60 |
| 8 |
0.327 52 |
0.386 87 |
0.281 61 |
0.397 92 |
0.469 24 |
0.466 33 |
0.423 48 |
| 10 |
0.324 57 |
0.386 77 |
0.279 97 |
0.397 15 |
0.467 98 |
0.465 25 |
0.419 34 |
| 12.5 |
0.324 52 |
0.384 07 |
0.280 33 |
0.397 01 |
0.468 95 |
0.464 87 |
0.419 24 |
| 17 |
$MTI_k$ – Compute mean transmission indices |
0.340 86 |
0.400 93 |
0.293 22 |
0.409 84 |
0.483 94 |
0.481 86 |
0.457 64 |
\[
MTI_k = \frac{\textsf{1}}{\textsf{14}}\sum^{\textsf{14}}_{m=\textsf{1}}TI_{k,\,f_m}
\]
|
|
Weighting factors of Male voice |
α |
0.085 |
0.127 |
0.230 |
0.233 |
0.309 |
0.224 |
0.173 |
Refer Table A.1. |
| β |
0.085 |
0.078 |
0.065 |
0.011 |
0.047 |
0.095 |
- |
| 18 |
STI |
0.427 |
\[
STI = \sum^\textsf{7}_{k=\textsf{1}}\alpha_k \times MTI_k - \sum^\textsf{6}_{k=\textsf{1}}\beta_k \times \sqrt{MTI_k \times MTI_{k+\textsf{1}}}
\]
|
