5.1.1 High-pass Filtering
26.4453GPPCodec for Enhanced Voice Services (EVS)Detailed algorithmic descriptionRelease 15TS
The input audio signal 
sampled at 8, 16, 32 or 48 kHz, 
being the sample index, is high-pass filtered to suppress undesired low frequency components. The transfer function of the HP filter has a cut-off frequency of 20 Hz (–3 dB) and is given by
(1)
The coefficients of the HP filter for a given input sampling frequency are given in the table below.
Table : Coefficients of the 20Hz HP filer
|
8 kHz |
16 kHz |
32 kHz |
48 kHz |
|
|
|
0.988954248067140 |
0.994461788958195 |
0.997227049904470 |
0.998150511190452 |
|
|
-1.977908496134280 |
-1.988923577916390 |
-1.994454099808940 |
-1.996301022380904 |
|
|
0.988954248067140 |
0.994461788958195 |
0.997227049904470 |
0.998150511190452 |
|
|
1.977786483776764 |
1.988892905899653 |
1.994446410541927 |
1.996297601769122 |
|
|
-0.978030508491796 |
-0.988954249933127 |
-0.994461789075954 |
-0.996304442992686 |
The input signal, filtered by the HP filter, is denoted as 
.