Adaptive Filters and Applications - Digital Signal Processing: Fundamentals and Applications - page 484

Mono Audio
Source

Mixing audio
and tonal noise

Corrupted
Audio

dn ()

sn ()

Left Line In
LCI1

Left Line Out
LCO1

TI TMS320C6713
DSP Board 1

Right Line In
RCI1

Right Line Out
RCO1

xn ()

Tonal
Reference
Noise

sn () en ()

dn ()

Enhanced
Audio

Left Line In
LCI2

Left Line Out

TI TMS320C6713
DSP Board 2

Right Line In
RCI2

Right Line Out

xn ()

FIR adaptive filtering

FIGURE 10.24B

Tonal noise cancellation with the adaptive filter.

interrupt void c_int11()
{

float lc; /*left channel input */
float rc; /*right channel input */
float lcnew; /*left channel output */
float rcnew; /*right channel output */
int i;
//Left channel and right channel inputs
AIC23_data.combo ¼ input_sample();
lc ¼ (float) (AIC23_data.channel[LEFT]);
rc

(float) (AIC23_data.channel[RIGHT]);
// Insert DSP algorithm below
s[0]

¼

¼ lc;

x[0] ¼ rc;

x[0];
// End of the DSP algorithm
lcnew ¼ d[0]; /* Send to DAC */
rcnew ¼ rc; /* keep the original data */
AIC23_data.channel[LEFT] ¼ (short) lcnew;
AIC23_data.channel[RIGHT] ¼ (short) rcnew;
output_sample(AIC23_data.combo);

D[0] ¼ s[0] þ

}

(b) Program segment for DSK 2 (LMS adaptive filter).

float x[20] ¼ {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; /*Reference input buffer*/
float w[20] ¼ {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; /*Adaptive filter
coefficients*/
float d[1] ¼ {0.0}; /* Corrupted signal*/
float y[1] ¼ {0,0}; /* Adaptive filter output */