SBAA600 October   2024 TAA5212 , TAC5111 , TAC5112 , TAC5211 , TAC5212

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Voice Activity Detection
    1. 2.1 VAD Configurations
      1. 2.1.1 User, Auto, Intermediate
      2. 2.1.2 VAD With ADC Recording
      3. 2.1.3 VAD Monitoring Channel
      4. 2.1.4 VAD Interrupt Pin
      5. 2.1.5 MICBIAS Enable During PDM Monitoring
      6. 2.1.6 VAD Clock Configurabilty
    2. 2.2 VAD Parameters
      1. 2.2.1 Initial Learning Period
      2. 2.2.2 Hold Over Counter
      3. 2.2.3 Wakeup Wait
      4. 2.2.4 Threshold
  6. 3VAD Performance Results
  7. 4Examples
  8. 5Summary
  9. 6References

2.2.4 Threshold

Threshold (TH) controls the decision boundary of the nodes of the decision tree. A higher value can increase the node thresholds of all the nodes of the decision tree, thus reducing the likelihood of false positives. Similarly, a lower value for the threshold parameter decreases the node thresholds, which reduces the likelihood of false negatives. Thus the threshold parameter can be adjusted to settle at the appropriate balance between false negatives and false positives.

Equation 4 shows the computation of the VAD_TH parameter.

Equation 4. T h r e s h o l d n e w = T h r e s h o l d d e f a u l t × 10 t h r + 12 20

where

  • thr is the threshold value in dB (–20dB to 0dB )
  • Thresholddefault is the default value in the Threshold register in decimal (4194304 )

The default value (4194304) corresponds to -12dB. Table 2-14 shows the registers that control the VAD_TH parameter.

Table 2-14 Programmable Coefficient Registers for Threshold
Coefficient Page Register Reset Value Description
VAD_TH 0x0D 0x5C 0x00 TH Byte[31:24]
0x0D 0x5D 0x40 TH Byte[23:16]
0x0D 0x5E 0x00 TH Byte[15:8]
0x0D 0x5F 0x00 TH Byte[7:0