SBAA395B May   2022  – December 2023 PCMD3140 , TLV320ADC3120 , TLV320ADC3140 , TLV320ADC5120 , TLV320ADC5140 , TLV320ADC6120 , TLV320ADC6140

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Near-Field and Far-Field
    1. 1.1 Definition
  5. 2Constituents in the Far-Field Application
  6. 3Understanding of Digital and Analog Microphone
    1. 3.1 Digital PDM Microphone System
    2. 3.2 Analog Microphone with ADC System
  7. 4Quantization Noise Density for Each Microphone
  8. 5Dynamic Range in Far-Field
    1. 5.1 DR
    2. 5.2 DR in Microphone
    3. 5.3 DRE in the TLV320ADC5140/PCM5140-Q1
    4. 5.4 DRE Performance in TLV320ADC5140/PCM5140-Q1
  9. 6Design of Any Microphone with the TLV320ADC51x0/PCM51x0-Q1
    1. 6.1 Structure of the TLV320ADC51x0/PCM51x0-Q1
      1. 6.1.1 Design Example 1: Only Analog Microphone System
      2. 6.1.2 Design Example 2: Only Digital Microphone System
      3. 6.1.3 Design Example 3: Analog and Digital Microphone Combination System
  10. 7Conclusion
  11. 8Revision History

1.1 Definition

Near-field and far-field are components of the physical distance from the sound source, as shown in Figure 1-1. It depends on how far away a listener is from the sound-projecting object. At different distances, the acoustic energy the wavelength emits is heard differently. It is a major issue to comprehend these differences and design measurements precisely. Figure 1-1 implies that up to the second wave length is near-field, while from the second wave length is a range of far-field.

GUID-803B9DF9-86FE-438F-AC56-7B662F3968FE-low.gifFigure 1-1 Near-Field and Far-Field from Sound Source

The essential idea within the range of a far-field is that 6 dB of sound pressure decreases for each doubling of distance away from the sound source. For the most of the voice recognition system, the commander stands within the range of a far-field.