LMV1089RLEVAL National Semiconductor, LMV1089RLEVAL Datasheet - Page 10

• Manufacturer Part Number: LMV1089RLEVAL
• Description: BOARD EVALUATION LMV1089
• Manufacturer: National Semiconductor
• Series: PowerWise®r

Specifications of LMV1089RLEVAL

• Main Purpose: Audio, Microphone Amp
• Embedded: No
• Utilized Ic / Part: LMV1089
• Primary Attributes: Dual Input, Single Output
• Secondary Attributes: Graphical User Interface, I²C Interface
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

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For a optimal performance of the Far Field Noise Reduction
system it is important to find the correct placement of the mi-
crophones. In many applications the microphones are placed
next to each other with a distance of 1.5cm to 2.5cm between
the microphones. The best noise cancelling performance will
Microphone Placement in the Application
Because the LMV1089 is a microphone array Far Field Noise
Reduction solution, proper microphone placement is critical
for optimum performance. Two things need to be considered:
The spacing between the two microphones and the position
of the two microphones relative to near field source.
If the spacing between the two microphones is too small, near
field speech will be canceled along with the far field noise.
Conversely, if the spacing between the two microphones is
FIGURE 11. Orientation of Microphones and Sound Sources
FIGURE 10. Connecting Microphones
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occur in systems where the far field signals comes from a
source orthogonal to the plane of the microphones and where
the desired signal is close to the microphones and is located
in line with the microphones as shown in Figure 11.
large, the far field noise reduction performance will be de-
graded. The optimum spacing between Mic 1 and Mic 2 is
1.5-2.5cm. This range provides a balance of minimal near
field speech loss and maximum far field noise reduction. The
microphones should be in line with the desired sound source
'near speech' and configured in an endfire array orientation
from the sound source (see Figure 13). If the 'near
speech' (desired sound source) is equidistant to the source
like a broadside array (see Figure 12) the result will be a great
deal of near field speech loss.
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