For best performance in microphone applications, maintain high input impedance of the amplifier circuit while also avoiding coupling noise into the input. Some best practices include:

• Reduce parasitic coupling by running the input traces as far away from the supply or output traces as possible. If these traces cannot be kept separate, crossing the sensitive trace perpendicular is much better as opposed to in parallel with the noisy trace.
• Place the external components as close to the device as possible.
• Keep the length of input traces as short as possible. Always remember that the input traces are the most sensitive part of the circuit.
• Keep high impedance input signals away from noisy traces.
• Make sure supply voltages are adequately filtered.
• Consider a guard ring without solder mask around the input trace to the JFET. The guard ring can be connected to the JFET source and reduces surface leakages from the JFET drain.
• Clean the PCB following board assembly for best performance.