Hi, i have implemented above circuit in our application but i have found it has background hamming (noise) sound continuously even though we are not speaking on microphone. So can any one suggest me how to reduce this audio noise?
Good quality components should be used, metal film resistors for the R1&R2, avoid cermet, metal glaze and very old carbon composition types.
Use a low noise transistor for T1 BC413, B414, BC109.