How to eliminate noise that has the same frequency of my signal I have an audio signal , and I want to remove noise from it. I have applied a bandpass filter in order to remove frequencies that are not part of mi signal. But if there is background noise (some people talking) , it is not removed , because it has the same frequency range that my signal. 
How can I filter my signal , to eliminate the noise that has the same frequency as my signal?
Whenever the desired signals and undesired signals are at the same 
frequency band, you can't use the bandpass filter because it will remove both the desired and undesired signals. 

In such cases statistical characterization for filter design is needed. Means you need to find out those statistical characteristics of background voice (noise) which differs your required signal from the noise. Examples include variance, expectation / mean or there can be others depending upon background noise, you might need to design adaptive filter if the noise characteristics changes with time.