Forums

Mains interference with fft problem

Started by Guybrush February 20, 2008
I've been working on a guitar tuner program (in C#) which uses FFT for
pitch detection. It's all working pretty well except for some
interference, which I assume is from the mains as it's usually 50Hz. I was
wondering what I can use to prevent this. 

Thanks


Guybrush wrote:
> I've been working on a guitar tuner program (in C#) which uses FFT for > pitch detection. It's all working pretty well except for some > interference, which I assume is from the mains as it's usually 50Hz. I was > wondering what I can use to prevent this. > > Thanks > >
Solving problem by processing data will be difficult. What have you already done to reduce the interfering signal. Based on old days of looking at signals on an oscilloscope, it may be beneficial to sync your sampling window to the mains.
On 20 Feb, 14:16, "Guybrush" <guybr...@hotmail.co.uk> wrote:
> I've been working on a guitar tuner program (in C#) which uses FFT for > pitch detection. It's all working pretty well except for some > interference, which I assume is from the mains as it's usually 50Hz. I was > wondering what I can use to prevent this.
You have two options: 1) Shield your recording system better, to prevent the 50 Hz to be recorded in the first place. 2) Filter the recorded data with notch filters. Both approaches have benefits and drawbacks. Shileding the system may be expensive or difficult to do (the interference might be caused by the power supply or through radiation) but once done, the dtaa are clean. Filtering the data is easier to implement, but filtering harmonics might remove the sound signal you want to use for the tuning. Rune