The axes are wrong in the spectrogram. I have an audio wav file, and I know the sampling rate. this is read into the audioData variable. The audio is 1 channel. selected window length I believe (can't remember) is 512. I believe overlap is 50% ( the default?), 1024 fourier points. sampling rate is 250,000.
Using Matlab 2014a.
spectrogram made using this: s = spectrogram(audioData, 512, , 1024, 250e3);
In the spectrogram, the bottom bit is near the 20kHz range and I want to get rid of this and concentrate on the thing at the centre (which is around 25khz). To my knowledge, I need a high pass filter to allow all of the frequencies above 20kHz. It seems like there are many ways to design filters which involve a lot of parameters and I'm a bit overwhelmed with how to start.
I essentially just want to cut out the bottom bit, so that I can image process the upper bit (ideally kept as close to intact, if not exactly, as possible)