Denoising old shortwave recordings with SDR#0
At home, I enjoy listening to "blowtorch" signals like All India Radio, Voice Of Greece and Voice of Turkey (although occasionally I try my luck and listen to weaker stations). Still, sometimes the propagation is poor and even these stronger transmissions start fading into the noise. This can be especially disappointing when I start recording a particular transmission and then go off to do other things, only to find out later that the recording is heavily ridden with static. Many of my night-time recordings have ended up this way and until recently I thought that they were generally beyond "repair".
Enter SDR#. It turns out that it can process a regular audio WAV file just as if it were a real-time radio signal, meaning that its noise reduction plugins can be used to clean up the sound.
|SDR# settings for denoising audio. Click the image to enlarge.|
To give an example, here's a rather noisy recording of All India Radio I grabbed last New Year's Eve:
And here it is after noise reduction with SDR#:
Although there are a few DSP audio artefacts in the denoised version, I do like the end result and I'm sure I will be repairing quite a few more of my noisy recording this way.