convert spectrogram to wav file? (3 Viewers)

[_birdwell_]

Hello bird forum -

I had a ton of recordings in Merlin and I accidentally exported spectrograms vs. .wav files. I then deleted the original audio recording from Merlin so I don't have the audio anymore. I am curious if the .jpg files (pictures of the actual spectrogram) can be converted back into a .wav file? I have 13 .jpg to convert so if anyone is handy with this kind of thing I sure would appreciate help. If not I can live with it, but I am not sure I will ever get as close to some of these birds as I was which is why I spent most of the afternoon looking for options to try to recover these lost files. I believe once they are deleted from the Merlin app there is no recovering them in your phone. Correct me if I am wrong here too.

 

[Lerxst]

Generally in making a spectrogram, the phase information from the FFT is thrown out, as it isn't needed to make the image -- only the magnitudes are used. To run the inverse process and build the exact time-domain signal, you'd need to know the phases corresponding to each frequency component. You could still put them back together using a some rule to assign phase but I don't know how good it would sound. It is an interesting question.

See https://www.dafx.de/paper-archive/2005/P_116.pdf for example. I'm not sure if anyone has released an app to implement anything like their algorithm. Perhaps they have.

Many years ago I played around with an early version of this software: Photosounder.com - Image-sound editor & synthesizer. I'm not sure what he does for phase. Note he does now mention "Synthesizing spectrograms created from other spectrographs, such as printed spectrograms of bird calls in books," but it isn't clear what that means, exactly.

 

[_birdwell_]

Generally in making a spectrogram, the phase information from the FFT is thrown out, as it isn't needed to make the image -- only the magnitudes are used. To run the inverse process and build the exact time-domain signal, you'd need to know the phases corresponding to each frequency component. You could still put them back together using a some rule to assign phase but I don't know how good it would sound. It is an interesting question.

See https://www.dafx.de/paper-archive/2005/P_116.pdf for example. I'm not sure if anyone has released an app to implement anything like their algorithm. Perhaps they have.

Many years ago I played around with an early version of this software: Photosounder.com - Image-sound editor & synthesizer. I'm not sure what he does for phase. Note he does now mention "Synthesizing spectrograms created from other spectrographs, such as printed spectrograms of bird calls in books," but it isn't clear what that means, exactly.

Thank you very much for that detailed information. That would explain why the few apps that claimed to convert jpg to wav didn't work. I will save the spectrograms in case something comes along in the future that can convert, but at least I know for now there isn't some magical app that can bring back my lost data.

 

[Stepgen]

Hello bird forum -

I had a ton of recordings in Merlin and I accidentally exported spectrograms vs. .wav files. I then deleted the original audio recording from Merlin so I don't have the audio anymore. I am curious if the .jpg files (pictures of the actual spectrogram) can be converted back into a .wav file? I have 13 .jpg to convert so if anyone is handy with this kind of thing I sure would appreciate help. If not I can live with it, but I am not sure I will ever get as close to some of these birds as I was which is why I spent most of the afternoon looking for options to try to recover these lost files. I believe once they are deleted from the Merlin app there is no recovering them in your phone. Correct me if I am wrong here too.

This is interesting. I would like to download the spectograms from Merlin.
How did you do it?

 

[_birdwell_]

Merlin > My sound recordings > click circle w/ 3 dots upper right corner > select export spectrogram

 

[Ruff-Leg]

Merlin > My sound recordings > click circle w/ 3 dots upper right corner > select export spectrogram

Is that an iPhone feature? I don't see it on my Android.

 

[Stuart Goodwin]

Is that an iPhone feature? I don't see it on my Android.

Afternoon.

I use an Iphone and I don’t have that option either.

Regards
Stuart

 

[Stepgen]

I have an android and I don't have that function either. Just Rename, Change location, Change date, Delete.

Stephen