Frequency analysis app/software

[Brian Stirling]

I'm looking for a decent app or program to analyze a wav file or other audio source in order to determine the frequency of various components of the audio signature. My more immediate need to to be able to determine the speed of a vehicle such as a train based on the change in frequency as it approaches and departs. The math for this Doppler calculation is fairly easy and straight forward and requires only that I know two of the following: the approach frequency, the center frequency and the departure frequency.

So, I'm not looking for a full feature program just something that can give me the frequency of various peaks in the spectrum. The source is not a simple sign wave so I would be looking at a certain peak in the spectrum and see how that changes as the vehicle moves passed.

There are some apps including free apps for both iOS and Android as well as programs for Windows and it doesn't much matter to me which so long as it does the job. The one thing that is needed is the ability to read a wav or mp3 or similar audio file as opposed to live listening by a device as I intend to use a Tascam digital recorder along with a Rode shotgun mic for recording in the filed so the app or program would need to be able to process an existing audio file. I suppose I could play back the audio and have the device listen to the playback but I'd prefer to avoid that inter-step if possible.


Brian

 

[slashbinslashbash]

You are looking for something called a Fourier Transform. Matlab does it. So do a lot of command-line utilities. I found a free Java Applet here:

http://arachnoid.com/FFTExplorer/

You will probably need to cut a snippet of the 2 samples you need. Something less than 0.5 second probably.

 

[Brian Stirling]

You are looking for something called a Fourier Transform. Matlab does it. So do a lot of command-line utilities. I found a free Java Applet here:

http://arachnoid.com/FFTExplorer/

You will probably need to cut a snippet of the 2 samples you need. Something less than 0.5 second probably.

Yep, pretty much all spectrum analysis uses FFT and there are many apps and programs that use it, but it's hard to know just what the capabilities are without trying. In the case of the Java app you linked I'm stuck because Win10 doesn't do Java using either Chrome or Edge -- not going to install a new browser only to discover it doesn't do Java either.

I'm looking at some other options but the main one I can see is the need for decent resolution in frequency determination. If the actual frequency is, say. 200Hz then a change in frequency of only 1Hz would equate to a speed of about 3.9mph so getting an accurate speed measurement requires an accurate frequency measurement. If the actual frequency was 2000Hz then a difference of 1Hz would equate to a speed of about 0.39mph so a higher frequency is preferred. However, the noise source doesn't contain much high frequency components so you're back to needing high resolution in frequency determination.

Doppler is a bitch!


Brian

 

[videogames101]

Matlab or it's free counterparts, see Octave or Scilab.

I wouldn't bother trying to find a niche spectrum analyzer program, just use the real thing.

Is there a reason you are opposed to using the "right" tool for the job?

 

[Brian Stirling]

Matlab or it's free counterparts, see Octave or Scilab.

I wouldn't bother trying to find a niche spectrum analyzer program, just use the real thing.

Is there a reason you are opposed to using the "right" tool for the job?

And what would the right tool be?

I carry a crap load of things when I go out in the field and I'm not looking to add something else. My kit includes:

1. At least two tripods
2. Two Nikon D800E cameras and a Nikon D7200 camera
3. Usually about 6-8 SLR lenses
4. A Panasonic GH-2 for video along with 7 lenses for it and
5. DJI Inspire 1 Pro drone with M43 camera that uses 4 of the same lenses as the GH-2
6. Eight 130WHr batteries and a 4 battery charger for the drone
7. iPad Pro and mount for operation of drone
8. Tascam DR-05 digital recorder and Rode shotgun mic
9. Tools and spares

And that's before you count the clothes and other essentials such as PC's and external HD's for storage as well as spare camera batteries etc.

So, in addition to all that what else should I take? If I have a high quality recording that I can analyze I would not need to take anything else and I could process later as needed.


Brian

 

[videogames101]

And what would the right tool be?

I carry a crap load of things when I go out in the field and I'm not looking to add something else. My kit includes:

1. At least two tripods
2. Two Nikon D800E cameras and a Nikon D7200 camera
3. Usually about 6-8 SLR lenses
4. A Panasonic GH-2 for video along with 7 lenses for it and
5. DJI Inspire 1 Pro drone with M43 camera that uses 4 of the same lenses as the GH-2
6. Eight 130WHr batteries and a 4 battery charger for the drone
7. iPad Pro and mount for operation of drone
8. Tascam DR-05 digital recorder and Rode shotgun mic
9. Tools and spares

And that's before you count the clothes and other essentials such as PC's and external HD's for storage as well as spare camera batteries etc.

So, in addition to all that what else should I take? If I have a high quality recording that I can analyze I would not need to take anything else and I could process later as needed.


Brian

I meant that the "right tool" is a full-featured software like MatLab or the above alternatives which you stated you were opposed to using. You load up your recording and run the frequency analysis with about 5 lines of script, if it's in .wav format it's very easy, there are many examples: http://www.mathworks.com/matlabcentral/newsreader/view_thread/164978

 

[slashbinslashbash]

If you're doing video recording as well as audio, then it is quite easy to determine the speed of something e.g. a train or a vehicle on a public road by timing their progress along evenly-spaced markers such as railroad ties or lane stripes. Not terribly difficult with a land-based camera, and super easy with a drone shooting down from above. I assume that you could manually measure some easy-to-use distances before or after your shoot.