Sample Data Export

[drumz]

Hey there! We are two physics majors working on a project where we analyze drumbeats. We need to be able to see the amplitude of a specific sound wave as well as the exact time that the amplitude occurs. Our thought was to use "Sample Data Export", but that doesn't seem to be giving us what we'd like. Preferably, we'd be able to see the data in a CSV or text file, as you can with "Sample Data Export". Is there any way to use "Sample Data Export" to see both time and amplitude? Any help is greatly appreciated! Thanks!

[steve]

Our thought was to use "Sample Data Export", but that doesn't seem to be giving us what we'd like.

How does "Sample Data Export" differ from "what you'd like"?

Is there any way to use "Sample Data Export" to see both time and amplitude?

That's what "Sample Data Export" does. Each value is an amplitude value. The time between each sample is 1/(sample rate) so for example, with a sample rate of 44100 Hz, the time between each sample is 0.000022676 seconds.
Tip: for easy calculation of time periods, record with a convenient sample rate, such as 100000 Hz.

[DVDdoug]

I believe most people doing "serious" numerical analysis use MATLAB (or a MATLAB clone).

MATLAB can open WAV files and apparently it can handle the massive amount of data from an audio file.

[steve]

MATLAB is also a lot more complicated to use than Nyquist.

[Robert J. H.]

MATLAB is also a lot more complicated to use than Nyquist.

In general, only short sounds can be analyzed with Matlab or Octave. You run rapidly out of memory or indexes.
Of course, there are always workarounds...

[jarydmiles]

Our thought was to use "Sample Data Export", but that doesn't seem to be giving us what we'd like.

How does "Sample Data Export" differ from "what you'd like"?

Is there any way to use "Sample Data Export" to see both time and amplitude?

That's what "Sample Data Export" does. Each value is an amplitude value. The time between each sample is 1/(sample rate) so for example, with a sample rate of 44100 Hz, the time between each sample is 0.000022676 seconds.
Tip: for easy calculation of time periods, record with a convenient sample rate, such as 100000 Hz.

But what frequency does the amplitude represent?

Is there are way to export spectrum data over time? Basically, like exporting the data from a waterfall plot?

[steve]

But what frequency does the amplitude represent?

Amplitude is not frequency.

Amplitude of a sound is how "big" the sound vibrations are and is represented in Audacity as the vertical height of the waveform. Amplitude of a waveform is the measure of the amount of displacement away from the mean position (distance from the "zero" centre line).

Frequency of a sound is "how rapidly the vibrations oscillate".

If you zoom in close on a waveform, you can see the waveform moving up and down, crossing the centre line many times. How far away from the centre line it moves is the "amplitude", whereas "how frequently it cycles between going up and going down" is the frequency. An approximation of the fundamental frequency can be derived from the exported sample data by counting the number of times the data crosses zero per second.

Is there are way to export spectrum data over time?

You can take a screen-shot of the track spectrogram view.
See: http://manual.audacityteam.org/man/spec ... _view.html
and: http://manual.audacityteam.org/man/help_menu.html#tools

[jarydmiles]

Ok, but is it possible to export numerical spectral data over time. I.e. Sound pressure level over say, 20 - 200Hz, over a recorded time of 5 seconds?

[Gale Andrews]

Ok, but is it possible to export numerical spectral data over time. I.e. Sound pressure level over say, 20 - 200Hz, over a recorded time of 5 seconds?

Or you can make small selections over five seconds and export each selection from Analyze > Plot Spectrum... .


Gale

[steve]

I.e. Sound pressure level over say, 20 - 200Hz, over a recorded time of 5 seconds?

Audacity cannot give you "Sound pressure level" (SPL)
(see: https://en.wikipedia.org/wiki/Sound_pressure)

To calculate the sound pressure level via Audacity, your "system" (microphone / pre-amp / sound card / sound card settings / recording software) need to be calibrated so that you know that a specific SPL produces a specific amplitude of the recorded signal. Alternatively you use a "SPL meter" (which is already calibrated).

What are you actually trying to do?
Is this a school project?