Hi Vincent, sorry for the delay but got some clarification for you:
The zip file that is generated includes the audio files solely for the purposes of playback, but the FFT data has already been previously extracted, this is the missing “frequencyFrames”.
heres a comment from the code that is processing it:
/**
 * The number of frames of frequency data to represent one sample,
 * for speech-commands this is 43, it corresponds to the models input shape
 * speech-commands input shape is [null, 43, 232, 1]
 */

Each “sample” is 43 frames consisting of the first 232 numbers in the FFTs array. Though another important detail is these numbers come from the WebAudio API’s Analyser and using something else is likely to shift performance.
My suggestion is, if you want to do with your own audio, it might be simple to:
1 - change their code (it’s open source) and enable a better input
2- try using one of the samples here:

Simple audio recognition: Recognizing keywords  |  TensorFlow Core 3
Transfer Learning for audio recognition 4