The processing that produced the masked audio sample is very similar to the processing behind low-bitrate lossy voice codecs. I wonder what sort of program they

The processing that produced the masked audio sample is very similar to the processing behind low-bitrate lossy voice codecs. I wonder what sort of program they used to produce it. Perhaps one method of doing this would be to compute the lapped discrete cosine transform of the input signal, and then turn that into power spectrum density over time. For each time interval, take the N most intense frequency bins, and then create N sine waves at those frequencies. It's kind of like having a set of beeping noises that follow the pitch of the loudest component of the sound.