Audio compression with STFT

1. What is STFT in audio?
2. What is STFT used for?
3. What is the difference between FFT and STFT?
4. Why would we use a STFT spectrogram for Analysing human speech?

What is STFT in audio?

DFT converts a sequence (discrete signal) into its frequency constituents just like FT does for a continuous signal. In our case, we have a sequence of amplitudes that were sampled from a continuous audio signal. DFT or FFT algorithm can convert this time-domain discrete signal into a frequency-domain.

What is STFT used for?

The short-time Fourier transform (STFT) is used to analyze how the frequency content of a nonstationary signal changes over time. The magnitude squared of the STFT is known as the spectrogram time-frequency representation of the signal.

What is the difference between FFT and STFT?

FFT has a resolution of 2048 lines, Blackman window, and 50% overlap and STFT also has Block size 2048, FFT size 16K, Blackman window used, and 50% overlap. As we can see, STFT performs better with the same block size (but more calculated lines). We improved frequency resolution for the same amount of scooped data.

Why would we use a STFT spectrogram for Analysing human speech?

The STFT is one of the most frequently used tools in speech analysis and processing. It describes the evolution of frequency components over time. Like the spectrum itself, one of the benefits of STFTs is that its parameters have a physical and intuitive interpretation.