Downsampled filter banks enable efficient DSP implementations like FFT for DFT.

Evidence

Downsampling discards excessive data by an amount where the core signal information is still preserved. Secondly, the computational efficiency of the transform operation itself can be optimized when the output channels are downsampled. It is typical of symmetric downsampled structures, such as that in Figure 15.2, that they can be implemented with efficient DSP techniques. Similarly, the fast Fourier transform (FFT) is an efficient implementation of the discrete Fourier transform (DFT). — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 2073

Categorization

• XREF: The FFT-as-efficient-DFT point is a foundational signal-processing axiom connecting to the reader’s broader acoustics knowledge base.