What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?
Why An adaptive filter continuously adjusts its own coefficients based on the incoming signal, typically using a least-mean-squares (LMS) algorithm. Speech is correlated from sample to sample while random noise is not, so the filter learns to pass the predictable voice content and cancel the unpredictable hiss. This is what radios label as DSP noise reduction or NR, and it can also notch out steady carriers automatically.
Watch out A crystal-lattice filter is a real analog IF filter made of quartz crystals, not DSP at all. A Hilbert transform is used in DSP for generating the 90 degree phase shift needed for SSB modulation and demodulation, not for noise removal.
Noise is random, speech is not: the filter that adapts learns the difference. NR = adaptive.