Frequency Selectivity

Frequency selectivity is the auditory system's ability to separate closely-spaced frequencies into distinct perceptual streams — the reason a typical listener can follow one voice in a crowd, hear the bass line under a melody, or distinguish similar speech sounds like 's' and 'f'. Sensorineural hearing loss typically reduces frequency selectivity: the internal 'auditory filter' widens, nearby frequencies smear together, and background noise masks speech more aggressively. Reduced frequency selectivity helps explain why hearing aids that simply amplify sound do not restore speech-in-noise performance — the underlying resolution problem remains. Accessibility-focused hearing simulations that include a spectral-smearing stage are substantially more accurate than those that apply flat frequency attenuation alone.