A hearing aid includes: a microphone configured to provide a microphone signal that corresponds with an acoustic stimulus naturally received by a user of the hearing aid； a processing unit coupled to the microphone, the processing unit configured to provide a processed signal based at least on the microphone signal； a speaker coupled to the processing unit, the speaker configured to provide an acoustic signal based on the processed signal； and a sensor configured to measure a neural response of the user to the acoustic stimulus, and to provide a sensor output； wherein the processing unit is configured to detect presence of speech based on the microphone signal, and to process the sensor output and the microphone signal to estimate speech intelligibility； and wherein the processing unit is also configured to adjust a sound processing parameter for the hearing aid based at least on the estimated speech intelligibility.
