A diagnostic system for recording auditory steady-state responses of a person comprises a) a stimulation unit for providing an acoustic stimulus signal to an ear of the person, and b) a recording unit for recording the auditory steady-state responses of the person origination from said acoustic stimulus signal, wherein the stimulation unit is configured to provide that the acoustic stimulus signal comprises a speech-like stimulus provided as a combination of a series of individual frequency-specific stimuli, each having a specified, e.g. predetermined, frequency bandwidth, presentation rate, amplitude and amplitude-modulation. The application further relates to a combined system comprising a diagnostic system and a hearing aid. The invention may e.g. be used for diagnostic instruments for verifying the fitting of a hearing aid.