An apparatus for determining cochlear dead region comprising a sound generation unit, an output transducer, and a control unit. The control unit causes the sound generation unit to provide a first electrical sound signal representing a first frequency band adjacent to a frequency region of interest, with a first bandwidth, a first sound pressure level and a first subsequent electrical sound signal representing a first subsequent frequency band comprising the frequency region of interest with a first subsequent bandwidth, a first subsequent sound pressure level, and a first subsequent time delay to the first electrical sound signal. In response, the output transducer generates a first output sound and a first subsequent output sound with the first subsequent time delay. A user compares the first output and first subsequent output sounds and decides, whether he hears a difference between the two sounds and gives a positive or negative decision input.