Speech audiometry:
Consists of two components:
Speech reception threshold: The minimum intensity at which 50% of the words are repeated correctly by the patient.
Speech discrimination score: The patient’s ability to understand speech.
Percentage of phonetically balanced words delivered 30dB above SRT which are identified correctly.
SDS is normally 90-100%, reduced in cochlear lesions, very poor and out of proportion to hearing loss in retrocochlear hearing loss, worst in cortical deafness.
Roll-over phenomenon: Feature of retrocochlear hearing loss.
When speech intensity is increased above a particular level, SDS falls instead of maintaining a plateau as in cochlear deafness.
Uses:
-To differentiate organic from non-organic hearing loss.
-To differentiate cochlear from retrocochlear lesions.
-To find the intensity at which discrimination score is the best which is useful for fitting a hearing aid.