SISI Test: Meaning, Procedure & Results

Short Increment Sensitivity Index (SISI)

The SISI test is still widely used to determine whether the patient is having cochlear pathology. This test is based on a phenomenon known as recruitment (abnormal loudness growth).

Short Increment Sensitivity Index (SISI)

What is the SISI test?
The SISI test, also called the short increment sensitivity test, checks how well a person can detect very small increases in loudness. A continuous tone is presented, and tiny 1 dB increments are added at regular intervals. At Muskan Speech & Hearing Centre, audiometry SISI is carried out by audiologists as a supporting test alongside other hearing assessments.
How is the SISI test performed?

The person wears headphones in a quiet, sound-treated room.
A steady carrier tone is played at 20 dB above the person's hearing threshold.
Brief increases in loudness are added every five seconds.
The person signals each time a change in loudness is noticed.
The audiologist calculates the score from the number of increments detected, out of 20.

How are SISI results interpreted?
In normal individuals, the score rises gradually as the carrier tone level increases, reaching 100% at about 60 dB above threshold. In sensory hearing loss, the maximum score is reached much earlier, at around 30 dB above threshold. Scores of 70% to 100% at lower levels are generally considered positive for a cochlear lesion.
Why is the SISI test useful?
As a cochlear lesion test, it helps distinguish cochlear (sensory) hearing loss from retrocochlear causes. Its findings, combined with pure tone audiometry and speech audiometry, give a clearer diagnostic picture.
Who may need a SISI test?