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Catching the Smallest Changes in Sound: Understanding the SISI Test - by Acoustik Hearing

Not all hearing loss behaves the same way. In some cases, a damaged inner ear becomes unusually good at noticing tiny loudness changes — a phenomenon called recruitment. The SISI Test (Short Increment Sensitivity Index) uses this quirk to help pinpoint whether a hearing problem originates in the inner ear or further along the nerve pathway.

What Is the SISI Test?

SISI measures a person's ability to detect very small, brief increases in loudness — as small as 1 decibel. A steady tone is played comfortably above threshold, and at intervals the volume briefly rises; the patient signals each time they notice it. The percentage correctly detected becomes the SISI score.

Test Specifications

Duration: 10–15 min
Equipment: Calibrated audiometer with SISI protocol, air conduction headphones
Preparation: Clear ear canal; pure tone audiogram required beforehand
Setting: Sound-treated room at the clinic
Age Group: Cooperative older children through seniors

Procedure of the Test

Otoscopy check, followed by pure tone audiometry to establish the threshold at the test frequency.
Presentation level set at 20 dB above the patient's threshold.
Patient instructed to respond each time the steady tone briefly gets louder.
A few easy training trials (larger, 5 dB jumps) confirm understanding of the task.
Actual test: 20 presentations of a 1 dB increment, each lasting 200 milliseconds.
Percentage of correctly identified increments is scored for each frequency and ear.

Why Is the Test Done?

Helps differentiate cochlear from retrocochlear hearing loss
Detects loudness recruitment, linked to reduced cochlear amplification
Supports hearing aid amplification decisions, including CROS/BAHA consideration
Provides behavioral cross-checking when objective tests are unavailable or inconclusive
Part of a broader special test battery alongside acoustic reflexes, ABLB, speech testing, and tone decay

What Will the Result Show?

The percentage of correctly identified loudness increments out of 20 presentations, at each frequency tested.

Interpretation

0–20%: "Consistent with normal hearing, conductive hearing loss, or retrocochlear pathology. Recruitment not indicated."
20–70%: "Inconclusive; to be interpreted alongside the audiogram and other special test findings."
70–100%: "Consistent with cochlear pathology and associated loudness recruitment."

SISI results are never used alone — they're interpreted with the audiogram and other tests. Objective tests like OAE, ABR, and imaging increasingly complement SISI in modern practice.SISI needs a sound-treated setting and precise, controlled increments, so it's done at our clinic. Acoustik Hearing and Speech Clinic brings pure tone audiometry and hearing aid trials to your home across @Mumbai, @Navi Mumbai, and @Thane — no travel, no waiting rooms.

Book your pure tone audiometry and hearing aid trial at home, or schedule your SISI test at our clinic.

#SISITest #ShortIncrementSensitivityIndex #Recruitment #CochlearHearingLoss #HearingDiagnostics #PureToneAudiometry #HearingAidTrial #AcoustikHearingAndSpeechClinic #HomeVisitAudiometry #HearingAidsMumbai #NaviMumbaiHealthcare #ThaneHealthcare #AudiologyIndia #SeniorCareAtHome #HearYourBest #MumbaiHearingClinic

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