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Balancing the Scales of Sound: Understanding the ABLB Test- by Acoustik Hearing And Speech Clinic

Imagine one ear hearing a sound as comfortably moderate, while the same sound in the other ear feels unexpectedly loud. This puzzling mismatch is what the Alternate Binaural Loudness Balance (ABLB) Test, also known as the Fowler test, investigates — comparing how loudness grows in each ear to detect recruitment.

What Is the ABLB Test?

ABLB compares how loud the same tone feels in the poorer ear versus the better ear, at levels above threshold. It's used for unilateral or asymmetric hearing loss, requiring normal hearing in the better ear as a reliable comparison point. If a tone at the same intensity is perceived equally loud in both ears despite one ear having a raised threshold, this indicates recruitment — abnormally rapid loudness growth linked to cochlear damage.

Test Specifications

Duration: 20–30 min
Equipment: Audiometer with ABLB protocol, headphones/insert earphones, response button
Preparation: Clear ear canal; pure tone thresholds established beforehand
Setting: Sound-treated room at the clinic
Age Group: Cooperative older children through seniors

Procedure of the Test

Otoscopy and pure tone audiometry first, to identify the asymmetry between ears.
A frequency showing significant asymmetry is selected.
In the poorer ear, a tone is fixed (commonly 20 dB above its threshold) and kept constant.
In the better ear, a tone starts soft and rises in 5 dB steps until the patient signals it matches the poorer ear's loudness.
The matching level is recorded; the process repeats at other fixed levels (10 dB steps) in the poorer ear.
Results are plotted on a laddergram, and the test is repeated at other frequencies as needed.

Why Is the Test Done?

Detects recruitment in unilateral or asymmetric hearing loss
Helps distinguish cochlear from retrocochlear causes
Complements tests like SISI, tone decay, and acoustic reflex testing
Guides hearing aid programming when loudness perception differs between ears
Supports referral decisions for unusual loudness growth patterns

What Will the Result Show?

A laddergram comparing loudness growth in the poorer ear against the better ear across intensity levels, revealing whether the two ears grow in loudness at a similar rate.

Interpretation

No Recruitment: "Loudness growth range similar in both ears — no recruitment present."
Complete Recruitment: "Poorer ear matches the better ear at higher intensities, shown by laddergram flattening — consistent with cochlear hearing loss."
Incomplete Recruitment: "Partial flattening — reduced dynamic range in the poorer ear, but not fully equal to the better ear."
Decruitment: "Loudness in the poorer ear grows slower than the better ear — may indicate retrocochlear involvement; further evaluation recommended."

ABLB needs precise, alternating tone presentation and a controlled setting, so it's performed 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 ABLB test at our clinic.

#ABLBTest #FowlerTest #Recruitment #AsymmetricHearingLoss #CochlearHearingLoss #HearingDiagnostics #PureToneAudiometry #HearingAidTrial #AcoustikHearingAndSpeechClinic #HomeVisitAudiometry #HearingAidsMumbai #NaviMumbaiHealthcare #ThaneHealthcare #AudiologyIndia #SeniorCareAtHome #HearYourBest #MumbaiHearingClinic

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