PERFORMANCE INTENSITY PHONETICALLY BALANCE (PIPB)

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The study of relative intelligibility of spondees at different intensity levels is termed as articulation curve. Similarly the study of intelligibility of PB word list at different intensity level is termed as PIPB function or PIPB curve... The study of PIPB function helps in determining the differential diagnosis of cochlea and RCPs. Jerger and Jerger 1971 describe the use of PIPB function as the method of screening for disorders of central auditory nervous system. They observed that patients with normal hearing sensitivity shown the differences in the score as the intensity increased with shapes of PIPB curve goes on increasing with the increase in intensity level upto such level where plateau is reached where there is no improvement in score with further increase in intensity level.
This similar curve is also obtained in patients with conductive hearing losses.. However it has been seen that in cases of RCPS as the intensity is increased the score reduces especially after reaching the plateau. This phenomenon is referred to as roll-over effect. ROE suggest a lesion on the side of the brain opposite the better ear whenever the ratio is less than 0.4. However the poorer ratio is obtained on the same side if the lesion is present on the same side. Jerger & Jerger further observed a significant difference in score between two ears though both ears have equal sensitivity for pure tones.
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While obtaining PIPB curve or ROE, the PB words are usually presented 10, 20, 30, etc. i.e. in 10 dB steps above the PTA & SRT level up to the maximum level of audiometer and MCL whichever is greater..

A RO Ratio can be calculated by the following formula-
                  Roll over ratio=      PBmax. - PBmin.
                                                          PBmax.
Where,
PBmax. Is the highest speech discrimination score
PBmin. Is the minimum score, the level at which further increases in intensity not causing any change. A ROR of 0.4 is suggestive of cochlear region while that of 0.5 or greater is suggestive of 8th nerve lesion.
 Image result for rollover index audiology

Limitations of PIPB

-          The procedure is not standardized and equally helpful for all test materials for WRS i.e. ratios vary from test to test.
-          For greater accuracy and precision of results more no. of levels should be tested.                    

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DIAGNOSTIC SIGNIFICANCE OF ROLL OVER ON PERFORMANCE INTENSITY FUNCTION
Jerger & Jerger 1962 obtained a performance intensity / articulation function using half list of PB 50th in subjects with cochlear hearing impairment, brainstem pathology and 8th nerve pathology.
They found that cochlear hearing impaired subjects had poor PB maximum scores in the hearing impaired ears and that subjects with 8th nerve pathology had even more poorer scores in the pathological ear. However, subjects with brainstem lesions had reduced PB maximum scores in the ear contra lateral to the lesion

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