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Re: Multifrequency Tympanometry

Delta B can be used to infer different pathologies as resonant frequency increases (in case of otosclerosis) or decreases (in case of ossicular discontinuity) in different pathologies. I'm not sure what you mean about negative or positive number; if you mean it does not cross zero line (resonant freq estimate) then either the resonant frequency is too high or it is some sort of artifact. The latter is more possible with delta B. you can always go to different probe tone frequencies and plot B/G simultaneously and look at the B tymp to see at what freq. the notch becomes equal to the positive/negative tail value (you have to use appropriate norm for each estimate). With regard to Delta G, you can plot the two together to infer different angle of rotation of the Y; e.g., if the two become equal you are at admittance phase angle of 45 degree.

Navid Shahnaz, Ph.D
Assistant Professor
School of Audiology & Speech Sciences
Faculty of Medicine
5804 Fairview Ave.
Vancouver, B.C. V6t 1Z3
Tel. 604-822-5953
Fax. 604-822-6569
E-mail: nshahnaz@xxxxxxxxxxxxxxxxxx
Website: http://www.audiospeech.ubc.ca/school/faculty/navid/

---------- Original Message ----------------------------------
From: megha jp <meghajp11@xxxxxxxxxxx>
Reply-To: megha jp <meghajp11@xxxxxxxxxxx>
Date:          Sat, 14 Oct 2006 19:09:23 +0100

>Dear sir, 
>  Thank you sir for your kind reply.
>  Sir, then delta B is done just to get the resonant frequency, and is not an independent value that can infer of a pathology? In many cases the value of delta B  displayed is on a negative  or or on a positive value. But has not reached zero. Is it an instrumental error, or should we set the cursor so that the delta B value becomes zero and then take the resonant frequency value in GSI. Or what could be the reason that the delta B value is not shown zero on the display? Then again on a delta G plot, we get the resonant frequency. But delta G is no way related to the calculation of RF, so what does this delta G value infer to us?
>  Thank you sir again,
>  regards,
>  Megha.
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