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Re: Multifrequency Tympanometry
Newborns middle ear is quite different from adults. The Middle-ear and external auditory canal undergo structural changes over the first two years after birth which can affect the physical properties by which sound is transferred into the cochlea. Some of these physical changes include: (a) an increase in size of the external ear, middle-ear cavity and mastoid, (b) a change in the orientation of the ear drum, (c) a decrease in the overall mass of the middle-ear (due to changes in bone density, or to loss of amniotic fluid in the middle-ear), (d) tightening of the joints of the middle-ear bones, and (e) fusing of the tympanic ring and formation of the bony ear canal wall. It seems that the middle ear in newborns at low freq. is mass dominated as oppose to adults which is stiffness dominated. I suggest to record B & G at different probe tone freq rather than delta B and look at component (especialy B) to see how notch varies in response to probe tone frequency. To access all p
rbe tone freq u need to run delta B any way. If u look at B & G at low freq the B is already notched and the notch is usually beloww the tails so it has already passed the RF, that may explain why ur delta B does not seem right.
Navid Shahnaz, Ph.D
School of Audiology & Speech Sciences
Faculty of Medicine
5804 Fairview Ave.
Vancouver, B.C. V6t 1Z3
---------- Original Message ----------------------------------
From: megha jp <meghajp11@xxxxxxxxxxx>
Reply-To: megha jp <meghajp11@xxxxxxxxxxx>
Date: Sun, 15 Oct 2006 05:48:42 +0100
> Thank you sir again for answering my questions with patience.
> So as RF increases or decreases, is it so that the delta B value becomes zero more quickly or late depending on the RF of the middle ear?
> Sir, we were planning to conduct a study on delta B, Delta G, delta theta and RF and establish a normative range for all the parameters in neonates from 1day to 1 month. As we did on few neonates, we noted that the delta B value displayed after the sweeps, is a negative value or a positive value and never showed zero (though the delta B graph crossed the RF estimate line).
> for example:
> delta B: -0.26mmho (as displayed on GSI after the 2 sweeps)
> delta theta: -41deg
> RF: 260 Hz
> Sir this means that at delta B -0.26, RF is 260, but this is wrong as delta B should be zero to get RF. Then what is the value of delta B is the GSI displaying?
> Then we thought its wrong to take as a range for delta B parameter, as it is frequency dependent value. Is it so sir? How can we refine our paper? I think then its not possible even to take as a range for delta G.
> Thank you sir, I would be pleased to know your reply.
> With regards,
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