Lloyd I think I failed to give this ......
: "A dynamic resistance." But "Non-reactive"? If the load
>is "totally resistive" aerodynamically it WILL affect the oscillation
>of the vocal folds.
...some special attention.
There is a very interesting electrical problem that applies to what
you say here. A resistive or non-reactive column load merely
extracts minimum energy from the cords which is then replaced
by energy drawn from the lungs. You'll need to understand that
this "resistive load," implies that cos theta, is ONE, so power is
simply E times I. (Cos theta is redundant.)
Here is the BIG BIG point... do you notice that
if we have the opposite condition..90 degrees .where cos theta
is ZERO, that pressure and air flow are still at MAXIMUM for a
total output of ZERO power. In an electrical condition this
means that a power station would effectively be outputting
maximum VxA but NIL power. The power authorities do NOT
like that, and as a singers, nor should we from our little power
houses.
To put it another way, with a phase difference between the
pressure wave and the rate of air flow wave of 45 degrees,
one would have to expend 30% more breath for the same
loudness as if they were in phase. Cos 45=0.707 I think. :)
Phase angles in between the zero degrees and 90 degrees
represent more or less wasted effort. Beyond 90 degrees it
all just starts over again.
Reg.
At 01:22 PM 8/04/02 +1000, you wrote:
>At 01:20 PM 7/04/02 -0700, you wrote:
>>Dear Reg and Vocalisters:
>>>Sally I understand your problem with inertance but while I try
>>>and see it from where you do, I have a problem with giving it
>>>a very serious impact on the cords as long as the tuning of
>>>the tract is in sympathy with the current operation of the cords.
>>>
>>>Different story if they are not tuned.
>
>From Lloyd....
>>COMMENT: May I refer you to an excellent discussion of inertance and
>>its effects on the vocal folds in Titze's book "Principles of Voice
>>Production" His research indicates strongly that the inertia of the
>>air column in BOTH the supra and sub glottal area provides a load on
>>the vocal folds that is necessary for continuation of vocal folds
>>oscillation. His book also does a good job of explaining Fourier
>>analysis of sound waves and its use in voice research.
>
>Lloyd I give in to your greater knowledge but I have a problem with the
>term 'inertance". This seems to be a term more recent than my
>education, still my objection, or confusion is centred on the dynamic
>fact that there should be TWO types of inertance. As I mentioned in
>the earlier piece, there are TWO sources of the 90degree shift in a
>resonant system. This also applies to ALL parts of the upper system.
>They used to be called "inductive reactance" and " capacitive reactance"
>in a resonant system. Each of these is a "reactive" impedance. BUT,
>their vector addition results in an over-all cancellation leaving only the
>REAL resistance and a very mysterious one called dynamic resistance.
>
>To refer to inertance of the vocal tract, leaves something missing.
>As I said before, an oscillating mechanical system has two characteristics,
>MASS and SPRING TENSION. Each of these has a direct relationship
>with an electrical resonant system. I know this is so, because I have
>used this fact to tune a mechanical system where the MASS is fixed
>so that all I have left to adjust is the spring tension. This spring tension
>equates with the "capacitance" in an LC circuit. (No not Low Carb:), but
>L for inductance and C for Capacitance.
>
>Perhaps I need to hear a clear definition of "inertance"
>
>The reflected load onto the cords would be very important, but the fact
>remains that whatever the value of the "inertance " reflected, if the upper
>area ...as a final result, is tuned, then it will not be an inertance,
>but a resistance, which implies a non-reactive characteristic...that is,
>the inertance of the effective MASS of the air column, is EXACTLY
>balanced by the SPRINGNESS of the upper walls, (or something,)
>to yield a final outcome of exact resonance with the oscillating folds.
>
>>>Such a condition is just what we all seek with varying
>>>degrees of success.
>>
>>COMMENT: "A dynamic resistance." But "Non-reactive"? If the load
>>is "totally resistive" aerodynamically it WILL affect the oscillation
>>of the vocal folds. Such may not be true of electrical processes
>>such as a "generator" with source "impedance" that is in reality a
>>dynamic "resistance", but it is true of aerodynamic processes. I
>>have nothing to indicate that what applies to one field will apply,
>>wholesale, to another. As mentioned above, the inertance of the
>>vocal tract is a necessary source of resistance energy to maintain
>>the continuous oscillation of the vocal folds; vocal fold elasticity
>>and the action of the Bernoulli Principle, of themselves, is not
>>sufficient.
>
>(me) Lloyd this is still a mechanical system and while I certainly
>agree that the air flow is the driving force behind the oscillation, the
>real problems seem to me to lie in the understanding of the upper
>area. Another difference is that all the displacements are "positive"
>that means there are no "negative" excursions of the air flow but
>that is not a problem for Fourier analyis for example, where there
>is provision for a DC or contant value.
>
>Just as the average value of a sine wave is ZERO, this fails to
>tell the whole story. Whether we deal with electron flow and
>voltage or, air flow and pressure difference. the resulting power
>is (EI cos theta) where E is voltage I is current and cos theta
>is the cosine of the phase difference between the two quantities.
>For power (energy) a positive value for one, times a positive
>value for the other still yeield a BIG + in the power stakes but
>also, a MINUS value, times a MINUS, also yields a BIG + in
>power. ONLY if cos theta is 90 degrees, do we have a big
>problem. (Of course even 45 degrees is not too good either.)
>Which brings me back to the problem of the "type" of the
>load reflected by the column onto the cords. (cos90" = 0 )
>
>I neglected to point out that those crico thingies represent
>the springs in the folds. :)
>
>Regards Reg.
>
>
>
>
>
>
>
|
