I searched both terms on Wiki

http://en.wikipedia.org/wiki/Self-Resonant_Frequency
and

http://en.wikipedia.org/wiki/Resonant_frequency
I still don't understand what is the difference between them. Let says,

what is the meaning of Self-Resonant Frequency in an Inductor compare

to Resonant Frequency of a Transducer?

Thanks.

Resonance (in electrical parlance) refers to the frequency where the

capacitive reactance is equal to the inductive reactance. At this

point, the phases cancel and you get a sharp change in the overall

impedance. For example, a parallel LC circuit (capacitor in parallel

with an inductor) will be in resonance at a frequency where 2*pi*f*L =

1/(2*pi*f*C). At this frequency, the impedance of this parallel LC

circuit will be extremely high due to the phase combination.

Normally, the term "self-resonant" frequency refers to the resonant

frequency of a component due to the parasitic characteristics of the

component. For example, the physical construction of a capacitor will

determine the parasitic inductance of the leads/connections to the cap.

The frequency where the capacitive reactance of the cap and the

inductive reactance of the lead's parasitic inductance, is the

self-resonant frequency. It is a property of the physical

characteristics of the device - and to some extent, defines where the

cap no longer behaves like a cap, but begins to behave like an

inductor.

When designing resonant circuits, you pick the capacitance and

inductance. Ideally, you will operate at frequencies that are far away

from the self-resonant frequency of the individual components. Of

course, there are special circumstances where you might do a design

that involves utilizing components near their self-resonant frequency,

but it isn't that common.