Klarinet Archive - Posting 000325.txt from 1994/11

From: Josias Associates <josassoc@-----.COM>
Subj: Transients
Date: Wed, 23 Nov 1994 18:06:56 -0500

On Wed, 23 Nov 1994, Fred McKenzie wrote:

> On Wed, 23 Nov 1994, Steve Prescott wrote:
>
> > I thought "transient", in Physics, refered to the sound decay. More
> > specifically, decay over time. I don't think the attack has much to do
> with
> > it other than initiating the tone...am I not thinking clearly? Please
> > explain.
>
> And Cary Karp responded:
>
> The term transient when applied to vibrating systems normally refers to
> the initial transient, which provides many of the cues used to identify
> the source of a sound.
>
> Cary and Steve-
>
> I think you are both "sort of" right! My understanding is that "transient"
> refers to the initial change, such as the mallet hitting the bell. The decay
> over time is the "transient response" or ringing of the bell. The sound of
> the decay (or ringing) of various transitions, may be what is really meant
> with respect to "national schools".
>
> Fred

Fred, Cary, and Steve,

I had hoped to avoid getting in this discussion for fear that my
contribution might be pedantic or of little or no interest to the list
subscribers. But, I seem to have weakened.

I have been a practicing electrical/electronic engineer for 43 years,
and a major part of what I have done has involved transient analysis of
electrical systems and to a lesser extent mechanical and acoustical
systems. However, there are well-known and meaningful analogs relating
the resonant, damping, and non-resonant behaviors of the three
regimes to each other.

Generally, in physics and engineering, the term "transient" refers
to a state change from steady state. The transient response or transient
state is what occurs immediately after a new or additional excitation or
transient event is applied to the system. Representative transient
electrical excitations are step functions, impulses, rectangular pulses,
ramps, trapezoids, and various combinations of those functions modulating
sinusoids. Many of these excitations (like step functions and impulses)
have obvious acoustical and clarinet-related analogs.

Fred is correct when he describes the exciting event as "the
transient." But, I guess through usage, the implication of the word as
employed in engineering has undergone some bending, so that, when people ask
about transients, they are often inquiring about what happens in response
to a transient excitation, namely the transient response. This might
explain the non-rigorous usage of the term "transient" (by older
standards) as widely seen today.

If what people are referring to is actually the response, the
transient response, once again, is what occurs to or in the system (or
musical instrument) after a transient event. The textbook, "Transients
in Linear Systems," by Gardner and Barnes characterizes the transient
state as being the period after the pre-excitation steady-state condition
and before a new steady-state response is established.

Connie Josias
Conrad Josias
Engineering Consultant
Josias Associates
La Canada, California
josassoc@-----.com

   
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