William Sommerwerck wrote:

For a broadband signal with low peak-to-average ratio, I
can
think of nothing worse than an impulse, and nothing
better
than a continuous swept tone.You can get the same data
out
of either one, but you get cleaner data faster with the
swept tone.

Please explain how waterfall displays can be derived from
swept tones.

Repeat after me - an impulse response derived directly from
an actual impulse is the same as an impulse response derived
by means of the cross-correlation of broadband signals.
Only, the latter probably has a far better SNR, when the
wall-clock duration of the test is held constant.

William Sommerwerck wrote:
For a broadband signal with low peak-to-average ratio, I can
think of nothing worse than an impulse, and nothing better
than a continuous swept tone.You can get the same data out
of either one, but you get cleaner data faster with the
swept tone.


Please explain how waterfall displays can be derived from swept tones.

Roughly, by doing FFT's of blocks that first contain the
whole IR, then moving the block out in fixed time steps,
dropping more and more of the start of the IR, and finally
plotting the data in three dimensions, time, frequency and
amplitude. Given an IR, no matter how you obtain it, the
procedure is the same.

In a noise free envioronment whether you give the system
under test a real impulse, a random noise sequence, a
sinusoidal sweep, or any full band sequence (along with the
calculated "inverse" for the last three) you get the same
IR. In an environment with noise, the impulse is ruled out
because the amount of signal in the stimulus relative to the
noise of the environment is usually _very_ low.

Yes, averaging can help (if you have a perfectly time
synchronized impulse source.) The noise goes down by
1/sqrt(n) where n is the number of them averaged. It takes
really large n to match what you can do with a sweep or
sequence that lasts 30 seconds or so. For equal noise
immunity you probably have to have an n on the order of the
number of samples in the sweep or sequence. Implicit in the
cross correlation of sequences which calculates the IR is a
very large degree of averaging. Each result sample is a
weighted sum of all the measurement samples, each containing
uncorrelated noise.

I followed the dead end path of actual impulse measurement
to its conclusion using a hefty spark generator I made (and
time synchronization of the data using fractional sample DSP
delays.) Total waste of time as everyone had tried to tell
me it would be. If I'd understood then the averaging
implicit in cross correlation of sequences I wouldn't have
wasted that considerable time.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

"Bob Cain" wrote in message
...
Why does it matter for this whether the stimulus is a sweep
or a pseudo random white noise sequence?

As I said, for speaker testing in a reflective environment, it can matter.
Near field measurements can help too, but may not properly show any
interaction between drivers near the crossover frequencies.

MrT.

"Phil Allison" wrote in message
...
"Phil Allison" = Repetitive, tiresome, moronic imbecile"

"Mr.T" = Mr Turd


** Trevor = another anonymous, autistic turd !!

You are and have always been a brain dead, trolling, useless,
psychopathic **** !!

You leave mere morons spinning in your wake.

Get back to your kiddie porn and public dunny trolling.





.......... Phil

Mr.T wrote:
"Bob Cain" wrote in message
...

Why does it matter for this whether the stimulus is a sweep
or a pseudo random white noise sequence?


As I said, for speaker testing in a reflective environment, it can matter.

I'm asking you to give me more detail on that. It isn't
true to my knowledge. I do a lot of that kind of thing and
if there is a better way that I don't understand I'd like to
hear about it.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

"Phil Allison" wrote in message
...

typical Phil ****e

It's not even a full moon Phil. Lost your meds or something?

MrT.

"Bob Cain" wrote in message
...
As I said, for speaker testing in a reflective environment, it can
matter.

I'm asking you to give me more detail on that. It isn't
true to my knowledge. I do a lot of that kind of thing and
if there is a better way that I don't understand I'd like to
hear about it.

Maybe the bit you snipped would tell you why near field swept measurements
have limitations too.
The best technique is to use all available methods to give you the best
possible picture, and understand the limitations of each.

MrT.

"Mr.T" = Mr Turd


** Trevor = another anonymous, autistic turd !!

You are and have always been a brain dead, trolling, useless,
psychopathic **** !!

You leave mere morons spinning in your wake.

Get back to your kiddie porn and public dunny trolling.





.......... Phil

"Phil Allison" wrote in message
...
the same crap yet again

You are slipping Phil, you used to come up with original insults at least,
once upon a time.

MrT.

"Mr.T" = Mr Turd


** Trevor = another anonymous, autistic turd !!

You are and have always been a brain dead, trolling, useless,
psychopathic **** !!

You leave mere morons spinning in your wake.

Get back to your kiddie porn and public dunny trolling.






.......... Phil

On 6/10/05 9:40 PM, in article
, "Mr.T" MrT@home wrote:


"Phil Allison" wrote in message
...
"Phil Allison" = Repetitive, tiresome, moronic imbecile"


You kids play with the fresh cow patties WITHOUT the crossposting.. Ok?
Good.