different measurement results with, length 1M, 512K etc..?

1301 Views 5 Replies 3 Participants Last post by crossrh, Apr 4, 2015

Stino

Discussion Starter · Apr 4, 2015

Something I don't quite understand is why I'm getting such significantly different measurment result with the different sweep length, I expected these to be similair. I thought it might have had something to do with the impulse time due to room accoustics, so I shortend this but with little effect.

Can someone explain this to me?

Thanks.

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Wayne A. Pflughaupt

· #2 · Apr 4, 2015

Welcome to the Forum! Please post a graph so we can see what you’re talking about. :T

Getting Graphs Ready to Post
Posting A Graph

Regards,
Wayne

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Stino

Discussion Starter · #3 · Apr 4, 2015

Nothing else was touched, just change sweep length. Differences are unexpectedly large.

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crossrh

· #4 · Apr 4, 2015

Are you running just one sweep, or multiple sweeps? Multiple sweeps made my results show a significant drop in the high-freq. John advised me to do just one sweep, and attributed it to timing errors with USB.

In another thread he mentioned doing "synchronously averaged" sweeps. I think the thread was called "@John" or something like that. I'm afraid to go back and look, only to lose this reply.

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Stino

Discussion Starter · #5 · Apr 4, 2015

Thanks Crossrh, I ran both sweeps 2x per measurement. I did notice this before, where the results from a single and multiple sweep where very different, and the latter being much worse.

How would I set "synchronously averaged", sounds intresting.

I'll try single sweeps again tomorrow.

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crossrh

· #6 · Apr 4, 2015

Your graphs, at least in the high-freq region, look like mine did when I ran multiple sweeps. Now I only run single, 1M sweeps.

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