Question about Waterfall graph first slice - Home Theater Forum and Systems - HomeTheaterShack.com

Old 05-17-15, 02:42 PM Thread Starter
Shackster
Alfredo

Join Date: Mar 2011
Location: Buenos Aires
Posts: 7
Question about Waterfall graph first slice

Hi
What is the meaning of the first slice of the waterfall graph, the one at 0.0 milliseconds? It shows the frequency response at this time but I can´t understand it well. This is the time where the first sound wave reaches the measurement microphone? It is the time when the first sound wave leaves the speakers? If I have the microphone at 10 feet of the speakers what represents this first slice at 0.0 milliseconds time?

I thank all the forum for your help!
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Old 05-17-15, 03:22 PM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,307
Re: Question about Waterfall graph first slice

It is the total response at the microphone including the initial arrival and the sound which arrives later, according to the window width chosen. Think of it as the contribution from first arrival at the microphone until the end of the window width chosen. Later slices omit the initial arrival part of the response, showing how the sound decays. The process by which the waterfall is generated is explained further in the help.
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Old 05-17-15, 03:51 PM Thread Starter
Shackster
Alfredo

Join Date: Mar 2011
Location: Buenos Aires
Posts: 7
Re: Question about Waterfall graph first slice

Hi John
Thanks for your quick answer! So if the first slice is at 0.0 ms and the second is at 6.0 ms this means that the first slice is the response of all the signal that arrived between 0.0 and 6.0 ms?
Best regards
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Old 05-17-15, 03:55 PM
REW Author

John

Join Date: Apr 2006
Location: UK
Posts: 6,307
Re: Question about Waterfall graph first slice

No, with the default window width (500ms) the first slice is everything from 0 to 500 ms, the second would be everything from 6 to 506 ms and so on.
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Old 05-17-15, 03:59 PM Thread Starter
Shackster
Alfredo

Join Date: Mar 2011
Location: Buenos Aires
Posts: 7
Re: Question about Waterfall graph first slice

Ok, I read the information that you recommend me but I misunderstood this part.
Now it starts to look clearer for me !
Many thanks!
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Old 05-19-15, 10:28 AM Thread Starter
Shackster
Alfredo

Join Date: Mar 2011
Location: Buenos Aires
Posts: 7
Re: Question about Waterfall graph first slice

Hi,
Under Tools-> IR Windows it is possible to select different windowing functions for the measured response. I read some information regarding the windowing effect on signals but I am missing an important point: How to relate windowing functions to acoustic measurements? I suppose they are windowing functions that highlight certain details of a response and other windows highlights other details.
In short: Do you have a link to a paper / tutorial that could help me and the rest of the forum to better understand which windowing function is better to use when we look to certain details?

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