Understanding decay in a Waterfall Graph

[Trdat]

I have a set of questions regarding understanding graphs I am well aware these have been presented and explained many timesbefore but I just can't wrap my head around some basic questions which should in essence catapult me as I am stuck on simple thoughts. I just want to know when looking at the waterfall graph we can see the particular frequencies take its time to drown out in the room(that I understand) such as the example given in the picture below at 180hz in red. But looking at the 40hz to 50 hz is that decaying longer than the 180hz? I am trying to understand more about that bubble at 40 to 50 and the one at 15 to 25 as it rises with a flat part splattering the page, not sure what that exactly means? Is that decaying significatnly longer? And how do i read what the decay time is what am I looking at?

Secondly can someone give me some of the limits or parameters or what to do in the controls to read a step response clearly, I cant seem to get a view of it properly.

 

[AudiocRaver]

The two areas you see "splattering" against the page, or splattering against the side of a "fish tank" (to be a little more accurate with the splattering metaphor), have simply reached the limit of measurement given the display settings. They are continuing to decay beyond 300 ms (the last number up on the right side of the "fish tank").

Click on the Controls gear wheel for the Waterfall, then the forth option down is Time Range. For your current view it must be set at 300 ms. Change it to 500 ms or some larger value, then press enter, and the Waterfall will update and you will see those two decaying areas continue their decay further down, maybe all the way to the bottom of the chart. Also notice how all the rest of the chart is "time compressed" much thinner than before.

Hope that helps.

 

[sm52]

to read a step response clearly

there is a box at the bottom of the impulse graph, which can be checked, then the step response graph will appear.

 

[Trdat]

The two areas you see "splattering" against the page, or splattering against the side of a "fish tank" (to be a little more accurate with the splattering metaphor), have simply reached the limit of measurement given the display settings. They are continuing to decay beyond 300 ms (the last number up on the right side of the "fish tank").

Click on the Controls gear wheel for the Waterfall, then the forth option down is Time Range. For your current view it must be set at 300 ms. Change it to 500 ms or some larger value, then press enter, and the Waterfall will update and you will see those two decaying areas continue their decay further down, maybe all the way to the bottom of the chart. Also notice how all the rest of the chart is "time compressed" much thinner than before.

Hope that helps.

Brilliant, thats what I thought but never had my suspicion confirmed. Thanks, so essentially its decaying past a point of about 300ms. And now that I can extend the decay ms with controls I can see it better.

 

[Trdat]

there is a box at the bottom of the impulse graph, which can be checked, then the step response graph will appear.

Yes, I have checked that box but due to playing around with the size I have lost what I am seeing and even then before I I made it extremely small it was continous waves never ending. I thought a step response is a rise then a drop with another rise, I cant seem to get that part on the screen, is there parameters I can put in controls which will zoom into the first part of the step response? Such as the picture below, I don't get it looking like this.

 

[sm52]

I didn't understand the last question. Do you need to increase your graph?

 

[Trdat]

I didn't understand the last question. Do you need to increase your graph?

It looks like this now and I want to make it look like the above.

 

[John Mulcahy]

Use the Limits button at the top right of the graph to change the span of the Axes. Use the Ctrl+Alt+F shortcut to fit the graph to the full range of the data.

 

[JStewart]

And how do i read what the decay time is what am I looking at?

I think you have the answer to this above.

I am trying to understand more about that bubble at 40 to 50 and the one at 15 to 25 as it rises with a flat part splattering the page, not sure what that exactly means? Is that decaying significatnly longer?

The 40-50 looks like a room mode and it also looks like it could be improved with Parametric EQ if you have access to it. EQ would help both the elevated frequency response and the decay time on the waterfall chart.
I don't know about the 15-25 business. @John Mulcahy could that be nearby traffic noise or forced air heat/cool running or would those not get picked up on a sine wave sweep?

There are a couple of excellent articles on understanding waterfall results by our member @Wayne A. Pflughaupt if you're interested:

Adventures in Waterfalling: Understanding Signal Levels in Time-Domain Graphs

Adventures in Waterfalling Understanding Signal Levels in Time-Domain Graphs Once upon a time in a land far, far away, the capability to generate waterfall graphs was limited to expensive software programs available primarily to professional speaker designers and acoustics engineers...

www.avnirvana.com

Adventures in Waterfalling Part Deux: Multiple Subs, Free Bass Traps, and More

Adventures in Waterfalling Part Deux Multiple Subs, Free Bass Traps, and More NOTE: Readers are encouraged to wade through my previous article on waterfalls and signal levels before delving into this one, to fully understand the terms and concepts presented. Do Positive-Gain EQ Filters...

www.avnirvana.com

 

[Trdat]

Use the Limits button at the top right of the graph to change the span of the Axes. Use the Ctrl+Alt+F shortcut to fit the graph to the full range of the data.

Ctrl + Alt + F worked but using the Limits button doesn't get me a grpah that looks like above. Is there a set of parameters that can be used to get it looking like the above?

 

[Trdat]

I think you have the answer to this above.



The 40-50 looks like a room mode and it also looks like it could be improved with Parametric EQ if you have access to it. EQ would help both the elevated frequency response and the decay time on the waterfall chart.
I don't know about the 15-25 business. @John Mulcahy could that be nearby traffic noise or forced air heat/cool running or would those not get picked up on a sine wave sweep?

There are a couple of excellent articles on understanding waterfall results by our member @Wayne A. Pflughaupt if you're interested:

Adventures in Waterfalling: Understanding Signal Levels in Time-Domain Graphs

Adventures in Waterfalling Understanding Signal Levels in Time-Domain Graphs Once upon a time in a land far, far away, the capability to generate waterfall graphs was limited to expensive software programs available primarily to professional speaker designers and acoustics engineers...

www.avnirvana.com

Adventures in Waterfalling Part Deux: Multiple Subs, Free Bass Traps, and More

Adventures in Waterfalling Part Deux Multiple Subs, Free Bass Traps, and More NOTE: Readers are encouraged to wade through my previous article on waterfalls and signal levels before delving into this one, to fully understand the terms and concepts presented. Do Positive-Gain EQ Filters...

www.avnirvana.com

Yeh, I saw those. I have read the one on subwoofers just need to read the first one in detail.

 

[AudiocRaver]

After you press Ctrl + Alt + F to get the bird's eye view, you can then L-click just to the LEFT of the beginning of the impulse to place the cursor cross-hair there, then move to the center of the panel and R-click/hold to drag the whole diagram to the left until the cross-hair is just barely still on screen, then release, then click on the "+" button on the lower right corner of the diagram to zoom back to the desired resolution.