confused about Waterfall vs Spectrogram info

[thothsong]

Attached is a sub measurement. When I look at a Waterfall chart, it looks like 60 Hz goes on for more than 800 ms, for example:

But when I look at a Spectrogram chart, it looks like 60 Hz stops in less than 300 ms:

What's accounting for the difference, and which one should I pay attention to?

 

[Wayne A. Pflughaupt]

Looks like it’s because the waterfall graph floor is 33 dB, while the spectrogram floor is 52 dB. T hus with the latter the display will fall off the graph “sooner.”

Regards,
Wayne

 

[thothsong]

Hmm, how did those floors get set? I don't see any direct controls for them.

 

[Wayne A. Pflughaupt]

Look for the "Limits" icon.

Regards,
Wayne

 

[thothsong]

For Waterfall Limits, I have SPL Bottom set to 41, not 33. The Spectrogram Limits have Top and Bottom in ms, not SPL.

 

[Wayne A. Pflughaupt]

Didn't know that, I've never used the spectrogram. Hopefully John will weigh in.

Regards,
Wayne

 

[sam_adams]

Waterfall limits (button labelled 'Limits', rectangle with four arrows inside) set to 100dB to 50dB (50dB span):

Waterfall limits set to 100dB to 30dB (70dB span):

Waterfall settings ('Gear' icon, labelled 'Controls'):

Spectrogram limits (button labelled 'Limits', rectangle with four arrows inside) setting:

Spectrogram settings ('Gear' icon, labelled 'Controls'):

Spectrogram appearance settings (Gear icon labelled 'Controls', button labelled 'Appearance settings'):

 

[thothsong]

I don't see how the screenshots you posted answer the question?

 

[sam_adams]

Your original settings. Waterfall set to 60dB range:

Your original settings. Spectrogram with 40 dB Scale Range:

Spectrogram with 50dB Scale range:

Spectrogram set with a 60dB scale range to match the Waterfall Scale Range:

As @Wayne A. Pflughaupt correctly pointed out earlier, your confusion is arising from the fact that you have different scaling applied to the different charts. As you can see from the first Spectrogram plot above, a scale range that is too small and doesn't show enough info. The third plot has a scale range that is too large and shows mostly useless info about the background noise of the room. The second plot shows relevant info and removes that which you probably won't even hear. Remember that the microphone "hears" better than we do—at all frequencies.

 

[thothsong]

Ah, OK, thanks, so what I was missing is that the Spectrogram SPL top and bottom settings are under Appearance, and should match the Waterfall SPL top and bottom settings to get equivalent results.