Re: Different results from sweep and pink noise

[Julian Bunn]

I wonder whether the sweep is slow enough? I'd want to be sure that the generator stays long enough in the 40Hz region so that the resonance in the vehicle is fully excited. But I am by no means an expert on this, so take that with a pinch of salt!

Perhaps others have ideas?

Julian

On Wednesday, September 24, 2025 at 5:24:38 PM UTC-7 randall...@gmail.com wrote:

Hello, I am trying to tune (flatten) my subs with a dsp and AudioTool. I have used pink noise and sweeps to see my vehicle response. I expect it (suv) to have a peak around 40hz, and audiotool shows that peak when I analyze pink noise, but different result when I analyze a sweep.

Basically a sweep shows me flat through the 40's with a peak at 56. Pink noise shows a peak at 40 with none at 56. I can't tell by ear. I don't know which one to trust or why they are different. I would appreciate and thoughts or guidance. 
The levels are different but I am using same source volume and using the generator in Audiotool.

[Myles Dexter]

I agree with Julian. What’s your start/stop frequencies and your sweep rate? If you sweep from 20-10000Hz over 120 seconds, the sweep is only spending a fraction of a second in the 40-70Hz range. I’m guessing your sweep time should be 500 seconds or more if you’re going to use this approach. 

I’d suggest you test at discrete frequencies (every 1Hz between 20-100Hz, every 10Hz between 110-300Hz, etc.), and then save a peak hold spectrum for each excitation frequency. You could then export those spectra to Excel and extract the excitation frequency and amplitude for each spectrum and build your own sweep frequency spectrum from that peak data. That would be more precise, but much more time intensive. 

- Myles Dexter

On Sep 24, 2025, at 8:31 PM, Julian Bunn <jjb...@gmail.com> wrote:

I wonder whether the sweep is slow enough? I'd want to be sure that the generator stays long enough in the 40Hz region so that the resonance in the vehicle is fully excited. But I am by no means an expert on this, so take that with a pinch of salt!

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[Myles Dexter]

Or, perhaps consider a logarithmic sweep rate. 

- Myles Dexter

On Sep 24, 2025, at 9:19 PM, Myles Dexter <my...@dexters.org> wrote:

I agree with Julian. What’s your start/stop frequencies and your sweep rate? If you sweep from 20-10000Hz over 120 seconds, the sweep is only spending a fraction of a second in the 40-70Hz range. I’m guessing your sweep time should be 500 seconds or more if you’re going to use this approach. 

[R C]

I was using log sweep 30-125hz 10sec but I will try longer and even individual freqs, interested to see if sweep time makes a difference.

[R C]

I'm sweeping 30-125hz   10 seconds.   I will try longer and individual frequencies. Thanks!

[Teemu Järvinen]

To my knowledge noise does not have enough stuff in subwoofer frequencies to produce accurate measurements 

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[R C]

Can you delete the thread please! I found the issue it was not the app I was using too high of volume for my microphone. A few clicks lower and the sweep matches the pink noise. Thanks!

[Julian Bunn]

Thanks for the update ... that's a good result! Let's keep the thread as I think it is probably useful to others who may be doing sweep/Pink comparisons.

[Philipus Donovan Tan]

i wonder why people want to have a flat curve in my opinion the "flat" curve dont sound good even with the best tuning microphone. I've done systems and FOH mixing for a great part of my live but use the spectrum analyser only as reference for tracing problems

Greetings

;Donovan

Op do 25 sep 2025 om 02:24 schreef R C <randall...@gmail.com>:

Hello, I am trying to tune (flatten) my subs with a dsp and AudioTool. I have used pink noise and sweeps to see my vehicle response. I expect it (suv) to have a peak around 40hz, and audiotool shows that peak when I analyze pink noise, but different result when I analyze a sweep.

Basically a sweep shows me flat through the 40's with a peak at 56. Pink noise shows a peak at 40 with none at 56. I can't tell by ear. I don't know which one to trust or why they are different. I would appreciate and thoughts or guidance. 
The levels are different but I am using same source volume and using the generator in Audiotool.

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