QA40x Feature request

Thanks for the reply, Matt.

Yes; the chirp is fast, but how accurate is it? What happens when there is a phase shift in the signal from sensor resonance or signal-conditioning electronics or imperfect mic placement? Can you even measure phase shift? I think there are some compelling reasons why the calibration lab uses the pulsed constant wave. With respect to imperfect mic placement: That is minimized in your example of two measurement mics using the “same air space”, but far less practical with larger acoustic sensors and ones of different design. Fast is great for production testing. For R&D, I’m looking for accuracy and repeatability.

I’ll try and have a look at the log sweep again. Does the windowing function work when the automated test is used? It is cumbersome to use the plots from the main window because there is no way to set overlays and compare one measurement to another.

Thanks, Clane, for your comment. We’re getting further off topic from what started as a simple feature request.

Regards, Robb

Hi @RobbN, you can effectively get a pulsed sine test out of the box if you set the FFT size very small. A 1k FFT at 48Ksps will be ~21 mS in duration. That would be about 20 cycles at 1 kHz. In air, you’d want to make sure any reflective surfaces were more than 10 feet away. Under water, you’d want to make sure any reflective surfaces were more than 40 feet away.

There is also the ability to set the silence dwell time between bursts. And you’d want to set that be long enough so that the reflections from your boundaries are ignored. The naval tank you note has a boundary that is 5 meters from the emitter and mic. So, about 15 feet. And so you’d not want to start another burst for 15 mS or so. Let’s set 100mS between bursts (this isn’t super precise, but it will be AT LEAST this long between bursts).


Here’s what the train of pulses look like in the time domain:

Now, in the scope shot the bursts look to be 100mS or in duration. That’s because they have a ramp up/down period. If you set the check box to “show truncated burst in Time Domain” in the settings dialog, then that means in the time domain display you’ll see the the actual waveform that is getting the FFT applied with all the ramp up/down removed. That Note that the burst is 21 mS as calculated.

Now, if you have a lot of path delay (more than 0.04 seconds), then you can add some more cycles in using the Latency Compensation in the Settings dialog. For example, Bluetooth path delay can be 100 to 200 mS in some cases, and growing the pre-buffer can allow you to compensate that out. But probably for your needs, you’ll be fine with the 40 mS max latency provided by the default Latency Compensation. You can inspect your captured waveform in the time domain and make sure it matches what you expected (that is, starts exactly at 0.0 mS and continues through the FFT divided by the sample rate).

And then, once you are sure you have captured the frame of data as expected, you can shift back to frequency domain. In the case below, I’m in loopback, so the 0 dBV input measures as 0 dBV input. But in your case, you should see a reflection-free signal level indicating the response of your mic.

And then, if you are convinced in what you see in the 1 kHz test, you can move to the AmpFreqResponseOptions automated test and sweep over the specified levels and frequencies. That will respect your FFT settings, your pre-buffers settings, and your Pause Between Bursts settings.


The only thing to be aware of is with a 21mS data buffer, you will have a lower bound on what frequency can be process. Again in loopback, I can get down to about 93 Hz and still see a meaningful amplitude reading:

At this point, the captured waveform is two cycles.

Finally, note while the Chirp can use the right channel as a reference, the stepped sine doesn’t do anything special with the right channel. You could put a reference mic on the right channel, and still capture it, and then dump the output to excel for additional processing if needed.

The neat thing here is that if you build confidence with stepped bursts of sine waves, you can easily then switch over to a chirp with windowing and see how it compares. All out of the box without any coding.

PS. If you went to 96K sample rate, your burst duration with a 1K fft s 1024/96k = ~10 mS. So, that would let you get down to 200 Hz using a 10 mS burst. And at 192k you’d have a 5 mS burst, and lower freq of 400 Hz or so. Round numbers. But this would let you get to a smaller tank (each doubling of sample rate would collapse the required tank size in half).

Thanks again for the suggestions. I’ve tried to follow you through this and it hasn’t gone perfectly. Just a few disparate questions and comments:

The automated AMP Frequency Response test does not appear to respect the pause time between acquisitions, or there is some limit to it. I tried to slow this down to 1 second, so I could watch how the scope visualizer change and it rips through the test, despite the fact that I can watch the delay in the main acquisition window.

I don’t really understand what the pre-buffer setting is doing. Maybe I need to put a scope between the loopback function and watch on two displays to figure it out, but if you have a reference, I’d be grateful for a more detailed explanation.

My time visualizer looks different than in your pictures and seems to have some bugs, despite updating the software. Is there a way that I’m missing to put the scope in the main window? Mine looks like this:

And, for the record, I don’t seem to be able to enable the right input. Before I updated the software (from 1.168), I had cursors that kind of worked, but the center and nudge buttons didn’t have any effect. After updating, the cursors went away. The image above is from v1.171.

Hi @RobbN,

My apologies, the PAUSE wasn’t applied to all plug-ins. That has been fixed in 1.173 (located HERE). There were only 4 plug-ins that respected the PAUSE. Instead of adding it to each plug-in, it has been moved to main handling so that future plugins will have it applied too and can’t be overlooked. The PAUSE, if enabled, was added to the REST code path too.

The pre-buffer is just adding additional cycles to the front of the waveform and as such it will only work for tones. So, as you add more pre-buffer, you are growing the duration of the burst. And then, when the path delay is considered, the latest X samples (where X is FFT size) are what is taken for analysis.

The time visualizer you are looking at is the experimental oscilloscope. It has some more work coming, but right now the main time domain display is the one you want. The one I was showing previously is in the DISPLAY control group. Click that and you’ll see the time domain, and click FREQ (to the right) and you’ll switch back to frequency domain.


And, for the record, I don’t seem to be able to enable the right input. Before I updated the software (from 1.168), I had cursors that kind of worked, but the center and nudge buttons didn’t have any effect. After updating, the cursors went away. The image above is from v1.171.

The right input is enabled in the DISPLAY control group:


You can enable the right or left (or both) traces, and then switch to the Cursor control group and enable Cursor 1 (C1) or Cursor 2 (C2). And then attach each of those to either the left or right traces.

The center button will move to the cursor the center of the screen (in case it is off screen), where you can then drag it as needed. The PEAK button will look for a nearby peak. So, drag the cursor as close as you can to the peak, and if you can’t get it precisely, hit the PEAK and it should snap over.

Please confirm if 1.173 fixes the issue you were seeing with PAUSE, and thanks for noting that!

If it is not too difficult to do, at some point it would be nice to be able to specify a specific Y axis range, even if only as a user Y User Preset…

It’s not like I stay up late at night thinking a program features, but a recent experience is prompting this one…
A DELTA ALARM that could be to play either a constant or on/off tone once that delta is tripped. I am thinking just for monitoring the power level at a fixed frequency or possible a swept range. It would be very handy when trying to trouble an intermittent problem, and possibly have it note how long it has been since the monitoring had started and the delta limit reached…

Hi @Var, that is a pretty interesting idea and I know exactly what you are talking about…

Thanks for considering it. I am sure that it would come in handy for businesses/shops as well. I was working on an integrated amp that supposedly had a problem where one channel lost its volume after an hour or two and so I thought it would be nice if the computer could alert me when happened as I would have been in another room, but would have been able to hear an alarm sound.

One thing that would be nice to have is a “screen lock” for the Trace portion of the display that could be toggled on and off as needed. The reason for this is when I am capturing the Trace portion of the display (via screen capturing software for a video) and I want to click on a signal or noise I will get a Marker warning (I almost always have both Left & Right Traces displayed) message pop or, if I click on an empty area, the scale will expand with the “bent arrow” indicator coming on…

Hi @Var, and the screen lock would do what precisely? Just ignore clicks?

Yes, just ignore any clicking in the trace area :grin:

Any chance that the automated test frequency response (non-chirp) could automatically reset to 1kHz at the end of the sweep instead of staying at the highest frequency where the test ended?

Would save me a lot of trouble going in and re-setting manually!


That is a great suggestion- I second it!!

Yes, this is a good idea I know the feeling well. Especially when the 20 kHz tone is barely visible.

How about a checkbox in the settings to save full settings state, and then restore that after the test is finished? That way you’ll go back to the same atten, generator type, gen amplitude, etc

Thanks, Matt

My main wish is that the generator just go back to 1kHz at the end of the frequency response automated test, so if what you are proposing accomplishes that, then that’s good with me. I frequently want to look at the FFT when the response sweep is finished and am sometimes frustrated when there is nothing on the FFT, not realizing the generator is at 90kHz!

So if I don’t have to lift a finger after the frequency response test, I’m happy. :smiley:


A checkbox for doing that would be great!

Would it be possible to have an option which removes the QuantAsylum logo on all graphs and automated graphs? I find that sometimes important data is covered up by the logo and would rather not jump through hoops to remedy that.


Hi @Rammis, yes, makes sense as the QA401 SW had this ability. It will go into next release. It also includes an option for date/time of acquisition on the main display

Thank you so much Matt!

Ability to shift completed traces up and down in level especially in the automated frequency response test. Handy for comparing traces taken at slightly different amplitudes over each other.