Tag Archive for: curves

100 Things #66: Quickly Post-Process Multiple Measurements With Average Curves

SoundCheck includes a powerful array of post-processing options, including Average Curves. This step allows for instant averaging of data sets with two averaging options: power and complex. Curve average is perfect for working with data from microphone arrays, making this tool great for automotive and smart device measurement applications, or any device with large microphone arrays. Since SoundCheck is not limited to hardware inputs and outputs, huge measurements can be done simultaneously including up to 64 channels simultaneous acquisition. Once measured, SoundCheck can perform curve averaging to this data even within a sequence.

Quickly Post-Process Multiple Measurements With Average Curves

Try average curves in a sequence

Check out our full library of test sequences. There are sequences for common and specific audio measurement applications, and they make the perfect starting point to add average curve post processing to a sequence.

Video Script:

SoundCheck comes with a lot of great post-processing options and one of my favorites is the Average Curves function which first appeared in SoundCheck 17.  This step lets you easily calculate the average of a group of curves and, although the step name doesn’t imply it, it can also be used to calculate the average of a group of waveforms. This is really useful for measuring microphone arrays such as those in automotive infotainment systems and smart devices.

First, we’ll place the data of interest into a Memory List group. Next, we select the group in the step editor’s Operand dropdown. There are two averaging options available; Power and Complex.  Power averaging excludes the phase from the calculation and should be used when the curves or waveforms aren’t from the same spatial position, for example when the data has been collected from a microphone array. A group of RTA curves is another example of where power averaging should be used since RTA analysis doesn’t calculate phase.  On the other hand, complex averaging should be used when trying to average out random background noise across many repeated measurements of the same device. Here we’ll apply Power Averaging, and you can see the result here.

SoundCheck can capture data from up to 64 microphones simultaneously, so whether the data is coming from multiple microphones, microphone arrays, or even multiple microphone arrays, you can capture the responses and analyze and average the results. Averaging steps can even be incorporated into a test sequence! As microphone arrays become more commonplace in many consumer devices, this measurement has many applications in smart device tests, automotive infotainment measurements, and beyond. How would you use this functionality? Let us know in the comments!

100 Things #64: Using Statistics to Create Test Limits

The statistics feature in SoundCheck adds the ability to perform a variety of statistical measurements. SoundCheck’s statistics step can work with data, results, or both. Statistics allows users to take a set of data, like frequency responses of multiple devices, and automatically calculate the best or worst fit to average, maximum, minimum, and more. This statistics functionality is not just confined to a sequence, since all the same functionality is available with offline statistics. This is a great solution of performing statistics independent of a sequence, for applications like finding golden units in production testing.

Using Statistics to Create Test Limits

Learn more about statistics and limits in SoundCheck

If you want to learn more about using statistics in SoundCheck, our four-part tutorial series on using statistics with SoundCheck is available to watch here. This series goes in-depth with statistics data, results, processing capability, and offline capability.

Our three-part tutorial series on limits in SoundCheck is available to watch here. This three part series covers the basics of limits functionality in SoundCheck, data, and advanced limit creation.

Video Script:

One question I often hear from customers is “I wrote a sequence to measure my devices. I have the frequency response, THD, sensitivity, but how do I know if this is good or bad?” We have statistics tools inside SoundCheck that can make this determination a lot easier. 

It’s important to remember that measurement targets are completely different depending on the device. For example, the acceptable level of distortion in a high end pair of bluetooth headphones, would be completely different than a cheap USB headset made for online meetings. A great place to start is picking out five units that are subjectively “good” devices. We can measure these units in SoundCheck, use statistics to help us generate limits, then compare other devices to this.

Let’s look at a standard headphone test sequence. Right now it’s configured to just run one test, but by adding in a statistics step to the end of the sequence, I can run this test as many times as I like and average all of those different units. 

The statistics step has many different features, but let’s look at Mean and Standard deviation. Mean takes the average point of the selected curve or value for every run. If I measure 5 devices and get their frequency responses, the mean is a running average of all 5 devices combined. We can use our mean as a reference curve, and compare each device to this. 

Standard deviation outputs plus minus sigma curves, which we define in the editor. For example if I want to make sure that all my devices fall within 3 sigma of my 5 reference devices, I set up my statistics step to output +/- 3 sigma, and after I run my 5 different units these upper and lower sigma curves are added to memory. I can then use these as the upper and lower limits in my test sequence, and pass a device if it falls within this range and fail it if it’s outside the range. 

And one final note… If you already captured measurements but didn’t run statistics on it while the sequence was running, all of these same features are available in the offline statistics editor. Just open up your curves from your good units in the memory list and you can run statistics directly through the offline menu.

With offline statistics, you can calculate the Best Fit to Average and Worst Fit to Average curves by finding which unit comes closest to, or furthest away from the average curve. Best Fit to Average can be used to find a reference or “Golden Unit”. This can be used as a sanity check when things go wrong on the production line and for developing limit curves. Some manufacturers prefer this approach because the factory environment e.g. temperature and humidity can vary from day to day and affect devices’ measurement performance.

By measuring the golden unit before measuring newly manufactured devices, the limits can be updated relative to the golden unit under current conditions. Worst Fit to Average can be used to find outliers or bad units that you don’t want to use in your statistical calculations when developing limits. Once you find a Worst Fit to Average curve, simply unselect it and re-run your statistics on the remaining good units. 

Do you use statistics to set pass/fail criteria? Let us know in the comments below.

100 Things #27: Recall Saved Data While Running A Sequence

SoundCheck can recall saved data such as EQ/Weighting  curves, limits, or prior measurements while running a test sequence, and use it within that test sequence. This feature is useful for measurement comparison to golden units, for comparison to repeated test measurements, and much more.

Recalling Saved Data in SoundCheck

Learn How to Recall Saved Data in SoundCheck

Check out our Recall Data Tutorial (section 9).

More information is also available in the  SoundCheck Manual.

 

Video Script: Recall Saved Data while Running a Sequence

Like every other program, SoundCheck allows you to open up previously saved data and run some sort of offline analysis with it. But, have you ever wondered if it is possible to bring in previously saved data into SoundCheck on the fly while running a sequence?

SoundCheck’s sequence editor comes with a ‘Recall’ step that allows you to import any kind of data – Curves, Values, Results, Waveforms, WAV file or even Text files into the memory list while running a sequence and use the imported data in any subsequent steps in the sequence. This is useful for test engineers in a lot of different ways.

Firstly, if you have previously saved data  like EQ/Weighting  curves, limit values of waveforms that you would like to use, you can bring these into a sequence automatically using the ‘Recall step’. The recalled data  will get populated in the memory list when the sequence is run and can be used in any subsequent steps in the sequence. The recall step can be configured to use an absolute path to the recall data, use a relative path using  automatic template naming option or prompt the operator to select the data for recall.

When exporting a sequence that uses a recall step with an absolute path, Soundcheck will automatically copy the recall data to the export folder and convert the recall path from absolute to relative

The recall step can also be useful to reference a previously saved measurement when you are making repeated test runs. Just to give you an example, if you are measuring passive noise cancellation with different headsets, you could measure the unoccluded ear response only once and in the next run, choose to recall the same unoccluded response curve to analyze with a different headset response. On a production line you might want to compare the speaker under test to a recalled reference or “golden unit” for limit comparison

Personally, I find this to be a very useful tool in troubleshooting sequences. When I do not have the hardware connected to take actual measurements, I use the recall step to simulate acquisition and bring in previously-recorded waveforms so that I can debug subsequent analysis or post processing steps in the sequence.

Overall, the ‘Recall’ Step serves as a multi-purpose utility to bring in previously saved data specific to a sequence, facilitate easy sharing of sequences,  save time when dealing with sequences that take repeated measurements and also help with troubleshooting sequences.

 

 

100 Things #8: Display Multiple Curves on One Graph

In SoundCheck, it’s easy to display multiple curves on one graph – simply drag and drop a set of measurement data, or even a group of data from multiple devices. This saves considerable amounts of time when comparing a batch of devices, or even testing multiple transducers within a device (e.g. microphone array). Watch this short video to see just how easy it is!

Display Multiple Curves on One Graph

Learn More About SoundCheck’s Customization Capabilities

Check out our SoundCheck tutorials on display (section 12)

 

Video Script: Display Multiple Curves on One Graph

Sometimes we take for granted how easy it is to perform certain tasks in SoundCheck until we see how difficult it is using other test systems.

Let’s say I wanted to measure a batch of devices and display the results on a single graph.  Other test systems might require you to go through a multi step process involving exporting, editing and re-importing data But in SoundCheck, all that’s required are a few mouse clicks. Let’s take a look, shall we?

I’m going to measure 5 speakers and show the results on the same graphs. My test sequence measures frequency response and distortion and writes them to SoundCheck’s memory list, and plots each response on their respective graphs. Here is my first measurement.  I have auto-protected the data so it remains in the memory list and doesn’t get over-written when I run the next test. Now let’s measure some more speakers.

As you can see, the data from each additional speaker is automatically added to the graphs so you have a convenient way of comparing devices.

Protected data remains in the Memory List until SoundCheck is closed. When the sequence is closed, the user then has the option to save or discard the protected data as they see fit.

And, like virtually all SoundCheck functionality, this can easily also be incorporated into test sequences for even greater automation.

This convenient functionality has always been available in SoundCheck, right back to the early days when it was just a 2-channel system. Of course with today’s multichannel, multi-transducer devices, it’s more important than ever.