Tag Archive for: limits

100 Things #77: Using Confidence Limits for Sequence Speed and Accuracy

SoundCheck’s Measurement Confidence is a powerful way to qualify factors that may influence measurements, like noise, settling time, latency, and quantization. Using the confidence limits feature in the analysis step, SoundCheck can display measurements along with any measured discrepancies. A sequence’s stimulus can be edited with tons of flexible options, including increasing both cycle count and minimum duration of a Stweep’s steps. Adjusting these stimulus parameters can fine tune your sequence, yielding high measurement confidence.

Using Confidence Limits for Sequence Speed and Accuracy

Learn more about using confidence limits in SoundCheck

Our Working From Home with SoundCheck video series features an even more in-depth demonstration of confidence limits, diving into the trade off between measurement speed and accuracy.

Video Script:

There are many factors that affect measurement accuracy. Noise, settling time, latency, quantization, sampling and other impediments, all affect the quality of your measurements.  SoundCheck’s powerful ‘Measurement Confidence’ tool helps you assess how these factors impact your measurements and helps you fine-tune any trade-offs between speed and accuracy. This feature is found in the HarmonicTrak analysis editor on the Distortion tab.

Let’s focus on noise as the source of our measurement error. SoundCheck’s HarmonicTrak algorithm uses FFT analysis to measure the levels for each step of a stepped sine sweep. The shorter the duration of a step, the larger the width of the FFT filter around its center frequency which allows a greater amount of noise to collect in the filter band.  Noise adds to the sinewave and if you measure it 10 times, you’ll get 10 slightly different results. The standard deviation of the 10 measurements is called the standard error which is directly proportional to the noise collected in the FFT filter and to the duration of the step. By evaluating the level of the noise present in the FFT, SoundCheck is able to give you the standard error at each frequency.

Additionally, SoundCheck can produce limits within which you can expect the true value to lie. These are called Confidence Limits and there’s even a sequence included in your Soundcheck installation which demonstrates this feature. Let’s take a look.

The sequence uses three different Stweep configurations to show how the Confidence feature works. SoundCheck’s stimulus editor gives us precise control over the duration and number of cycles per step in our Stweep. In this example sequence, the first stimulus is configured so that each step contains 3 cycles. In the second stimulus, each step contains 10 cycles and in the third stimulus we add a minimum duration value of 10 ms in addition to the 10 cycle requirement. Let’s run the sequence and take a look at the results.

In sweep 1, the confidence limits are quite wide and drop off dramatically at the low frequency and high frequency where the signal to noise decreases due to the lower levels. It’s no surprise, considering the small number of cycles per step. Increasing the minimum number of cycles to 10 dramatically improves the results.  Confidence is overall very good with the exception of the very high frequencies.  In the last sweep, by introducing a minimum duration requirement of 10ms, we can see a further improvement at high frequencies since we are extending the duration of the steps at the highest frequencies.

I hope that this demo gives you a taste of what you can do with the Measurement Confidence feature in SoundCheck.  There’s a more extensive demo of this feature in our Working From Home with Soundcheck video series and further details in the SoundCheck user manual.

Learn more about SoundCheck features and functionality.

Transitioning Audio Tests from R&D to the Production Line

Steve Temme discusses the transition from R&D to production testing in this March 2023 issue of AudioXpress. Production line audio testing poses many challenges such as noisy environments, harsh operating conditions, high throughput, relative limits, and more. In this article, Steve Temme shares his observations and outlines the main considerations to ensure a successful operation.

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Introduction to Production Line Audio Testing Article

Your product design is finalized, your prototypes are close to perfect, and your audio product is ready to move to production. But how do you ensure that the product hitting the retail shelves sounds exactly as you intended?
Your production line is probably thousands of miles away, with time zone and language complications. Pandemic-related restrictions make it hard to visit to configure, supervise, and train factory personnel. Furthermore, production is often outsourced to a contract manufacturer, adding another layer of complexity to both culture and information transfer.
Every production facility has one priority: to build products that meet the specifications with the greatest efficiency and highest yield possible for optimum profitability. Think about what that means for end-of-line tests. Their goal is to have as many units pass as possible. Tests must be fast to avoid slowing down the production line, and the test environment is generally noisy, often with variable temperature and humidity. The quest for high yields and manufacturing efficiency, along with challenging operating conditions and sometimes poor training, can result in unreliable measurements. When this happens, the only loser is you and your brand’s reputation.
I’ll never forget being told about a production line operator who increased pass-rate by opening the test box during measurements so that the factory background noise would mask the high-order harmonics to fool the perceptual Rub & Buzz algorithm. This might improve his yield, but it’s not so good when these products ship to customers! While this is one of the more outrageous violations of end-of-line test protocol, I have also seen many other questionable measurement practices over the years. In this article, I’ll try to de-mystify production tests and look at some simple measures that you can take to ensure a smooth transition.

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21: Limits (working from home with SoundCheck)

While you are working from home, optimize your SoundCheck sequences by tweaking your limits for optimum quality and yield. Devin Vaillancourt explains the different types of limits available (absolute, floating, aligned, and more), and once you have explored the different types, you can test out different limit configurations using saved data from products that you have already measured.