Technical Resources
With over 100 combined years of audio measurement experience, our team has created a wealth of technical papers, sequences, articles and other useful information to assist you with your audio test needs. Please browse the collection below, or filter by type of resource.
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.
VR Headset Leakage Measurement Sequence
VR headset leakage measurement is a useful parameter for VR headset characterization. While they are sometimes connected to headphones, most VR headsets also contain built-in speakers, often on the strap close to the ear. These small speakers often have considerable audio leakage due to their positioning on the band, where there is some transmission through air before reaching the ear. This is annoying to others in the room, so efforts are made to minimize this.
For this measurement, the headset is positioned on a head and torso simulator mounted on a turntable, and a log sweep played from 20Hz-20kHz at user-defined level and distance. The sequence measures leakage and frequency response for one ear in 10° increments from 0 to 180°, and mirrors it to provide a complete 360° polar plot. The final display produces a polar plot for four frequencies, and all eighteen measurements are shown on a frequency response graph.
100 Things #76: Using SoundCheck to Test Communications Devices
Modern devices let us communicate with each other more than ever, in new and exciting ways. Telecommunications devices have evolved, so have the methods to test them. Today’s communications standards test the functionality of devices connected via USB, Bluetooth, and the cloud. SoundCheck facilitates testing these devices with the ability to connect to multiple devices with different hardware connectivity. Configuring SoundCheck to run these often complex test sequences saves time, allowing the whole test to run without operator interruption.
Using SoundCheck to Test Communications Devices
Watch more
Our full Communications Testing seminar features Listen president Steve Temme and Communications Consultant John Bareham giving a deep dive on tests like Doubletalk, TIA-5050, POLQA, TIA-920B
Learn more about using SoundCheck for communications tests
Our main page on communications testing details the benefit of using SoundCheck for telecommunication tests, possible measurements, communications test configurations, and pre-written sequences testing to standards like TIA 920-B, ETSI ES 202 396-1, and more.
Video Script:
You know that SoundCheck measures acoustic parameters, but did you know that you can also implement industry-standard tests on a wide range of communications devices?
Speech communication always involves talking and listening. Today we frequently communicate using various consumer electronic devices such as headphones, hearables, smart glasses, watches, smart speakers, intercom systems, 2-way radios and, of course, smartphones.
To accommodate this shift, industry-standard communications tests have evolved from tests on old-fashioned wired “telephones” to more sophisticated tests on these more complex devices. These devices also connect in different ways, including USB, Bluetooth, and the cloud.
Although it’s often not required to test these devices to industry standards, it’s very worthwhile to make these measurements from a product performance perspective, especially if you anticipate needing to pass 3rd party verification.
With SoundCheck, you can measure voice quality performance to TIA, ETSI and other standards. It’s easy to test via direct connection, USB, or a Bluetooth interface. Seamless integration with your computer’s audio also makes it easy to route signals between the device, the cloud, and your computer for open loop measurements.
Several features recently introduced in SoundCheck facilitate more advanced communications tests, such as Active Speech level, RMS level versus time, silence stimulus step and histogram post-processing steps. These support measurement of Doubletalk, echo detection, background noise evaluation, and more. The optional POLQA module also enables speech quality analysis using the POLQA algorithm directly within SoundCheck.
Standardized communications test sequences can be very complex, and SoundCheck contains all the functionality to create these tests. We also offer shortcuts with our pre-written test sequences for TIA-920-B, TIA-5050, and Doubletalk to ITU-T P.502 and ETSI TS 126132. These complex test sequences automatically implement entire tests according to the standards, saving considerable development time, and ensuring that measurements are made correctly.
All these tests are fully demonstrated. in Listen’s communications seminar – check it out to learn more.
100 Things #75: Test Automotive Audio via A2B Interfaces
SoundCheck features full integration with A2B interfaces, allowing seamless audio measurements with all of SoundCheck’s features and functionality. A2B interfaces connect to SoundCheck using an ASIO stream, which appears in the hardware table just like any other audio device. A2B devices are great for automotive infotainment systems as they are lightweight and easily configured, replacing traditional heavy copper wiring. A custom VI in SoundCheck even allows for A2B interface configuration during a sequence.
Test Automotive Audio via A2B Interfaces
Learn more about using testing automotive audio with SoundCheck
Learn more about connecting to automotive infotainment systems, and using SoundCheck for testing automotive audio, infotainment systems, active road noise cancellation, and more.
Video Script:
Did you know that SoundCheck can be used to test audio devices using the A2B interface? A2B is a high bandwidth, bidirectional, digital audio bus. It transports data, and controls information, clock and power, using a single, 2-wire unshielded twisted pair cable. A2B was developed for automotive applications, replacing heavy copper wire in vehicles with an easy to configure, lightweight system. But it has expanded to be used in other applications, such as distributed audio. For example A2B could be used to wire speakers and microphones used in an office conference room.
SoundCheck can access the audio streams of A2B audio interfaces, such as those from Mentor or Analog devices. Once the A2B configuration is set using the third party setup, ASIO streams can be selected in SoundCheck’s hardware table and used to test an audio components such as hands-free microphones. I’m using the Analog Devices A2B Soundcard connected to nodes with 4 PDM microphones. I can configure my current setup using Sigma Studio. Once that is done, I select “Link Compile Download” in Sigma Studio. This sends the project configuration I made to all my connected devices.
Now in SoundCheck, I’m able to go to Setup > Hardware, and choose the Analog Devices A2B SoundCard ASIO stream as my audio interface. Now that this is setup, I can get data in and out of the A2B interface just like any other audio interface. This means I can use SoundCheck to test all components of an infotainment system or A2B based distributed audio system, ranging from speakers and microphones to more complex communications and voice recognition tests.
100 Things #74: Easily Save Measurements in Any Format
SoundCheck offers flexible options for data processing, allowing measurement data to be saved in a variety of formats. For fast and reliable operation, saving data can be automated with autosave steps in a sequence. SoundCheck can save measurements to a .tdms file for including important metadata with your measurements, Excel for reporting test data and comparing results, text files for lightweight information transfers. and more. All of SoundCheck’s data including waveforms, results, curves, values can be saved in various formats.
Easily Save Measurements in Any Format
Learn more about saving data in different formats in SoundCheck
Learn more about supported data formats in SoundCheck for R&D, Production, and more.
Video Script:
It’s often useful to save your SoundCheck measurement data for statistical analysis, offline post processing, sharing with others, or saving to a database. SoundCheck offers multiple ways to easily save measurement data in many different formats. Let’s take a look!
When you’re running a SoundCheck sequence, the memory list manages all the data generated. This includes curves, values, limit results and waveforms. This measurement data can be manually saved by right clicking the item in the SoundCheck’s memory list.
Curves, Values and Results can be saved as .dat (SoundCheck’s native binary data format), .txt, .MAT – that’s a MatLab file, or .TDMS – that’s National Instruments’ structured binary file format. Multiple items can be selected and saved into a single file.
From the WFM tab, waveform data can also be saved directly as .wav, .wfm (SoundCheck’s native waveform), .txt, .MAT and .TDMS.
.TDMS is a new file format supported in SoundCheck 21 and later. TDMS not only supports system and user metadata, but the data is also a fast binary format, minimizing read and write times when a sequence is running. It can also be opened in Excel and Matlab using a converter plugin.
If you use SoundMap, SoundCheck’s time frequency analysis option, you can even save time frequency data directly to a .mat file for further analysis in MATLAB.
Naturally, saving data in a SoundCheck sequence can be automated. An autosave step in your sequence lets you automatically save to any of the formats I just demonstrated, plus an SQL database, and Excel. This makes saving data with each run of your sequence automatic, fast and easy. If you’re familiar with the WATS Test Data Management software, we’ve even developed a utility to convert SoundCheck generated text files directly into WATS for further analytics and process management.
So, as you can see, SoundCheck is supremely flexible when it comes to working with your existing lab or production line workflows, whether you’re someone who likes to run your own calculations and analytics in Matlab or Excel, or when you need fast, automated writing to your own custom database. For more details, check out the instructional videos on saving data in our “Tutorials” playlist.
100 Things #73: Active Speech Level Control in SoundCheck
SoundCheck’s incorporation of active speech level allows for stimulus to conform with telephony testing standards. This means testing to IEEE and TIA standards can be automated within a sequence, allowing an entire test to be run without operator intervention. Active speech level is incorporated directly into SoundCheck’s stimulus step, and becomes available when selecting dB RMS. Active speech level can also be used for setting voice activation levels or wake word testing for smart devices.
Active Speech Level Control in SoundCheck
Learn more about active speech level in SoundCheck
Our Telephones application page details all of the benefits of using SoundCheck to test your communications devices.
Video Script:
Did you know that SoundCheck offers Active Speech level control in both the stimulus editor and post-processing?
Many telephony standards such as IEEE and TIA specify speech stimulus levels in terms of active speech level, or ASL. It can also be used for setting voice activation levels or wake word testing for smart devices.
When active speech level is used, signal levels are scaled using only the parts of the waveform where speech is actually present, rather than the overall RMS level. Silent gaps are excluded but utterances that are part of normal speech are included. This removes variability due to different speaking speeds and content when making measurements, and provides better consistency for standardized measurements.
Configuring ASL in SoundCheck is easy. Let’s take a look.
If you’re testing with speech, you’ll be loading a speech file as a WAV file stimulus. Simply select the file, or open it from the memory list. In the level drop-down, select dB RMS and this will enable the ASL checkbox. Make sure the ASL checkbox is selected, and set the level of your stimulus.
ASL is also available as a post-processing step. Here, you have some additional parameters. You can adjust the Time Constant – that’s the time constant of the exponential averaging used to measure the level of active speech . You can modify the Hangover Time – that’s the allowable time for silence between utterances, 200ms is the default. And you can also set the Margin – that’s the difference between threshold of activity and the active speech level. This is useful because if the background noise is high, you can reduce the margin to exclude the noise.
When you are using Active speech level in post-processing, The ASL value in the Memory List displays the Percentage of time during the waveform where speech is active, the mean power of speech measured over the aggregate time of activity and the mean power of the waveform measured over its entire duration.
Active Speech Level is an optional module, and can be added to any SoundCheck system.
100 Things #72: Transient Distortion Analysis With enhanced Loose Particles
Listen’s enhanced Loose Particles algorithm measures transient distortion independently of harmonic distortion, with correlation to human hearing and offering high accuracy, easy perception, and fast analysis. eLP is ideal for identifying transient distortion in any environment, like identifying rattling buttons in audio devices, and automotive Buzz, Squeak and Rattle (BSR) measurements. SoundCheck sequences can quantify measurements into an eLP event count, making limit setting reliable in production environments.
Measure transient distortion independently from Rub & Buzz distortion
Try it Yourself
You can try this algorithm for yourself! Visit our enhanced Loose Particles page for all things eLP including methodology, algorithm research, and more
Learn more about enhanced Loose Particles
Listen founder and president Steve Temme, and support manager Steve Tatarunis, co-wrote a technical article on practical impedance measurement. The paper dives into both single channel and dual channel measurement methods, considerations, techniques, measuring thiele-small parameters, and more.
Video Script:
Did you know that SoundCheck’s new enhanced Loose Particle algorithm measures transient distortion independently of harmonic or Rub & Buzz distortion? This has many applications ranging from production line driver testing to detecting rattling buttons, wires, fasteners and other loose parts being vibrated by the loudspeaker driver, for example, in a car door or smart speaker.
This is really useful to help you find the root cause of many production line problems. It’s also really easy to correlate with what you hear. Let’s take a look.
This is a very simple set-up I have here, pretty much what you might use on a production line – a measurement microphone, SoundCheck, and an AmpConnect 621 audio interface with a built-in amplifier. I have 2 loudspeakers, a good one, and one that exhibits significant transient distortion.
Here’s the good one…
And here’s the bad one…
Let’s look at how our new enhanced loose particle algorithm analyzes them.
This one’s the good speaker. You can see a nice smooth response waveform.
And here’s the speaker with transient distortion – this actually has a loose solder bead trapped inside the voice coil gap. You can see these little glitches on the waveform, that’s the rattling solder bead.
In the first step of our algorithm, we remove the fundamental, leaving just the distortion artifacts. And we can play this through SoundCheck to listen to the recorded artifacts and correlate what you hear to the measured results. Here’s the good speaker… and here’s the bad one…. This really helps us understand how the measurement relates to what we hear, and helps us set limits.
Next we apply an envelope analysis to get a time domain measurement… you can see the energy in the recorded waveform, plotted against time. You can see the transient defects as random bursts of energy. And you can also see that we have a lot more defects in the bad-sounding speaker than the good one.
Now we calculate the Prominence of each of these energy bursts. In this context, prominence describes the magnitude of the peak relative to the adjacent minimums. It’s actually an established mathematical concept used in other branches of science, but we’re the first to apply this concept to audio measurements. This was actually the result of extensive research at Listen, in which we determined that the prominence of a peak reflects the impulsiveness of the distortion artifacts more accurately than the absolute magnitude of the peaks.
So, calculating the prominence results in a numerical magnitude for each event in the time envelope, and we then set a threshold – that’s the level above which the event will be counted as a transient artifact. I’m using 10dB – this is generally a good starting point, although it varies depending on the acceptable distortion for the product. And remember, to help with setting limits you can play back the filtered artifact waveform to correlate the prominence level with audibility.
Finally, we count the number of events that exceed the threshold over the measurement duration – you can see that the Loose Particle count for the bad speaker is 110, compared to 0 for the good speaker.
We use the loose particle count to set a pass/fail limit. This gives us reliable results under a variety of conditions because, in a typical fast production measurement, background noise events typically only occur once or twice compared to many loose particle transients. So as long as you set the limit according to your environment, you can always get reliable results.
So there we have it! This new transient distortion measurement, accurately and reliably detects transient distortion, analyzing it separately from harmonic and rub & buzz distortion. It’s accurate even with background noise, and easy to correlate to audibility. Limit-setting is easier than with other methods, and it also works well in applications beyond driver testing such as Buzz Squeak and Rattle measurements in cars, and rattling components in audio devices.
100 Things #70: Make Smarter Tests with Sequence Logic
SoundCheck has sequence logic integration through every step. The ability to use If/Then logic with sequence steps means sequences expand beyond a linear path. Loops are easily created, perfect for using turntables to create polar plots. Incrementing and measuring level increases means it’s easy to automate testing devices to specific SPL, distortion, and perceptual distortion levels. Conditional branching can also help production line efficiency, where operators can be guided through calibration procedures if DUTs change.
Make Smarter Tests with Sequence Logic
Learn more about sequence logic in SoundCheck
If you want to see sequence logic in action, check out conditional branching in our pre-written M-Noise sequence.
Video Script:
Conditional branching is a powerful tool that lets you alter the order of step execution in the sequence based on the pass or fail status of a particular step. Using sequence logic in this way offers unrivaled flexibility in complex sequences.
If we right click on any step in our sequence, we can see a variety of options within the configuration window. These two options, Jump on Pass and Jump on Fail, let us use conditional branching and looping within our sequence. From the dropdown, we can select any other step for the current step to jump on pass or fail to. This can be used to skip particular sections of the sequence, or even to create loops.
For example, if I am measuring the frequency response of a loudspeaker, I can configure the Analysis step to “jump on pass” back to our stimulus step. I can then define the loop to last for a certain amount of repetitions and then end the loop. So here I could say after 4 repetitions, jump to my final display. This will give us a total of 5 runs through our stimulus and acquisition.
Every time the loop occurs, our index will increment. This can be used to simply track the number of times the sequence has looped. It will start at 0, then increase by 1. But we can reference this value in other steps in the sequence. I could define a starting level, and then increment that level by 3dB on each one of our loops. I’ll point to this value in the stimulus step, and now when I run my sequence I play the signal out 5 times, each time increasing the level by 3dB.
Conditional branching can also be used to jump around entire sections of sequences. For example, the sequence could ask the operator if they need to run a pre-conditioning test and jump accordingly. Another application would be to check for a signal near the beginning of a long sequence and if it fails then jump to a message step that warns the user that no signal was detected instead of running the entire sequence.. This way, the operator doesn’t waste time testing a bad device, and different autosave steps can be used to mark the data as a failure.
