100 Things #82: Measuring Audio Leakage From A VR Headset

Virtual Reality Headsets may be new to the market, but users already expect excellent sound quality to enhance the immersive experience. SoundCheck’s flexibility means you can measure almost any device including VR headsets, by leveraging it’s step-based sequence functionality. VR headset measurements can be made with the same parameters as any other headset; frequency response, perceptual distortion, phase, and more. With the addition of the MDT-4000 turntable, headset audio leakage can be measured to better quantify what people nearby would hear from a user’s VR headset.

Measuring Audio Leakage From A VR Headset

Try VR headset measurements for yourself

Our pre-written VR Headset Leakage Measurement sequence takes the guesswork out of VR headset measurements, with commands pre-programmed to work with the PT&D MDT-4000 turntable.

Video Script:

Virtual Reality and Augmented reality headset measurements are made in pretty much the same way as other headphone and headset measurements. However, one thing to be aware of is that VR and AR headsets often have the speakers located in the headband. This means that you need to use a head and torso simulator where the speaker can be in a realistic position relative to the ear, rather than lower cost couplers or headphone test jigs that rely on the headphone sitting directly in, or on the fixture to create a tight seal. 

With this setup, you can use any of our standard headphone test sequences to measure frequency response, phase, distortion, impedance, sensitivity and other parameters.

Another measurement that is particularly useful for virtual reality headset characterization is headset leakage. With the speakers unoccluded on the headband – not sealed on the ear canal –  there can be considerable acoustic leakage, and designers try to minimize the noise emanating from the device so as not to annoy other listeners nearby. 

Here, we’ll use a measurement microphone to simulate what the nearby listener hears from the person wearing the VR headset and a turntable to produce a polar plot showing the level of leakage from the VR headset versus angle. You can set the microphone position to whatever distance you want to measure, and define the test level. When we run the sequence, it plays a test signal and the microphone records the acoustic leakage. The turntable then rotates through 10 degrees and re-measures. We repeat this through 180 degrees, and mirror the results to get a full 360 degrees plot. This test sequence also shows the frequency response at each angle. This sequence is available free of charge on our website if you want to try it out.

Headphone Measurements Demonstrations

In this short video, Steve Temme demonstrates two different headphone measurements with SoundCheck.

In the first demo, he measures a pair of Bluetooth earbuds in an open loop test to obtain frequency response, left/right tracking, THD and sensitivity. He also measures frequency response and sensitivity for the built-in microphone. In the second demonstration, he measures both active and passive noise cancellation of a pair of over the ear headphones with pink noise and speech.

These measurements are made with SoundCheck, the AudioConnect audio interface and the PQC-4149 Bluetooth interface. The SoundCheck test sequences to run these tests are available free of charge on our website.

Headphone measurements demonstrated include:

  • Headphone frequency response
  • Headphone left/right tracking (L/R tracking)
  • Total Harmonic Distortion (THD)
  • Sensitivity
  • Microphone frequency response
  • Microphone sensitivity
  • Active noise cancellation with pink noise and speech
  • Passive noise cancellation with pink noise and speech
  • Total noise cancellation with pink noise and speech

Presenter: Steve Temme
Duration: 10 Mins

Headphone Measurement Resources

Learn more about our headphone complete test sequence (available in the sequences folder of your SoundCheck installation).

Try our ANC Headphone measurement test sequence

Check out our main pages on Headphone Testing, Bluetooth Headphone Testing and ANC Headphone measurements, which includes links to test sequences, relevant products and more.

 

 

100 Things #67: Measuring Active and Passive Noise Cancellation for Hearing Protection

SoundCheck makes testing to standards simple by automating precise measurements into a single sequence. In this test sequence hearing protection devices can be tested to the ANSI S3.19-1974 standard to find their NRR rating. Sequences in SoundCheck make testing simple, with message steps instructing operators when interaction is needed with removing or placing hearing protection DUTs, for example. ListenInc.com features an extensive list of pre-written test sequences for any application including noise protection devices, hearing aids, bluetooth devices, and more.

Measuring Active and Passive Noise Cancellation for Hearing Protection

Try our hearing protection sequence for yourself

The hearing protection measurement sequence featured in this video is available in our sequence library.

Video Script:

Did you know that you can test hearing protection devices to industry standards using SoundCheck? Let’s take a look. 

Hearing protection devices are often measured to the ANSI S3.19-1974 standard which measures the Noise Reduction Rating or NRR of the device. This rating is a numerical representation of the device’s sound attenuation.

Our test sequence first measures the response spectrum of the unoccluded hearing protector test fixture, then makes a second measurement with the hearing protection DUT affixed. SoundCheck’s signal generator generates the pink noise stimulus while its Real Time Analyzer simultaneously records the A and C weighted noise spectrums. The unoccluded and occluded measurements are analyzed with a series of post-processing steps according to the ANSI S3.19-1974 standard. The final display shows the NRR numerical value, RTA spectra of the left and right side of the unoccluded and occluded hearing test fixture, average attenuation level of the DUT, and the standard deviation of the DUT on the test fixture.  The sequence prompts the user to recall previously saved unoccluded measurements and standard deviation values, saving time if the test fixture and DUT have been measured previously. When a new unoccluded measurement is taken, the user can save these measurements for a future data recall. 

We have many SoundCheck test sequences written by experts to  save hours of time writing them yourself. Most of these, including this NRR sequence, are free to use and come with well written step-by-step instructions.

100 Things #57: Measuring Headphone Active Noise Cancellation in Real Time

Active Noise Cancellation technology is more advanced than ever, and SoundCheck is well-equipped with all the features needed for measuring headphone active noise cancellation. We have a pre-written test sequence to measure all aspects of noise cancellation including passive, active, and total noise attenuation. This sequence is a great fully complete test, or you can use it as a template to expand your test setup to include multiple background noise sources, or add an additional microphone for an even more detailed test of how the ANC circuit responds to dynamic signals.

Measuring Headphone Active Noise Cancellation in Real Time

Try ANC headphone measurements for yourself

Find our free sequence for measuring Noise-Cancelling Headphones here. This sequence first measures the passive attenuation of the headphones, then the active attenuation, and finally calculates the total attenuation.

Video Script:

Did you know you can measure headphone Active Noise Cancellation with SoundCheck, as well as standard acoustic tests such as frequency response and distortion? When measuring noise canceling headphones there are three important measurements to make: passive attenuation, active attenuation, and total attenuation. Passive Attenuation is the amount of noise the headphones block without ANC enabled. Active Attenuation is the amount of noise ANC blocks out. Total Attenuation is the combination of the two measurements.

We even have a pre-written sequence showing off this functionality, called Noise Canceling Headphones, available on our website. You will need a Head and Torso Simulator (HATS) or an acoustic ear simulator with an artificial pinna, at least one speaker for background noise generation, and a set of headphones with ANC.

The first measurement is taken without headphones on the HATS, the unoccluded measurement. The pink noise stimulus is played out of the speakers, and the signal from the HATS is recorded. Next, the sequence pauses while the operator places the headphones on the HATS, then makes the occluded measurement. The sequence again pauses for the operator to enable the headphone’s active noise cancellation, and The third measurement is taken, and the results are calculated.

This test can be modified to work with a diffuse, multi-speaker configuration, and in an environment with two or more speakers, both ears could be measured at the same time. Our new AmpConnect 621 interface has six inputs, and two outputs so you can even measure both the left and right channel simultaneously, while also generating stereo background noise. Using SoundCheck’s new Multichannel RTA, you can measure the acoustic seal  of both the left and right headphone channels simultaneously, and even visualize it in real time. Also, with the Multi-RTA and an external reference measurement microphone positioned immediately next to the outside of the headphone, you can play any complex signal you like out of the source speaker(s) such as real recorded background noise from an airplane and watch in real time how the noise attenuation changes. This is a more realistic representation of how the ANC circuit responds to dynamic signals.  

There are many ways you can modify this sequence, for example, instead of playing out of one source speaker, play out of multiple equalized source speakers to create a more realistic spatial background noise environment. With the new Signal generator’s delay offset feature, this is much easier to do.

How do you measure active noise cancellation? And what are your favorite noise-canceling headphones? Let us know in the comments below! And for more information on all things SoundCheck, head to our website at ListenInc.com.

100 Things #41: Easily Measure Headphones to EN 50332 with a Pre-written Sequence

We provide many pre-written sequences for testing to standards across many applications, including a suite of sequences testing to the EN 50332 Standard. This test suite consists of two parts to accurately measure the device and included headphones, together and separately. All of the sequence development work has been done, saving your hours of sequence writing. These sequences also include operator instructions, making headphone adjustments on a head and torso simulator easy. You can test in confidence knowing this sequence suite includes everything you need to get up and running fast.

Easily Measure Headphones to EN 50332 with a Pre-written Sequence

Try EN 50332 for yourself

We offer two sequences testing to the EN 50332 standard: EN 50332-1 and EN 50332-2. These sequences are pre-written and ready to run.

Video Script:

Did you know we offer a test sequence for measuring headphones headphones and earphones associated with portable audio equipment to the European standard, EN50332?

This standard specifies the maximum sound pressure level and input / output voltage measurements for portable audio playback devices. These characteristics are usually evaluated at the design and engineering stage as compliance is mandatory in many countries.

Our off-the-shelf test sequence saves hours of development time, and ensures that measurements  are correctly made.

The standard consists of two parts.

Part 1 measures the portable music players together with the headphones they are bundled with. In this measurement, we load an IEC 268 weighted pink noise stimulus file onto the portable device and play it through the earphones at maximum volume. 

The earphones are positioned on a head and torso simulator, or HATS. We record the signal from each ear, and a 1/3rd octave curve is analyzed. A-weighting and free field correction for the HATS are applied, the values between 20 Hz and 20 kHz summed, and the A-weighted equivalent sound pressure level is calculated.

The sequence runs 5 times, with the headphones repositioned between each measurement to average out any variability in the fit and sealing of the device under test. We average these measurements to calculate the final LA eq values.

In part 2, the portable device and the headphones are measured separately. 

To test the music player, we load a weighted pink noise stimulus file onto the portable device and play it through the headphone jack connected to a 32 ohm load at maximum volume. The RMS voltage is averaged over 30 seconds, and the result must be less than 150 mV.

The headphone test is a little more complex. We connect the headphones to an amplifier with less than 2 ohms output impedance. The amplifier’s outputs are split, connecting one side to the headphone and the other directly to the audio interface. This lets us measure the voltage at the headphone while the amplifier is under load. You can see here we are using the AmpConnect 621 audio interface as we need at least 4 inputs – 2 are connected to the amplifier outputs and the other two to the HATS ears via the microphone preamps.

First the electrical loopback from the amplifier is used to measure the amp’s gain using the IEC weighted pink noise file, and this is used as calibration data for the subsequent measurements.

We then put headphones on the HATS and play noise while monitoring the signal through the ears on the multimeters to position the headphones for maximum output.

Next, we play IEC weighted pink noise at 50 mV while the signal from each ear is recorded, and a 1/3rd octave curve is analyzed. As before, A-weighting and free field corrections are applied and the values summed from 20 Hz to 20 kHz to indicate the overall weighted sound pressure level. 

Finally, the ratio between stimulus level and sound pressure level is used to calculate the stimulus level required to produce 94 dBSPL at the ears. This value, the wide band characteristic voltage or WBCV, must be greater than 75mV to comply with the standard.

So that’s how easy it is. You could of course program this from scratch yourself in SoundCheck, but the pre-written sequence will save you hours!

100 Things #38: Digital Measurements – USB Headphones & Microphones

SoundCheck’s testing capabilities go beyond the analog domain. It has always been able to measure digital devices and make both analog and digital domain audio measurements simultaneously on different channels. The digital inputs and outputs inside SoundCheck are easily configured to measure USB Headsets, MEMS microphones and so on. Watch this short video to learn more.

Measuring Digital Devices with SoundCheck

Learn More About SoundCheck’s Signal Generator and other Virtual Instruments

Check out our pre-written test sequence on measuring digital MEMS microphones

 

Video Script: Measuring Digital Devices such as USB Headphones & Microphones in SoundCheck

When we talk about measuring traditional transducers such as microphones and loudspeakers, we are measuring analog devices that respond to voltage and pressure. Nowadays, most microphones and loudspeakers have become quasi analog/digital devices because their analog signals are immediately transformed into the digital domain built into the design and transducer package.  With digital devices dominating the consumer electronics market today, have you wondered if you can set up digital inputs and outputs inside SoundCheck to measure USB Headsets, MEMS microphones and so on? The answer is yes.

SoundCheck supports both analog and digital inputs and outputs for measurement. Setting up digital inputs and outputs is very straightforward. All you need to do is create a new digital channel on your Hardware editor, set it to  input or output and select the appropriate digital calibration reference e.g. AES-17 when configuring the signal path inside the calibration editor. It is as simple as that and you should be ready to use your connected digital device to make audio measurements.

The digital interface can be as simple as a USB headset plugged in directly to your computer or a device plugged into a supported audio interface, or as complex as a bunch of MEMS microphones going through a digital circuit board before interfacing with the test system. You can also use a USB headphone as an input monitor if your audio interface doesn’t have one, and analog and digital inputs and outputs can be used simultaneously.

SoundCheck offers great flexibility for testing both analog and digital devices. If you’d like to take a closer look at how this works, please contact your sales engineer for a demo.

 

 

100 Things #33: Comparing Measured Data to a Target Curve

You can import any target curve into SoundCheck. This enables quick and easy comparison of your measured data to any reference data.

Comparing Measured Data to Target Curves in SoundCheck

More Target Curve Resources

To see an example of using Target Curves in SoundCheck, take a look at the work we’ve done with the Harman Target Curve. This page also links to the sequence that you can download to use with SoundCheck.

 

Video Script: Comparing Measured Data to Target Curves

Did you know that you can import any target curve in SoundCheck? This lets you compare your measured data to any reference data, fast and easy.

This functionality is simple to use – simply import the curve into the memory list and from there, use it in a sequence or drag and drop it onto any graph.

One of the simplest examples of this capability is to compare measured results to a golden unit.  All you have to do is  import the data from the golden unit into the memory list, then plot it on the same graph as the measured unit. You can use mathematical functions to statistically compare the curves, or you can use the curve offset by a fixed dB level, and use it as a limit.

Another example is live tuning. Matching a frequency response and sound pressure level is a common audio test, from measuring loudspeakers in a shop environment to tuning an automotive infotainment system. In these tests, you can compare RTA generated live curves to the imported target curve, and adjust the microphone location or manipulate the sound source in real time to match the target curve.

We also offer a more advanced application of target curves in a free test sequence that calculates a listener preference rating for headphones based on the Harman Target curve, developed by Sean Olive. This sequence measures the frequency response of your headphones and calculates an error curve, which is derived from subtracting the Harman Target Curve from an average of the headphone left/right response. The standard deviation, slope and average of the Error curve are used to calculate the predicted preference score.

So whether you are performing real-time measurements with live curves, setting limits based on golden units, or predicting listener preference of headphones, SoundCheck’s curve-importing capability makes your audio testing easier.

 

 

 

 

 

100 Things #26: Production Line Polarity Measurement

SoundCheck offers a rapid production line polarity measurement that can identify correct wiring at the same time as other production line acoustic tests. This is valuable as the conventional method of polarity measurement –  determining if a diaphragm moves outward or inward when voltage is applied – is not practical on the production line.

Production Line Polarity Measurement in SoundCheck

Learn How to Measure Polarity in SoundCheck

Check out our knowledgebase article on Polarity Measurement.

More information is also available in the  SoundCheck Manual.

 

Video Script: Production Line Polarity Measurement

Having the proper polarity marking or wiring is a critical requirement for any transducer, particularly those that are used in conjunction with others.  If there are errors in wiring or terminal markings, the intended performance of the transducer and how it interacts with other transducers in a system can be compromised.

The simplest test for polarity might be applying a DC voltage to a speaker and determining if its diaphragm moves outward or inward as the voltage is applied.  If everything is wired or marked correctly, we would expect the diaphragm to respond with an outward motion when a positive voltage is applied.  While this method is simple and accurate, it is not practical for production line test.

For production line testing, SoundCheck has a couple of useful methods for polarity detection. The first option is to place limits on the phase response curve of the device under test. Since the phase response changes by 180 degrees when the polarity changes, this can be an accurate method for polarity detection. The other option is to enable the Polarity check box which can be found on the Time tab of most of SC’s analysis editors.  Once enabled, every time the Analysis step is applied, SC will calculate an impulse response of the current measurement. The impulse response is then analyzed to determine if the largest peak has a positive or negative value.  If positive, a value of 1 will be generated into the Memory List, if negative, a value of -1 will be generated into the Memory List. A limit can then be applied to this value to create a Pass/Fail verdict in the ML Results tab.

These polarity detection options have been available in SC since 2011 and provide the user with two accurate methods for measuring the polarity of your transducer.

 

 

 

100 Things #10: Low Cost Audio Measurement with SoundCheck ONE

SoundCheck’s low cost audio measurement software, SoundCheck One, is a budget-friendly solution for basic audio tests. It is simple to use with sequence templates to quickly test simple devices such as headphone, microphones and speakers. Using the same advanced algorithms as the regular version of SoundCheck, it is fully compatible with the regular version, and may be upgraded at any time.

Low Cost Audio Measurement with SoundCheck ONE

Learn more about SoundCheck ONE

SoundCheck Packages and Modules

 

Video Script: Low Cost Audio Measurement with SoundCheck ONE

SoundCheck One is an entry level SoundCheck package designed for basic transducer measurements. It is low-cost and easy to use, making it ideal for production, end-of-line testing and benchmarking applications.

Under the hood it features the same unique algorithms and advanced test methods as the full version of SoundCheck; the difference is in the user-interface.

SoundCheck ONE is supplied as a complete package including software and an audio interface – either an AmpConnect ISC or AudioConnect. Instead of SoundCheck’s sequence editor for test development, pre-configured test templates for speakers, headphones and microphones are provided.

Each template contains all the typical measurements for those devices. The tests themselves cannot be edited but individual steps can. For example frequency range, levels and limits can be modified and measurements toggled on or off to generate product-specific sequences. This makes it fast and easy to configure basic tests that can be deployed across multiple products.

Because SoundCheck ONE uses the same data format as full-featured versions, its curves, waveforms and results can be shared for deeper analysis with users who might have an advanced license.

At approximately half the price of a regular SoundCheck system, SoundCheck ONE is a great entry-level option. While it doesn’t offer the limitless flexibility of the full versions of SoundCheck, its template-based approach makes it extremely simple to configure and use.

Furthermore, because the SoundCheck platform is modular, your investment is not wasted if future testing demands more flexibility. SoundCheck ONE can be upgraded to a more advanced SoundCheck package with full sequence development capabilities at any time. The test sequences will continue to work on the upgraded system, where they can be expanded and developed to meet all your measurement challenges.

 

 

 

 

Advanced Headphone Test Seminar

In this online seminar, Listen, Inc. founder and president, Steve Temme discusses Advanced Headphone Tests. Modern devices have more complexity than ever, including connectivity, noise cancellation, and measurement standards. This seminar will show important measurement considerations, examples, and strategies to perform a modern headphone test.

Seminar topics include:

  • Measurement Standards e.g. IEC 60268-7
  • Measuring USB and Bluetooth headsets including True Wireless Stereo (TWS) headphones/headsets
  • Measuring headphone and headset microphones (including Send performance)
  • Measuring Active Noise Cancellation (ANC)
  • Voice activation and Open Loop measurements
  • Distortion measurement methods including Non-coherent Distortion
  • Measurement considerations for AR & Hi-Res

Presenters: Steve Temme
Duration: 52 Mins

Headphone test resources

Our pre-written sequence for measuring Active Noise Cancellation can be found in our sequence library. This library includes a sequence for testing stereo headphones connected to a portable audio device using open loop measurements.

We also offer tests to measurement standards in our sequence library, like the IEC 60268-7 headphone test sequence. More information about the ANSI IEC 60268-7 standard can be found from the official ANSI site.

More about headphone tests

Check out our main page on Headphone and Headset tests, which includes links to test sequences, relevant products and more.