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Bluetooth Headset Test Sequence

The purpose of this sequence is to test a Bluetooth headset using a mixture of analog and digital channels. First, a Multitone stimulus is created with SoundCheck, played back over the Bluetooth headset (at 8 kHz) and recorded by a head and torso simulator’s ear (at 44.1 kHz). Then the same Multitone stimulus is played back through the head and torso’s mouth simulator (at 44.1 kHz) and recorded via the Bluetooth headset (at 8 kHz).

Due to inaccuracies of clock frequency, the Bluetooth device playback sampling rate is often slightly different than it is specified. Therefore, in SoundCheck, the Recorded Time Waveforms are frequency shifted to correct for the inaccurate sampling rate. The exact device playback sampling rate is displayed.

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Automotive Audio Testing Seminar

July 21st, 2022. 9.00am and 2.00pm Eastern US time (6.00am and 11.00am West Coast time)
July 27th, 10.00am China time

In this practical online seminar, Steve Temme will demonstrate in-car measurement of frequency response, Max SPL, and Buzz, Squeak and Rattle using a Bluetooth connection. He will discuss considerations such as physical setup, infotainment system controls and the measurement parameters. Steve and his colleagues will then discuss connectivity for automotive testing, explaining and demonstrating the various connectivity options including USB drive, Bluetooth and A2B bus. Finally, we’ll take a look at some of the other audio measurements that you can make using SoundCheck, for example active noise cancellation and voice assistance readiness. 

在这个实用的网络研讨会中,Steve Temme 将演示如何使用蓝牙连接进行车内测量,以测量频率响应、最大 SPL 以及异常音。 他将讨论物理设置、信息娱乐系统控制和测量参数等考虑因素。 然后,Steve和他的同事将讨论汽车测试的连接性,解释和演示各种连接选项,包括 USB 驱动器、蓝牙和A2B 总线。 最后,我们将看看其他您可以透过SoundCheck进行的音频测量,例如主动降噪以及voice assistance readiness测量。

Bluetooth Testing Seminar

Les Quindipan of Listen, Inc. and Kristopher Hett of Portland Tool & Die demonstrate Bluetooth testing with a variety devices, test parameters, and testing considerations. Kris Hett introduces the Portland Tool & Die Bluetooth interfaces that are used to connect the device under test to the measurement system. He discusses the technical specifications, and explains the differences between these and other types of Bluetooth interfaces. Les Quindipan then demonstrates how these have been fully integrated into SoundCheck for simple plug and play operation, and how they can be used in test sequences. He also highlights some of the algorithms included in SoundCheck that overcome Bluetooth-induced time delays, thus enabling these devices to be tested in a similar way to their wired counterparts. A complete test on a Bluetooth speaker and a Bluetooth Headset is demonstrated.

Seminar demonstrations include:

  • Overview of Portland Tool & Die Bluetooth interfaces features and functionality
  • Portland Tool & Die software control integration with SoundCheck
  • SoundCheck configuration and calibration for testing Bluetooth devices
  • Software control of Portland Tool & Die devices within a SoundCheck sequence
  • Demonstrations of sequence measuring Bluetooth headsets and speakers

Presenters: Les Quindipan, Kristopher Hett
Duration: 30 Mins

Bluetooth testing Resources

  • Our sequence library contains many ready-to-run sequences for testing Bluetooth devices, available for download for no charge.

More about testing Bluetooth devices

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

蓝牙音频测试 / Bluetooth Testing Seminar

June 3rd 2021. 10am (China Time)

This seminar has now passed, but you can watch the video.

In this 1hr online seminar, S&V Samford presents Les Quindipan of Listen, Inc. and Kristopher Hett of Portland Tool & Die demonstrating how to test Bluetooth devices.

Kris Hett will introduce the Portland Tool & Die Bluetooth interfaces that are used to connect the device under test to the measurement system. He will discuss the technical specifications, and explain the differences between these and other types of Bluetooth interfaces. Les Quindipan will then demonstrate how these have been fully integrated into SoundCheck for simple plug and play operation, and how they can be used in test sequences. He will also highlight some of the algorithms included in SoundCheck that overcome Bluetooth-induced time delays, thus enabling these devices to be tested in a similar way to their wired counterparts. A complete test on a Bluetooth speaker and a Bluetooth Headset will be demonstrated.

There is no charge for this seminar, but registration is required.

 

2021年6月3日,上午10点(中国时间)

在这1小时的在线研讨会中,声振环保仪器有限公司, Listen,Inc. 的Les Quindipan以及Portland Tool&Die的Kristopher Hett,会向大家演示如何测试蓝牙设备。

届时Kris Hett会介绍Portland Tool&Die蓝牙接口,该接口用于连接戴测试至测量系统。他将会讨论技术规范,并解释这些和其他类型的蓝牙接口之间的区别。

Les Quindipan将演示如何将它们完全集成到SoundCheck中以进行简单即插即用的操作,以及如何将它们用于测试程序中。他还会重点介绍SoundCheck的一些算法,这些算法可以克服蓝牙引起的时间延迟,从而使这些设备能够使用与有线等同类产品类似的方式进行测试。除此之外还会演示蓝牙扬声器和蓝牙耳机的完整测试。

该研讨会不收取任何费用,但需要注册。

 

Bluetooth Device Measurement Seminar

May 27th, 2021. 9.00am and 2.00pm Eastern US time (6.00am and 11.00am West Coast time)

In this 1hr online seminar, Les Quindipan of Listen, Inc. and Kristopher Hett of Portland Tool & Die demonstrate how to test Bluetooth devices.

Kris Hett will introduce the Portland Tool & Die Bluetooth interfaces that are used to connect the device under test to the measurement system. He will discuss the technical specifications, and explain the differences between these and other types of Bluetooth interfaces. Les Quindipan will then demonstrate how these have been fully integrated into SoundCheck for simple plug and play operation, and how they can be used in test sequences. He will also highlight some of the algorithms included in SoundCheck that overcome Bluetooth-induced time delays, thus enabling these devices to be tested in a similar way to their wired counterparts. A complete test on a Bluetooth speaker and a Bluetooth Headset will be demonstrated.

There is no charge for this seminar, but registration is required.

This event has passed, but you can view the recording here.

Updated Bluetooth Interface Supports High Definition and Low Latency Bluetooth

The updated BTC-4149 Bluetooth measurement interface now supports the aptX HD and aptX-Low Latency Bluetooth protocols for accurate measurement of high definition and low latency Bluetooth devices, in addition to the standard aptX, CVSD and mSBC codecs previously available. This enables manufacturers of Bluetooth audio devices to accurately test the audio of the latest high performance Bluetooth sink and Bluetooth source devices, making the same measurements as on traditional audio devices. In addition, the device has a new, larger color screen for improved ease of operation.

 

The BTC-4149 is designed as a R&D interface, testing both sink and source devices with full control over Bluetooth protocol settings, including explicit control over codec choice and transmitter power, as well as various pairing options.

 

Also available is a lower cost production tool, the BQC-4149. This tests Bluetooth Sink devices only, and offers only the standard aptX, CVSD and mSBC, along with more limited control of Bluetooth parameters. This model has been updated to use the same chipset as the BTC-4149 to ensure accurate production line replication of R&D tests for those customers who use both interfaces.

 

Both interfaces integrate seamlessly with SoundCheck, so that all parameters can be set and modified from within a test sequence for fully-automated testing of Bluetooth devices. This accelerates testing, particularly on the production line as it avoids the need to manually adjust Bluetooth settings, reducing the possibility of error. It also enables a device to be tested using multiple Bluetooth protocols and settings by taking sequential measurements using different settings in one continuous test.

Product Information

Practical Measurement of Bluetooth and Lightning Headphones

Picture of Bluetooth Headphone Testing Article reprint

Bluetooth Headphone Testing Article

Author: Daniel Knighten.  Reprinted from the July 2017 issue of Voice Coil.

In this article, Dan Knighten discusses Bluetooth headphone testing and Lightning headphone testing, specifically how to overcome the challenges of measuring headphones with wireless and digital interfaces such as Bluetooth, Lightning and USB-C to make the same measurements as on conventional wired headphones.

Full Article

 

 

 

Article Text

Practical Measurement of Bluetooth and Lightning Headphones

For decades, headphones have been passive devices with a direct, analog interface. Today, we are seeing a proliferation of headphones with wireless Bluetooth interfaces and various kinds of new and often proprietary digital interfaces. These new interfaces include Apple’s Lightning port and USB-C. In all cases these headphones present unique challenges to measurement because they cannot be directly connected to traditional test and measurement systems. In this article, we will explore how to overcome these interface challenges in order to make standard measurements on devices with nonstandard audio interfaces.

Closed Loop and Open Loop Testing
To begin, let’s define what we mean by open and closed loop testing. The test configuration for conventional headphone measurements, as seen in Figure 1, is what we term a “closed loop measurement.” This traditional type of audio measurement has been done for years with
all types of transducers (e.g., loudspeakers, headphones, microphones, etc.), and audio measurement systems can make these measurements without problems. The test signal passes from the audio interface through the speaker/headphone where it is converted to sound
pressure. Then, it goes through the microphone where it is converted back to voltage for analysis. The entire path from input to output is on the same interface, usually in the same domain (analog), and most critically, the analysis system’s input and output sample rate are
perfectly synchronous. The entire measurement from signal generation to capture of the device response simultaneously occurs with just a small amount of input to output delay added by the speed of sound.

In headphones with Bluetooth, Lightning, or other unconventional digital audio interfaces, this loop is broken. The input and output are on two different physical devices, which do not share a sample clock, and the signal goes through one or more analog to digital conversion stages. The delay from input to output of the device is likely quite long, compared to classic analog headphones. In fact, the delay might effectively be infinite. In the case of Lightning-connected headphones, there is currently no third-party solution available for injecting a test stimulus into a Lightning port. In Bluetooth systems, the connection is intrinsically non-synchronous. Bluetooth does not provide a synchronous sample clock across the wireless connection and instead relies on asynchronous sample rate conversion and various other techniques to maintain a glitch-free audio stream. This is what we mean by “open loop.” A closed loop system has a closed loop, synchronous signal chain.

An open loop system does not have a continuous or synchronous signal chain. However, SoundCheck makes it possible to measure all conventional parameters of a device, even when those devices are open loop devices, with a variety of tools including:
• Triggered acquisition—support for capturing measurements on playback devices
• File analysis—the ability to analyze signals captured by recording devices
• Resampling—conventional asynchronous sample rate conversion
• Frequency shift—the capability to align signals between non-synchronous systems

Let’s explore how these tools are applied in some typical test scenarios.

Bluetooth Testing
Figure 2 shows a typical Bluetooth setup. Since we are testing the Bluetooth headset using a Bluetooth interface, it is nominally a closed loop scenario. The audio signal comes out of the analog interface and is transmitted via the Bluetooth interface to the headset. It is then played
by the headset and picked up by the ear couplers where it is returned to the analog interface and computer for analysis. However, what makes this an open loop test is that Bluetooth does not transmit a sample clock and, therefore, the receiver and transmitter are asynchronous.

In this case, we will use frequency shift to align or synchronize the stimulus and response waveforms. Frequency shift uses a stationary reference tone to precisely find the difference in sample rate between two waveforms. Once the exact difference in sample rate is found, one waveform is then resampled with reference to the other. Frequency shift enables precise, conventional measurements to be made on Bluetooth devices despite their asynchronous nature.

When compared to a conventional test, only two changes need to be made. First, a short, stationary tone is pre-pended to the stimulus signal (see the Sidebar article). Typically 1 kHz for as little as 250 ms, this signal provides the frequency reference that the frequency shift step needs to align the stimulus and response signals in an asynchronous test scenario. Second, a
post-processing, frequency shift step is inserted into the test sequence between the acquisition and analysis step.

The rest of the sequence is identical to a conventional headphone test sequence and all normal parameters including frequency response, THD, polarity, rub and buzz, and so forth can be measured.

Lightning Headphone Testing
Any device that does not provide an analog or digital input and output is intrinsically an “open loop” device from a test perspective. Headphones that use the Apple Lightning port for connection are considered open loop because Apple does not provide Lightning audio
output adapters. The only device that can currently play audio into a Lightning headset is an iPhone. Measuring Lightning headphones requires an iPhone or similar Apple device to be used to store and play back the test signal (see Figure 3). This creates several open loop testing
challenges. To test a Lightning connected headphone, we will use three specific tools: triggered acquisition, resampling, and frequency shift.

Again, our test sequence will use a short 1 kHz tone, pre-pended to the normal test stimulus but this time it serves two purposes. First, it triggers a record-only acquisition, so that the test is automatically triggered when playback of the test signal begins. It is also used as the reference tone for frequency shift. Also, if our playback device, the iPhone, is using a different sample rate to the audio interface, we may need to use a resampling step. Finally, frequency shift will again be used to synchronize the stimulus and response waveforms. After the response waveform is captured via a triggered acquisition step and has been resampled and frequency corrected, calculation of the desired measurement parameters can proceed as with any conventional headphone.

Pre-written test sequences for both Bluetooth and Lightning headphones are available at no charge from Listen’s website, www.listeninc.com.

Lightning Headphone Microphone Measurements
Since most headphones now also include a microphone, it is worth mentioning how the microphone on a Lightning- connected headset is tested. The test sequence and method
for this is a little more complex, although ultimately it is really just the converse of testing the earphones. Figure 4 shows a typical test configuration. The preparation of the test signal and the use of resampling and frequency shift steps are identical to testing the earphones of a Lightning connected headset.

The difference is that instead of playing back the stimulus through the earphones and using a triggered, record-only acquisition, the stimulus is instead generated using a calibrated speaker or mouth simulator and recorded on an iPhone. The recorded signal is then transferred back
to the computer hosting SoundCheck and analyzed using a recall step to import the waveform into memory from storage on the iPhone.

Conclusions
Bluetooth and Lightning interfaces add an additional level of complexity to testing that is not there with their analog counterparts. However, because the SoundCheck test system is completely agnostic about where the stimulus and the response waveform are generated and
captured, these tests can be carried out with relatively simple modifications to existing test sequences. In fact, it pretty much comes down to a simple modification to the stimulus signal and some additional post-processing steps prior to analysis—all of which are easily automated.
This enables easy characterization and measurement of Bluetooth, Lightning, USB-C, and future devices with advanced digital audio interfaces.

 

Preparation of the Stimulus Signal (sidebar)
In SoundCheck’s frequency-shift algorithm, a Fast Fourier Transform (FFT) is used to extremely accurately calculate the centroid of a stationary tone. The result of this calculation can then be used to align or synchronize two signals even if they are sampled at different rates. A short, stationary signal is necessary for the frequency shift algorithm to lock on to. This is easily achieved by pre-pending a 1 kHz, 250 ms sine wave to the stimulus signal. Since SoundCheck enables the creation of compound stimuli, this short, single-tone burst can be followed with absolutely any test signal (e.g., a Farina log sweep, noise, speech, or other non-sinusoidal
waveforms).
The short sine wave also serves as the trigger tone for triggered record, as is necessary for testing Lightning headphones. The trigger tone clearly identifies the start of the signal. Care must be taken to set an appropriate trigger level. If it is too low, ambient noise can cause false
triggering; too high and it will never trigger. The trigger level should be set so that it is above the ambient noise and below DUT output level. The Multimeter virtual instrument is an ideal tool for finding the optimal trigger threshold.

A typical stimulus signal for open loop headphone test is shown in Figure 1. This compound stimulus works for both Bluetooth headphones where the sine wave is used for frequency alignment and for Lightning headphones where it additionally serves as a trigger and reference for frequency shift.

 

Additional Headphone Test Resources

More about Bluetooth headphone testing

Headphone Testing main page

 

Headphone & Headset Measurements – Tokyo, Japan – March 9, 2018

Presented by:

listen_gras_logos2

headphones

 

 

 

Due to popular demand, we are now holding our headphone testing seminar in Tokyo!

Learn about the latest in headphone test systems and methods from design to EOL Test. Industry experts Steve Temme (Listen, Inc.) and Peter Wulf-Andersen (G.R.A.S.), as well as guest speaker Dr. Sean Olive (Harman International) will discuss test equipment (ear couplers, test fixtures, test software and hardware) and demonstrate practical test setups for both R&D and QC headphone testing. It will cover in-ear monitors, Bluetooth, lightning/USB, noise-cancelling and high resolution headphones, in addition to conventional analog headphones. You can even measure your own headphone using our equipment in the hands-on session. Please see the full agenda below.

There is no charge for this one-day seminar. Lunch will be provided. Space is limited, so please RSVP today.

Location and Dates:

Tokyo: Friday March 9th, 2018. Otemachi SUNSKY ROOM 27th floor, room #B  Asahi Seimei Otemachi Bldg. 2-6-1 Otemachi, Chiyoda-Ku, Tokyo.

 

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See what people are saying about this event (we presented similar last year in the US)

Agenda (10am-4pm)

  • Introduction
  • Overview of Headphone Test Systems and tools
    • Traditional tools vs. modern consumer demands
      • Introduction to head and ear related terminology and definitions.
      • Historical perspective and background for the tools and standards used today.
      • Limitations vs. Possibilities in term of the measurement capabilities. How does that relate to the modern challenges with Bluetooth and ANC related testing tasks?
    • Tools for Next Generation Headphone Testing
      • Solutions to some the challenges addressed above.
      • Examples based on products and measurements.
    • What about frequencies above 20kHz? Science or marketing? Measurement Consistency – Development vs. Production
      • Progress in measurements from Head and Torso Simulator (KEMAR) to Production Test Fixture (45CC – flat plate). How the different components affect the measurements:
    • Software and hardware for headphone testing including typical headphone measurements and test setups
  • Practical examples of headphone measurements on.
    • Analog Headphones
    • Bluetooth Headsets
    • ANC Headphones
    • Lightning/USB Connected Headphones (using triggered recordings)
    • Hi-Res Headphones
    • In-ear monitors
  • Measurements including:
    • Frequency Response relative to a target response
    • Left/Right tracking
    • Impedance
    • Noise attenuation
    • Distortion including Non-Coherent Distortion
    • Standards including Max SPL EN-50332 & IEC-60268-7
  • Headphone Design: Perception and Measurement of Headphones – What is the Preferred Target Response? (Guest Speaker: Dr. Sean Olive, Harman International)
  • Hands-on testing: Bring your own device and test it using one of our measurement setups

Reserve your space

Headphone & Headset Measurements – Seoul, Korea – March 6, 2018

Presented by:

listen_gras_logos2

 

headphones
Due to popular demand, we are now holding our headphone testing seminar in Seoul!

Learn about the latest in headphone test systems and methods from design to EOL Test. Industry experts Steve Temme (Listen, Inc.) and Peter Wulf-Andersen (G.R.A.S.), as well as guest speakers Dr. Sean Olive (Harman International) and Prof. Lee (New Media Communication Joint Institute of Seoul National University) will discuss test equipment (ear couplers, test fixtures, test software and hardware) and demonstrate practical test setups for both R&D and QC headphone testing. It will cover in-ear monitors, Bluetooth, lightning/USB, noise-cancelling and high resolution headphones, in addition to conventional analog headphones. You can even measure your own headphone using our equipment in the hands-on session. Please see the full agenda below.

There is no charge for this one-day seminar. Space is limited, so please RSVP today.

Location and Dates:

Seoul: Tuesday March 6th, 2018. Korea National University, 1 Gwanak-ro, Gwanak-gu, Seoul.

 

Print

 

 

See what people are saying about this event (we presented similar last year in the US)

Agenda (9am-4pm)

  • Introduction
  • Overview of Headphone Test Systems and tools
    • Traditional tools vs. modern consumer demands
      • Introduction to head and ear related terminology and definitions.
      • Historical perspective and background for the tools and standards used today.
      • Limitations vs. Possibilities in term of the measurement capabilities. How does that relate to the modern challenges with Bluetooth and ANC related testing tasks?
    • Tools for Next Generation Headphone Testing
      • Solutions to some the challenges addressed above.
      • Examples based on products and measurements.
    • What about frequencies above 20kHz? Science or marketing? Measurement Consistency – Development vs. Production
      • Progress in measurements from Head and Torso Simulator (KEMAR) to Production Test Fixture (45CC – flat plate). How the different components affect the measurements:
    • Software and hardware for headphone testing including typical headphone measurements and test setups
  • Practical examples of headphone measurements on.
    • Analog Headphones
    • Bluetooth Headsets
    • ANC Headphones
    • Lightning/USB Connected Headphones (using triggered recordings)
    • Hi-Res Headphones
    • In-ear monitors
  • Measurements including:
    • Frequency Response relative to a target response
    • Left/Right tracking
    • Impedance
    • Noise attenuation
    • Distortion including Non-Coherent Distortion
    • Standards including Max SPL EN-50332 & IEC-60268-7
  • Design & sound tuning of earphones  (Guest Speaker Prof. Lee, New Media Communication Joint Institute of Seoul National University)
  • Headphone Design: Perception and Measurement of Headphones – What is the Preferred Target Response? (Guest Speaker: Dr. Sean Olive, Harman International)
  • Hands-on testing: Bring your own device and test it using one of our measurement setups

Reserve your space

Bluetooth Headset Testing

Screenshot of final SoundCheck display of Bluetooth Headset Testing Sequence

Final display of Bluetooth Headset Testing Sequence

This Bluetooth Headset testing sequence for SoundCheck measures the send and receive performance of a stereo Bluetooth headset with a built-in microphone using a mixture of analog and digital channels. The left and right earphones are measured simultaneously with a stepped sweep from 20kHz to 20 Hz using two Bluetooth profiles: A2DP and HFP. The mic is measured with a stepped sweep from 8kHz to 100Hz using the HFP profile.

A short 1kHz tone is pre-pended to the test stimulus which serves as a reference tone for resampling and frequency shift operations. Post-processing resampling and frequency shift precisely synchronizes the stimulus and response waveforms prior to analysis. In this case, the HarmonicTrak algorithm is used for frequency and THD analysis. A2DP frequency response and THD curves are displayed on the first display, followed by A2DP & HFP curves superimposed on a subsequent display. Lastly, the Bluetooth headset’s microphone is tested with HFP and its frequency response is shown on the final display along with the previously collected data.

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