Posts
Headphone Test Sequence
/in Free Headphone & Headset Sequences /by Devin Vaillancourt
This headphone test sequence measures a stereo headphone. Both left and right earphones are measured simultaneously using a standard 1/12th Octave stepped-sine sweep from 20 Hz to 20 kHz.
The analysis is then performed using Listen’s HarmonicTrak™ algorithm that measures harmonic distortion and fundamental frequency response simultaneously. Then the diffuse-field and free-field corrected Fundamentals are calculated. The diffuse-field correction curve compensates for the overall frequency response from the diffuse-field (sound in every direction) to the eardrum and includes the effects of the head, torso, pinna, ear-canal and ear simulator. The free-field correction curve compensates for the overall frequency response from the free-field (sound at 0 degree incidence to the nose of the Head and Torso Simulator – HATS) to the eardrum.
Further post-processing of the signal compares left and right earphone responses to show the difference curve (magnitude and phase are available). The average sensitivity from 100 to 10 kHz for both left and right earphone is calculated and the total harmonic distortion displayed.
End of Line Distortion Measurements
/in Article Reprints /by ZarinaSteve Temme discusses the importance of detecting manufacturing-induced defects such as Rub & Buzz and Loose Particles during end-of-line testing, and explains the various algorithms that are used. He compares conventional and perceptual metrics for the measurement of Rub & Buzz, including Listen’s new enhanced Perceptual Rub & Buzz algorithm, and discusses why it can be beneficial to use both conventional and perceptual measurements in tandem.
The Future of Audio Measurements – SoundHub Denmark
/in Past in-Person Events /by ZarinaWeds May 25th, 8.30-12.30
Presenters: Steve Temme, Listen Inc.; Michael Trolle, VibrAkustik
Join us at SoundHub in Struer for a great day of presentations and discussion on the latest in audio measurement. The presentations will cover a variety of audio test topics including the end of line testing for improved efficiency and yield, measurement in real-world conditions, free-field measurements without a test chamber and more. There will also be consultation time when we are happy to answer your questions or discuss any aspect of audio test. This event is highly relevant for anyone needing to test audio products, both in R&D and production.
Schedule
8.30-9.00: Check-in, coffee & Welcome by VibrAkustik & Sound Hub Denmark (Michael Trolle and Rie Kold Pripsø)
9.00-9.30: Perceptual distortion measurements
9.30-10.00: Accurate measurement of headphones and hearing assistance devices under real world conditions
10.00-10.30: Coffee and discussion time
10.30-11.00: New features in SoundCheck version 20
11.00-11.30: Free-field speaker measurements without an anechoic chamber
11.30-12.30: Consultation time: Bring us your audio devices and your measurement challenges and we’ll discuss your measurement options and demonstrate how your devices can be measured
Note: there will be live demonstrations on all topics, and a display of hardware for a complete measurement chain including fixtures, measurement microphones and sensors, audio interfaces and turntable.
Detailed Content Information
Perceptual Distortion Measurements: Perceptual distortion measurements enable production line yield to be increased by rejecting only devices with audible Rub & Buzz defects rather than any distortion defects, and Listen’s new enhanced Perceptual Rub & Buzz (ePRB) algorithm is the first to perform even better than the human ear! Through proprietary noise reduction technology and advanced perceptual algorithms, its performance in a noisy factory environment is comparable to the performance of a trained listener under normal listening conditions. Learn more about the science behind this algorithm, see the results, and learn how to implement it in your end-of-line tests.
Accurate Headphone Measurements in Real World Conditions: In this demo-focused session, we will demonstrate how to accurately measure Headphones and Hearing Assistance Devices under real world conditions with real world signals such as speech and music. For example, we will demonstrate, in real time, how to adjust the headphone fit for a proper seal on the head and torso simulator and measure headphone ANC with real background noise with our Multi Signal Real Time Analyzer
New Features in SoundCheck: The newly released SoundCheck 20 is at the forefront of audio measurement with new features for multichannel and communications, increasing its capabilities for audio measurement of smart speakers, infotainment systems, headphones and hearables, and other voice-activated and multichannel devices. In this 30 minute session, we will demonstrate the new features and explain how they are used for testing a variety of audio products and applications.
Free-field Speaker Measurements without an anechoic chamber: Can’t afford or get time in an anechoic chamber? That’s not a problem if you have SoundCheck! In this practical session, we will demonstrate a method first developed by Listen president Steve Temme back in 1993, known as the ‘splice’ technique. This measurement technique is easy to configure and enables you to make highly accurate free-field measurements in an ordinary room, avoiding the expense of an anechoic chamber and enabling measurements in your home or office.
Registration is not available as this event has passed.
Headphone Measurement Basics
/in Past On-line Events, Past Training Events /by Zarina耳机测试基础篇网络研讨会
Aug 5, 2020 at 10.00am (China time)
中国时间2020年8月5日星期三上午10点
在这个60分钟的在线研讨会中,声振环保仪器有限公司授权Listen公司的创始人兼总裁Steve Temme先生,与大家探讨耳机测试的基础知识。
Listen公司的SoundCheck电声测试系统广泛用于全球领先的原始设备制造商及其合约制造商的成千上万条生产线。虽然它可以用于测试各种各样的设备,包括扬声器、微型扬声器、耳机、耳麦、智能设备、手机等等,但本次研讨会将着重讨论耳机。
在这次在线研讨会中,Steve Temme先生将涵盖耳机测试的基础知识,包括:
- 耳机的工作原理
- 如何测试耳机(包括不同种类的耳机和声学耳模拟器)
- 研发和产线测试的环境
- 重要的测试如校正的频率响应、左右声道平衡度、失真等等。
In this 60 minute online seminar, S&V Samford presents Listen, Inc. founder and president, Steve Temme, discussing Headphone Measurement Basics.
Listen, Inc’s SoundCheck electroacoustic test system is used by the world’s leading OEMs and their contract manufacturers on thousands of production lines worldwide. Although it can be used for testing a wide range of devices including speakers, microspeakers, headphones, headsets, smart devices, cellphones and more, this seminar will focus on headphones.
In this online session, Steve Temme will cover the basics of headphone testing, including:
- How a headphone works
- How to measure headphones (including considerations for different types of headphones, and acoustic ear simulators)
- R&D and production test environments
- Important measurements such as corrected frequency response, left/right tracking, distortion etc.
View Recording
Viewers in China WATCH HERE
Use the Harman Target Curve to Predict Headphone Preference
/in Sequences - blog /by ZarinaIn their landmark papers “A Statistical Model that Predicts Listeners’ Preference Ratings of In Ear Headphones – Parts 1&2” presented at the AES 143rd in October 2017, Sean E. Olive, Todd Welti, and Omid Khonsaripour of Harman International introduced a model that predicted listener preference ratings of headphones based on the Harman Target Curve. We have created a SoundCheck sequence that measures any headphones and predicts the listener preference rating based on comparing its measured results to the Harman Target curve using this model. Listen acknowledges and thanks the authors of the Harman paper for providing the spreadsheet which is used as the basis for the excel template used in this sequence.
This sequence, inspired by the Harman research referenced above, applies the Harman target curve for in-ear, on-ear and over-ear headphones to a measurement made in SoundCheck to yield the predicted user preference for the device under test. The measurements are made in SoundCheck and then saved to an Excel template which performs the necessary calculations to produce a Predicted Preference score using a scale of 0 to 100. The spreadsheet calculates an Error curve which is derived from subtracting the target curve from an average of the headphone left/right response. The standard deviation, slope and average of the Error curve are calculated and used to calculate the predicted preference score. The sequence also provides the option to recall data rather than making a measurement, which saves time for engineers who already have large quantities of saved data, and enables historical comparison with obsolete products.
Check out our short video where we demonstrate this sequence in action
Get the test sequence for predicting headphone preference based on Harman Target Curves
Learn more about headphone testing using SoundCheck
References
A Statistical Model that Predicts Listeners’ Preference Ratings of In-Ear Headphones: Part 1—Listening Test Results and Acoustic Measurements
A Statistical Model that Predicts Listeners’ Preference Ratings of In-Ear Headphones: Part 2—Development and Validation of the Model
A Statistical Model that Predicts Listeners’ Preference Ratings of Around-Ear and On-Ear Headphones
Practical Measurement of Bluetooth and Lightning Headphones
/in Article Reprints /by ZarinaAuthor: 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.
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
/in Past in-Person Events, Past Training Events /by ZarinaPresented by:
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.
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
- Traditional tools vs. modern consumer demands
- 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
Headphone & Headset Measurements – Seoul, Korea – March 6, 2018
/in Past in-Person Events, Past Training Events, Uncategorized /by ZarinaPresented by:
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.
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
- Traditional tools vs. modern consumer demands
- 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
Headphone & Headset Measurements – Chicago and Boston Dates
/in Past in-Person Events, Past Training Events, Uncategorized /by ZarinaPresented by:
Due to popular demand, we are now holding our headphone testing seminar in Chicago and Boston!
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 and lunch will be provided. Space is limited, so please RSVP today.
Locations and Dates:
Chicago: Friday October 13th, DoubleTree by Hilton Hotel Chicago Wood Dale-Elk Grove, 1200 N Mittel Blvd, Wood Dale, IL 60191
Boston: Monday October 16th, Hilton Garden Inn, 450 Totten Pond Rd, Waltham, MA 02451 NOTE: THIS VENUE HAS CHANGED. DUE TO HIGH DEMAND FOR THIS SEMINAR WE HAVE HAD TO MOVE IT TO A LARGER VENUE. Note that this is 2 days before the start of the AES show in New York – a short flight or 3.5 hour train ride away. Consider combining this informative seminar with your AES travel!
See what people are saying about this event (we presented similar earlier in the year on the West Coast)
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
- Traditional tools vs. modern consumer demands
- 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