Tag Archive for: automotive

100 Things #94: Road Noise and Active Road Noise Cancellation Measurements

Road Noise and Active Road Noise Cancellation Measurements are easy with SoundCheck. Everyone’s familiar with measuring headphone active noise cancellation with SoundCheck, but did you know it’s also great for in-car measurements of road noise and evaluation of road noise cancellation systems? Simply connect the USB-powered AudioConnect 2 to your microphones and laptop, and start making measurements. Watch this short video to see how easy it is with this compact and cost-effective package.

Make Road Noise and Active Road Noise Cancellation Measurements

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Read more about in-car road noise measurements.

Learn more about automotive testing using SoundCheck.


Video Script: Road Noise and Active Road Noise Cancellation Measurements

Everyone’s familiar with measuring headphone active noise cancellation with SoundCheck, but did you know it’s also great for measuring active road noise cancellation and road noise reduction in cars?

In this application, you want to measure the road noise at the location of the driver or passenger ears. A simple and cost-effective way to do this is to position two microphones near the outside of your ears or use a Head and Torso simulator. Here, we attached two SCM microphones to a Listen hat using some clips – we call this a low-budget HATS. This has the added advantage that if you are out on real roads, you can measure in the driver’s position.

Our configuration is simple. The microphones are connected to an AudioConnect 2 audio interface for microphone power and signal conditioning. This is a great application for this interface, as it’s USB powered, so you don’t need a power outlet in your car – you can just run it off your laptop. The AudioConnect 2 is connected via a single USB cable to the computer that is running SoundCheck for analysis.

As you can see, it’s a compact setup that easily fits on your dashboard or passenger seat.

To measure road noise, we simply need to drive at a fixed speed, remain silent – that means no talking, coughing, or children in the back seat –  and record for a fixed period of time. You can then look at both the sound pressure level and the frequency spectra of the road noise.

To evaluate a road noise reduction system, simply repeat the measurement with the noise cancellation turned on and subtract one result from the other to provide a value for the noise-reduction system of the car.

This is just one of many automotive audio measurements you can make with SoundCheck. Others include end of line QC, evaluation of components, tuning, Max SPL, impulsive distortion, Buzz, Squeak and rattle, POLQA analysis of communications systems and more. Check out the automotive section of our website for more information.



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.

Automotive Test Sequence Including BSR, Max SPL and Frequency Response

We have a new automotive test sequence to measure Transient Distortion (also known as buzz, squeak, and rattle, Rub & Buzz, or impulsive distortion), Frequency Response, and Max SPL to the suggested measurement methods set out in the AES Technical Committee on Automotive Audio’s recently published white paper on in-car acoustic measurements. The three measurements are incorporated into one overall test sequence, making it fast and simple to run the entire suite of tests. This sequence facilitates evaluation of the committee’s proposals, and also serves as a basis for any similar in-house measurements. The white paper, which may be obtained from the TC-AA, outlines both measurement methods and physical configuration such as microphone and seat positioning in an effort to simplify comparison between vehicles.


100 Things #42: Measuring Max SPL of a Vehicle Infotainment System

SoundCheck is ideal for making in-car measurements such as Max SPL, frequency response and distortion. In fact, SoundCheck is the only full-featured audio test system that offers true nth octave real-time multichannel analysis of 6 microphones simultaneously, that we need for some in-car measurements.  In this short video we demonstrate how we can make Max SPL measurements using a 6 microphone array with SoundCheck and an AmpConnect 621 audio interface. You could make these measurements as part of an end-of-line QC test, in the R&D lab, or to compare various car infotainment systems.

In-Car Max SPL Measurement

Learn More About Automotive Measurements

Watch our Automotive Measurement Seminar in which we make in-car measurements of Max SPL, Frequency response and Buzz, Squeak & Rattle.

Read a short article about the work that the AES Technical Committee on Automotive Audio is doing on Max SPL measurements.

A free pre-written SoundCheck test sequence is available to measure both the Max SPL Spectrum and a single, power averaged value for Max SPL in line with the AES TC-AA working group’s proposed guidelines.

A comprehensive resource on in-car Max SPL measurements is the Audio Engineering Society Technical Committee on Automotive Audio (TC-AA). Their in-vehicle measurements white paper (draft) aims to define repeatable and defined car audio system measurements and in addition to the measurement methods, contains information on standardized test configuration, for example microphone and seat positioning.

Main webpage on SoundCheck for Automotive Measurements.


Video Script: Measuring Max SPL of a Vehicle Infotainment System

Did you know SoundCheck can make in-car measurements such as Max SPL, frequency response and distortion? In fact, SoundCheck is the only full-featured audio test system that offers true nth octave real-time multichannel analysis of 6 microphones simultaneously, that we need for some in-car measurements.  In this short video I’m going to demonstrate how we can make Max SPL measurements using a 6 microphone array with SoundCheck and an AmpConnect 621 audio interface. You could make these measurements as part of an end-of-line QC test, in the R&D lab, or to compare various car infotainment systems.

In this test, we use a 6 microphone array to represent the driver’s head. We mount it on a tripod so that it’s easily adjusted to the position where the head would be.

This is placed in the driver’s seat of the car, with the tripod legs as far back on the seat as they’ll go, right against the backrest. The height and angle of the seat are set to the minimum or lowest position. The AES is working on a proposed standard for this type of measurement that defines some very specific dimensions between the pedal and backrest, the height of the stand, and the inclination of the back rest. For this demo, I’m not going to be that precise, but as you can see, I am making sure that I have recorded the dimensions I am using, and the mic array is in a fairly typical driver head position.

Now let’s measure Max SPL. We’ll use broadband monophonic pink noise and we’re going to crank the volume to the max   – even outside of the car this is going to be loud!

It’s hitting 110 dB and we’re going to play it for 30 seconds and take the linear average or Leq. Here you can see the readings on the six microphones, and the black line representing the spatial power average. The test sequence is calculating the overall Max SPL as 111 dB C weighted, and also displays the Max SPL spectrum from 20Hz to 20 kHz.

If you’d like to learn more about in-car measurements, check out our automotive measurement seminar, in which we also demonstrate frequency response and distortion measurements. You can find this in the audio measurements playlist on our Youtube channel! This test sequence that I just used for measuring Max SPL is also available for download, free of charge, from our website.


Automotive Audio Measurements (Seminar): Frequency Response, Max SPL, Buzz, Squeak & Rattle

In this practical online seminar, Steve Temme demonstrates in-car measurement of frequency response, Max SPL, and Buzz, Squeak and Rattle using a Bluetooth connection. He discusses considerations such as physical setup, infotainment system controls and the measurement parameters. We then discuss connectivity for automotive testing, explaining and demonstrating the various connectivity options including USB drive, Bluetooth and A2B bus. Finally, we 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.

Automotive Audio testing demonstrations include:

  • Frequency Response
  • Max SPL and Max SPL Spectrum
  • Buzz, Squeak & Rattle
  • Connectivity Options – USB, Bluetooth, A2B bus
  • ANC and Voice assistance readiness

Presenters: Steve Temme
Duration: 32 Mins

Automotive Audio Measurement Resources

This seminar was originally broadcast on July 21st 2022. The recording below does not include the live Q&A at the end for attendee confidentiality reasons. However, several links to additional resources were provided during the Q&A session, and these are provided below.

  1. Test sequence for in-car audio measurements. This sequence measures the impulsive distortion, frequency response, and maximum sound pressure level of a vehicle
  2. An article by Steve Temme on automotive Max SPL measurements. Originally published in VoiceCoil magazine, June 2022.

More about how to Measure Automotive Audio

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

Learn more about Connecting to Automotive Infotainment Systems

Maximum SPL measurements in cars

Buzz, Squeak and Rattle measurements

AES Technical Committee on Automotive Audio. Listen, Inc. works closely with this group to ensure that our measurement capabilities align with the measurements recommended by the AES.

Automotive Max SPL Measurements

Measuring Automotive Max SPL ArticleIn this short article, Steve Temme discusses measurement of automotive Max SPL, and introduces the efforts of the Audio Engineering Society (AES) technical committee working on automotive audio to standardize the way essential attributes of complex automotive audio systems are measured across the industry. He explains why Max SPL measurements are important, defines this measurement, and describes the standardized measurement procedure suggested by the committee. Test configuration and physical setup is discussed, and example results presented.

Full Article




Full article text:

Measuring Automotive Max SPL
By Steve Temme Listen, Inc.
I am currently a participant in an Audio Engineering Society (AES) technical committee working group on automotive audio. This diverse group of about a dozen worldwide experts has focused on trying to standardize the way essential attributes of complex automotive audio systems are measured across the industry. Three specific measurements have been our initial focus: Frequency Response, Max SPL, and Impulsive Distortion. The committee’s proposals for measurements were presented for feedback at the AES Fall Online 2021 conference in a session titled “In-Car Acoustic Measurements.”

I presented our work on Max SPL Measurements, Hans Lahti (Harman) presented Frequency Response, and Stefan Irrgan (Klippel) presented Impulsive Distortion; the session was chaired by Jayant Datta. Here, I will describe our proposed method for Max SPL measurements.

Let’s start with why this is important. People need to be able to compare how loud an infotainment system can play in a car— manufacturers like to quote this in specifications, and consumers enjoy bragging rights about the sound level of their car stereo. Max SPL is defined as the maximum sound pressure level (SPL) that a car’s infotainment system can reproduce inside the cabin with the windows, sunroof, and convertible top closed. There are many ways this can be measured, but to keep it simple, two different measurements are recommended—overall Max SPL and Max SPL Spectrum regardless of distortion level. The reason we don’t take into account distortion when we measure the Max SPL is because it is difficult to characterize distortion in a modern-day infotainment system—these devices frequently contain much signal processing, and this makes them unsuitable for playing back the sine wave stimuli that are typically used for harmonic distortion measurements.

First, let’s examine the physical test setup. Our proposed test configuration replicates the position of an average person’s head in the driver’s seat using a precisely and specifically positioned six- microphone array in the driver’s seat. The height and the angle of the seat, the positioning of the microphones with respect to the seat, and the height and the angle of the microphones are clearly defined to ensure standardized measurements across all vehicles.

The sound system settings on the head unit—the tone control and fader—are set to the factory default setting; in most cases this is neutral or flat with no equalization. The head unit’s volume control is set to its maximum level using the volume control knob or digital user interface equivalent (e.g., volume level slider). Overall Max SPL can be measured using a microphone array with the six microphone signals power averaged by analog or digital means and connected to either a conventional or software-based sound level meter that can measure true RMS and be C-weighted, as described in the IEC-61672 standard. However, if a software-based system is used for measuring the Max SPL Spectrum, it is simpler to also measure the overall Max SPL through the software. Figure 1 shows a test configuration that makes both measurements simultaneously using SoundCheck software, and an AmpConnect 621 audio interface.

For both the overall Max SPL and Max SPL Spectrum measurements, a broadband (20Hz to 20kHz) monophonic pink noise stimulus is used. It has a crest factor of 15dB and is played for 30 seconds to make sure the system can sustain that level continuously. This is played at maximum volume to ensure the system is tested at the loudest signal the car will play. The sound source may come from any source—a memory stick, a CD, or Bluetooth from a smartphone or auxiliary line in. The average SPL in dB(C) is measured for 30 seconds. This is called a Leq measurement, and it takes the spatial average of the six-microphone array, power averaged, to get the overall Max SPL level (Figure 2).

The Max SPL Spectrum is measured using a real-time analyzer set to 1/12 octave resolution, 30 second linear averaging time and no waiting. This enables us to measure the level versus frequency irrespective of the human ear’s perception. The Max SPL is recorded at each microphone simultaneously from 20Hz to 20kHz and the power average calculated (Figure 2).

Listen offers a pre-written SoundCheck test sequence that measures both the Max SPL Spectrum and a single, power averaged value for Max SPL in line with the working group’s proposed guidelines. This enables consumers and manufacturers to measure the maximum overall SPL and maximum SPL versus frequency that a car’s infotainment system can reproduce inside its cabin. The sequence uses the method and test configuration with a six-microphone array in either the driver or passenger seats. It takes advantage of Listen’s 6-in, 2-out AmpConnect 621 audio interface, which seamlessly integrates with the software-based multichannel analyzer to measure, display, and average the results from the six microphones in real time, and power average them to calculate Max SPL. This sequence may be downloaded free of charge from Listen’s website. More details about these measurements, and the other measurement proposals developed by the technical committee, will be presented at the 2022 AES International Conference on Automotive Audio, June 8-10, in Dearborn, MI.


Further information on the AES Technical Committee on Automotive Audio, including a link to the working group’s draft white paper on can be found here: https://www.aes.org/technical/aa/

More about measuring automotive Max SPL.

Enhanced Perceptual Rub & Buzz Measurement for Testing Automotive Loudspeakers

Loudspeaker Rub & Buzz faults are a problem for automotive manufacturers as they sound harsh and immediately give the perception of poor quality. There are two places such faults can occur – during speaker manufacturing and installation of the speaker in the car. A buzzing loudspeaker in a car is disappointing to a customer and is costly to replace. It is also challenging for a service center to determine exactly where the buzzing is coming from and whether it is caused by a faulty loudspeaker or bad installation. Perceptual distortion measurements are often considered the holy grail of end-of-line testing because rejecting speakers with only audible faults increases yield. Although such measurements have been around since 2011, production line adoption has been slow because until now, sensitivity to background noise has made limit-setting challenging. In this paper, a new algorithm is introduced that uses advanced technology to reduce the impact of background noise on the measurement and offer more repeatable results. This facilitates limit setting on the production line and makes it a truly viable production line metric for increasing yield. This same metric may also be used for end-of-line automotive quality control tests. Results from various algorithms will be shown, and their correlation to subjective and other non-perceptual distortion metrics explained.

Author: Steve Temme, Listen, Inc.
Presented at 2022 AES Automotive Conference, Dearborn, MI

Full Paper



The automotive industry’s stringent quality expectations make end-of-line quality testing on automotive speakers and drivers absolutely critical. End-of-line tests typically measure a range of parameters including frequency response, THD, and polarity. Manufacturing-introduced defects such as Rub & Buzz and Loose Particles are also measured. Reliable, automated testing has been available for decades now, and most large manufacturers rely on these software-based systems for identification and rejection of defective products. While these tests do an excellent job of identifying defective units, there is always a certain level of false rejection where units with some distortion fail even though it is completely inaudible to the human ear. From a manufacturing perspective, higher yields and therefore greater profitability is always desirable.

Perceptual Distortion Measurements

This has driven the development of perceptual distortion measurements – automated measurements that replicate the human hearing to detect only audible distortion defects. Such metrics increase production line yield by passing products with inaudible distortion, as the product will still sound exactly as the manufacturer intended. Perceptual methods are very simple to configure for production line use. Since they return a result in Phons, an absolute measurement that can be easily correlated to the listener’s threshold of hearing, the operator can set a fixed limit across the board, regardless of product. Naturally, the price point and quality expectations for the product may influence the level of distortion that is deemed acceptable.

Perceptual Distortion Algorithms

Our algorithm, introduced in 2011, was the first commercial perceptual distortion metric, although in the past couple of years, other test system manufacturers have also started to offer perceptual distortion tests. It offers excellent correlation with human hearing and performs well in laboratory tests. However, like the human ear, repeatability decreases in the presence of background noise. This is not a failure of the algorithm as such, but an indication that the algorithm performs just like a human listener; when background noise is high, audible distortion is masked. This limitation restricts the value of such algorithms on the production line, as with today’s high-volume manufacturing, there is only time for one fast test sweep. If this sweep gets a different result under changing background noise conditions, limit setting becomes challenging, and repeatability and reliability is decreased. Similar algorithms from other test system manufacturers also suffer from the same problems.

New Perceptual Distortion Algorithm Development

This paper details efforts to create an algorithm that hears like a human in quiet conditions, e.g. in a living room or passenger automotive cabin, under the less-than-perfect conditions of a manufacturing environment where considerable and varying background noise may be present. In other words, a perceptual model that is more independent and reliable than the human ear when it comes to noisy environments. The resulting new algorithm overcomes these limitations to offer repeatable end-of-line test results, even in noisy environments. It incorporates noise reduction techniques and enhanced perceptual filters to overcome the reliability and high frequency masking issues of earlier versions. In short, the algorithm offers the performance of an ‘enhanced’ human ear – it detects distortion like an ear in a quiet environment, even when there is background noise. This makes it a viable solution for production line use.

In this paper we explain how the algorithm works, demonstrate how the results compare with earlier perceptual algorithms and show its correlation with human hearing and conventional distortion algorithms. We also compare its performance in the presence of background noise to other perceptual algorithms by adding recorded factory background noise to the signal before passing it through the algorithms.

Read More

More about Listen’s enhanced Perceptual Rub & Buzz algorithm

More about in-car measurement of  impulsive distortion / Buzz, Squeak and Rattle.

Automotive Max SPL (Maximum Sound Pressure Level)

Screenshot showing final display of automotive Max SPL sequence

Final display of automotive Max SPL sequence showing individual Max SPL curves, Max SPL average curve and Max SPL value.

This sequence measures Automotive Max SPL, the Maximum Sound Pressure Level (SPL) of a car infotainment system in the vehicle’s interior. It calculates a single value for Max SPL and displays the Max SPL Spectrum, showing the six individual microphone responses plus the average curve.

The sequence uses a 6 microphone array mounted at either the driver or passenger locations. A 30 second pink noise stimulus having an RMS level of -12 dBFS is played through the infotainment system and captured by SoundCheck’s Multi-channel Real Time Analyzer (RTA). The Multi-channel RTA produces 6 RTA curves which are then power averaged to produce a Max SPL Spectrum. The spectrum is then power summed to produce a single value for Max SPL.


Testing Voice-Controlled & Smartphone Integrated Infotainment Systems

A tutorial and accompanying paper on testing infotainment systems that was presented at the AES Automotive Conference, Sept 11-13, 2019, Neuburg an der Donau, Germany.

Voice-controlled and smartphone integrated vehicle infotainment systems are notoriously complex to test. They have numerous connections from wired to wireless and contain much signal processing, both on the record and on the playback side. This means that their characteristics change according to ‘real world’ conditions of the vehicle’s environment, including cabin acoustics and background noises from road, wind and motors. Furthermore, their multifunctional nature means that there are many aspects of the device that may need to be tested, ranging from voice recognition to music playback and operation as a hands-free telephone. Due to their complex non-linear use cases, these devices often need to be tested at different levels and different environmental conditions.

This tutorial offers practical hands-on advice on how to test such devices, including test configurations, what to measure, the challenges of making open-loop measurements, and how to select a test system.

Download presentation (slides)

Download accompanying paper


Paper Introduction

Audio Tests for Infotainment Systems

Infotainment systems have become increasingly challenging to test. They have many possible interfaces; hard-wired or auxiliary input, radio, CD, memory card, hard drive, USB, Bluetooth, smartphone (including Apple CarPlay and Android Auto) and even voice. They contain much signal processing, both on the record side (e.g. beamforming, background noise filtering, voice activity detection, and on the playback side (e.g.loudness, compression, equalization, and active noise cancellation). Some even have wake word detection, e.g. “Hey Siri”, “OK Google”, and “Alexa”. Due to their complex non-linear use cases, these devices often need to be tested at different levels and in different environmental conditions, for example with different background noises and different test signals. To further complicate matters, the test signal may need to be in the cloud to enable playback for testing voice recognition systems. Each manufacturer’s ecosystem is different in how it plays and records.

Smartphone integrated infotainment systems usually require an internet connection with voice services in order to process commands. On the playback side, some enable you to upload your own recordings such as iTunes (although bear in mind that these will probably be compressed). Others require them to be on a media streaming platform such as Spotify. For microphone testing, some systems such as Alexa allow access to recordings made; others do not for security and privacy reasons, which makes microphone testing challenging. Although the actual physical testing setup is very similar from vehicle to vehicle, for each it is necessary to understand how to wirelessly route the signal. Furthermore, each device needs activating with a different wake word, needs different delay compensation, and records for a different amount of time after it hears the wake word. This needs figuring out (largely by trial and error) for each infotainment system that you need to test.

Infotainment System Testing Standards

Although, there are currently no standards for testing infotainment systems with smartphone integration, principles and test configurations can be borrowed from many other audio devices and use existing standards such as IEC for loudspeakers, IEEE/TIA/ITU for speakerphones, and ETSI for background noise. Flexibility of the test system and experience with testing a wide range of acoustic devices is critical to enable a device to be completely characterized. This paper focuses on how to implement basic acoustic tests and some of the more complex real-world tests along with the techniques and standards that may be used.

The rest of the paper covers:

Basic Acoustic Tests
Advanced or ‘Real World’ Testing of Infotainment Systems
Speech Recognition
Background Noise
Voice Quality
Measurement System Requirements

Full Paper


More about testing infotainment systems.

SoundCheck/Mentor A2B for Automotive Audio

mentor_a2bWe are excited to announce that SoundCheck fully integrates with the Mentor A2B interface for testing automotive audio connected via the Analog Devices A2B digital bus. The Mentor Analyzer, which handles the transmission of signal in to and out of the bus, is viewed as an ASIO interface by SoundCheck, enabling SoundCheck to read/write to the device and therefore analyze any transducer connected to the A2B bus. A custom VI permits control of the Mentor A2B interface configuration via SoundCheck. This means that it can be controlled from within a SoundCheck sequence, for example loading configurations and starting/stopping ASIO streams. This makes it an ideal R&D or production line test solution for automotive audio, or for anyone testing transducers connected via A2B bus.

Watch a video demonstration of an automotive audio test using SoundCheck and the Mentor A2B interface:


Please see our knowledgebase article for download links and installation instructions.

Learn more about connecting to automotive infotainment systems.

Contact your Listen sales engineer for more information.