By Lars Winberg, Business Development Manager, GRAS Sound and Vibration

The field of noise testing is evolving at breakneck speed. The increasing demand for advanced audio technologies like active noise cancelling and voice-controlled smart systems make high precision measurements to guarantee superior sound quality a necessity. This means that customers (or project owners) tasked with developing consumer electronics, cars, aircraft, or other applications, will increasingly face test situations where business as usual just isn’t good enough anymore. When they reach this point, they will often need to decide whether to go for a customized solution, that caters to their needs exactly, or whether to choose an off-the-shelf product that gets close enough. In my opinion, customers too often choose off-the-shelf solutions. And I believe this is because a few common concerns scare them away from customization.

The ascent of electric vehicles (EVs) marks a monumental shift toward sustainability and innovation. But the transition amplifies a challenge that was once overshadowed by the rumble of internal combustion engines (ICEs): road and tire noise. In the age of EVs, understanding and mitigating these noise sources has become more crucial than ever. In this blog post, we delve into the significance of road and tire noise testing in EVs, highlighting why it's a pivotal aspect of automotive engineering and design.

 The founder of GRAS Sound & Vibration, the renowned acoustical engineer Gunnar Rasmussen, passed away on the 17th of April 2024.

 By Thomas Robson

The rapid integration of advanced technologies in consumer audio products is changing the industry on a day-to-day basis. New features like Active Noise Cancelling, Hybrid Noise Cancelling, and voice-controlled smart systems are hardy considered premium options anymore, but simply what customers have come to expect. This directly impacts audio testing on production lines, where precise measurements to ensure sound quality are more vital than ever. This demand applies to mid- and low-end products, too, leading to increased production line costs and potentially strained relationships between contract manufacturers and audio brands. To successfully adapt to this trend, both electronics manufacturers and test microphone manufacturers need to embrace customized measuring products and solutions as the way forward. In GRAS Sound & Vibration, we have successfully adopted customization as a core principle driving product development and innovation.

Balancing Innovation, Quality, and Efficiency: A Dialogue Between Audio Brands and Contract Manufacturers

The world of audio product manufacturing is a dance between innovation, quality, and efficiency. This blog post explores the interplay between audio brands and contract manufacturers, revealing how their goals align and diverge in the quest for excellence.

Point: The Audio Brand Perspective

Audio brands are the visionaries, constantly pushing the envelope on quality and innovation. They face the challenge of maintaining their reputation for excellence while expanding their product lines. For them, the primary concern is ensuring that every product bearing their name meets stringent quality standards, which necessitates rigorous testing and compliance measures. The introduction of intelligent production line test microphones with EQset™ technology represents a solution to these challenges, enabling brands to achieve consistent, high-quality audio performance across their product range.

Counterpoint: The Contract Manufacturer's Standpoint

Over the years, many of our customization projects have turned into industry standards. By tailoring both technical specifications and form factor, as well as carefully considering where, how, and by whom the microphone will be used, we’ve succeeded in creating a number of bestsellers. Here are a few of our favorites.

Over the years, many of our customization projects have turned into industry standards. By tailoring both technical specifications and form factor, as well as carefully considering where, how, and by whom the microphone will be used, we’ve succeeded in creating a number of bestsellers. Here are a few of our favorites.

At GRAS Sound & Vibration, we take great pride in our Operators.

They are the highly skilled men and women who handcraft, assemble, and test every GRAS microphone at our HQ in Holte, Denmark. They come from Denmark and around the world, and with various specialist backgrounds. Some have trained as watchmakers, others in pharmaceutical production. On top of that, each Operator undergoes rigorous training before joining our production, building on their unique skills to meet our exacting standards.

The Main Challenges in Production Line Testing of Audio Devices

In a recent webinar, GRAS Sound & Vibration Product Manager, Santiago Rayes, explored the main challenges in production line testing of audio devices and how to mitigate them. It’s all a question of finding the right balance – and choosing the right equipment. According to Santiago Rayes, the main challenges are:

Meeting the Demands of Modern EV Sound Measurement:
The Rise of the ¼” Microphones

In the rapidly evolving landscape of electric vehicle (EV) technology, a recent GRAS whitepaper sheds light on the critical role of ¼” microphones in acoustic testing. They represent a significant step forward in ensuring consistent, high-quality acoustic testing across the industry that aligns with recent recommendations from the AES.

From one dedicated family to another: The GRAS story continues

In 2024, it is 30 years since visionary acoustics pioneer, Gunnar Rasmussen, founded Gunnar Rasmussen Acoustic Services – today known as GRAS Sound & Vibration. What has followed since then is a fairy tale story of growth and acoustic achievements, all built on Gunnar Rasmussen’s guiding vision of innovation and customization. Today, GRAS is part of the Axiometrix family of measurement solution providers. But Gunnar’s vision and values still guide the company.

Pass-fail windows

On a production line, the devices under test (DUTs) have a set of specifications from R&D or the customer that they must comply with. This can be viewed as a window on a graph.

The shaded red areas indicate a simplified hypothetical pass-fail window.

A day without EQset versus one with EQset™

There are many factors involved with running a production line that can affect its efficiency. Some of them are controllable and others are just facts of life.  Calibration (particularly calibration frequency) is one area that can be adjusted and have a considerable impact on the performance of the line. Of course, there is a trade-off. The trade-off for traditional microphones on a production line is increased uncertainty. Reduced calibration is more uptime on the line, but it results in an increase of good units being tagged bad and bad units making their way into the market, damaging customer satisfaction and adding the expense of returned products. Another option is a microphone that is stable and accurate without frequent calibration.

Electroacoustic Engineer, Brian Johansen, has tested sound in everything from airplanes and cars to refrigerators and satellite launches.

It took over 40 years for someone to come up with a better ear simulator than the 711 coupler originally developed by acoustic engineering pioneers Per Brüel and Gunnar Rasmussen. That someone was Brian Johansen.

What's the connection?

They are not directly related, as such. An initial guess might involve how much ash plane engines can take. While that would be on the right track, it is not the connection in this particular case. 

How do I correct a measurement with them?

Microphone specifications may contain a group of specs related to microphone behavior under different environmental conditions. These are the environmental specifications, and they are usually presented as environmental coefficients. These specifications are typically forgotten or misunderstood by many users. So, what are they and how should they be used?

Understanding laminar flow, turbulent flow and the transition region

As examined in the What is the difference between acoustic and aeroacoustics? article, the studies of aerodynamics and aeroacoustics are bound together. Using microphones, surface- or flush-mounted, in a wind tunnel focuses on measuring the characteristics of air pressure in the boundary layer of an object in flow through a medium (or the medium around the object).

The discovery of SysCheck2

Julie works for a leading audio brand manufacturer in China and is preparing to set up and oversee a new production line. The line will produce high-end audio components that will need a full audio test for each product at the end of the line.

The answer is…

Aeroacoustics is a subset of the field of acoustics. The end...

But before you go, it’s not quite so simple as it may seem, and it is much more interesting.

Remove the grid for better data

Measurement microphones are highly specialized and fine-tuned devices designed for sensing minute dynamic variations in the ambient pressure. These variations are so small that measurement microphones use a very thin (only a few micrometers thick) metal foil as a diaphragm to be able to sense those variations. The thinness of the diaphragm allows it to deform even when the excitation is extremely small, making the detection of pressure variation possible even at very low sound pressure levels.