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.
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.
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.
Why so small?
The Accuracy at high frequencies is vital, and... post, deals with the benefits of using a ¼″ microphone compared to the more commonly used ½″ mics and measurement scenarios where those benefits outweighed the drawbacks, or where the drawbacks weren’t relevant. The obvious question, of course, is why stop at the ¼″ microphone? If there are benefits to smaller microphones, and the areas of interest in noise mitigation and sound quality trending to hi-res and higher frequencies, how small can microphones get and still be viable?
Microphone size matters
In any measurement scenario, the measurement equipment and the measurement environment interact in two ways. The first and simplest way is how the microphone ‘adds’ data to the environment, and the second is how the microphone ‘extracts’ data from the environment. And size has a great impact in both directions.
Where does your noise come from?
Our perception of what is and is not an acceptable noise level has changed a great deal in the past 100, or even 25 years. The change in designs for improvements in transit times, fuel economy and even energy production are visible all around us and impact our daily lives. Vehicles on the motorway, local commuter and high-speed trains, aircraft, and wind turbines all impact our lives in various ways, including the addition of noise.
