GRAS Sound & Vibration


About us

Founded in 1994 by Danish acoustics pioneer Gunnar Rasmussen, GRAS Sound & Vibration is a worldwide leader in the sound and vibration industry. We develop and manufacture state-of-the-art measurement microphones and related equipment to industries where acoustic measuring accuracy and repeatability is of utmost importance. This includes applications and solutions for customers within the fields of aerospace, automotive, audiology, consumer electronics, and other high-demanding industries.

Our measurement microphones are developed to support critical areas of R&D, QA and production and therefore must undergo the most thorough tests. Using a series of “Highly Accelerated Life Tests”, GRAS microphones are designed to live up to the high quality, durability and accuracy that our customers have come to expect and trust.


As a family owned company we safeguard our heritage by constantly striving to push the boundaries of what is possible and help our customers improve their products. This is why we have the industry’s most advanced microphones – a broad range of high-quality microphones for general acoustic applications complemented by an even broader range of highly specialized microphones and test solutions developed and fine-tuned to match specific challenges. 

This is a reflection of our unique willingness to help solve our customers’ measurement needs and provide solutions for tomorrow. Listening to our customers is at the core of who we are.








GRAS Industries

Aerospace and Defense

All industry applications bring their own challenges, but aerospace testing can be one of the harshest, pushing microphones to their limits. At GRAS we know that measurements often need to be carried out in high speed, turbulent air-flows, where it is vital that the microphone itself does not affect the measurements - and where the testing equipment has to be durable under extreme conditions. Often you only have one chance to record data so validation is vital.

And because we work closely with you, we are well aware of your needs and the challenges you face in such a unique industry. If we can improve your testing, you can improve your products.

GRAS has become an integral part of the aerospace industry, dedicated to finding new ways of testing. From standard microphones, customized flyover arrays or microphones for extreme sound pressures, GRAS has the right microphones to help you develop tomorrow’s airplanes today.

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Since the founding of GRAS Sound & Vibration we have been deeply involved in the audiology industry. Through close cooperation with leading manufacturers in the hearing aid industry we know that the technology for and the design of hearing aid devices has experienced a tremendous development over the latest decades.

Intelligent and adaptive hearing aid devices bring new challenges especially within measuring and testing such as how the devices should adapt to the surroundings and when to shift channel to give the user the best possible experience and perception of sound and own voice adjusted individually.

To help you meet the industry standards IEC 60118 and IEC 60318 we are deeply involved in research and development bringing new products to the market. We can assist you in improving your testing with all of these challenges taken into consideration, you can improve your products and hence the life quality for your customers.


Acoustic Sensors for NVH Testing

Valid data and efficient test methods have always been important in acoustic noise, vibration and harshness (NVH) testing, but the need for better test methods and more reliable data has never been greater.  New types of cars:

  • electric, hybrid, autonomous 
  • pose new challenges and call for new, informed and clever trade-off decisions.

Add to this, the constant push for shorter time to market and more efficient NVH test methods

  •  more urgently than ever before.

As the world leader in developing cutting-edge acoustic sensors, GRAS provides new and improved microphones for more efficient and reliable acoustic NVH testing.  This includes a rugged and very versatile standard microphone for a wide variety of acoustic NVH applications as well as highly specialized microphones for very specific applications

Consumer audio and electronics

The ever-increasing demand from consumers for new features, better quality and lower prices put a constant strain on audio and electronics manufacturers to differentiate on cost efficiency, shorter time to market and outstanding performance. At GRAS, we acknowledge your challenges and try to overcome these by pushing the boundaries of what is possible within precision measurement microphones.

We know about the consumer audio and electronics industry as it is in our DNA. We were the first measurement company to introduce the ½” microphone which has since been copied by most of our competitors in the market. We also make microphones or solutions to custom, and we are known for our exemplary design of innovative and groundbreaking products. Our product portfolio within consumer audio and electronics is the most extensive presently available on the market. Whatever your challenge, we understand the importance of precision, accuracy and reliability in your measurement results. 

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education and research

At GRAS our focus on education and research has paved the way for new world standards for measurement microphones – including the world’s most popular and probably most copied acoustic sensor: the 1/2′′ measurement microphone.

In recent years we have been working closely with universities such as Brigham Young University in the United States. The result? A 3D Vector Probe Head with four 1/4” phase-matched measurement microphones arranged in an Ø30mm spherical shell, making it possible to make measurements in confined spaces that cannot be accessed with traditional intensity probes.

Regardless of the project, we are ready to help you identify the best possible solutions and guide you with our knowledge and world-class expertise.

Find out more about some of the other projects we have been involved in

  1. Energy-Based Acoustical Measurements of    Rocket Noise 
  2. Wind-tunnel Testing 
  3. Measure beyond the threshold of human hearing 

enviromental noise and monitoring

Environmental noise affects us all, whether it is a whine from a distant power station or the increased aircraft and vehicle traffic. Noise monitoring is a complex field driven by regulations and legislation with the aim to protect the environment and the citizens from noise pollution.

Implementing measurements can be difficult and making sure your microphone not only measures correctly today but also next week and next year is critical. The GRAS Outdoor Microphones are among the most stable and robust microphones on the market.

At GRAS we provide quality measurements and offer accredited calibration, which is your guarantee for correct and reliable measurement data every time.

GRAS Products

Measurement microphone sets

 The measurement microphone sets have been combined so they fulfill our users’ typical measurement needs. Independently of your measurement system and application you should be able to find a set that suits your needs. The microphone sets can be connected directly to all professional measurement systems and as indicated they are available for both CCP and 7-pin LEMO inputs. 

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Measurement microphone cartridges

GRAS measurement microphones are available in many types covering various frequency ranges, dynamic ranges and suiting different application situations.  To select the microphone that suits your specific measurement needs, your considerations can most likely be summarized as:

• Prepolarized vs. Externally-polarized

• Free-field, Pressure or Random-incidence

• Dynamic range & Frequency range

Preamplifiers for microphone cartridges

The output from a condenser microphone is a very high-impedance signal and is therefore very sensitive to the capacitive loads of cables. This makes it necessary to introduce a driver with high input impedance and low output impedance. Such a driver is called a preamplifier.

The frequency range of a preamplifier is determined by its electronic circuit and is typically more than 200 kHz at the high end and 1-10 Hz at the lower end. The lower end is determined by the input impedance of the preamplifier and the capacitance of the microphone. High microphone capacitance gives a low cut-off frequency

Ear simulator kits

Ear simulators were designed to replicate acoustical characteristics of the average adult ear. Due to variability of ear-canal geometry and eardrum impedance among individuals, the possibility of any one person exhibiting such "average" characteristics--especially if that person is a child and/or has a conductive pathology--is remote. 

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Special microphones

Special microphones are often required for applications where there are particular requirements regarding the methods of measurements and configurations.

GRAS special microphones are categorized as

-  Array microphones

-  Flush-mount microphones

-  Infra-Sound Microphones

-  Intensity Microphones

-  Intensity Probes

-  Lownoise measuring systems

-  Outdoor microphones

-  Plate microphone kits

-  Probe microphones

-  QC microphones

-  Surface microphones

-  Turbulence Screen Microphones

Artificial ears, ear & mouth simulators

GRAS artificial ears and ear & mouth simulators are designed to enable measurements under well defined acoustical conditions. The solutions available include

-  Externally polarized cartridges (200 V)

-  Mouth simulators

-  Prepolarized cartridges (0 V)

-  Without microphone cartridges

Head & Torso Simulators

 Audio design is becoming a vital part of the development of a lot of daily products like automobiles, computers, hearing aids, mobile phones, etc. Either to improve on its basic function, or to optimize the clients' experience with the product.

KEMAR was initially invented in collaboration with the audiological industry for the use of hearing aid development, and is still the defacto standard for this industry – however, since then, the usage of KEMAR has spread into a multitude of other industries like telecommunications, hearing protection test, automotive development etc.

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Power modules

An externally polarized condenser measurement microphone cannot work on its own.  It needs to be connected to hardware that can act as an interface between the raw signal output and the data acquisition unit or measurement device. The Power Module is such an interface that improves the performance and reliability of the measurement chain.

Test fixtures

Including products for ear- and headphone testing, hearing-protector testing and telephone testing GRAS' test fixtures are top of the line solutions to fulfill your every need.

Hemisphere kits

 The GRAS hemispheres are compliant with the ISO 3744, 3745 and 3746 (ANSI S12.54, S12.55, S12.56) standards and accommodate for 4, 10 and 20 positions. These are clearly marked to ease the mounting and maintain measurement repeatability.

Two hemisphere structures are available; a 1 m measurement radius and a 2 m measurement radius. Each structure is available in CCP, LEMO and LEMO lownoise variants

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Calibration equipment

Calibration is an essential step in every precision measurement. It establishes the relationship between the sound pressure and the electrical output of the microphone.

Calibration can be performed at either 250 Hz or at 1 kHz. Both frequencies have their advantages and disadvantages.

Cables and Accessories

GRAS manufactures and carries a wide range of cables for their product.  You can find their cables here:

Cable Offerings:  CLICK HERE


Learn More about Consumer Audio & Electronics

Headphones & Headsets


GRAS offers a broad suite of ready-to-use acoustic test fixtures and ear simulator kits for headphone and headset testing. Together, they cover all testing needs in the complete development and production cycle – from early Research and Development (R&D) to Production Line (PL) and Quality Assurance (QA)/Quality Control (QC) 

Speakers & Smart Speakers


 A great set of loudspeakers for a home entertainment system, or a massive PA system, immediately improves the end user experience of the event. Make sure the signature sound you are looking for is easily captured, logged and implemented in every set or array of speakers you manufacture, deliver and install. 

Laptops & Tablets


Achieving the right audio signature on laptops and tablets is important as it is crucial for their usability as well as for the perceived product quality.  GRAS has a number of tools to help you get your designs to match your design goals as well as meet your customers' expectations.



The right audio signature in a smartphone is an important part of the user's perception of product quality. GRAS has a number of tools to help you emulate real-world use, and get your designs fit for your audience.

The GRAS solutions cover the needs of the whole development and production process, from R&D to the final EOL testing to ensure that your audio design vision is met. Use our products to fine-tune and optimize the audio response, intelligibility, sensitivity, phase, feedback, and noise cancellation. .

Household Appliances


 Household appliances are a key metric for regulatory compliance, benchmarking and competitor analysis, as well as being useful for promotion. Depending on the size and the emitted acoustic level of the device under test, the GRAS hemispheres allow for sound power measurements on everything from small size personal electronics, office machines and IT products, household appliances to power tools and smaller engines. Have you ever tried positioning 10 tripods in a hemisphere? If so, you'll appreciate the ease, accuracy and repeatability of the GRAS Hemisphere.  



There are plenty of things you have to worry about as you design your IC and chipsets. One thing is to deliver a set of algorithms, another is to deliver a set of curves with measured improvements in audio response, feedback and noise cancellation, noise and distortion.  This speaks volumes when talking with your customers. Let GRAS help with the acoustic validation portion.  

GRAS Video

Watch the video on the company Head-Fi testing high-quality products using GRAS equipment: 

GRAS Video

Watch the video on measuring beyond the threshold of human hearing:

The Measurement Microphone Guide


Select the right microphone

Measurement microphones are available in many types covering various frequency ranges, dynamic ranges and application situations. The G.R.A.S. measurement microphones are amongst the world's best.  Below you can find help to select the right measurement microphone for your applications.

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Externally polarized vs. prepolarized

Can you tell the difference?

All GRAS measurement microphones are of the condenser type.

This requires a polarization voltage which can either be supplied from an external power supply or the microphone itself can be polarized by injecting a permanent electrical charge into a thin PTFE layer on the microphone backplate.



Which one should you choose?

There are three types of measurement microphones: Free-field, Pressure, and Random incidence.

You can see the differences between these three types of measurement microphones at the higher frequencies, where the size of a microphone becomes comparable with the wavelengths of the sound being measured.

Dynamic range of a microphone

Which levels can the microphone handle?

The dynamic range of a microphone is defined as the range between the lowest level and the highest level which the microphone can handle.

This is not only a function of the microphone alone, but also of the preamplifier used with the microphone. The dynamic range of a microphone is, to a large extent, directly linked to its sensitivity.

Frequency range of a microphone

Which one should you choose?

The frequency range of a microphone is defined as the interval between its upper limiting frequency and its lower limiting frequency.

With today’s microphones you can cover a frequency range starting from around 1Hz and reaching up to 140 kHz.

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