A Family of Future-Proof Ear Simulators

Two improved versions of the IEC 60318-4 (711) ear simulator

Hi-Res audio has become a major market driver in wearable audio. Test equipment must be able to handle high frequencies but at the same time present test objects with a realistic, human-like load - requirements that until now could not be met at the same time.

Our new improved 60318-4-based ear simulators change that. They combine realistic loading of the transducer up to 10 kHz with much improved high-frequency capabilities.

High-Frequency Ear Simulators


  • RA0401 Externally polarized
  • RA0402 Prepolarized


Hi-Res Ear Simulators


  • RA0403 Externally polarized
  • RA0404 Prepolarized

Evolution of the IEC 60318-4 (711) Ear Simulator

For more than three decades, the IEC 60318-4 ear simulator has been the recognized industry standard for testing audio transducers. However, its undamped resonance at 13.5 kHz makes it difficult to use for high-frequency testing. Therefore, GRAS has introduced two improved variants of the IEC 60318-4 ear simulator. They retain a firm footing in the standard but improve the ability to measure at high frequencies.

Hi-Res Audio Ear Simulator for Measurements at Very High Frequencies

Presentation by CTO Peter Wulf-Andersen at
the 2019 AES International Conference
 on Headphone Technology in August.

The Standard IEC 60318-4 (711) Ear Simulator (GRAS RA0045)

The RA0045 has a step half-wave resonance at 13.5 kHz which effectively limits its usefulness to below at least 10 kHz. It uses a ½" microphone.

The High-Frequency Ear Simulator (GRAS RA0401/02)

The RA0401 has a dampings system that attenuates the half-wave resonance at 13.5 kHz and thus extends the useful frequency range to 20 kHz. It uses a ½" microphone.

The Hi-Res Ear Simulator (GRAS RA0403/04)

The RA0403 also has a damping system that attenuates the length-related resonances above 10 kHz, but the use of a ¼” microphone extends the useful frequency range to 50 kHz and beyond.

Explore the benefits

Our new ear simulators build on industry standards - and improve upon them in important ways. They introduce major improvements: High-frequency capability and improved repeatability. When combined with our anthropometric pinna, improved collapsibility, fit and seal are added benefits.

And the perfect companion...

...the GRAS Anthropometric Pinna

  • Drop -in replacement for 60318-4 ear simulator in any test setup
  • Improved distortion measurements
  • Improved repeatability
  • Human-like load up to 10 kHz
  • Extended and stable frequency response
  • IEC 60318-4 compliant/compatible

What solution are you looking for?

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 End-of-Line, including Production (PL) and Quality Assurance (QA)/Quality Control (QC).

Test Stages - From R&D to End-of-Line


Research and development testing includes all testing from early product development over design for production until final manufacturing.

Developing new headphones and headsets is not only a question of great sound. Today, the list of requirements is long and complex: Voice recognition, noise cancellation, wireless and Bluetooth functionality, virtual and augmented reality, etc.

On top of this, they must be fit for use virtually anywhere - and look great too.

GRAS test solutions for R&D cover the complete development process. We offer a wide range of test solutions, ranging from simple and easy-to-use table-top test fixtures (like e.g. 43AG), over state-of-the-art R&D test solutions with Head & Torso Simulators (45BB or 45BC), to production line test fixtures (45CC) that help verify the headphone can be/is produced within specifications. Read more about test types

PL, QA and QC

Production line, QA and QC testing ensure that the actual production matches the target quality and that no sub-standard samples hit the market.

Test equipment must provide repeatable and precise measurements every day to ensure that headphones and headsets that do not meet specifications are not launched in the market.

The complexity of test setups increases as the number of features increase. Also, it is important to ensure the quality of the measurements: Data consistency and repeatability across multiple testing locations.

Downtime and low yields are no-go’s on production lines and this is why the products offered by GRAS for Production Line and Quality Assurance testing have been developed in close collaboration with leading companies in the global headphone and headset industry. Read more about test types



Testing according to IEC 60268, IEC 60318-1, IEC 60318-4 and ITU-T Rec P.57, etc.

Equipment for testing according to all the most important standards for headphone testing. These tried and tested solutions do not allow for low-noise testing or testing at frequencies above 10 kHz - this is why we offer equipment for testing at high frequencies or low levels.


GRAS test fixtures and ear simulator kits for low-noise testing allow for measurements down to the threshold of human hearing.

These systems are ideal for testing of headphones with electronic circuits, eg. ANC, Bluetooth, etc. 


GRAS equipment for high-frequency testing builds on the proven, standardized ear simulators, but now allows for measurements up to 20 kHz. 

Even though these ear simulators surpass the performance defined in IEC 60318-4, great care has been taken to ensure full compliance with these standards.


GRAS equipment for hi-res testing allows for measurements up to 50 kHz and beyond, and for microphone-based systems, up to 70 kHz.

The ear simulators surpass the performance defined in IEC 60318-4, but great care has been taken to ensure compatibility with these standards.

Check the specifications

The sensitivity of the RA0403 Ear Simulator is significantly lower compared to the original RA0045 and the RA0401 due to using a 1/4" microphone which results in a higher noise floor. The GRAS RA0403 Ear Simulator, therefore, is not suited for low-level measurements.

Read our papers on ear simulators

These two papers compare the new RA0403/RA0404 Ear Simulator to the original RA0045 Ear Simulator and the more recent RA0401 High-Frequency Ear Simulator. They show the evolution of ear simulators whereby RA0045 extended the volume with the anthropometric pinna and RA0401 introduced a frequency up to 20 kHz. The RA0403 goes even further to measure up to 50 kHz and, at the same time, improves repeatability.