Fig 2. The half-wave resonance of a typical RA0402 High-Frequency Ear Simulator with IEC and GRAS tolerances
It can readily be seen that the amplitude and shape of the half-wave resonance are very different. Where the standardized ear simulator has a peak that tops above 36 dB, the RA0402 is 14 dB lower. At the same time, the slopes of this resonance are more rounded in the RA0402. The overall result is a much more useful response whose effects on measurements are much easier to identify.
Typical applications and use
The RA0402 is for measurements on earphones and hearing aids coupled to the human ear by ear inserts such as tubes, ear molds, or ear tips and for measurements where the influence of the pinna and the head and torso are part of the investigation.
GRAS has a large portfolio of test devices for such measurements, ranging from fairly simple tabletop test setups to comprehensive configurations based on the KEMAR manikin, with or without mouth simulation.
KEMAR
A drop in-replacement for KEMAR already configured with RA0045 for testing
- Hearing aids, monaural or binaural
- Headphones, in-ear, supra- and circumaural
- Headsets
GRAS 43-series tabletop Ear Simulator Kits
If you already own one of our tabletop testbeds, the RA0402 is a drop-in replacement for 43AC, 43EA, and 43AG already configured with RA0045.
GRAS 43AC, GRAS 43AE, GRAS 43AG
Low and High Leak Pinna Simulators
In accordance with ITU-T Recommendation P.57, it can be used with the following GRAS pinna simulators for testing telephones:
- GRAS RA0056 Low-leak Pinna Simulator
- GRAS RA0057 High-leak Pinna Simulator
A comprehensive range of accessories for making measurements in accordance with IEC 60318-4 is available.
For upgrade information, contact GRAS for further information.
Audiology
Advances in hearing-aid design have made it possible to increase the frequency range of hearing aids. This is the basis for a need for a method for measuring above 10 kHz, in ways that are precise, consistent and offer good repeatability. A traditional 60318-4 ear simulator has poor repeatability above 10 kHz and is ill-suited for measurements on wide-band hearing aids.
The High-Frequency Ear Simulator meets the demand for an accurate broadband measurement method where the measurements at high frequencies can be trusted. It is within the IEC limits, so the link to historical data can be maintained and existing test procedures can still be used - full backward compatibility is ensured.
It is therefore well suited as a high-frequency supplement to the standardized 60318-4 (former 60711 ) ear simulator – or as a new reference tool for hearing aids manufacturers R&D testing and design verification.
Consumer electronics: Headphone testing
Realistic test of headphones and earphones requires that they are presented with an acoustic load that simulates the human ear. The traditional 60318-4 coupler does exactly that, but testing above 10 kHz does not produce reliable and reproducible results because of the sharp and very dominant resonance at 13.5 kHz. In practice, this limitation has made it necessary to measure the high-frequency behavior of the transducer under test with other means, such as mounting it on a baffle and measure in the near field with a ¼” microphone.
With the RA0402, it is now possible to measure below and above 10 kHz in the same measurement setup, at the drum reference point and with the same acoustical loading of the transducer under test. This makes tests of headphones much easier, with improved repeatability.
RA0402 can be used as a development tool for the development of insert type headphones as well as supra- and circumaural types.
For R&D of headphones, the RA0402 can be mounted in a KEMAR. When furnished with the anthropometric pinna, tests of supra-aural and circum-aural headphones can be done to a much higher degree of realism than previously possible. When a headphone is mounted, the anthropometric pinna collapses against the head much like the real ear, and sealing and leakage related effects can better be investigated. For insert type of headphones, the better shape of the ear canal improves seal and fit, vastly improving the repeatability of measurements.
The combined advantage of the anthropometric pinna and the RA0402 is better test results at low frequencies and improved resolution at high frequencies and much-improved repeatability.
For QC purposes, the RA0402 can be mounted in a 45CA Headphone/Hearing-protector Test Fixture.
Compatibility
The RA0402 can be used with a standard CCP preamplifier, e.g. the GRAS 26CA 1/2" Preamplifier or the GRAS 26CB 1/4" Preamplifier fitted with an adapter. For the 1/4" preamplifier, use either the straight RA0003 Adapter or the right-angled RA0001 Adapter.
Like the RA0045 the RA0402 has a dust protection filter to prevent dust and dirt from entering the internal volume. This filter should be kept clean and replaced when needed as dust build-up will influence the performance of the coupler.
