The new High Resolution Ear Simulator is available in two versions: The GRAS RA0401 Externally Polarized and the GRAS RA0402 Prepolarized and is available on multiple test platforms for R&D, production testing and verification. Both are full backwards compatible with the standard IEC 60318-4 (711) ear simulator.
"The High Resolution Ear Simulator is precise, consistent and allows you to measure with confidence," the company states. A unique feature is a special dampening system that extends its useful frequency range to 20 kHz. This has significant advantages when measuring sophisticated earphones and headphones and technologically advanced, wide-band hearing aids. Now, for the first time it is possible to obtain accurate, reliable and repeatable measurements above 10 kHz.
Outstanding benefits include improved repeatability of measurements above 10 kHz, allowing for measurements below and above 10 kHz in the same measurement setup. The dampened resonance means better distortion measurements, even from as low as 3-5 kHz, while the solution improves accuracy and minimizes operator error.
According to Senior Product Manager Jan Hansen from GRAS, the High Resolution Ear Simulator has clear benefits when testing sophisticated products such as headphones. “They demand testing microphones that can measure what the human ear can hear – and that’s what they get with the new high resolution ear simulator,” he says. “Measurements can now be carried out 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 and the like much easier and with improved repeatability.”
The GRAS RA0401/402 is a high resolution version of the well-known standardized 60318-4 ear simulator which has gained wide acceptance as the preferred tool for measurements with simulation of the acoustic load presented by the human ear. According to GRAS Sound & Vibration, The RA0401/402 embodies a number of carefully designed volumes connected via well-defined and precisely tuned resistive grooves. In an equivalent electrical circuit, capacitors would represent the volumes, and inductance and resistance would represent respectively air mass and air flow within the resistive groves. The solution is delivered with a built-in GRAS 40AG 1/2" externally polarized pressure microphone, or GRAS 40AO 1/2" prepolarized pressure microphone, both with an individual calibration chart for the ear simulator.
Where the standard ear simulator has a high Q resonance at about 13.5 kHz, the high resolution version has a built-in dampening system that attenuates the volume related resonances by about 14 dB. Also the shape of the resonances has been softened. In this way, the useful frequency range of the coupler is extended to 20 kHz. The advantages of the design with resonance dampening are clearly visible when comparing the standardized RA0045 Ear Simulator and the RA0401/RA0402 Ear Simulators.
The RA0401/RA0402 are designed 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. The High Resolution Ear Simulator meets the demand for an accurate broadband measurement method where the measurements at high frequencies can be trusted, and is well suited as a high resolution 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. RA0401/RA0402 can be used as a development tool for development of insert type headphones as well as supra- and circumaural types.
For R&D of headphones, the RA0401/RA0402 can be mounted in a KEMAR. When furnished with the anthropometric pinna, tests of supra aural and circumaural 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 improve seal and fit, vastly improving repeatability of measurements and test results at low frequencies. For QC purposes, the RA0401/RA0402 can be mounted in a 45CA Headphone/Hearing-protector Test Fixture.
The RA0401 can be used with a standard LEMO preamplifier, e.g. the GRAS 26AK 1/2" Preamplifier or the GRAS 26AC-1 1/4" Preamplifier fitted with an adapter. 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.
For more information, in the US, contact Ed Okorn, General Manager, North America, GRAS Sound & Vibration at 330.425.1201 or visit www.gras.us