GRAS 45BC-15 KEMAR with Mouth Simulator and Hi-Res Simulators for Headset Test, 2-Ch LEMO

Introduction

The KEMAR head and torso simulator was introduced by Knowles in 1972 and quickly became the industry standard for hearing-aid manufacturers and research audiologists (visit KEMAR.us to read the full story). It is based on worldwide average human male and female head and torso dimensions. It meets the requirements of ANSI S3.36/ASA58-2012 and IEC 60318-7:2017.

The current KEMAR Head and Torso has the same dimensions and acoustical properties as the original KEMAR, but has been developed further by GRAS to meet the industry’s demand for realistic measurements of hearing aids, headphones, and headsets. It provides acoustic diffraction similar to that encountered around the median human head and torso, both in the proximity and in the far-field.

As all the preconfigured 45BC KEMARs consist of the same basic 45BC KEMAR Non-configured, plus a set of application-specific accessories, the full information about a given KEMAR configuration is obtained by combining the information about the 45BC KEMAR Non-configured and the information for a given configured version as found in the present text. Read about the non-configured KEMAR here.

Design

The 45BC-15 is a KEMAR for 2-channel headset test, with externally polarized hi-res ear simulators and anthropometric pinnae.

It is delivered fully configured, individually calibrated and ready for use. In addition to a system calibration certificate, a USB flash memory with simulation data is included.

The main configuration-specific components of the 45BC-15 are the GRAS RA0403 Hi-Res Ear Simulator and the KB5000/KB50001 Anthropometric Pinnae.

The 44AA Mouth Simulator according to ITU-T Rec. P51 with built-in power amplifier
The maximum continuous signal the mouth can produce in 1/3-octave bands is 100dB re. 20µPa in the frequency range of 100Hz to 16kHz. Its loudspeaker accepts an external signal either directly or via its built-in power amplifier (when power is applied).

The Hi-Res Audio Ear Simulator
The acoustic input impedance of the RA0403 Hi-Res Ear Simulator closely resembles that of the human ear and, as a result, loads a sound source in very much the same way.  It 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 RA0403 Hi-Res Ear Simulator mitigates the limited usefulness of the standard IEC60318-4 ear simulator above 10 kHz. The steep resonance at 13.5 kHz has been replaced by a damped resonance and the useful frequency range is now extended to 20 kHz. It complies with IEC60318-4 and its acoustic transfer impedance is within the tolerance band specified by IEC60318-4. From 10 to 20 kHz the transfer impedance is within ± 2.2 dB, from 20 kHz to 50 kHz it is within ±3.2 dB, resulting in much-improved repeatability. Also, realistic THD measurements are now possible.

It is measured and calibrated according to IEC60318-4 and ITU-T Recommendation P.57 and delivered with a calibration chart specifying its sensitivity and frequency response.

It is delivered with a built-in GRAS 40BP 1/2″ externally polarized pressure microphone.

Read more about RA0403 here.

The Anthropometric Pinna
Compared to the standardized pinna, the anthropometric pinna embodies several improvements to the concha and ear canal, combined with increased collapsibility of the helix, and improved mounting of the pinna. It is made of soft silicone, 35 Shore OO hardness.

The external shape of the pinna is identical to that of the standardized KEMAR pinna, but concha and ear canal have been modified so that they closely mimic the properties of a real human ear. The ear canal has been extended and is now an integral part of the pinna which seals directly against the ear simulator. Like the human ear, the ear canal has the 1st and 2nd bend, and the interface with the concha is oval. Fit and insertion consistency are much improved over the cylindrically or conically shaped ear canal extensions that are used with the standardized pinna.

The flexibility of the outer ear has been improved, and when mounting supra-aural and circum-aural headphones the pinna now collapses against the head very much like a human ear.

In addition to the traditional push mounting from the outside, the pinna is secured with two screws from the inside of KEMAR’s head. These two screws ensure that the pinna is held firmly in place. Therefore, it seals perfectly against the ear simulator and the head, and it is now possible to mount and dismount DUTs repeatedly without compromising the seal.

Read more about the Anthropometric Pinnae.

Typical Applications

The anatomical shape of the pinna makes it possible to achieve an excellent fit and sealing with anatomically shaped in-ear transducers. Controlling the insertion depth is easy, leading to good insertion consistency and highly improved repeatability and accuracy of measurements. The improved fit and seal also means that the low-frequency response is improved. It will allow you to reproduce bass notes, as well as effectively measure (active & passive) attenuation.

With the high-resolution ear simulator, it is now possible to make reproducible measurements up to 50 kHz. The 45BC-15 KEMAR is ideal for accurate and repeatable testing of headphones, earphones and in-ear hearing protectors. In addition to this, the built-in mouth simulator makes it ideal for accurate and repeatable testing of headsets. Read more about the advantages of the high-resolution ear simulator here.

Performance and warranty

KEMAR is made of components from our standard portfolio, all manufactured of high-quality material and branded parts that were chosen and processed to ensure life-long stability and robustness. This enables us to offer 2 years warranty against defective materials and workmanship.
Exceptions: Microphones included in KEMAR as for these our normal 5-year warranty apply. The warranty period for cables is 6 months.