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 60318-7:2011.
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
Design
The 45BC-13 is a KEMAR for 2-channel headset test, with externally polarized high-frequency 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-13 are the GRAS RA0401 High-Frequency 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 High-Frequency Ear Simulator
The acoustic input impedance of the RA0401 High-Frequency 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 RA0401 High-Frequency 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 much-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, 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 40AG 1/2" externally polarized pressure microphone.
