GRAS RA0045-S4 Externally Polarized Ear Simulator Based on IEC 60318-4 (60711), High Sensitivity

Introduction

The RA0045-S4 Ext Pol Ear Simulator is a special type of ear simulator for making low level acoustic measurements on earphones coupled to the human ear by ear inserts such as tubes, ear moulds, or ear tips. It has an input impedance closely resembling that of an average human ear, and, as a result, loads a sound source in very much the same way.

It is based on the following international requirements:

• IEC 60318-4: Occluded-ear simulator for the measurement of earphones coupled to the ear by ear inserts.
• ITU-T Recommendations P.57 (08/96) Series P: Telephone transmission quality, Objective measuringapparatus: Artificial ears.

It is measured and calibrated according to the ITU-T Recommendation P.57.

Design

The RA0045-S4 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.

It includes a GRAS 40AP 1/2″ Ext. Polarized Pressure Microphone, High Sensitivity and each RA0045-S4 is individually calibrated with this specific microphone.

Typical Applications and Use

The RA0045-S4 is for measurements on earphones and hearing aids coupled to the human ear by ear inserts such as tubes, ear moulds, or ear tips.

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 are available. See the tab Ordering info.

Compatibility

The RA0045-S4 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. For the 1/4″ preamplifier, use either the straight RA0003 Adapter or the right-angled RA0001 Adapter.