Getting Started Guide
APx511 B Series Hearing Instrument Analyzer: Getting Started Guide 41
ETLS
For hearing aids with an inductive input coil (T-coil), first
find HFA-SPLI, the high frequency average SPL in a mag-
netic field. Subtract from this (RTG+60 dB) to find ETLS,
the equivalent test loop sensitivity.
HFA MASL
Orient the hearing instrument in the magnetic field for max-
imum pick-up sensitivity, measure HFA output SPL and cal-
culate MASL (magneto-acoustical sensitivity level).
Using the APxHITest API
Introduction
The APxHiTest DLL (HiTest.dll) is a class library used to
aid in the development of user applications that will be used
to test hearing instruments with APx500 and the APx511.
Based on .NET, it can be used with C#, VB or LabVIEW.
A detailed Help file (HiTest_API_PRG.chm) for the API is
provided via a shortcut in the Windows Start menu. Sample
files are listed on page 46. The DLL and the Help file are
included in the APxHia download.
A Quick Tour of the DLL
The APxHITest DLL provides functions for making basic
measurements that can satisfy ANSI or IEC requirements. It
also provides for saving or restoring settings from file. The
DLL provides all required communications with the APx
API.
APx500 software must be installed and of the correct ver-
sion.
The DLL and support files are installed with the APx pro-
gram files, in a subfolder named HearingInstrumentTest.
A Layer View
The interaction of the different components of the system is
based on layers of software on top of the B Series APx511
Analyzer, as shown in the diagram below.
The first layer above the analyzer is the APx500 API. It
provides a functional interface for access to the instrument
and all of its measurement capabilities.
In the diagram, the second layer above the APx511 ana-
lyzer contains a user created application and the APxHiTest
DLL. The HiTest DLL is designed to provide a simplified
interface to the instrument that is tailored for hearing instru-
ment testing.
The top layer in the diagram shows a user-created applica-
tion (User App) that is designed for testing hearing instru-
ments. This top level application can access the APx511
analyzer completely through the HiTest DLL without any
reference to the APx500 API. The APxHia application
installed from the APxHia download is an example of such
an application.
APx511 analyzer
APx500 API
HiTest
dll
User
app
User
app
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