Audio Precision APx511 B Series Hearing Instrument Analyzer

APx511 Hearing Instrument Analyzer

Installation Instructions, Specifications, and Getting Started Guide
B Series

Introduction
This document provides installation instructions, specifications, and a getting started guide for the APx511 B Series Hearing Instrument Analyzer.

Documentation and Support
For detailed information on the operation of the APx511 B Series Audio Analyzer, refer to the APx500 User’s Manual available in the APx500 measurement software, on the APx500 Application USB, and online at ap.com. Printed copies can be ordered from Audio Precision or your local distributor.

Contact Technical Support at techsupport@ap.com or call 503-627-0832 ext. 4, or 800-231-7350 ext. 4 (toll-free in the U.S.A.).

Safety Information

For continued fire hazard protection, replace fuses only with the exact value and type indicated on the rear panel of the instrument. The product is classified as Measurement Category I (CAT I) and should not be used within Categories II, III, or IV. The APx511 measurement terminals are intended for audio signals only. Do not substitute parts or make modifications without written approval from Audio Precision.

Safety Symbols

• WARNING! – Alerts you to potentially hazardous conditions such as dangerous voltage.
• ATTENTION! – Alerts you to important operating considerations that could damage equipment.
• FUNCTIONAL EARTH TERMINAL – Indicates a terminal connected to a reference point for functional purposes other than safety.
• PROTECTIVE EARTH TERMINAL – Indicates a terminal bonded to conductive parts for external protective earthing.

Installation

Software
The APx511 uses APx500 measurement software, compatible with APx525 and APx585 analyzers. B Series analyzers have enhanced security and do not require an APx KeyBox but may need authorization codes.

Setting up the Hardware
Ensure the APx511 mains power configuration matches your area’s electrical supply. Check the voltage selection and fusing arrangement before connecting the power cord.

PC System Requirements
The APx500 software requires a PC with a recommended video resolution of 1900 x 1080 or greater. Faster processors yield better performance.

Connecting the Instrument
Install the APx500 software before connecting the APx511 to your PC. Use the included USB cable for best performance. Connect the APx511 to mains power and turn it on. Windows will detect the device and install the necessary drivers.

Specifications

Characteristic	Specifications	Supplemental Information
Number of Channels	2, independent amplitude control
Waveforms	Sine, continuously swept-sine, noise, IMD test signals, multitone, wave file playback	Speaker and telecoil output on DB-15 on rear panel
THD+N	Typically 0.005%
Dynamic Range	Typically 110 dB when Fs 20 kHz

Getting Started Guide

Overview
The APx511 B Series Audio Analyzer is designed for precise audio measurements and analysis.

Software Control
The APx500 software provides a user-friendly interface for controlling the APx511 and conducting measurements.

Front Panel Indicators
The front panel includes indicators for power, speaker, tele-coil, battery, and microphone status.

Rear Panel Connections
The rear panel includes connections for USB, power, and audio inputs/outputs.

Basic Test Configuration
Follow the setup instructions to configure the APx511 for basic audio testing.

Accessories
Various accessories are available to enhance the functionality of the APx511.

FAQ

1. What is the APx511 used for?
   The APx511 is used for analyzing and measuring audio signals in hearing instruments.
2. Do I need an APx KeyBox for the B Series?
   No, B Series analyzers do not require an APx KeyBox but may need authorization codes.
3. What software is compatible with the APx511?
   The APx511 uses the APx500 measurement software.
4. How do I connect the APx511 to my PC?
   Install the APx500 software first, then connect the APx511 using the provided USB cable.

Copyright © 2011–2023 Audio Precision, Inc.
All rights reserved.

• Printed in the United States of America.
• No part of this manual may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher.
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Audio Precision
9290SW Nimbus Ave
Beaverton, Oregon 97008
503-627-0832
800-231-7350
ap.com

Documentation and Support
This booklet contains safety information, installation instructions and full specifications for the Audio Precision APx511 B Series Audio Analyzer.

The APx500 User’s Manual
Detailed information on the operation of the APx511 B Series Audio Analyzer is available from the embedded Help installed with the APx500 measurement software, in the APx500 User’s Manual PDF on the APx500 Application USB, and on the Web at ap.com; printed copies can be ordered from Audio Precision or your local distributor. ap.com
Visit the Audio Precision Web site at ap.com for APx support information. APx resources are available at  ap.com. You can also contact our Technical Support staff at  techsupport@ap.com, or by telephoning 503-627-0832 ext. 4, or 800-231-7350 ext. 4 (toll free in the U.S.A.).

Safety

Safety Information

• Do NOT service or repair this equipment unless properly qualified. Servicing should be performed only by a qualified technician or an authorized Audio Precision distributor.
• Do NOT defeat the safety ground connection. This equip-ment is designed to operate only with an approved three-conductor power cord and safety grounding. Loss of the protective grounding connection can result in electrical shock hazard from the accessible conductive surfaces of this equipment.
• Do NOT exceed mains voltage ratings. This equipment is designed to operate only from a 50–60 Hz ac mains power source at 100–240 Vac nominal voltage. The mains supply voltage is not to exceed ±10 % of nominal (90–264 Vac). For continued fire hazard protection, fuses should be replaced ONLY with the exact value and type indicated on the rear panel of the instrument and discussed on page 25 of this booklet.

The International Electrotechnical Commission
(IEC 1010-1) requires that measuring circuit terminals used for voltage or current measurement be marked to indicate their Measurement Category. The Measurement Category is based on the amplitude of transient or impulse voltage that can be expected from the AC power distribution network. This product is classified as Measurement Category I, abbreviated “CAT I”. This product should not be used within Categories II, III, or IV. The APx511 measurement terminals are intended to be used for the measurement of audio signals only.

• Do NOT substitute parts or make any modifications without the written approval of Audio Precision. Doing so may create safety hazards. Using this product in a man ner not specified by Audio Precision can result in a safety hazard.
• This product is for indoor use—Installation Category II, Measurement Category I, pollution degree 2.
• To clean the enclosure of this product, use a soft cloth or brush to remove accumulated dust. A mild detergent may be used to remove remaining dirt or stains. Do not use strong or abrasive cleaners. Wipe all surfaces with a damp cloth.
• This unit is supplied with four feet on the bottom surface and four feet on the right side surface. The unit should only be operated while resting on the bottom surface feet. The feet on the right side are provided for convenience and stability when transporting the unit. DO NOT operate the unit while it is sitting on the side feet.

Safety Symbols
The following symbols may be marked on the panels or covers of equipment or modules, and are used in this manual:

• WARNING!—This symbol alerts you to a potentially hazardous condition, such as the presence of dangerous voltage that could pose a risk of electrical shock. Refer to the accompanying Warning Label or Tag, and exercise extreme caution.
• ATTENTION!—This symbol alerts you to important operating considerations or a potential operating conditions that could damage equipment. If you see this marked on equipment, refer to the Operator’s Manual or User’s Manual for precautionary instructions.
• FUNCTIONAL EARTH TERMINAL—A terminal marked with this symbol is electrically connected to a reference point of a measuring circuit or output and is intended to be earthed for any functional purpose other than safety.
• PROTECTIVE EARTH TERMINAL—A terminal marked with this symbol is bonded to conductive parts of the instrument and is intended to be connected to an external protective earthing system.

Disclaimer
Audio Precision cautions against using their products in a manner not specified by the manufacturer. To do otherwise may void any warranties, damage equipment, or pose a safety risk to personnel.

Installation

Software
The APx511 hearing instrument analyzer system uses the award-winning APx500 measurement software, whether using the GUI in the foreground or controlling APx500 in the background using the API. This is the same software used in the APx525 and APx585 analyzer families.

APx “B Series” analyzers
All analyzers shipped in late December 2018 (or afterward) have a new embedded processor and enhanced security provisions. These analyzers are designated “B Series” and carry “B Series” nomenclature. “B Series” APx analyzers do not require an APx KeyBox (see below), but may require authorization codes to enable APx500 software or software options.

The APx KeyBox
If you are using APx500 software version 4.6 or later with an earlier APx analyzer (non “B Series”), you must attach an authenticated APx KeyBox to the Software Options connector on the analyzer rear panel.
The APx KeyBox must be programmed with your analyzer’s serial number at the Audio Precision factory, and cannot be used with any other APx analyzer. You may require authorization codes to enable APx500 software or software options.
Note that without a properly authenticated APx KeyBox attached, APx500 version 4.6 or later will only run in demo mode. If you need a KeyBox, locate your analyzer serial number and go to https://ap.com/get-keybox/ to complete the order form.

Analyzer serial numbers are located on the configuration label on the analyzer rear panel, and on the calibration label on the forward edge of the top panel.

PC system requirements
The APx500 measurement software requires a personal computer (PC) with the following features and capabilities:

• Operating system: Microsoft Windows 10 (64-bit) or Windows 8.1 (64-bit). Windows 10 (64-bit) is recommended.
• Intel i5 or better processor running at a clock speed of at least 2.5 GHz. AMD Processors with similar specifications are also supported.
• At least 8 GB of RAM. 16 GB is recommended.
• At least 1.5 GB of free hard disk space. An SSD for the operating system drive is highly recommended.
• A CD-ROM optical disc drive or Internet connection to download and install software.
• A USB 2.0 port or USB 3.0 port; two are required for optional switcher use.
• A color monitor with SXGA (1280 x 1024) video graphics support. Video resolution of 1900 x 1080 or greater is recommended.

System performance is sensitive to processor speed; faster processors will yield faster results.
APx500 is data intensive and it is recommended that other data-intensive applications not be run concurrently.

This includes Audio Precision’s AP2700, APWIN or ATS.

Installation

To install the measurement software, insert the APx500 application disc into the optical drive on the PC and follow the instructions in the installation dialog. If you don’t have the APx500 application disc, you can download APx500 from the Audio Precision Web site at ap.com.
NOTE: You must have local administrator rights to install APx500 software. Go to User Accounts in the Windows Control Panel, or check with your network administrator.

Running the software without instrument hardware attached

NOTE: You must have standard user rights or administrator rights to operate APx500 soft-ware. Guest users are not supported.
You can launch the APx500 software without instrument hardware attached. When no hardware is detected, APx500 will present you with the following dialog box:
Select “Demo Mode.” APx500 will run in demo mode, which allows you to explore the user interface but does not enable any measurement functions. Input data shown in Demo Mode is false data, generated for display only.
At first launch, Demo Mode runs simulating attachment to an APx585. To run Demo Mode simulating anther instrument, select that option from the Instrument Type menu.

Running the software with instrument  hardware attached

NOTE: You must have standard user rights or administrator rights to operate APx500 software. Guest users are not supported.

Connecting the instrument to your PC
Before connecting your APx511 instrument to your PC, install the APx500 measurement software as described above. Connecting the instrument prior to software installation may cause Windows to select an incorrect USB driver for the instrument.

USB driver selection
The measurement software communicates with the APx511 using a USB 2.0 interconnection. Once the software is successfully installed, connect one end of the USB cable to a USB 2.0 port on the PC, and the other end to the PC INTERFACE port on the rear of the APx511. We strongly recommend that you use the USB cable included with your instrument (AP part number CAB-APSI). We have tested other USB cables that perform poorly.

• Note: Some PCs have optional USB ports on the front of the PC, or on extension brackets on the rear. In many cases these convenience ports have compromised performance due to the extra cable length within the PC. We recommend using USB ports directly connected to the PC motherboard, typically at the rear of the PC.
• Connect the APx511 mains power cord to the instrument and to a source of ac mains power. See Setting up the hardware below for more information about mains connections.
• Turn the instrument on by rocking the mains power switch up to ON ( | ). The mains power switch is located in the power entry module on the rear of the APx511. Windows will detect the presence of the APx511 on the USB port and will open the Hardware Update Wizard to search for the correct software driver. Select “Install the software automatically.” Windows will find the Audio Precision driver software installed with APx500 and connect to the APx511.
• Launch APx500 by double-clicking on the installed shortcut. With the APx511 connected, you may be asked to update the instrument firmware during the first launch of the measurement software. APx500 will start, and in a short time you will be presented with the opening screen. Refer to the APx500 User’s Manual for more informa-tion about making measurements.

The APx500 User’s Manual is available as a PDF on the APx500 Application Disc and online at ap.com; a hard-copy version can be ordered from Audio Precision or your local distributor.

Setting up the hardware

Connecting your instrument to the electrical mains supply

• The APx511 instrument must be connected to a 50–60 Hz alternating current (ac) electrical mains supply, maxi-mum voltage 250 Vrms.
• The instrument has been configured at the factory for the expected voltage at its intended destination, as ordered. The voltage setting and fusing arrangement will normally be correct unless the instrument has been transported into another area. The power entry module has a strip of indicator tape showing its mains voltage setting. This tape must be removed before use.
• You MUST be sure that the APx511 installment mains power configuration is correct for the electrical mains power supplied in your area. If you are not sure, do not plug the instrument into the mains power. Follow the instruc-tions below to check or change the instrument mains supply voltage selection.
• The mains power supply is applied to your APx511 instrument through the power entry module located on the rear panel. Before connecting the power cord, confirm that the input voltage selection and fusing arrangement in the power entry module are correct for your mains power supply.

Checking the mains supply voltage configuration
The white plastic voltage indicator pin protrudes through one of the four labeled holes in the module cover to indicate the selected input voltage. Figure 2 shows the pin in the second position, indicating 120 V. Check to see that the indicated voltage matches your mains supply voltage. If it does not, change the mains supply voltage configuration as described below.

Opening the power entry module
Unplug the power cord from the instrument before changing fuses or performing any other operations described in this section.

To open the power entry module, refer to Figure 3 and proceed as follows:

• Remove the mains power supply cord from the power cord connector.
• Locate the slot in the module cover door hinge. The hinge is a the left side of the cover door, and the slot in the hinge is visible in the power cord connector cavity. Insert a small screwdriver or similar tool in the slot and pry the cover door hinge outward. The cover door will snap out, and then can be pivoted on its hinge for access to the fuse block assembly and voltage selector card.

Changing the Mains Supply Voltage Configuration

• Open the Power Entry Module as described above.
• The voltage selector card is a small circuit board fitted with a white plastic indicator pin, installed in a housing on the right side of the Power Entry Module as shown in Figure 4. Pull the voltage selector card straight out of the housing, using narrow pliers to grab the card. Do not use the indicator pin as a handle.
• Orient the selector card so that the desired input voltage is readable at the bottom, shown in Figure 5. Then move the indicator pin to point UP, opposite the indicated voltage. Seat the pin assembly in the notch on the board edge.
• Insert the voltage selector card into the housing with the printed side of the card facing toward the mains power connector. The card edge indicating the desired voltage should enter the housing first.
• Confirm that the correct fuse or fuse combination is installed for the intended input voltage (refer to the fuse ratings marked on the instrument rear panel). If necessary, change the fuse type as described in the following section
• Close the module the cover door and verify that the indicator pin shows the desired voltage.
• Once you have verified that the line voltage selection is correct, connect the power cord from a main power outlet to the power cord connector on the instrument rear panel.

Fuse information
The power entry module accommodates two fusing arrangements, as illustrated in Figure 6.

100/120 VAC operation
The 100/120 VAC fusing arrangement uses a single type 3AG (0.25″ x 1.25″) slo-blo fuse. Audio Precision recommends only the following replacement fuse:

1 each Littelfuse 313 Series, 800 mA 3AG 250 V slo-blo glass fuse.

230/240 VAC operation
The 230/240 VAC fusing arrangement uses two 5 x 20 mm IEC-approved type T fuses. Audio Precision recommends only the following replacement fuses:

• 2 each Littelfuse 213 Series, 400 mA 250 V 5 x 20 mm Time Lag (slo-blo) glass fuses or
• 2 each Littelfuse 218 Series, 400 mA 250 V 5 x 20 mm Time Lag (slo-blo) glass fuses.

Refer to the label on the instrument rear panel for fuse current ratings.

Changing the fusing arrangement

To replace a fuse or change the fusing arrangement, proceed as follows:

• Remove the mains power cord from the power cord connector and open the Power Entry Module as described above.
• Using narrow pliers, pull the fuse assembly out of the housing.
• Change or add the correct fuses as necessary, refer-ring to Figure 6. Refer to the instrument rear panel for the correct fuse electrical current rating.
• Insert the fuse assembly in the housing, with the side of the assembly that carries the fuse(s) for your desired fusing arrangement facing into the housing. Press the fuse assembly firmly into the housing.
• Confirm that the line voltage selection is correct for your mains voltage and your fusing arrangement.
  Once you have verified that the line voltage selection is correct, connect the power cord from a mains power out-let to the power cord connector on the instrument rear panel.

APx511 B Series

Hearing Instrument Analyzer Specifications

with APx500 v5.0 or higher measurement software January 2023 NP0020.00040 r001

Notes to Specifications

1. System specification including contributions from both generator and analyzer. Generator-only and/or analyzer-only contributions are typically less.
2. Generator load must be ≥ 8  (speaker output), or ≤ 4  telecoil output for specified performance.
3. Analyzer input must be ≥ 150 mV for specified performance. Analyzer set to measure “d2+d3” IMD products for MOD and DFD modes.
4. Maximum low-pass filter frequency is limited by analyzer input bandwidth setting.

Getting Started Guide

Overview
The B Series APx511 is an analog-only audio analyzer with connectivity and features specifically designed to test hearing instruments. The front panel provides five LED indicators, and the rear panel provides all the audio, control and mains power connections, and the mains power switch.

• Hearing instrument testing is typically accomplished using a test chamber such as the Interacoustics TBS25. The chamber is fitted with an internal loudspeaker and a telephone magnetic field simulator (TMFS, or telecoil) for telecoil stimulation, and provides a means of connec-tion for a measurement microphone / acoustic coupler combination and a battery simulator, both provided by the user.
• The APx511 has an internal 4 watt power amplifier to drive the loudspeaker, a telecoil output, a powered microphone input and DC connections for the battery simula-tor.
  See the Installation chapter earlier in this booklet for information about APx500 measurement software installation, mains power connection, and fusing. See the Specifications chapter for B Series APx511 performance characteristics.

Software control
The analyzer hardware runs under Audio Precision’s APx500 measurement software. Although it is possible to use the APx511 using the APx500 user interface, a more typical use is to address the APx500 API using your proprietary automation software, with APx500 running in the background.

A .NET library of functions to perform and automate the tests described in IEC60118-7 and ANSI S3.22 is provided, with programming samples in LabVIEW, VB.NET and C#, and a program to illustrate usage of the DLL. See page page 62.

• Front Panel Indicators
  There are 5 LED indicators on the B Series APx511 front panel. From left to right, these are:
• POWER
  This indicator is lit when mains power is applied.
• SPEAKER
  This indicator is lit when the Speaker output is selected.
• TELE-COIL
  This indicator is lit when the Telecoil output is selected.
• BATTERY
  This indicator is lit when the battery reference voltage is on.
• MIC
  This indicator is lit when power is applied to the microphone input.
• Rear Panel Connections
  All connections to and from the B Series APx511 are provided on the rear panel. From left to right these are:
• Power Input Module
  The mains switch, the mains power input, and mains line fusing are provided in the module. See the Installation chapter earlier in this booklet for detailed information.
• Ground connection
  This ground lug provides a convenient point to bond the chassis and technical ground of the APx511 to other equipment as part of a test setup.
• Software Options
  The APx511 is provided with all the software features and measurements required for hearing instrument testing. If you also require PESQ or POLQA testing, optional software keys can be purchased. The software keys are connected at the Software Options connector.
• Aux Control In
  Aux Control (sometimes referred to as GPIO) provides the capability to communicate with external devices by transmitting and receiving control commands. The APx511 supports Aux Control Input only.
  Aux Control In is a general-purpose 8-bit digital port, available on a 9-pin D-Sub connector. Pin 9 is the common (ground) connection; pins 1–8 are numbered to correspond with the Aux Control bits 1–8.

Aux Control In commands can be read in the APx500 software, or can be used to trigger actions in an APx500 sequence. Applications include input of operator controls (such as a foot switch) and reading of device states.

PC Interface
Use this connector to connect the B Series APx511 to a USB port on the PC running APx500.

• Output to Test Chamber
  This connector provides connectivity to elements in the test chamber, as shown in the diagram on the opposite page, and are detailed in the connector pin-out diagram shown here.
• Microphone Input
  Connect the measurement microphone to this BNC connector. The APx511 is designed to be used with a prep-polarized measurement microphone that uses constant current power (CCP).A 24 Vdc, 4 mA constant current power source to power the microphone can be switched ON or OFF in software.
• Basic Test configuration
  Hearing instrument testing is typically performed in an acoustically isolated test chamber, which is fitted with a loudspeaker, a telecoil, a battery simulator and a measurement microphone with a 2 cc acoustic coupler.
  The APx511 is shipped with either a DB-15 to DB-15 cable, or a DB-15 breakout cable, selected at time of purchase. Use this cable to connect the elements in your test chamber to the APx511 as shown in this diagram. The microphone cable shown here is provided with the measurements microphone when purchased as an option from Audio Precision.

Accessories

Measurement microphone, dummy mic, HA-1 and  HA-2 couplers.

Audio Precision offers these accessories for the APx511:

• Measurement Microphone, 0.5 in. diameter.
• Measurement Microphone, 14 mm diameter.
• Microphone coupler, 2 cc, HA-1-05, 0.5 in.
• Microphone coupler, 2 cc, HA-2-05, 0.5 in, with BTE tubes.
• Microphone coupler, 2 cc, HA-1-14, 14 mm
• Microphone coupler, 2 cc, HA-2-14, 14 mm, with BTE tubes.
• Dummy mic, 0.5 in diameter
• Dummy mic, 14 mm diameter
• Microphone calibrator, 0.5 in fitting
• Calibrator adapter, 0.5 in. to 14 mm
• APx511 Self test kit

G.R.A.S. Microphone Calibrator

Please contact your representative or Audio Precision for more information.

APxHia
We have created a program called APxHia to illustrate the hearing instrument testing functions available in the .NET function library.
The program provides tools for microphone calibration and chamber leveling and other common tasks. It also runs a series of tests satisfying the two defining standards for hearing instrument testing.

Installing APxHia
APxHia can be downloaded from the Audio Precision Web site at ap.com. Go to Audio Analyzers > APx511 Audio Analyzer > and choose Downloads. Go to Latest Software, and choose APxHia (Hearing Instrument Analyser) x.x. An archive called APX_HIA_x-x.zip will be downloaded to your PC. Extract the archived files.
Run HearingInstrumentAnalyzerSetup.exe to install APx-Hia on your system.

Note that APxHia is provided for illustrative purposes only. For production testing a user-created program in C#.NET, VB.NET or Lab-VIEW should be created to address the API. See page page 62.
The graphs displayed in APxHia are images.

To access the graph data, go to the corresponding graph in the APx500 user interface.

Running APxHia
After installing APxHia, choose APxHia from the Windows Start menu under Audio Precision > APx500 x.x Hearing Instrument Analyzer.

When APxHia first launches, it also launches APx500 (in the background, not visible) and opens an APx project file. If APxHia has been run on this system before, previous settings are read and applied.
From the APxHia View menu, choose APx500 to make APx500 visible. If you are familiarizing yourself with the APx511, it can be instructive to watch the APx500 dis-plays while the testing progresses.

You can also choose to turn the APx signal monitors ON or OFF from the View menu. The signal monitors consume considerable PC resources, and you may find that your system is more responsive with the monitors off.

Calibrating the microphone
A first step is to set microphone calibration for the sys-tem. Go to Tools > Microphone to open the Micro-phone Calibration dialog. If the microphone has been previously calibrated with this system, the calibration date will be shown.

Using a Calibrator
APxHia provides two methods of obtaining calibration references. The preferred method is to use a third-party microphone calibrator device. Choose Use Calibrator from the Reference menu.

• Microphone calibrator devices typically provide acoustic output levels of either 94 dBSPL or 114 dBSPL. Enter the calibrator output level in the dBSPL (nominal) field.
• Check the Mic Power checkbox to apply power to the microphone. With APx visible, you can verify connections and power by tapping the microphone while watching the Level display in APx500.
• Fit the microphone to the calibrator and turn the calibration ON. In APxHia, Click Calibrate.
• The program will measure the microphone output and set Mic Sensitivity (measured) value as required to calibrate the microphone.

Bypassing acoustic calibration
If you do not have a microphone calibrator, you can bypass acoustic calibration and instead enter the micro-phone sensitivity from the microphone specification sheet.

Leveling the test chamber

This tool will set chamber acoustic output to a calibrated level, and equalize the analyzer output to compensate for loudspeaker response.
If no leveling data is on file for this system, the Leveling Date field will read “No Leveling Data.”

• Leveling uses the regulation function in APx.
  Put the microphone on the chamber test point spot. Fit the dummy mic to the coupler to maintain a constant acoustic space. Close and seal the chamber.
  Click Level. The program finds the generator level required to achieve the target level and sweeps the chamber at that level. A compensation curve is created and applied to the generator output. The chamber is swept again with leveling compensation, and the maximum deviation from flat response at the reference frequency is shown in the Leveled Deviation field.
• Preparing the DUT
  For testing purposes, hearing instruments are considered to be one of two types: “behind the ear” (BTE), which uses a short acoustic tube to route the instrument output to the ear canal, and “in the ear” (ITE) which outputs sound directly into the ear canal.
  Fit the appropriate microphone coupler to the acoustic output of your device under test (DUT). Fit the measure-ment microphone into the coupler.
• Powering the DUT
  For testing purposes, the internal battery is replaced with a battery simulator (or pill). Fit the battery simulator into the DUT and connect it to the battery adapter jack within the chamber.
• Testing the Acoustic input
  The hearing instrument is typically tested in an acoustic chamber, where a loudspeaker stimulates the instrument’s receiver (internal microphone). Set the DUT in the chamber’s optimal acoustic test point (the “sweet spot”), and attach the microphone coupler and measurement microphone.
  Set the DUT’s program switch to acoustic mode.
• Testing the Magnetic input
  The acoustic chamber is also fitted with a telephone magnetic field simulator (TMFS, or telecoil) to induce a signal into the DUT’s telecoil input. The optimal placement of the DUT for magnetic coupling must be discovered by trial, as described in the procedure below.
  For telecoil testing, set the DUT’s program switch to telecoil mode.
• Running the standard tests
  Place the DUT (with the battery simulator installed), the measurement microphone/coupler combination and the dummy mic in the chamber.
  Follow the prompts in the measurements to set the DUT volume control to the correct level.
• ANSI S3.22 / IEC60118-7
  Hearing instrument testing is defined in two standards: ANSI S3.22 from the American National Standards Institute, based in Washington, D.C., and IEC60118-7, from the International Electrotechnical Commission based in Geneva, Switzerland.

The two standards are largely the same, with only a few minor differences in methods, values and nomenclature. Refer to the standard of interest for an explanation of terms and procedures.
APxHia provides a series of measurements for each standard, selectable by the Standards buttons.

Measurements for ANSI S3.22
These ANSI S3.22 measurements are supported:

• OSPL90 curve
  OSPL90 Curve measures coupler output sound pressure level (OSPL) as a function of frequency, for a 90 dB input SPL.
• HFA OSPL90
  HFA OSPL90 displays the high frequency average (average SPL at 1 kHz, 1.6 kHz and 2.5 kHz) for a 90 dB input SPL.
• Full-On Gain
  Full-On Gain (FOG) displays gain for an input of 60 dBSPL when the gain of the hearing instrument is at its full-on position.
• HFA Gain
  HFA Gain displays the HFA gain for an input of 60 dBSPL when the gain of the hearing instrument is at its full-on position.
• Set RTS
  An interactive dialog to set the Reference Test Setting, using the volume control on the DUT.
• Frequency Response
  Coupler SPL as a function of frequency for a 60 dB input SPL, with gain control at RTS.
• Harmonic Distortion
  Ratio of sum of the powers of all the harmonics to the power of the fundamental at various levels and frequencies.
• Equivalent Input Noise
  SPL of an external noise source at the input would result in the same coupler SPL as that caused by all the internal noise sources in the hearing aid.
• Battery Current
  Electrical current drawn from the battery when the input SPL is 65 dB at 1000 Hz and the gain control is at RTS.
• Input Output
  For hearing aids with AGC, the coupler SPL as a function of the input SPL, at one or more of 250, 500, 1000, 2000, 4000 Hz, with the gain control at RTS
• Attack and Release
  Attack: For hearing aids with AGC, the time between an abrupt change from 55 to 90 dB input SPL and the time when the coupler SPL has stabilized to within 3 dB of the steady value for a 90 dB input SPL, at one or more of 250, 500, 1000, 2000, 4000 Hz, with the gain control at RTS.
  Release: For hearing aids with AGC, the time between an abrupt change from 90 to 55 dB input SPL and the time when the coupler SPL has stabilized to within 4 dB of the steady value for a 55 dB input SPL, at one or more of 250, 500, 1000, 2000, 4000 Hz, with the gain control at RTS.
• SPLITS Response
  For hearing aids with an inductive input coil (T-coil), the coupler SPL as a function of frequency when the hearing instrument, with gain control at RTS, is oriented for maximum output on a telephone magnetic field simulator
  (TMFS).
• IEC60118-7
  These IEC60118-7 measurements are supported:
• OSPL90 curve
  OSPL90 Curve measures coupler output sound pressure level (OSPL) as a function of frequency, for a 90 dB input SPL.
• HFA OSPL90
  HFA OSPL90 displays the high frequency average (average SPL at 1 kHz, 1.6 kHz and 2.5 kHz) for a 90 dB input SPL.
• Full-On Gain
  Full-On Gain (FOG) displays gain for an input of
  50 dBSPL when the gain of the hearing instrument is at its full-on position.
• HFA Gain
  HFA Gain displays the HFA FOG for an input of 50 dBSPL when the gain of the hearing instrument is at its full-on position.
• Set RTS
  An interactive dialog to set the Reference Test Setting, using the volume control on the DUT.
  Frequency Response
  Coupler SPL as a function of frequency for a 60 dB input SPL, with gain control at RTS.
• Battery Current
  Electrical current drawn from the battery when the input SPL is 65 dB at 1000 Hz and the gain control is at RTS.
• Equivalent Input Noise
  SPL of an external noise source at the input that would result in the same coupler SPL as that caused by all the internal noise sources in the hearing instruement.
• Harmonic Distortion
  Ratio of sum of the powers of all the harmonics to the power of the fundamental at various levels and frequencies.
• Input Output
  For hearing aids with AGC, the coupler SPL as a func-tion of the input SPL, at one or more of 250, 500, 1000, 2000, 4000 Hz, with the gain control at RTS.
  Attack and Release
  Attack: For hearing aids with AGC, the time between an abrupt change from 55 to 90 dB input SPL and the time when the coupler SPL has stabilized to within 3 dB of the steady value for a 90-dB input SPL, at one or more of 250, 500, 1000, 2000, 4000 Hz, with the gain control at RTS.
• Release: For hearing aids with AGC, the time between an abrupt change from 90 to 55 dB input SPL and the time when the coupler SPL has stabilized to within 4 dB of the steady value for a 55 dB input SPL, at one or more of 250, 500, 1000, 2000, 4000 Hz, with the gain control at RTS.
• ETLS
  For hearing aids with an inductive input coil (T-coil), first find HFA-SPLI, the high frequency average SPL in a magnetic 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 maximum pick-up sensitivity, measure HFA output SPL and calculate 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 69. 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 program 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.

User app	User app
	HiTest dll
APx500 API
APx511 analyzer

In the diagram, the second layer above the APx511 analyzer contains a user-created application and the APxHiT-est DLL. The HiTest DLL is designed to provide a simplified interface to the instrument that is tailored for hearing instrument testing.
The top layer in the diagram shows a user-created application (User App) that is designed for testing hearing instruments. 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.

The user-created application shown in the upper left corner of the diagram can access the APx511 analyzer through the APx500 API or through the HiTest DLL, or both. A sample use case for this would be an application to test hearing instruments that needs some of the more advanced features available in the APx500 API as well as the standard measurements available in the HiTest DLL. In this case, the application would reference the APx500 API as well as the HiTest DLL

Initialization
The first step in any application is to create an instance of the APxHiTest object. This is done in C# or VB by declaration and assignment.

C#.NET

Using AudioPrecision.HiTest; Private APxHiTest apxHiTest; // Create a new instance apxHiTest = new APxHiTes();

VB.NET

Imports AudioPrecision.HiTest Private apxHiTest As APxHiTest ‘ Create a new instance apxHiTest = New APxHiTest()

The module will require access to the DLL, which should be referenced in the project. Once referenced, then a using statement will bring in the functionality of the dll. Within a class constructor, the call to declare an instance the APxHiTest can be made.
Once an object is created, it must be initialized

C#.NET

var r = apxHiTest.Initialize(); If (!r) // throw an initialization error or display // a messagebox.

VB.NET

Dim r as Boolean ‘ Initialize it R = apxHiTest.Initialize() If (r == False) // Initialize failed

The Initialize function will load the APx project file that is specific to the Hearing Instrument DLL. It is found in the SupportFiles folder of the installed directory for the DLL.

Configuration
The DLL provides file handling for the storing and retrieval of microphone calibration and speaker leveling. These files reside in a default directory. The location can be assigned for opening different files.

C#.NET

apxHiTest.ConfigurationFullPath = “myPath”; apxHiTest.RestoreConfiguration();

VB.NET

‘ Set the path to the target configuration apxHiTest.ConfigurationFullPath = “myPath” ‘ Load the configuration apxHiTest.RestoreConfiguration()

By setting ConfigurationFullPath, the application can bring in settings from different locations or save settings to folders other than the default folder.

Calibration
Two main areas are the focus of calibration. The microphone and must be calibrated and the speaker must be leveled for proper measurements to be made.

Microphone Calibration
The microphone may be calibrated with the use of a standardized calibrator that provides a known level, or entering the specifications from a microphone data sheet.

Calibration Technique	APXHITest Function Name
Using a calibrator	CalibrateMic (calibrator level, acceptable tolerance)
Using a data sheet	CalibrateMic (Signal path, spec in mV/Pa)
Measuring applied level	MeasureCalSPL (signal path, MeasSplType.ReferenceLev- els)

The second CalibrateMic function (above) should be used to set the mic cal value for each signal path in the project, insuring that all signal paths are properly set up for the microphone.

Two methods provide status of the calibration by indicating if a calibration has been performed (by calling IsMicCalibrated), and the time of the last attempt (by calling MicCalibrationTimestamp). The time of the last calibration will reflect when it was last performed, regardless of its success.

Speaker Leveling
The system must determine what levels are required to generate a flat response through the speaker. This is accomplished by performing the leveling. It applies the full range of frequencies to the speaker and the microphone will capture the level at that frequency. The resulting table of frequencies and levels can be applied to the APx, so that future measurements using the speaker will have a flat response curve.
There is one function for performing this, called LevelAcousticPath. It takes several arguments. As a result of a successful leveling, the instrument will be loaded with the proper equalization table for each measurement used.

Calibration Persistence
Each time the APxHiTest is initialized, it will read in the calibration and leveling data from previous sessions. If there has been a change in either the microphone or speaker parameters, the data will be saved at the close of the
APxHiTest.

Measurements
The supplied functions for performing measurements are written as such to allow a generalized use, where levels can be provided based on the needs of the specific test being performed.

For instance, to measure

OSPL90, a call to MeasureFrequencyResponseLevel is made.

C#.NET

double level = 90.0; SignalType sweep = SignalType.frequency response; SignalPath path = SignalPath.Acoustic; APXHiTest.XYarrayPair results = apxHiTest. MeasureFrequencyResponseLevel(level, path, sweep);

VB.NET

‘ Declare a variable to hold the results Dim ospl90 As APxHiTest.XYarrayPair Dim path As APxHiTest.SignalPath Dim signal As APxHiTest.SignalType path = APxHiTest.SignalPath.Acoustic signal = APxHiTest.SignalType.FrequencyResponse ‘ Call the measurement function on the Acoustic path using Frequency Response ospl90 = apxHiTest.MeasureFrequencyResponseLevel(90.0, path, signal)

The value returned from the call will be a structure containing two arrays, the X array is the list of frequencies, and the Y array is the list of levels found at each frequency. To complete the measurement, scan through the X array to find the index of the three HFA frequencies of 1.0K, 1.6K and 2.5K, and find the matching levels. Perform an average of the three levels to provide OSPL90.

Instrument Parameters
There are several functions that support the APx500 directly. With these functions, the version or serial number can be queried. Also the APx500 UI can be made visible or hidden. The signal monitors can be turned on or off.

C#.NET

// Hide the APx apxHiTest.Visible = false;

VB.NET

‘ Make APx visible apxHiTest.Visible = False

Closing
At the end of the application, before it exits, a call to close the DLL should be made. If the Close function is called with True as its argument, then the APx500 will shut down as well..

C#.NET

// Close the HiTest apxHiTest.Close();

VB.NET

‘ Close the HiTest apxhiTest.Close()

API Help File
Refer to the HiTest_API_PRG.chm help file included in the APxHia download and available via a shortcut in the Windows Start menu.

Measurement Overview
To accomplish measurements that are in line with the ANSI standards, refer to the following table for guidelines of functions to call and what parameters to supply.

 

• APxHiTest Graphics
  Two measurement functions support capturing the plot screen as a bitmap that can be displayed by the application. They are MeasureFrequencyResponse and Measure-InputOutput. They make use of optional arguments beyond the required arguments. The default is to skip the screen capture. If a string file name is supplied, then the image will be stored in the named file with the dimensions of 640 by 480. The call can also include the x and y dimensions of the desired image size. The file name should be a fully qualified name of path and file name.
• APxHiTest SignalType
  Several of the measurements allow for a choice in the underlying test method. The caller can provide the selection. These are basically Chirp (or Frequency Response), Stepped Frequency Sweep, or Composite (Multitone).
• Programming samples
  We provide a number of programming samples to illustrate operating the APx511 in a production environment using the API. These files are typically installed in the user area, e.g. ~\User Docs\APx500 x.x|HI Analyzer
• ample Files
  The content of the C# and VB solutions and files and the LabVIEW VIs is similar, providing the same capabilities.
• C#.NET solutions and files
  These are typically installed in ~\User Docs\APx500 x.x |HI Analyzer\Examples\CSharp. Specific documentation can be found in the interactive help available while running the solution in Visual Studio, or in the Help file HiTest_API_PRG.chm.
• VB.NET solutions and files
  These are typically installed in ~\User Docs\APx500
  x.x|HI Analyzer\Examples\VBNET. Specific documentation can be found in the interactive help available while running the solution in Visual Studio, or in the Help file HiTest_API_PRG.chm.
• LabVIEW VIs
  These are typically installed in ~\User Docs\APx500
  x.x|HI Analyzer\Examples\LabVIEW. Specific documentation can be found within the LabVIEW VIs.

Running Self Test

APx511 Self Test Kit (Self Test Fixture, cable and terminator)

• Audio Precision provides a group of “Self Test” APx projects, under control of a program called SelfTest.exe. Download Self Test from ap.com. Be sure to select the Self Test for the version of APx500 you are currently running. Instructions are in the ReadMe.txt file included in the Self Test zip file.
  For the APx511, a special fixture is required to connect the APx511 outputs to its input, and to provide proper loading and termination. This fixture with a cable and a terminator are in the SLFT-KIT, available from Audio Precision.
• Plug the DB-15 connector on the self test fixture directly into the DB-15 connector on the APx511 rear panel. Connect the BNC cable and the 75  terminator as directed by prompts in SelfTest.exe.

Documents / Resources

Audio Precision APx511 B Series Hearing Instrument Analyzer [pdf] Instruction Manual APx511 B Series Hearing Instrument Analyzer, APx511 B Series, Hearing Instrument Analyzer, Instrument Analyzer, Analyzer

References

• User Manual