Welch Allyn AM 232 User manual

Audio Menu

Service Manual

Operating

Instructions

Contents

Section 1 — Introduction

1.1 Description ...................................................................1

1.2 Unpacking and Inspection ............................................ 1

1.3 Connectors, Controls and Indicators............................ 2

1.3.1 The Front Panel Controls and Indicators (Fig. 1-1).... 3

1.3.2 Rear Panel Connectors and Indicators (Fig. 1-1)....... 3

1.3.3 Symbols .................................................................... 3

1.4 Installation..................................................................... 4

1.5 Pre-Test Procedure ...................................................... 4

1.5.1 Pre-Test Noise Recover Period ................................. 5

1.5.2 Elimination of Ambient Noise..................................... 5

Section 2 — Battery Option

2.1 Description ...................................................................6

2.2 NiCad Battery Operation .............................................. 6

2.3 Recharge NiCad Batteries ............................................ 7

2.4 To Replace NiCad Batteries ......................................... 8

2.5 Alkaline Battery Installation/Operation .......................... 9

Section 3 — Operation

3.1 Preliminary Check.......................................................10

3.2 Instructing the Subject................................................ 10

3.3 Placement of Earphones.............................................11

3.4 Response Handswitch................................................ 11

3.5 Audiogram Form......................................................... 11

3.6 Routine Calibration Check .......................................... 12

3.7 Routine Test Administration........................................ 12

3.7.1 HL Control (F3) ........................................................ 12

3.7.2 Range Extension Push-Button (F2) ......................... 12

3.7.3 Tone Type Selector (F9) .......................................... 13

3.8 Typical Testing Session .............................................. 13

3.8.1 Pre-Test Review ...................................................... 13

3.8.2 Familiarization.......................................................... 13

3.8.3 Threshold Determination (Pure Tone) ...................... 14

3.8.4 Testing Procedure ................................................... 14

Section 4 — Routine Maintenance

4.1 Calibration...................................................................15

4.2 Earphone Cords ......................................................... 15

4.3 Hum and Random Noise ............................................15

4.4 Distortion and Frequency Shift ................................... 15

4.5 Special Messages....................................................... 16

4.5.1 CAL .........................................................................16

4.5.2 Exx ..........................................................................16

Service and Warranty Information

Service and Repair................................................................ 17

Recalibration ......................................................................... 17

Warranty ...............................................................................17

Rechargeable Battery Warranty ............................................ 17

Specifications ................................................................18

Bibliography ................................................................... 20

Section 1 — Introduction

1.1 DESCRIPTION

The Welch Allyn AM 232 Manual Audiometer is a single-channel, pure
tone, air conduction, portable instrument designed to provide basic
audiometric capability for physicians’ offices, schools and industry. The
lightweight design allows easy transport to a variety of testing locations
and the built-in storage cavity and case provide enough room to contain
all instrument accessories. The clearly labeled front panel controls and
full frequency range make accurate, reliable testing a simple matter for
any user.

The Welch Allyn AM 232 Manual Audiometer is a precisely designed
and calibrated instrument. With proper care it will deliver accurate
sound-pressure levels for years to come. The Welch Allyn AM 232
Manual Audiometer should be recalibrated yearly (or sooner if a prob­lem develops). See Section 4.

1.2 UNPACKING AND INSPECTION

Although your Welch Allyn AM 232 Manual Audiometer was carefully
tested, inspected and packed for shipping, it is good practice after re­ceiving the instrument to immediately examine the outside of the con­tainer for any signs of damage. Notify your distributor if any damage is
noted.

Carefully remove your Welch Allyn AM 232 Manual Audiometer from its
shipping container. If the instrument appears to have suffered mechani­cal damage, notify the carrier immediately so that a proper claim can be
made. Be certain to save all packing materials so that the claim adjuster
can inspect it as well. As soon as the carrier has completed the inspec­tion, notify your Welch Allyn representative.

If the instrument must be returned to the factory, repack it carefully (in
the original container if possible) and return it prepaid to the factory for
necessary adjustments.

Check that all accessories itemized in Table 1-1 are received in good
condition. If any accessories are missing, contact your Welch Allyn rep­resentative immediately. See Specifications Section of this manual for
the catalog numbers of accessories and also for a listing of optional
accessories.

TABLE 1-1: Accessories Supplied

Test Headset Assembly (TDH39)
Audiogram Pad (1 Pad of 50)
Battery Pack Assembly (used with model #23210 and #23215 only)
AC Power Cord

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1.3 CONNECTORS, CONTROLS AND INDICATORS

FIGURE 1-1: Front and Rear Panel

F2

Front Panel

F1

F3

F10

LO BAT

F4

F3

90

F5

F8

F9

F6

F7

Rear Panel

2

R3 R2

12 VDC
200 MM

R1

1.3.1 The Front Panel Controls and Indicators (Figure 1-1)

F1 Power switch and indicator for ON and OFF
F2 Range extension push-button allows operator to increase the

stimulus intensity 10 dB above the standard maximum HL at
any frequency. When in use, a “+” appears on the LCD.

F3 HL control for setting stimulus intensity level. Level is indicated

on LCD.

F4 Present bar for stimulus presentation.
F5 Stimulus being presented via earphone. Presentation indicated

by illuminated green LED.

F6 Subject response indicator shows the operator when the test

subject has pressed the handswitch button by an illuminated
green LED (with optional handswitch only).

F7 Control for setting stimulus frequency. Frequency is indicated

in window adjacent to control.

F8 Routing switch for stimulus presentation to the earphone. Left

or right indicated by illustration of subject.

F9 Switch for setting the stimulus tone type.

FM = warble tone

= steady tone
= pulsed tone

F10 Low battery indicator to alert the operator of a limited oper-

ating time. Recharge or replace batteries (dependent on
whether NiCad or Alkaline batteries are used).

1.3.2 Rear Panel Connectors and Indicators (Figure 1-1)

R1 Power input jack (5-pin DIN Connector) with front panel illus-

tration showing its location and a rear panel label giving the
input power specifications.

R2 Earphone output jacks (standard phone jacks). Front panel

illustration shows left and right phone.

R3 Response handswitch input jack (standard phone jack) with

front panel illustration showing location.

1.3.3 Symbols

Attention, consult accompanying document for instructions or
warnings pertaining to these parts.

Entry by qualified service personnel only.
This symbol is located inside the storage compartment.

It denotes a Type B, Class II product per IEC 878 as refer­enced in IEC 601 Standard.

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1.4 INSTALLATION

Warning

The AM 232 Manual Audiometer is designed to be used with a hospital grade
outlet. Injury to personnel or damage to equipment can result when a three­prong or two-prong adapter is connected between the AM 232 Manual Audio­meter power plug and an AC outlet or extension cord. Additionally, the AM 232
Manual Audiometer is equipped with a specific power transformer which
should not be interchanged with any other transformer or supply.

The above symbol indicates the location of a service adjustment part and is
intended for service personnel use only. The AM 232 Manual Audiometer is
a specifically calibrated audiometer and the periodic service and adjustments
which the instrument may require should be done only by an authorized Welch
Allyn service technician.

Plug the power module into the appropriate jack (R1) on the back panel
of the instrument, then plug the other end into a line power (mains) outlet.
Plug the earphones into the earphone jacks (R3) on the rear panel. Note
the symbol along the top of the front panel which indicates which is
right and which is left. The right earphone is red, the left earphone
is blue. Turn the power switch to ON.

NOTE

For battery operation, please refer to Section 2.

1.5 PRE-TEST PROCEDURE

NOTE

The AM 232 Manual Audiometer is a versatile audiometer designed for use in
doctors’ offices, schools, industrial settings, the military, etc. This manual,
therefore employs the generic term “subject” to identify the person whose
hearing is being evaluated.

Although the AM 232 Manual Audiometer is simple enough to be oper­ated by practically anyone, any program aimed at obtaining reliable re­cords of hearing thresholds should be staffed and supervised by appro­priately-trained individuals. Training courses leading to certification are
available for audiometric technicians in most urban areas.

Two prerequisites are of particular importance to the procurement of
reliable audiograms:

• Prior to testing, allow adequate time for the subject to recover
from the effects of previous exposure to high-level sound.

• Tests should be done in a quiet area.

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1.5.1 Pre-Test Noise Recover Period

Exposure to high levels of sound (unmuffled lawn mowers, many power
tools,

loud music, gunfire) tends to create a temporary threshold shift
(TTS) which diminishes with time after exposure. Any subject tested
soon after such exposure may manifest a hearing loss that does not re­flect his or her normal hearing threshold. It is, therefore, important that
the testing procedure prescribe some time interval — usually at least 16
hours — between the last exposure to high-level sound and the adminis­tration of any hearing test.

1.5.2 Elimination of Ambient Noise

Excessive noise in the test environment such as that produced by con­versation, typewriters, or other machines also reduces test validity be­cause it tends to mask the test signals, particularly at the lower fre­quencies where earphone cushions provide less effective attenuation.
An acoustically-tested room may be required if ambient noise at the
subject’s ears reaches an objectionable level—i.e., sufficient to cause
apparent hearing loss at the low frequencies. Also, Audiocups are avail­able from Welch Allyn as an optional accessory. If the test subject is in
the same room as the audiometer, it is recommended that the subject
be seated about one meter (3 ft) away from the instrument.

Maximum permissible test environment sound-pressure levels are spe­cified by American National Standard Criteria for Permissible Back­ground Noise during Audiometric Testing, S3.1-1991. Table 1-2 shows
the maximum background levels that can be present inside the room
while a valid hearing test is being conducted. For more comprehensive
information about hearing testing and hearing conservation, refer to the
Bibliography.

TABLE 1-2: Permissible Noise Levels

Test Tone

Frequency (Hz) 125 250 500 750 1000 1500 2000 3000 4000 6000 8000

Test Room

Ears covered 34.0 22.5 19.5 21.5 26.5 26.5 28.0 33.5 34.5 38.0 43.5
maximum
permissible octave
band levels

Ears covered
maximum
permissible one-third
octave band levels

29.0 17.5 14.5 16.5 21.5 21.5 23.0 28.5 29.5 33.0 38.5

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