From Dr M.N. Nagaraja / July 2009
SPECIFICATIONSFOR AUDIOMETERS
Standards provide specifications about the features to be found in each type of audiometer.Equipment should be maintained according to manufacturer's specifications and recommendations. Instruments are properly calibrated at recommended intervals and calibration records are maintained. The specific parameters – must be checked.
These are outlined in standards provided byANSI,IEC. ASA & ANSI both list & sell IEC & ISO standards. In general, the ANSI,ISO, & IEC standards are in close agreement.
Standards for Audiometers include ANSI S3.6 1996. The specification were developed in 1969, revised in 1989 & again revised in 1996. There were further revisions in 2004. The ANSI S3.6-1996 Specification for Audiometers represents our most current and best resource for information regarding audiometers. It also contains reference threshold levels for all commonly used transducers in one standard.
The ICE (1980) classifies the audiometers as under:
•Type 1 – Advanced Diagnostic Audiometer
•Type 2 - Diagnostic Audiometer
•Type 3 – Simple Diagnostic audiometer
•Type 4 – Screening Audiometer
•Type 5 – Simplest Audiometer
The minimum requirements for the audiometers decrease from type 1 to type 5.
Type 1 includes many features. In comparison, the Type 5 has no required minimum or maximum features.
Minimum required features / Pure Tone / Speech1 / 2 / 3 / 4 / 5 / HF / A / B / C
Transducers
Two earphones / Yes / Yes / Yes / Yes / No / Yes / Yes / Yes / Yes
Insert earphones / Yes / No / No / No / No / No / No / No / No
Loudspeakers or electrical output / Yes / Yes / No / No / No / No / Yes / Yes / No
Bone vibrator / Yes / Yes / Yes / No / No / No / Yes / No / No
Hearing Levels, Test Frequencies
Yes / Yes / Yes / Yes / Yes / No / Yes / No / No
Test Signal Switching
Presentation / interruption / Yes / Yes / Yes / Yes / Yes / Yes / Yes / Yes / Yes
Pulsed tone / Yes / Yes / No / Yes / No / Yes / No / No / No
Frequency modulation (FM) / Yes / Yes / No / No / No / No / No / No / No
Reference Tone
Alternate presentation / Yes / Yes / No / No / No / No / No / No / No
Simultaneous presentation / Yes / No / No / No / No / No / No / No / No
Speech Input
Replay device / No / No / No / No / No / No / No / No / No
Or electrical / Yes / Yes / No / No / No / No / Yes / Yes / Yes
Input for recorded material
Microphone / No / No / No / No / No / No / Yes / Yes / No
Masking
Narrow band noise / Yes / Yes / Yes / No / No / Yes / No / No / No
White noise / Yes / Yes / No / No / No / No / No / No / No
Speech Spectrum noise / No / No / No / No / No / No / Yes / Yes / Yes
Routing of Masking
Contralaterial earphone / Yes / Yes / Yes / No / N / Yes / Yes / Yes / Yes
Ipsilateral earphone / Yes / No / No / No / No / No / Yes / No / No
Loudspeaker / Yes / Yes / No / No / No / No / Yes / Yes / No
Routing of Masking
Contralateral earphone / Yes / Yes / Yes / No / N / Yes / Yes / Yes / Yes
Ipsilateral earphone / Yes / No / No / No / No / No / Yes / No / No
Loudspeaker / Yes / Yes / No / No / No / No / Yes / Yes / No
Bone Vibrator / Yes / No / No / No / No / N / No / No / No
Subject Response System / Yes / Yes / Ys / Yes / No / Yes / Yes / No / No
Signal indicator / Yes / Yes / No / No / No / Yes / Yes / Yes / Yes
Audible Monitoring / Yes / No / No / No / No / No / Yes / Yes / No
Operator to subject speech communication / Yes / No / No / No / No / No / Yes / No / No
Talk Back system / No / No / No / No / No / No / Yes / Yes / No
Type 1 / Type 2 / Type 3 / Type 4
Freq (Hz) / AC / BC / AC / BC / AC / BC / AC
125 / 70 / - / 60 / - / - / - / -
250 / 90 / 45 / 80 / 45 / 70 / 35 / -
500 / 120 / 60 / 110 / 60 / 100 / 50 / 70
750 / 120 / 60 / - / - / - / - / -
1000 / 120 / 70 / 110 / 70 / 100 / 60 / 70
1500 / 120 / 70 / 110 / 70 / - / - / -
2000 / 120 / 70 / 110 / 70 / 100 / 60 / 70
3000 / 120 / 70 / 110 / 70 / 100 / 60 / 70
4000 / 120 / 60 / 110 / 60 / 100 / 50 / 70
6000 / 110 / 50 / 100 / - / 90 / - / 70
8000 / 100 / - / 90 / - / 80 / - / -
Table 2: Minimum required freq. and HLs for Pure Tone Audiometers
(ANSI S 3.6, 1996)
TYPE 4 - AUDIOMETER
•Technical specifications:
•HearingLevelRange: -10 to 90 dB HL in 5 dB steps
•Tone Stimulus: Pure tone
•FrequencyRange: 125 to 8,000 Hz
•Accuracy:
a) Frequencies: better than ± 3%
b) Hearing Level: within ± 3 dB of indicated level from 125 to 5000Hz & ±5 dB at 6000 Hz and higher.
•Total Harmonic Distortion: < 2%
•Standards: EN 60645-1 for Audiometers, Type 4
•Calibration: IEC 645, ANSI S3.6 for Type 4 audiometers.
TYPE 3- SIMPLE DIAGNOSTIC AUDIOMETER
•Single Channel: one oscillator.
•(Variation includes Channel and a half: tone to one ear & masking noise to the opposite ear.
•The spilt half single channel: ABLB).
•Outputs: Phones, bone, insert, free-field
•loudspeaker via ext. amplifier
•Tone Stimuli: Pure, pulsed or warble tones
•FrequencyRange: Air, FF: 125 to 8,000 Hz
•Bone: 250 to 6,000 Hz
•Masking Signals: Contralateral; Speech Noise or Narrow Band Noise
•HearingLevelRange: (maximum output limited by transducer capability)
•Air: -10 to 120-125 dB HL at 500 - 6000 Hz
•Bone: -10 to 70 - 80 dB HL at 500 - 4000 Hz
•Speech Input: Microphone or CD/Tape 1-2
•Special Tests: S.I.S.I., Stenger, Auto Threshold, Auto Screening.
•Power Supply: AC 50-60 Hz, 100 -120 V or 200 - 240 V, ± 10%
•Patient Safety: Complies with EN 60601-1, Class I, Type B
Standard Accessories:
•Patient Response Signal, ME70 Noise-Excluding Headset w. TDH39/TDH49 or TDH50 Earphones, in telephonic type cushions
•Insert phones
•Bone Vibrator (B71)
•Calibration: ANSI S3.6 & IEC 645:1 & 2 for Type 3 audiometers.
TYPE 2- DIAGNOSTIC AUDIOMETER
PURE TONE – CHANNELS 1 & 2
FrequencyRange:
•Air: 125 Hz to 12,000 Hz
•High Frequency: 8,000Hz to 20,000Hz
•Bone: 250 Hz to 8,000 Hz
•Sound Field: 250 Hz to 12,000 Hz
Intensity range
•Air Conduction: -10dB HL to 120dB HL
•High Frequency: -20dB HL to 100dB HL (Sennheiser DA 200 phones)
•Bone Conduction: Mastoid -10 to 80dB HL
Forehead -20 to 70dB HL
•Sound Field: -10dB HL to 90dB HL
•Inserts: -10 to 110dB HL
Masking intensity range
•EL Calibration
•NBN: Maximum 0- 100dB HL
•WN: Maximum 0 - 90dB HL
Tone stimuli
•Continuous Tone
• Pulse Tone
• warble tones
Speech & sound field
•Channel 1 & Channel 2
•Microphone for live voice
•External A & External B for recorded speech material from external stereo tape cassette or CD player
•Intensity range – AC -10 to 105dB HL
BC -10 to 65dB HL
•Sound Field -10 to 90dB HL
•Inserts -10 to 95dB HL
•MaskingIntensityRange: Speech Noise
•0 to +100dB HL in 10 dB HL steps
Special test capabilities
•ABLB , SISI, MLD
•High Frequency: Frequency range of 8000 Hz to 20,000 Hz
Communications & monitoring
•Talk Forward
• Talk Back
• Monitor
Accessories
•Head phones TDH 39 (49/50)
•Bone Vibrator B71
•Test Microphones
•Talk Back Microphones
•Power Cords
•Instruction Manual
•Sound Field System
•Paired Insert Phones (Ear tone 3A)
•High Frequency Head Phones
Frequencies and Maximum Hearing Levels:
Hz / AC dBHL / BC dBHL / NB dBHL125 / 90 / 80
250 / 110 / 45 / 100
500 / 120 / 65 / 100
1000 / 120/130 / 70 / 110
2000 / 120 / 75 / 110
3000 / 120 / 80 / 110
4000 / 120 / 80 / 110
6000 / 120 / 55 / 110
8000 / 120 / 50 / 100
TYPE 1 - AUDIOMETER WITH EXTENDED HIGH FREQUENCY
Standards:
•EN 60645-1, EN 60645-2, EN 60645-4/ANSI S. 3.6.
•Calibration: ISO389-1, ISO389-2, ISO 389-3, ISO 389-4.
Channels: Two independent channels.
•Channel 1: Input: Tone, Microphone 1&2, Tape/CD 1&2, NB, SN, WN, PN. Output:
•Channel 2: Input: Tone, Microphone 1+2,Tape/CD, 1&2, NB, SN, WN, PN. Output for both channels:
•Left, Right, Free Field 1+2, Insert phones, HF-phones, Insert masking.
Test Types:
•Tone , Speech,
•Auto thresholds, Bekesy test,
•Difference Limen Intensity, Difference Limen Frequency,
•Loudness Balancing, Difference masked unmasked, Weber, ABLB. TT Decay,
•Masking Level Difference, MLB, SISI
•Stenger, Lombard, Doerfler-Stewart
•Sound Field
Accessories
•TDH39 (49/50) Headset
•B71 Bone Conductor
• High Frequency Headset
•Audiocup Enclosures
•EAR-Tone 5A Insert Phones for audiometry
•Insert Earphone for masking and monitoring
Specifications of basic model audiometer are listed below:
Frequency range:
Air conduction (AC) : 250Hz, 500 Hz, 1KHz, 2KHz,4KHz,6KHz and 8KHz
Bone conduction (BC) : 250Hz, 500 Hz, 1KHz, 2KHz,4KHz,
Intensity range:
Air conduction (AC) : 0dB to 110dB
Bone conduction (BC) : 0dB to 70dB
Noise type : Narrow band noise & white noise
Levels : 0 dB to 100dB
Input for Speech : live voice / recorded voice
Levels : 0 dB to 100dB
V.U meter & :Transducers: i) 2 supra aural head-phone for sound field testing other controls with rubber ear cushion and head band – one each for
separate ears considered equivalent to TDH 39.
ii) Bone conduction Vibrator Type Radio ear B71 or
equivalent
Routing of signal : either to Right ear or left
Selector for signal routing: A. Head Phones Right/Left/or Bone Vibrator.
B.Tone or speech
Signal selection : Continuous tone or Pulsed tone or warble tone
Attenuation : In 5 dB steps; after 100 dB a change in intensity will be
Separately controlled by push button increase of 5 dB
till the maximum (pushing button will result in only
single step increase).