A pure tone audiometry test is used to find out actual hearing levels as well as type and degree of hearing loss by means of two pathways the Air conduction and Bone conduction.

1. PURE TONE AUDIOMETRY
Test of Hearing
BY
Daniel Akhtar
(Consultant Audiologist)

2. PURE TONE AUDIOMETRY
(PTA)
• It is a subjective test.

3. PURE TONE AUDIOMETRY
(PTA)
• First we know about “PURE TONE”
• A single frequency sound is called PURE TONE.
e.g. a sound of 250, 500, 1000Hz.
• Audio means “to hear” & Metria means “to measure”,
now the definition of “PURE TONE AUDIOMETRY” is:
• PURE TONE AUDIOMETRY is a hearing test in which
we measure the hearing threshold levels of an individual
in decibels for various pure tones from 125 to 8000Hz.
• In PTA we find out the type & degree of patient’s HL.

4. AUDIOGRAM
• A graphic record produced by
audiometry.
• An audiogram shows a quietest
sounds you can just hear.
• In audiogram, red circles shows
right ear & blue crosses shows left
ear.
• On the top of the graph there is
frequency range from left to right.
• On the side of the graph there is
intensity range from top to
bottom.
• Any points that are heard at 20dB
or quieter are considered to be
within the normal range.

5. TERMS USED IN PTA
• FREQUENCY:
Is the number of sounds per second.
It is measured in Hertz (Hz).
• INTENSITY:
Is the strength of sound which determines its loudness.
It is measured in decibels (dB).
• AIR CONDUCTION:
When sound is given through the external ear. e.g.
headphones , insert ear phones.
• BONE CONDUCTION:
When sound is given through mastoid process. e.g. bone
vibrator.

6. TYPES OF HEARING LOSS
• CONDUCTIVE HEARING LOSS:
When there is problem in EAC, tympanic membrane & in
ossicles.

7. • SENSINEURAL HEARING LOSS:
When there is problem in cochlea & in 8th nerve.

8. • MIXED HEARING LOSS:
When there is problem in external ear, middle
ear & in inner ear.

9. DEGREE’S OF HEARING LOSS
 -10 – 25 dB HL = Normal range
 26 – 40 dB HL = Mild hearing loss
 41 – 55 dB HL = Moderate
 56 – 70 dB HL = Moderately Severe
 71 – 90 dB HL= Severe
 Greater than 90 dB HL = Profound

10. AUDIOMETER
• AUDIOMETER is an electronic device used to measure
hearing threshold level of an individual.
• It can measure Air-Conduction thresholds between
125-8000Hz & Bone-Conduction thresholds between
250-6000Hz.
• Max intensity level for air conduction is 120dB &
Max intensity level for bone conduction is 50 dB.

11. COMPONENTS OF AUDIOMETER
• Oscillator
• Interrupter switch
• Hearing level attenuator
• Equalization circuit
• Output power amplifier

12. OSCILLATOR
• This generates pure tones
• Frequencies generated include 125, 250, 500, 750, 1000,
1500, 2000, 3000, 4000, 6000, and 8000 Hz.
• These sounds are electronically generated

13. INTERRUPTER SWITCH
• It controls the duration of signal presented
to the patient
• It is typically in off position when pure
tones are presented and can be turned on
only on pressing the button.
• It is typically in on position for speech
signal

14. EQUALIZATION CIRCUIT
• This contains resistors which help in
equalization of sound generated
• Human ear is highly sensitive to 2khz
frequency

15. OUTPUT POWER AMPLIFIER
• Signals produced by oscillator needs to be
amplified
• This amplifier produces very little distortion
• It has a good signal to noise ratio

16. HEARING LEVEL ATTENUATOR
• It controls the level of signal from the
audiometer within 110-120 dB
• The intensity can be varied in steps of 5 dB
• Attenuator steps should be very accurate

17. INSTRUMENTS USED IN
AUDIOMETER
To check the patient’s hearing level through audiometer,
There are some instruments that is used in audiometry.
They are as following:
• HEADPHONES
• INSERT EAR PHONES
• BONE VIBRATOR
• LOUD SPEAKERS

18. • HEADPHONES:
Used for air conduction.
Placed properly on the
opening of the EAC & sound
is presented to patient
through it.
• INSERT EAR PHONES:
Also used for air conduction.
In this, there is probe which
is inserted into the ear canal.
It is used if there is a
problem in sound presented
to patient by headphones.

19. • BONE VIBRATOR:
Used for bone
conduction. Placed on
the mastoid process &
gives direct signal to
cochlea.
• LOUD SPEAKERS:
In this sound is presented
to patient through loud
speakers in a sound proof
or noise free room from
various directions.

20. THE LEGENDS

21. HUGHSON – WESTLAKE
TECHNIQUE
• Up 5 and down 10 method.
• Tones of short duration is used.
• Better ear is tested first to decided whether masking is
necessary.
• Started at 1000 Hz at a level above threshold. This
frequency is selected because it is an important
frequency.
• In pts with profound hearing loss the test should be
started with 250 Hz because these patients have residual
hearing only in low frequencies.

22. CONTIUNED………….
• Stimulus is started at 0 dB and increased in steps of 10
dB till the patient responds
• On positive response the volume is decreased by 10 dB.
If the pt responds it is decreased by 10 dB and repeated
till he does not respond
• On no response the intensity is increased by 5 dB till the
pt confirms hearing the tone
• This should be repeated till the pt gives positive
response in two out of three attempts at the same dB
level
• Tone presented should last between 1-3 seconds

23. MEASURING A THRESHOLD
• There is another technique of measuring a hearing
threshold level of patient is:
• First the tone is presented to patient of 40dB at 1000Hz.
• If no response occurs, the tone is increased to 60dB at
same Hz.
• If response occurs, then 10dB is decreased. Now the tone
is 50dB. If no response occurs , add 5dB in it. Now the
tone is 55dB. This is the threshold of a patient.
• THRESHOLD:
The lowest level at which the patient can correctly
identify the tone presentation at least 50% of the time,
with a minimum of 3 responses at a given level.

24. PURE TONE AVERAGE
• Pure-tone average (PTA)
• Average of air conduction thresholds
obtained at 500, 1000, and 2000 Hz in one
ear.
• This average should approximate the
speech reception threshold (SRT)