PTA.

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

8. d 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. d 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. d 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)

25. d h