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Pure Tone Audiometry

K. Dayalan Faculty ( Sp & Hg) AYJNIHH, SRC. Pure Tone Audiometry. AUDIOLOGICAL TESTING. NEO - NATES. CHILDREN & ADULTS. INFANTS / TODDLERS. BEHAVIOURAL RESPONSES, Tymps,OAE, ABR (click or tone burst). Pure tone AUDIOMETRY, IMPEDANCE, SPEECH ESTS. BOA, VRA, Play Audiometry Tymps.

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Pure Tone Audiometry

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  1. K. DayalanFaculty ( Sp & Hg)AYJNIHH, SRC Pure Tone Audiometry

  2. AUDIOLOGICAL TESTING NEO - NATES CHILDREN & ADULTS INFANTS / TODDLERS BEHAVIOURAL RESPONSES, Tymps,OAE, ABR (click or tone burst) Pure tone AUDIOMETRY, IMPEDANCE, SPEECH ESTS BOA, VRA, Play Audiometry Tymps

  3. PURE TONE AUDIOMETRY • Routine test used for children and adults. • Non – invasive procedure • Can be used for screening & detailed assessments

  4. Pure-tone audiometry is a behavioral test measure used to determine hearing sensitivity. • This measure involves the peripheral and central auditory systems. • Purpose : • The usual primary purpose of pure-tone • tests is to determine the • Type of hearing loss • Degree of hearing loss • and configuration of hearing loss

  5. Air Conduction Tests Using earphones Using pure tone signals. The threshold is the faintest level where the client can detect the signal at least 50% of the time. Tests the frequencies of 250Hz,500Hz, 1000Hz, 2000Hz, 4000Hz, 8000Hz Left Ear response: X Left Ear No Response: X Rt. Ear response: Rt. Ear no Response:

  6. BONE CONDUCTION (BC)TEST Using Bone – Conductor placed on the mastoid bone of the better ear. The ‘Better ear’ is the ear with the lowest PTA. The frequencies of 250Hz, 50Hz, 1000Hz, 2000Hz, 4000Hz are tested using the pure tone signals. For patient responses: Left Ear BC > Right Ear BC < No response > No response <

  7. MASKING This test is carried out when there is unilateral hearing loss / asymmetrical loss. The better ear cochlea is engaged with noise signal, so as to find out the exact hearing thresholds of the worse ear. Symbols for AC Masking: Right Ear: Left Ear: Symbols for BC Masking: Right Mastoid: ⊐ ⊐ Left Mastoid:⊏ ⊏

  8. Pure Tone Thresholds • 1. Important components of diagnostic procedure. • 2. Evaluation & optimization of hearing aid. • 3. Rehabilitation planning. • 4. Defining hearing impairment. • 5. Defining handicap for certification for various benefits.

  9. Extrinsic Variables • Physical environment ( temp., humidity, light, ambient noise etc) • Calibration of hardware • Methodology – frequency sequencing • Listener information, instruction & positioning • Earphone placement, ear selection • Response strategy can be controlled

  10. Intrinsic Variables • Neuro-physiologic factors governing organic sensations. • Subjective considerations such as motivation, intelligence, attention, familiarity with listening task etc. • Physiologic activity linked with vascular, digestive, respiratory functions, tinnitus etc.

  11. AUDIOMETRY • THE TECHNIQUE USED FOR MEASURING THE HEARING ACUITY WITH THE HELP OF AN ELECTRONIC DEVICE.

  12. PURE TONE AUDIOMETRY • FIRST BASIC TEST IN AUDIOLOGICAL TEST BATTERY • TO MEASURE HEARING ACUITY USING PURE TONES – SINGLE FREQUENCY, SINGLE INTENSITY • TESTING IN 2 MODES • - AIR CONDUCTION – WITH EARPHONES • - BONE CONDUCTION – BONE VIBRATOR

  13. TYPES OF AUDIOMETERS • PURE TONE & SPEECH AUDIOMETER. • SCREENING, DIAGNOSTIC & RESEARCH AUDIOMETER. • INDIVIDUAL & GROUP AUDIOMETER.

  14. PARTS OF AUDIOMETERS • ON-OFF SWITCH • ATTENUATOR • FREQUENCY DIAL • TONE INTENSITY DIAL • MASKING NOISE DIAL • OUTPUT SELECTOR • MODE SELECTOR • EAR PHONES & B. C. VIBRATOR • FACILITIES FOR SPEECH & SPECIAL TESTS

  15. ENVIRONMENT • SOUND TREATED SUIT ACCORDING TO SPECIFICATIONS – IDEAL. • SINGLE ROOM / DOUBLE ROOM SETUP DEPENDING ON THE PURPOSE PLACE & SPACE AVAILABILITY. • WELL ILLUMINATED & AIR CONDITIONED.

  16. PRELIMINARY CONDITIONS • CALIBRATION CHECK – LISTENING CHECK TO CONFIRM PRESENCE OF TONE TO EAR PHONES & BONE VIBRATOR • LISTENERS POSITION • LISTENERS INFORMATION • EAR SELECTION – CHOOSE BETTER EAR FIRST

  17. LISTENERS INSTRUCTION • INITIALLY TONE WILL BE AUDIBLE & GRADUALLY DECRESING IN INTENSITY. • RESPOND AS SOON AS THE TONE IS PRESENT BY PRESSING A BUTTON OR RAISING THE FINGER OR HAND & DO SO EVEN IF THE SOUND IS VERY FAINT & JUST AUDIBLE. • CEASE TO RESPOND AS YOU STOP HEARING THE TONE.

  18. THRESHOLD DETERMINATION • MODIFIED HUGHSON – WESLAKE PROCEDURE • PRESENT A TONE AT 1000 Hz AT A CLEARLY AUDIBLE LEVEL • REDUCE THE TONE IN 10 dB STEPS TILL THE LISTENER STOPS HEARING. • INCREASE BY 5 dB STEPS TILL IT IS • JUST HEARED. • AT THE MINIMUM LEVEL IF RESPONSES ARE PRESENT 2/3 TIMES OF PRESENTATION OF THE STIMULS.

  19. THRESHOLD DETERMINATION • REPEAT THE PROCEDURE FOR OTHER FREQUENCIES & OTHER EAR BOTH FOR AIR & BONE CONDUCTION. • MASK THE BETTER EAR WHENEVER NECESSARY. • PLOT THE THRESHOLD FOR AC & BC FOR EACH EAR SEPARATELY. • ALSO NOTE DOWN • - THRESHOLD OF DISCOMFORT • - MOST COMFORTABLE LEVEL.

  20. INTERPRETATION OF AUDIOGRAM • TYPES OF HEARING LOSS • PATTERN OF HEARING LOSS • DEGREE OF HEARING LOSS • TYPES OF HEARING LOSS • COMPARE AC & BC THRESHOLDS • A – B GAP 1. CONDUCTIVE 2. SENSORI NEURAL 3. MIXED

  21. Normal hearing

  22. CONDUCTIVE HEARING LOSS A. C. – HEARING LOSS B. C. – NORMAL A B GAP GREATER THAN 10 dB HL. DOES NOT EXCEED 60 dB HL.

  23. SENSORI NEURAL HEARING LOSS • AC & BC – HEARING LOSS • A – B GAP < 10 dB HL.

  24. MIXED HEARING LOSS • AC & BC – HEARING LOSS • A – B GAP > 10 dB HL.

  25. Patterns of hearing loss • GENERALLY RECOGNISED ONES ARE CARHART (1945), DAVIS (1978), HOGDSON (1980). • HIGH FREQUENCY HEARING LOSS • SLOPING FROM LOW FREQUENCY TO HIGH FREQ. • (S.N.H.L., M.H.L. & C.H.L IN discontinuity) • TYPES 1. GRADUAL S.N.H.L. 2. SHARP S.N.H.L. SEEN IN PRESBUCUSIS & NIHL.

  26. LOW FREQUENCY HEARING LOSS • SIGNIFICANT LOSS AT LOW & MID • FREQUENCIES • RELATIVELY NORMALOR NEAR NORMAL HEARING IN HIGH FREQUENCIES • CONDUCTIVE HEARING LOSS • M. D. EARLY STAGES.

  27. FLAT HEARING LOSS: • EQUAL LEVEL OF HEARING IN ALL FREQUENCIES • SEROUS OTITIS MEDIA • COLLAPSED EAR CANAL • MODERATE OTOSCLEROSIS • MODERATELY ADVANCED M. D.

  28. TROUGH/SAUCER SHAPED LOSS • BETTER HEARING AT LOW & HIGH FREQUENCIES WITH POOR HEARING IN SPEECH FREQUENCIES. • RUBELLA • MELINGERING

  29. CORNER AUDIOGRAMS • RESPONSE ONLY IN 250 Hz & 500 Hz AT • VERY HIGH LEVELS. • CONGENITAL HEARING LOSS • VIRAL DISEASES • OTOTOXICITY. • IRREGULAR HEARING LOSS.

  30. DEGREE OF HEARING LOSS • COMPARE A.C. VALUE WITH STANDARDS. MINISTRY OF HEALTH, GOVT. OF INDIA. • PTA OF 500 Hz., 1000 Hz., & 2000 Hz. • dB HL CATEGORY • 00 – 25 NORMAL • 26 – 40 MILD • 41 – 55 MODERATE • 56 – 70 SEVERE • 71 – 90 PROFOUND • 91 & ABOVE TOTAL

  31. PERCENTAGE OF HEARING LOSS • FOR EACH EAR PERCENTAGE: • RE : PTA – 25 x 1.5 • LE : PTA – 25 x 1.5 • BOTH EARS PERCENTAGE: BETTER EAR % x 5 + POOR EAR % 6

  32. Need for Speech Audiometry • Pure tone hearing assessment provides valuable information regarding sensitivity, but only limited information concerning receptive auditory communication ability. There appears to be no satisfactory means of accurately predicting speech understanding ability from pure tone results.

  33. Speech Audiometry • Using a variety of speech stimuli to assess practical handicap of hearing sensitivity of a person for discriminating & understanding speech. • provides information on auditory receptive communication ability.

  34. SPEECH THRESHOLDS • Speech detection/awareness threshold – SDT / SAT – The lowest level at which speech can be detected. • Speech reception threshold – the level at which the listener can repeat 50 % of the speech materials presented • & is + or - 8 dB of Pure Tone Average.

  35. Speech reception threshold materials • Spondaic words ( spondees) – two syllable words with approximately equal stress on each syllable. • Criteria for such words are • Familiarity • Phonetically dissimilarity • Normal sampling of speech sounds • Homogeneity with respect to audibility.

  36. Speech discrimination • The materials used are phonetically balanced mono-syllabic words. • Starting at 25 dB HL with 10 PB words, increasing in 5 or 10 dB steps until 100% scores obtained – PB-Max. • PB words are presented usually at 40 dB SL • No. of correct repetitions for 25 words are calculated into percentage.

  37. Clinical application • Determine site of lesion • Evaluate social adequacy & effectiveness • of communication • Determine candidacy for surgery / post operative assessment • Plan & evaluate aural rehabilitation program • Hearing aid evaluation, selection & fitting • Assess for Cochlear Implantation. • Assess central auditory function

  38. Factors affecting speech discrimination scores • Physical factors • Level of presentation • Frequency composition • Distortion • Signal to noise ratio • Duration • Linguistic factors • Articulation & dialect • Contextual cues • Redundancy • Familiarity

  39. Test administration variables • Manner & rate of presentation • Response mode • Scoring • Stimulus material • Talker difference • Hearing loss of the listener • Motivation • Intelligence • Instruction • Cooperation & experience

  40. CLINICAL MASKING • ANSI DEFINES MASKING AS • “ the amount by which the threshold of audibility is raised by presence of another ( masking) sound”.

  41. Why Masking • TO ELIMINATE THE PARTICIPATION OF NONTEST EAR (NTE) WHILE TESTING THE TEST EAR (TE). • A SECOND SOUND ( NOISE THRO’ EAR PHONE ) IS EMPLOYED TO SHIFT THE SENSITIVITY OF NONTEST COCHLEA TO PREVENT THE NTE FROM RESPONDING TO SIGNAL TO TEST EAR.

  42. VARIABLES AFFECTING MASKING • TEST EAR – POORER EAR • NON TEST EAR – BETTER EAR • SENSORI NEURAL LEVEL OF N.T.E. • SENSORI NEURAL LEVEL OF T.E. • ACCURATE MASKING LEVEL • STARTING LEVEL FOR MASKING • OCCLUSION EFFECT

  43. MASKING SIGNALS • COMPLEX NOISE – MULTIPLES OF LOW FREQUENCY FUNDAMENTALS • BROAD BAND WHITE NOISE – ENERGY PRESENT IN ALL FREQUENCIES IN EQUAL INTENSITY • NARROW BAND NOISE – CB NOISE PRODUCED AROUND THE TEST FREQUENCY.

  44. WHEN TO MASK • AIR CONDUCTION THRESHOLD • Difference bet. AC threshold TE & NTE > IA – 40 dB • Difference bet. AC threshold of TE & BC threshold of NTE > IA • BONE CONDUCTION THRESHOLD • AC threshold of TE & BC threshold of the same ear differ by more than 10 dB ( IA is 0 dB as the skull vibrates as a whole if the stimulation is given to any part of the skull & reach both cochlea equally).

  45. SPEECH RECEPTION THRESHOLD • Difference bet. SRT of TE & SRT or PTA of NTE > 45 dB • Difference bet. SRT of TE & BC PTA of NTE > 45 dB • SPEECH DISCRIMINATION AUDIOMETRY • Difference bet. presentation level to TE & SRT or PTA of AC or BC of NTE .45 dB

  46. HOW MUCH TO MASK • STUDEBAKER formula. • For AC masking • presentation level (PL) – inter aural attenuation (IA) + masking factor (MF) + air–bone gap (ABG) of the ear being masked. • RE: – AC 70 dB; BC 15 dB • LE: - AC 15 dB; BC 10 dB, masking level required to mask the left for RE thresholds is • 70 dB (PL) – 40 dB (IA) + 15 dB (MF) + 5 dB = 50 dB. • With the introduction of noise if the patient responds to pure tone in the test ear, look for the response for further 2 increments of noise in 10 dB steps. If there is no shift in threshold that level is the masked threshold of RE AC. If there is a shift in presentation level increase the presentation level & masker until a plataeu is obtained for three levels of masking noise. …cont.

  47. For BC masking • presentation level (PL) + masking factor (MF) + air bone gap (AGB) of the ear being masked. • RE : AC – 70 dB; BC – 15 dB • LE : AC – 15 dB; BC – 10 dB • masking level required in the LE for RE BCT. • 15 dB + 15 dB + 5 dB = 35 dB • to establish the masked BC threshold the same procedure as to AC threshold to be employed. • …cont.

  48. Masking for speech reception threshold • presentation level (PL) - inter aural attenuation (IA) + Masking factor (MF) + air bone gap (ABG) of the ear being masked. • 70dB (PL) – 45dB (IA) + 15dB (MF) + 5 dB (AGB) = 45 dB. • To establish the masked threshold the same procedure as for pure tone AC masking is to be employed. Instead of pure tone spondees are presented as stimuli.

  49. THANK YOU

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