Hearing Measurement 2025 - Pure Tone Audiometry (PDF)

Hearing Measurement Lect.02 Pure-Tone Audiometry Dr. Steve J Aiken, Dalhousie University, 2025 Why Measure Thresholds? The Strange Nature of Speech Perception The Role of Detail Why Measure Thresholds? Too Focal? Too Soft?? 5 mm to an octav...

Hearing Measurement Lect.02 Pure-Tone Audiometry Dr. Steve J Aiken, Dalhousie University, 2025 Why Measure Thresholds? The Strange Nature of Speech Perception The Role of Detail Why Measure Thresholds? Too Focal? Too Soft?? 5 mm to an octave 1 mm (1 Band) Frequency-Specificity and Place-Specificity  Frequency-Specificity and Place- Specificity Place specificity is only possible (at all) if we use: – Frequency specific tones – Low sound pressure levels Importance of Audiometry  What Affects Performance in Real Life? t the audiogram is single best predictor of performa The Audiogram Audiogram and Thresholds Role of Outer and Middle Ear in Hearing Human Hearing  dB SPL to dB HL Transform RETSPL: Reference equivalent threshold sound pressure level – level of average threshold – this is subtracted so that average is zero Audiogram and Thresholds  What is a Threshold? Yes No Tone Hit Miss hit rate False Correct No Tone Alarm Rejection the level at which a person hears a tone 50% of the time (i.e., a hit rate of 50% or.5) Likelihood of Responding The Role of the Criterion Sensory Magnitude (Level) The Audiogram The Audiogram ©2008 League for the Hard of Hearin The Audiometer The Clinical Audiometer — Madsen Astera Oscillator Noise generator Amplifier Attenuator Signal router Presentation Ctl Interrupt put sound on uninterrupted now: “continuous on” Talk Forward Lvl level of your voice when talking to them Talk Forward Btn The Clinical Audiometer — Madsen Astera The Clinical Audiometer — Madsen Astera GSI Audiostar GSI Audiostar Automated Testing The Screening Audiometer First Things First: Control Ambient Noise Air Conduction Audiometry Transducer Choice: Pros and Cons TDH 49/50 ER-3A ER-3C Reference Equivalent Threshold Sound Pressure Levels dB SPL to dB HL Transform  Transducer Choice When would you use speakers (sound field)? Dial Readings: What do they mean? KEMAR’s Famous Ear (a dummy) KEMAR’s Family  What about? Huge Ears? – Need more sound to hear for hearing testing, but real world this is not as drastic Baby Ears? – Grow substantially in first 5 years What Happens When the Baby Grows Up? Bone Conduction Audiometry Transducer Choice: The Bone Oscillator  Cochlear Fluid Inertial Stimulation when the bone is vibrating, the perilymph will try to “stay put” – this is fluid inertia (from the mass of the fluid) Inertial Stimulation Osseotympanic Stimulation  Types of Hearing Loss Derived: AC-BC (The Air-Bone Gap) BC Measured: Bone Oscillator AC Measured: Earphone or Speaker  Types of Hearing Loss Conductive Hearing Loss Sensorineral Hearing Loss  Types of Hearing Loss Conductive vs Sensory/Neural Hearing Loss Sensory vs. Neural Hearing Loss ABG = Conductive Loss (no ABG in this audiogram!) Describing Hearing Loss  Describing Loss: Percentages (AMA) % Impairment avg (.5,1,2,3 kHz) - 25 dB x 1.5 0% = 25 dB 100% ≈ 90 dB % Disability (better ear x 5 + worse ear) / 6  Describing Loss: The Pure Tone Average average of 500, 1000 & 2000 Hz the Fletcher average: best two of three Degree of Hearing Loss ©2008 League for the Hard of Hearin Configurations of Hearing Loss: Rules of 20 Configurations of Hearing Loss: Rules of 20 Configurations of Hearing Loss: Rules of 20 Configurations of Hearing Loss: Rules of 20 Configurations of Hearing Loss: Rules of 20 Configurations of Hearing Loss: Rules of 20 Audiometric Procedures Audiogram Symbols Red – right – round Blue – left – x Bone symbols look like ears from your perspective VT: vibrotactile S: soundfield Drawing an Audiogram Arrangement: Screening Typical screening arrangement Martin & Clark, 2006 Arrangement: Diagnostic Martin & Clark, 2006 Transducer Placement Who should do it? What is important? – TDH – Inserts – Bone oscillator – Sound field The ‘Button’  **Obtaining AC Audiogram, ANSI S3.21 (1978) Begin in better ear first – check levels – if the same really does not matter Start at 1000 Hz for 1-2 sec Begin @ 40 – 60 dB HL (case history/previous agram) No response increase 20 dB (until ~80) Follow the “down 10 up 5” rule 50% detection i.e., 2/4 or 3/6 is threshold Repeat at other frequencies, retest 1000 Hz – See if improved – If >20 dB between freq’s test inter-octaves Test other ear  False Responses False responses are common during behavioral audiometry – Can cause erroneous results and this can cause serious errors in interpreting the results – False negative – failing to respond to a tone – False positive – responds when no tone present ician must always be vigilant during the testing and propriate action when dealing with false responses  Patient Reponses False positives – Patient responds when there was no stimulus – Reasons: tinnitus, equipment error, tester error – Be careful – not to present stimuli rhythmically – STOP IMMEDIATELY & CORRECT THE SITUATION – Give the patient a way out and start with tester error – exact thresholds are a fiction Examples of Audiograms Sensorineural Hearing Loss Conductive Hearing Loss Mixed Hearing Loss Appendix (Notes)  Onset Congenital : present at birth Acquired: obtained after birth Adventitious: acquired from an external source (not innate)  Time Course Acute: sudden and short Chronic: long duration (not used for pure tone thresholds) Sudden: rapid onset Gradual: occurring in small degrees Temporary: limited duration Permanent: irreversible (PTS vs. TTS) Progressive: advancing in severity Fluctuating: a periodic change in degree  Tuning Fork Tests: the Weber – principle: sound heard on side with better cochlea, or on side with conductive loss – tuning fork is placed on center of forehead  Tuning Fork Tests: the Rinne – principle: sound decays faster via bone conduction – fork is held on mastoid until no longer heard, then immediately placed in from of canal – if sound is still heard (via AC), this means no conductive loss: a POSITIVE RINNE – if sound is not heard (via AC), this suggests conductive loss: a NEGATIVE RINNE  Rinne and Weber Weber heard Weber Weber heard center of heard left ear head right ear Positive normal greater SNHL greater SNHL Rinne (no hearing or in left ear in right ear conductive symmetrical loss) SNHL Negative unlikely conductive mixed loss in Rinne on loss in right right right ear Negative unlikely mixed loss in conductive Rinne on left left loss in left ear  Tuning Fork Tests: the Bing – tuning fork is held on mastoid, while tragus is held against canal – sound should get louder when ear is plugged (occlusion effect), but this will not likely occur with conductive loss – if sound gets louder (no conductive loss), this is a POSITIVE BING – if sound does not get louder (conductive loss), this is a NEGATIVE BING