CDS 290 1st Edition Exam #2 Study GuideAudiometry: Using audiometer to test patient’s hearing sensitivity or degree of hearing lossI. Determine how well they understand speech J. Estimate the site-of-lesion K. Testing battery Pure tone tests- Air conduction- tests entire auditory system - Bone conduction- bypasses the outer and middleear Speech test - Speech recognition threshold (SRT) - Speech discrimination score (SRS)Why use Pure tone tests? - Pure tone contains only one frequency, it can be used to test each specific location inthe cochlea - Threshold: the quietest level which you can hear a sound - Hearing tests use the pure tone threshold to estimate the sensitivity of auditorysystem over a range of frequency :250 - 8000 Hz Air conduction (AC) tests- Headphones/earphones produce to acoustic signal to ear channel. Sound delivered tothe auditory system goes through the OE, ME, and IE - Sound is delivered through changes in “air” pressure - Supra-aural earphone - Insert ear phone Bone conduction (BC) tests- Bone oscillator vibrates the skull to set the fluid in the cochlea into motion, BC can test cochlear function without passing the OE or ME. BC simulates bilateral cochlea, so mayneed to mask the non-testing earHow to read an audiogram?These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- Graphic plot of threshold by frequency - Typically test from 250-8000 Hz at octave frequencies - Intensity is graphed from -10 to 110 dB HL - Audiogram will always have key to symbols How to test?- Otoscopic examination: always check the ear canal before the test - Cerumen - Foreign objects - Inflammation - TM perforation - Wearing headphone/insert ear phone - Instruction - Test - Air conduction - Bone conduction- MaskingObtaining Thresholds- Threshold: the quietest level which you can hear a sound - Usually considered threshold if patient can detect the tone 50% of the time - Basic hearing test: 250 – 8000 Hz, -10 to 110 HL - Start testing at 1000 Hz, easiest for the patient to identify its presence Testing Method- Start at 40- 50 dB HL; if they don’t respond, increase in 20 dB increments until they do - “Down 10 – up 5”: when patient responds, decrease by 10 dB; if patient does notrespond, increase by 5 dB - Threshold rule: must get at least 2 out of 4 responses on an ascending trail - Continue this for all frequencies - Test order: 1000, 2000, 4000, 8000, 500, 250 - Start with better ear or right ear so they get used to the task Patients Response- Hand Raise - Often used with children - Button Response - Can be used with anyone as long as they have the needed dexterity - Behavioral changes Clinician may see behavioral change even if patient does not actively respondInteraural AttenuationAir conduction:- Loss of energy of a sound travels from the test ear to the non-test ear; the numberof decibels loss in cross hearing - Supra aural earphones: 40 dB - Insert earphones: 60 dB - Bone conduction: 0 dB Sound Crossover- The sound presented to the testing ear is heard by the non-testing ear - Sound leaks out from headphone or travels through skull - Bone conduction - When is crossover greatest? - BC always crosses over - AC crosses over if sound is loud enough - Low Frequency > High Frequency - Low Frequency bends around head moreeasily Masking - If both cochleas are stimulated, how do you know which ear you tested? - Masking allows us to isolate the testing ear - What is masking effect? - The threshold of audibility for one sound (testing tone) is increased by thepresence of another sound (masking sound) - Mask by using narrow band noise masker to the non-testing ear. - Masking is required if ACTE – ACNTE ≥ 40 dB Hearing LossConductive HL: air bone gap, Due to a disorder ofouter or middle ear, The effect of this loss is to attenuate or decrease the sound energy Sensorineural HL: Inability of the system to transduce mechanical energy into electrical energy, Attenuates incoming signal and may add distortion, Reduced frequency selectivity causes the distortion, Loudness recruitment abnormally fast growth of loudness, Audiogram shows elevated but similar AC and BC thresholdsMixed HL: Involves both Sensorineural and Conductive components, BC thresholds reflect Sensorineural components, and AC thresholds reflect both Sensorineural and Conductive componentsRetrocochlear HL: Results from a change in neural function in the peripheral or central nervous system, Does not always produce a change in hearing sensitivity, but often has more influence on suprathreshold function, e.g. speech recognition, Other tests will help determine if hearing loss is Retrocochlear or SensorineuralSymmetrical HL: HL degree is symmetric Asymmetrical HL: HL degree is asymmetric.Speech AudiometryEssential to the overall test battery: assessment of the ability to understand everyday communication - A relatively quick way to estimate threshold in children and elderly - A fairly sensitive indicator of a retrocochlear disorder - Confirms pure-tone audiometry findings Speech Recognition ThresholdThe lowest level that speech is understood- Slightly higher than speech detection threshold (SDT – for some patients cannot getSRT, profound hearing loss or difficult to repeat the word) - SRT stimuli: spondees - Two syllable word, equal stress on each syllable - Testing rule: use the Down 10-Up 5 Rule - SRT result should correspond closely to pure tone average (PTA) (±5 dB), otherwisemay reflex unreliable test or pathology - PTA is the average pure tone test threshold for 500, 1000 and 2000 Hz Speech Detection ThresholdThe lowest level you can detect speech- You don’t have to understand it, Can use any speech stimuli - Follow down 10 up 5 method - Not routinely tested, but may be used if SRT cannot beestablished Word Recognition Score - This is for testing the patient’s ability to correctly identify phonetically-balanced (PB)monosyllabic words - Most common way of describing supra-threshold hearing ability - Ability to correctly identify phonetically-balanced words presented at a comfortable levelabove threshold (~40 dB SL) Most Comfortable Level (MCL)- ◦ Usually ~40 to 55 dB SL - ◦ How to test: use continuous speech, start around SRT and increase - gradually (usually in 5 dB steps) Uncomfortable Level (UCL) or Loudness Discomfort