Amp 2 Test 1 Flashcards
Describe how frequency resolution changes with SNHL. Why does reduced frequency resolution make it difficult to understand speech in noise?
- Frequency resolution helps the healthy cochlea detect discreetly intense signals in narrow frequency regions within complex listening environments
- When the cochlea’s outer hair cells no longer amplify soft input signals the basilar membrane no longer produces sharp tuning curves.
- Lose the sharp peaks on the tunning curve
- When frequency resolution is decreased, the primary signal is no longer enhanced making it difficult to differentiate the desired signal (speech) from the undesired signal (noise)
- The brain can’t “untangle” the desired speech signal from the undesired noise, so understanding is diminished
Define temporal resolution and the auditory processes which support it.
- The auditory system’s ability to detect small time-related changes in acoustic stimuli over time.
- Good auditory temporal resolution processing is needed to understand speech in noise.
Describe the benefits spatial hearing supplies
- Makes it possible to tell where a sound is coming from in space.
- Focus attention on one acoustic signal from another simultaneous signal.
Which frequencies supply the most information on interaural level differences?
- ILD = difference in sound pressure level reaching the two ears
- High frequency
Which frequencies supply the most information on interaural timing differences?
- ITD = difference between the times sounds reach the two ears
- Low frequency cues (<850 Hz)
How are receivers designed differently to achieve the greatest high frequency output for severe hearing losses
The greatest HF is achieved with small receivers because of the quicker aperture movement.
For severe losses we achieve this by doing the dual receivers so we do not sacrifice the lows to get the highs.
Differentiating high vs. low values
- Low value: WDRC? Low CR 1.1:1 to 4:1, Low TK between 20 and 50 dB
- Expansion really low CR, attenuates signal below TK
- High Value: OLC? High CR Above 5:1, High TK > 80 dB
Define OLC and its purpose. List the TK, CR, AT, and RT ranges associated with OLC
Purpose: detects loud signals after amplification, and protects the ear from over amplified sounds by compressing them more to stay under the max power output level (MPO)
TK: above 80dB SPL
CR: above 5:1
AT: fast
RT: variable
Differentiate those services Medicare will and will not reimburse
WILL - suspected change in hearing, medical necessity
WILL NOT - anything with hearing aids, when status is already known
Describe 3 methods used to reduce external feedback
- Reduce external feedback loop by : Increase snugness of mold to reduce size of slit leaks or Decreases vent size to stop feedback path
- Digit notch filtering : Words by removing a narrow band of frequencies around the feedback i. Manually reduce gain between 2-4k Hz until feedback stops
- Digital feedback cancellation : When feedback is detected, the phase cancellation algorithm mimics the feedback creating an out-of-phase close of this signal. This digital close is subtracted from the amplification path to attenuate the feedback
Frequency lowering: describe the 3 types, their uses and limitations
Linear Frequency Transposition - Aims to improve audibility for high-frequency sounds by moving a high frequency band on octave down to a lower-frequency region.
Nonlinear Frequency Compression - A range of high frequencies is “compressed” into a lower frequency range. The tonotopic order of frequencies is maintained within the order of the frequency spectrum.
Spectral Envelop Warping - Copy and keep approach.
High frequency signals are transposed into a lower frequency band but simultaneously remain present in its original tonotopic position.
Describe how inclusion of a case history review of systems assists clinical decision-making -
We need to include a review of systems because we are doing whole person healthcare, and it doesn’t do any good to just look at the ear alone. Comorbidities result in a progression of hearing loss in many cases.
Systemic disease = progressive loss
cognitive/motor function = impaired clinical decision making
reduced social life = cognitive decline and depression)
Explain this statement- “The audiogram is not and indicator of the degree of communication deficit”
A person’s ability to detect quiet tones does not accurately represent a complex speech signal in noise that they are encountering outside of the testing booth. It also doesn’t explain how the auditory system codes incoming sounds, or how a patient is restricted to participate in their life.
Puretone threshold loss is:
o A good indicator… of overall degree of functional impairment
o A moderate indicator… of “activity limitation”
o A poor indicator… of “participation restriction”
Describe all the factors which limit an audiologist’s ability to use word recognition scores to predict communication difficulties.
Sensitivity/specificity: Calculation error when only 25 PB words are presented (test specs are meant for scoring out of 50)
Presentation level: if it’s not audible, there isn’t any way that we can get an accurate score… and 35% of audibility is at 2kHz so if we aren’t giving an audible presentation at this level, we are automatically getting a poor word req. score
Lack of audibility: will always result in a lower WRS even with hearing aids (if there is loss in the high frequencies, the /s, k, f, th, h, and g/ sounds will never be audible)
*** using WRS as part of a fitting process for HA’s has no predictive value of hearing aid benefits!
Describe test techniques offering a more realistic assessment method of speech understanding for improved identification of patient concerns.
Replace or add: binaural speech assessments, sentence-based stimuli, with and without visual cues, and in the soundfield with 50-60dB HL to create a more realistic listening environment
WHO ICF Classifications- explain the meanings of the term:
functional limitations: diagnosis of a problem with body function or structure (ex: a moderate SNHL)
activity limitations: difficulties people experience when trying to complete a task (ex: poor resolution reduces speech intelligibility in noise)
participation restrictions: involves a person’s comfort level with doing things they want to do (ex: avoiding their favorite restaurants because it is too noisy)
Create a list of common activity limitations and participation restrictions that hearing impaired individuals face (differentiate activity limitations and participation restrictions) -
Activity limitations: Detection of sounds, discrimination of sounds (freq. resolution), intelligibility in quiet and in noise, localization, temporal and spatial recognition
Participation restrictions: Social withdrawal, tv too loud, mumbling, stop driving or leaving the house, asking for repetitions, being fired from job, can’t follow conversation, etc.
Explain the ICF “backward synergy” concept
Audiologic Rehabilitation results lead to more participation which leads back to improved neural networks and less activity limitations
Increased participation = improved auditory processing
Increased participation = improved lip reading skills
Increased participation = improved auditory closure skills
