Choosing a Prescriptive Approach Flashcards
What was the audiogram mirroring prescriptive method?
Adding the exact amount of gain that was present in their loss
Doesn’t take recruitment into account
What is the half-gain rule?
Gain that equaled 1/2 the threshold of the loss
Still loud for a lot of people
What is the libby method?
1/3 gain
Milder losses don’t need as much gain in real life
What were the non-linear prescriptive approaches?
Prescribes different gain or output targets based on the input level of the signal
Recommended gain or output varies for soft, moderate, loud input levels
The objective of nonlinear prescriptions maximize audibility for speech intelligibility for 55 & 65 dB, while keeping loud input signals (75 dB and MPO) below loudness discomfort
What is the loudness normalization prescriptive formula?
DSL
Strives for an output that’s audible and comfortable (doesn’t consider relative important of specific frequencies)
Theorizes aided loudness perception should be the same as normal loudness perception
Output based formula (uses an individuals perception of loudness to create REAR output targets)
Soft signals are increased until they are audible and perceived as soft
Moderately loud signals are increased or adjusted until they’re perceived as comfortable.
Loud signals adjusted until they’re perceived as loud, but ‘okay’
What is recommended for the first TK in DSL 5.0?
Recommended TKs are based on degree of loss
For milder thresholds applies a low TK (~30 dB SPL)
For severe thresholds applies a higher TK (~60 dB SPL)
Too much gain of soft input signals result in a loss of intelligibility when loss is severe
What is the expansion recommendation for DSL 5.0?
Applied to low input levels
What are the WDRC recommendations for DSL 5.0?
Multi-stage compression to the input signal (multiple TKs)
Wants to expand dynamic range
What does the DSL 5.0 adult fitting formula do to mid-frequency gain?
Reduces this gain by 7 dB
Find that adults don’t need that much mid-frequency gain
What is the loudness equalization prescriptive formula?
NAL
Increases the intensity of mid and high frequencies until their energy equals the lows (lows have more energy)
Strives to balance the perception of loudness over a range of frequencies
Recognizes audibility of mid and high frequency cues are critical for intelligibility
Equalizing low, mid, and high frequency energy winds up boosting high frequency output improving audibility of high-frequency sounds
Uses threshold to create REIG targets
What rules did early formulas follow?
Lyberger half gain rule
Revised formula calculates gain targets as 46% of threshold loss
Redesigned after finding evidence that individuals wanted less insertion gain in mid-frequencies (NAL-NL1)
What does NAL-NL2 base gain recommendations on?
SII
More gain is prescribed to those sounds that contribute the most to speech intelligibility
Does NAL-NL2 provides gain targets for nontonal and tonal languages?
Yes
Low frequencies are more important in these languages
NAL-NL2 targets of tonal languages provide different prescriptive targets to support improved intelligibility of tonal languages
What is NAL-RP?
Revised and profound
Patients with severe to profound hearing loss preferred more gain and less HF emphasis
Gain is calculated as 66% of the threshold loss rather than 46% of loss
What is the NAL-NL2 calculation for ABG?
Additional gain is needed to overcome the attenuation caused by the mechanical loss
25% of the air-bone gap is added to the NAL-NL2 formula
Gain recommendations are greater (louder) than those with SNHL
