Speech Audiometry

This week on facebook someone asked why when they only say "Morning" people still hear the Good.

It is because of extrinsic and intrinsic redundancy that people still hear the good in your "morning"

Extrinsic redundancy of the speech signal (top down processing). Language is very rich, so people have many cues available to them to receive the same information. So while someone omits the word good. Morning is sufficient to imply the "good". There are also contextual cues that would imply the word "good".

There is also intrinsic redundancy of central nervous system (bottom up).Sensory info is duplicated via rich neural connections at many levels of a normal auditory system.

still unfinished

X Speech audiometry basics
Role ; High face validity, crosscheck principle with other tests, predictor of handicap, assess effectiveness of rehab, function of higher auditory pathways, decide which ear to fit Hearing aid (HA)
Identify ear surgery candidate and assess surgical outcomes.

Relationship with PTA (pure tone audiometry)
Speech recognition scores 90-100% normal , 80-100% Conductive HL; increase level of speech presentations,
big range for sensorineural HL (SNHL) could be outer hair cells (OHC) or inner hair cells(IHC). OHC most common not significant effect, Lesion IHC distortion of speech signal therefore, large effect on speech scores
8th Nerve lesions create a bottle neck limiting speech discrimination and perception (rollover) abnormally low speech recognition scores (retrocochlear).
 Cortical Lesion-signs of central auditory dysfunction are more subtle the further up the auditory pathway the lesion is.



Lots of different types of speech tests most commonly AB word lists - 12 lists each list 10 CVC words, 10 vowels 20 consonants. 30 phoneme score-- larger sample size, less listener fatigue.

Speech masking = filtered white noise correlated to speech spectrum. Masking stops the non test ear hearing and responding. When itmay be cross heard
1 When to mask
Presentation level -40 (interaural attentuation) > or equal to average or Best Bone Conduction of the non test ear? yes then mask
2 How much masking?
If calibrated
Masking Level=  PL -40 (IA) + max air bone gap of the non test ear 
not calibrated
Masking level= PL - 40 = max air bone gap of the non test ear +ESML
3 Could we be overmasking?
Masking level -40 (IA) is greater than or equal to the BEST Bone Conduction of the TEST EAR

Rollover Index
PB max- PB min/ PB max greater than > or equal to 0.45 = Rollover - possible retrocochlear lesion