How are SOAEs generated
Generated automatically through the motility of the outer hair cells of the cochlear.
What are the advantages of SOAEs (2)
- Passive response
- Energy comes from central auditory system, in the form of resonators at different frequencies giving accurate pitch and intensity discrimination
What are the disadvantages SOAEs
Can’t separate noise from signal
How are TEOAEs generated
The majortiy of the emissions are generated from the motility of the outer hair cells, only a minor portion from the stereocilia.
How do you measure TEOAEs
Start recording 3ms after the stimulus is played to separate the noise from the signal. Noise is random and the signal is correlated, this is how we separate the noise from the response.
*What are the advantages of TEOAEs (6)
- High specificity
- Can be used to diagnose Meniere’s disease and Presbycusis
- It does not require a behavioural response
- Frequency specific
- Best for detecting auditory dysfunction below 3 kHz
- Provides a overview of cochlear activity
What are the disadvantages of TEOAEs (5)
- Fails may be false positive
- he test is affected by ambient and physiological noise
- Infants have a higher failure rate (10%)
- Impacted by ear canal size, probe fit, ME function, calibration
- Too sensitive to cochlear conditions in older adults
What are the TEOAE pass criteria screening for adults and children (3)
- Pass result is a response that exceeds the noise floor by 3 dB or more
- 4 out of 5 frequencies
- Reproducibility of 70%
- Signal reaches
What are the pass criteria for TEOAE for screening of newborns (3)
- Infant screening SNR .3 dB at 1 and 1.5 kHz and 6 dB at 2-4 kHz
- 4 out of 5 f
- 70% reproducibility
What are the generation sites for DPOAEs
Majority of the emissions are generated from stereocilia (IHC)
How do you measure DPOAEs
Stimulus is made up of a pair of tones and the outcome is a distortion product. A filter is used for f1 and f2 and neighbouring bins set outside of the filter collects the frequencies of the noise. This separate the noise from the signal.
What are the pass criteria for DPOAEs (3)
- Signal exceeding the noise floor by 6 dB or more
- Stimulus tones reaching 55 dB and 65 dB
- Amplitude greater than -10 dB
What are the advantages of DPOAEs (4)
- Measures up to 8 kHz
- Has higher cut-off for losses (>35-60 dB)
- Best at detecting auditory dysfunction above 3kHz
- Provides a snapshot of the cochlear
What are the disadvantages of DPOAEs (3)
- Affected by physiological noise
- Only captures the response at one frequency at a time
- Too insensitive to cochlear conditions in older adults
How do pathologies impact on DPOAEs (4)
- Conductive pathology impacts low frequencies
- SNHL impacts high frequencies
- ET dysfunction (negative ME pressure) low frequencies
- Retrocochlear does not impact results
What is a sensory transmissive loss and how big is the loss
OHC dysfunction (no OAEs) causing elevated hearing thresholds (36-60 dB)
What is a sensory transduction loss and and how big is the loss
Dysfunction of IHC because IC fail to respond and activate synapsed auditory nerves. This could cause any degree of loss.
What types of stimulus are used for TEOAEs and what are they
- Click or tone bursts
- One full click contains 2 sets of 4 sub-clicks.
- Three identical and the fourth inverted (fourth click is 3 x greater amplitude)
- Each sub-click is of 0.08ms duration
What type of stimulus is used for DPOAEs
Two pure tones of different frequencies
TEOAEs and conductive losses
TEOAEs are reduced in the low f more than high f and are absent in ears with a mild-conductive loss
TEOAEs and sensory losses
- OHC dysfunction would result in reduced or absent OAEs when thesholds are elevated by 35-60 dB HL.
- High f are highly vulnerable to noise damade, ototoxic drugs
TEOAEs and retrocochlear losses
- OAEs are expected to be present in sensory losses with IHC dysfunction, neural and central losses
- OAEs can be present or absent with an acoustic neuroma depending on blood supply to the cochlear
TEOAE pass criteria for diagnostic purposes (2)
- 3dB (adults and children) 6 dB (infants)
2. All test frequencies
How can you have normal TEOAEs and poor hearing
Poor hearing is due to IHC damage, or retrocochlear lesion or ANSD
