10_Coupling to the ear/Venting Flashcards
If there was something unusual going on in the high frequencies (e.g. 3000 - 10,000 Hz), what would you suspect: venting, damping, or horn effects?
Horn Effects
**These are the frequencies responsible for the “brilliance” of a sound
What frequency range is responsible for the “presence” of a sound?
Mid-range (roughy 1000-3000 Hz)
**Also where we see damping effects
What frequency range would we expect to show effects from venting?
Lows: 20-~1000 Hz (Body)
What are the 2 ways to get a good high frequency response (hint: type or style of HA)?
Horn tubing or RIC
Name 3 coupling options (e.g. Earmold styles)
- special
- skeleton
- full shell
- half-skeleton
- 1/4 skeleton (canal lock)
- half-shell
- canal
- RITE earmolds
- SpiralFlex (thin tube) earmolds
Can a custom earmold be “open”?
Yes, but have to be ordered that way
- free-field or IROS molds (just a retention bar and the rest open with a little tubing)
- tube fitting
- mold with large vent
- fitting tip with multiple large vents
Is earmold tubing the only tube?
No
- BTE earhooks
- tiny tubing inside the ITE/ITC/CIC that leads the sound out of the device from the receiver
- slimtubes
What style of hearing aid has the least tubing?
RIC, but custom instruments are a very close second
**Hint: can try blocking the end of a custom instrument. If feedback still present, there could be a crack inside the instrument
Which type of earmold tubing is most common?
13
Which type of tubing helps control feedback?
Hard-walled
Which type of tubing is used with infants?
Sometimes 13 tubing, then step down to 16 to fit in baby’s ear (causes roll-off in high frequencies)
Describe the key difference between the effects of belled vs step-bore tubing
Stepped horns will have a shorter effective length than smooth bores b/c the change in diameter occurs closer to the medial tip
- stepped horns provide required boost in high frequencies very well, but originally, the glued tubing would come apart
The shorter the effective horn length, the ___ the cutoff frequency
Higher
What does addition of a damper do to the frequency response of a hearing aid?
Addition of a damper, either at the nub or tip, will decrease the primary resonance, and smooth out the others also
What 3 things is the resulting SPL at the TM made up of?
Amplified sound
Direct sound
Bone-conducted sound
As vent diameter increases, real-ear low frequency output ____, and the frequency at which vent-associated resonance occurs _____
Decreases; increases
What is SelectAVent?
When a large vent is drilled and fitted with a tube or valve to alter the size of it to account for changes in ear geometry, or effects of slit leak venting that are not known beforehand
The bigger the vent, the _____ (narrower/broader) the frequency range over which the vent will act
broader
A pressure vent is
500
Open vents extend just above 1000 Hz and have a _____ (smaller/larger) effect in dB than pressure vents
larger
Name some of the outgoing acoustic paths that can cause feedback
- Vent paths (intentional and unintentional)
- cracks in tubing (external or internal)
- soft tissue radiation
- hard material radiation
What are the 2 forms of occlusion?
- the “occlusion effect”: the increase in BC sond in the occluded vs unoccluded ear
- the “real ear occluded response” (REOR): the dB amount of attenuation provided by an object placed in the ear (can test by placing HA in ear, turning it off, and measuring REOR compared to REUR)
Can you measure venting in the test box?
No - need on ear verification.
- if client has normal hearing at lower frequencies, can be under targets
