1
Q
What is the occlusion effect?
A
- The increase the level of sounds in the low frequencies (greatest at 500 Hz and below) when the canal is occluded
- This increase can be between 20-30 dB in an occluded canal vs. “open” canal
- Sound is trapped in the canal and redirected to the TM
2
Q
What does the occlusion effect result in?
A
Own voice sounds “loud”, “hollow”, “boomy”, chewing becomes aggravating
3
Q
____ is the way to balance feedback and occlusion
A
Venting
4
Q
What is one of the most important things with a HA?
A
- A Good Ear Impression
- The quality of the ear impression dictates the quality of the product created!
- An ear impression is a casting of the ear
5
Q
What 4 materials are needed for ear impressions?
A
- A block to protect the TM (otoblock)
- Impression material (fills the ear canal)
- Syringe to put the material in the ear
- Or an all in one tool that loads the impression material into the ear for us
6
Q
What are the 8 steps of taking ear impressions?
A
- Step 1: Hand washing/Infection Control, gathering of materials. Gloves are advised
- Step 2: Otoscopic examination, familiarizing yourself with individual characteristics of shape— be cautious of irregularities, seek medical clearance accordingly
- Step 3: Select a dam or “otoblock” that fills periphery of the canal — you are protecting the tympanic membrane!
- Step 4: Place the otoblock past the second bend using a lighted device such as a “penlight”. Have your patient seated comfortably. Recheck the placement of the otoblock (redo otoscopy)
- Step 5: Prepare the syringes. Prepare the impression material (mix by hand or with spatula). Fill the ear with material— the canal, the concha— the more “information” provided by the impression, the better
- Step 6: Once the material has hardened (indentation check), break the seal of the material to ear by moving the pinna “up” and “out”. Rotate the impression forward to remove from the ear
- Step 7: Examine the impression. Are there gaps? Is the otoblock attached to the material? Do you see the landmarks of the ear canal bends and concha?
- Step 8: Examine the ear. Ensure there is no impression material left behind, or significant irritation. Slight redness is normal.
7
Q
What are some examples of what you may need medical clearance prior to taking impressions?
A
–active fluid discharge
–inflammation
–bony growths in ear canal/exostosis
–perforated eardrum
–previous surgery (e.g., mastoidectomy)
8
Q
What do you need to get out of the ear before taking an impression?
A
Need wax out of the ear (can deform the impression and can be painful)
9
Q
What is the most invasive/dangerous things we do?
A
Ear impressions are the most invasive and dangerous things we do (and cerumen management)
10
Q
____ will stop bleeding in the ear canal
A
Nasal decongestant spray
11
Q
Why do we want to place the otoblock past the second bend?
A
- Provide information on the length of the canal
- Where the sound port of the HA should be cosest to the TM
12
Q
How do we know when the ear impression is set?
A
We know the ear impression is set when we can’t make a fingernail indent in it
13
Q
When are deep impressions needed?
A
- Phonak Easy-View Otoblocks
- Ideal for IICs— when deeper impressions are required
- Placed into the ear with an otoscope
14
Q
Why would you need to use an open-jaw impression marking?
A
- Open-jaw impressions with a bite-block can be useful when a tighter fit needs to be achieved.
- When you open your mouth, the ear canal opens and lengthens a little bit (this gives a tigther seal for when talking or chewing)
15
Q
Why would you mark a horizontal impression on the earmold?
A
- Marking the impression of the horizontal place during the cure process can determine the position of the directional microphones in the manufacturing process
- Gives the manufacturer information on the specific angle of the patient
16
Q
What are 4 components of impression material?
A
- Viscosity
- Shore value
- Contraction ratio
- Stress relaxation
17
Q
What is viscosity?
A
- Viscosity (before its cured)
- In reference to impression material, viscosity is the consistency of the material before it hardens in the process.
- Low=soft/runny
- High=thick/dense/firmer
- Lower viscosity material is generally preferred. High viscosity material may be better for canals with hair, or in open-jawed impressions
18
Q
What do type of viscosity material should you use if an ear canal has a lot of hair?
A
When a canal has a lot of hair, low viscosity material can grab onto the hair, which can be difficult and painful (high viscosity material pushes the hair over instead of running over it)
19
Q
What is shore value?
A
- Shore value (after its cured)
- Once the impression material parts have been mixed, an impression has been taken, and impressions form, its “hardness” has a particular shore value.
- Furthermore, shore value refers to the hardness of the created earmold
- This is important for keeping shape, and for shipping
20
Q
Shore hardness scale picture
What level is impression material generally between?
A
Impression material is generally between 20-70 shore value
21
Q
Hardness changes as the _____ value increases
A
Shore
22
Q
What is contraction ratio?
A
- How much does the impression shrink over time?
- Less than 3% is acceptable
- How do you ensure an acceptable ratio? Mix material according to directions of the package
23
Q
How long should impressions be kept in clinic?
A
Impressions should not be kept in clinic for more than a year
24
Q
What is stress relaxation?
A
- Does the impression keep its shape after it is stretched or bent?
- Does it change when we physically pull the impression out of the ear?
25
What are 3 types of impression material?
1. Condensation-cure silicone
2. Addition-cure vinylpolysiloxane
3. Powder and liquid
26
Explain condensation-cure silicone
- Impression material consisting of 2 parts: one part silicone base, and a tube of catalyst (to harden the material)
- Material is mixed, and begins to harden (usually within 20-30 seconds)
- Impressions are taken with all the aforementioned steps
- Generally, they are a medium to higher viscosity (putty like)
- Limited shelf life (has to be used up within a few months)
- Not the most popular
27
Explain addition-cure vinylpolysiloxane
- Impression material consisting of 2 parts: 2 bases (2 different colours); will know if it is mixed well
- Viscosity ranges: generally medium to high viscosity for hand mix material, lower viscosity for cartridge mixes
- Material is mixed, and begins to harden between 1-4 minutes
- Hand mixed material: 2-4 minutes generally
- Cartridge material: 1-2 minutes generally
- Impressions are taken with all the aforementioned steps
- Most popular
28
Explain powder and liquid
- Impression material consisting of 2 parts: powder and liquid
- Viscosity rapidly increases once the powder and liquid are mixed
- Not very popular today as these impression have generally poor contraction ratio and stress relaxation, effected by temperature, and they are considered easily damaged when shipping
- These are for skilled clinicians that can make a mold on site
29
What are 3 earmold styles?
1. Full shell
2. Skeleton
3. Canal
30
Who are full shell earmolds suitable for?
1. Severe to profound loss
2. Those who need added retention (*pediatric patients, sports); more contact to the ear and is a tight fit
3. Materials can vary for patient needs
4. May have a “carved” lateral facing (cosmetic); for patients that need a full shell, but a bit more cosmetically appealing
31
Who are skeleton earmolds suitable for?
1. Wide range of losses/ configurations
2. For those who need retention but have lesser degree of hearing loss (a bit more cosmetically appealing)
3. Patients who prefer “less visible” mold
4. Can be made from different materials
32
Who are canal earmolds suitable for?
1. Mild to moderate losses (*generally)
2. For patients who want a discreet mold
3. Can be modified with a “canal lock”; sits in the bowl of the ear to hold it in the canal a bit more
33
What are 3 types of earmold materials?
1. Acrylic/Lucite
2. Silicone
3. Polyvinyl Chloride/Polyethylene
34
Pros of Acrylic/Lucite earmolds
- Acrylic/Lucite earmolds are hard material
- Durable- shape does not change over time
- Easily modified (can be done in clinic)
- Easy to insert and remove, smooth surface (good for dexterity issues)
- Generally suitable for losses up to severe
- Hypoallergenic (most people won’t have any skin sensitivity)
- Tubing changes usually involved gluing
- Ideal for “soft-textured” ears
35
Cons of Acrylic/Lucite earmolds
- Not generally recommended for children… why would this be? Cause they grow so fast, more breakable, fall out more easily, any impact on the side of the head can be very painful
- Tubing changes usually involved gluing (adhesive helps to hold tube in place)
- Over time, material can be brittle and prone to breaking if dropped
- If fitting earmolds with severe to profound loss, higher chance of feedback
36
Pros of silicone earmolds
- Silicone earmolds are soft material
- More variability in the finish: flexible, tacky material (a grippy quality = ideal for retention and pediatrics)
- Generally recommended for the greater degrees of loss (severe to profound losses); holds a tight seal very well
- Hypoallergenic
- Tubing must be attached via a tubing lock (adhesive glue does not bond well!)
- Ideal for “hard-textured” ears
- Several options for paediatric patients (color options!)
37
Cons of silicone earmolds
- Not easily modified in clinic (need to send back to manufacturer)
- Color changes over time (can be undesirable for patient)
- Caution advised with fragile skin (elderly patients who have very thin skin; this can make removing and putting the ear mold in irritating)
38
Can you have an earmold made of two different materials?
Yes
- Hard material on the outside
- Soft/silicone material in the canal
39
Pros of Polyvinyl Chloride/Polyethylene earmolds
PVC/ Polyethylene earmolds are an “in-between” in texture and softness (a waxy texture)
40
Cons of Polyvinyl Chloride/Polyethylene earmolds
- Not recommended for those with vinyl allergies
- Not as easy to modify in clinic compared to acrylic
41
Earmold maintenance
- Wipe the mold with a soft, lint-free cloth Remove any wax buildup in the bore
or the vent with a tool
- Earmolds may be deep-cleaned by soaking in solution (drying is very important before re-attaching to the hearing aid)
42
What is tubing?
- The tubing that attaches the mold to the earhook has specific characteristics.
- Tubing is fastened to the earmold by adhesive (lucite molds) or by tubing locks (soft/silicone, and PVC molds)
- There is consensus/standardization of tubing sizes, with ranges of internal and external diameter
43
How often does tubing need to be changed?
- Tubing must be changed periodically as it is prone to harden over time, and shrink. This affects the frequency response!
- Tubing needs to be changed every 6 months (if the tubing is hardened, it needs to be changed)
44
We want tubing to have good ____
Flexibility
45
Size ____ is the standard BTE tubing
13
46
What is a thick wall tube?
More insulation
47
What is a double wall tube?
For profound HL
48
What is a dry tube?
For someone who is prone to sweating or is living in very humid clients
49
What is a double bend tube?
To contour to the side of the face (cosmetically appealing)
50
What is an earhook?
- BTE earhooks function to retain the device on the ear and direct sound from the device to the tubing, which then directs sound from the earmold to the ear canal
- It is important to select an earhook that contours to the ear (pediatric vs. adult)
51
The ____ is the first part of sound exiting the HA
Ear hook
52
What are dampers?
- Earhooks may be modified by use of DAMPERS, small material items that smooth the frequency response of the aid’s output by resisting acoustic energy. This attenuates the peaks of the frequency response
- Acoustically alters the output (smooths the response)
53
How is the impedance of a damper measured?
The IMPEDANCE of a damper is measured in ohms. The higher the number, the greater the impedance effect.
54
What is the impedance of a white damper?
680 ohms
55
What is the most impeding damper?
Yellow
56
What are bores?
- The sound bore is the “tunnel” within the earmold which houses the tubing.
This is different from the vent
- The vent is the channel of air that goes through the HA
57
What are horns?
- A “horned” tube, or an “acoustic horn” is a physical way to boost high- frequency gain.
- These were more popular before the development of digital programming that could achieve high-frequency gain
- A horn gives you an additional gain of high frequencies
58
We generally see ____ tubing
Parallel
59
What does venting impact?
Venting impacts the possibility of feedback (sound coming back out of the vent and getting picked up by the microphone)
60
Who experiences the occlusion effect?
Patients with low-frequency hearing better than 50 dB HL often experience an occlusion effect with their hearing aid earmolds (i.e. their voice sounds boomy)
61
What size of vent helps to reduce the occlusion effect?
Large vents (~3mm or larger)
62
____ vent (pressure vent) has no effect on occlusion
1mm
63
A ____ vent is a good place to start
2mm
64
How does the vent size effect the gain in the low-frequencies?
- Gain see the 2mm vent has a little bit reduction of gain in the low frequencies
- An open vent has the greatest reduction of low frequency gain
65
How do we begin to choose an appropriate vent size?
66
How do we minimize occlusion?
67
Patients with LF poorer than ____dB at ____Hz do not experience the occlusion effect
50, 500
68
Venting configurations are often dictated by the space of the earmold itself and how it aligns with the ____
Bore
69
What is a parallel vent?
A bore and a vent side by side
70
What 4 purposes does venting serve?
- For bone-conducted, low-frequency sounds to escape (think occlusion effect)
- To allow for environmental, un-amplified sounds to reach the TM
- To relieve sensations of pressure (with a completely closed ear, patients may feel some pressure)
- To provide ventilation (especially for ears prone to otitis externa)
71
What does venting modify?
Venting modifies the delivery of sound— particularly to the LOW-FREQUENCY gain that can be achieved
72
Do manufacturers help with venting?
- Manufacturers can help in the selection of vent sizes by calculating the combined effects of the audiogram, risk of feedback, model of the ear, and creating a vent that is most ideal to the patient needs
- Examples: Phonak AOV (acoustically optimized venting), Unitron Intellivent
- Note: the earmold/invoice will often have a code that will need to be provided in the software
73
Venting for custom earpieces on RICs
- Custom earpieces attached to RIC devices also have venting and material consideration
- The receivers are contained within the custom piece, attached to the body of the hearing aid via a wire
- In “sleeve” models (non-enclosed) the receiver can be changed
Amplification I
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