Audiology Lecture Notes

Flashcards for key audiology concepts related to earmolds, tubing, and venting.

Shell (earmold)

A full ear mold hearing instrument that fills the external ear and ear canal, typically used for severe to profound hearing losses for the best acoustical seal.

Skeleton Mold

An earmold with a cutout, offering retention benefits without filling the entire ear canal, providing a better cosmetic appearance compared to a shell mold.

Half Shell

Similar to a shell mold but without the upper portion, sitting in the bowl of the ear canal without covering the helix area.

Semi-Skeleton Mold

An earmold with the rear rim removed, featuring locking extensions at the bottom and top for canal lock and helix lock.

Cross/Freefield/Janssen Molds

Earmolds that leave the canal unoccluded, minimizing low-frequency amplification; used for open-fit, thin-tube fit, and RIC hearing aids.

Retention (Hearing Aids)

The ability of a hearing aid or earmold to stay securely in the ear. If more retention is needed, larger mold styles can be used, even with RIC or thin tube BTEs.

Dome

A soft, flexible, typically silicone or foam tip which attaches to the receiver of a RIC (receiver-in-canal) style hearing aid. Domes come in various shapes and sizes (open, closed, etc.)

Vinyl Earmold Modification

Requires caution due to the material's softness; buffing wheels can remove additional material during modification.

Silicone Earmolds

Allergy-free, comfortable, and provide a good acoustical seal, especially for high-gain fittings; however, they can be difficult to modify.

Earmold Modification Tools

Use tools recommended by the manufacturer of the earmold product for modification.

Hard vs. Soft Earmold Material

Use a harder material for soft, flaccid pinnae; use a soft material for firm ears. Consider materials that soften with body heat for a compromise.

Combination Earmold Materials

Options include a solid acrylic body with a flexible canal portion for enhanced comfort and fit.

Tubing Inside Diameter

Affects frequency response in hearing aids.

Tubing Outside Diameter

Affects the ability to resist feedback in hearing aids.

Common Tubing Size

Number 13, available in medium, thick, and double-wall variations.

Tubing Degradation

Over time, tubing can shrink, discolor, and stiffen, causing acoustic changes and affecting hearing aid output; should be checked at every office visit.

Tubing Measurement

Measure new tubing on the person's ear to ensure proper length and avoid discomfort.

Tubing Replacement

Usually performed in the office, requiring proficiency in different retubing techniques.

Moisture in Tubing

Water droplets in the tubing can block sound, leading to complaints of a dead hearing aid; dry tubing may be used to resist moisture.

Laser SLA Molds

Industrial strength superglue is required to hold their tubing in place.

3D Printed Earmolds

Should not be reamed, as they could shatter.

Tube Locks

Come in a variety of shapes and sizes made from either brass or plastic material.

Venting

Generally affects frequencies below 1000 Hz. The bigger the vent, the greater the roll-off in low frequencies.

Open Fit

Offers minimal low frequency control.

Occluding Fit

Offers the most low frequency control.

Venting Purpose

Acts as pressure relief for the member. It equalizes the pressure on the outside of the hearing aid and in their ear. Critical for physical comfort.

Parallel Venting

Preferred type of venting and modifies the low frequency response without affecting the highs.

Diagonal Venting

Should only be used if there's an unusually small shaped ear canal and they can affect high frequencies and are more prone to feedback.

External Vent

Can be effective if there's ear drainage, and then it can also reduce feedback more than other vent configurations.

Select-A-Vent (SAV) / Mini-Vent Plug (MVP)

Allows on-the-fly venting adjustments without remaking the earmold, useful for accommodating ear changes due to aging.

Pressure Vent Size

0.04 inches or 1 millimeter.

Mostly Open Vent (MOV)

A very large vent for those who need it, made by ReSound.

Ear Canal Resonance

Earmolds that occlude the canal impact the ear canal's natural resonance. Because anytime we stick something in that open tube, it's gonna affect the natural resonance of the ear canal.

Horn Effect

A large change in the diameter of the sound tubing in the earpiece system will result in improved high frequencies.

In-Office Earmold Modifications

Include reducing helix curl, reducing canal length, creating external vents, trenching the vent, removing eye spots, and drilling out vent holes.

Earmold Repurposing

You can change it from one style to another. So you can make a shell into a half shell, or you could turn a skeleton into a canal.

Sound bore positioning

The sound bore must be positioned so it's aiming right at the TM. Any time we direct it into the wall, we run the risk of getting feedback and we also run the risk of them not hearing because maybe if it's directly going into the wall, it'd cut the sound off and it'd act like it was dead.

REM Verification

Any changes to an acoustic fit must be verified using REM (real ear measurements) and may require reprogramming for domes and earmolds.