Novel Technology Adoption in the Audiology Clinic: Investigations of Ear Tip Performance, Perceptions, and Experiences
Phase: NA
Conditions: Hearing Aids
Sponsor: University of Arizona

 
 
 
 
 
 
 
 
Investigations of Ear Tip Performance, Perceptions, and Experiences 
(IETPPE) 
NCT05725824 
May 5th, 2024 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

PROTOCOL 
General Procedures 
 
Participants completed three phases: Listening Session #1, Earmold Fabrication, and a 
Listening Session #2. See Figure 4.2. The primary distinction among listeners was the material-
type of earmold they received first. There are three material-types and thus three groups that 
participants could be initially assigned to. All participants received and were tested with each of 
the three material-type groups. Earmolds were connected to the same Unitron T-Stride M 
behind-the-ear hearing aid.  
 
Figure 4. 1 Participant-study flow chart for RCT study. 
 
 
 
Specific Procedures 
Listening Session #01 
 
Participants completed intake questionnaires that included questions about hearing health 
history, demographics, and study eligibility information. At this stage, researchers also informed 
participants of procedures, risks, and benefits of the study. If participants met eligibility criteria 
up to this point, they underwent conventional audiologic testing to evaluate hearing and ear 
function following best-practices for audiology. Otoscopy, a visual exam of the ear, was used to 
ensure patent ear canals, normal appearing tympanic membrane, and normally aerated middle 
Earmold
Fabrication

ear. Air conduction and bone conduction pure tone audiometry were used to establish hearing 
thresholds from 250 to 8000Hz, bilaterally. Normal hearing was considered thresholds equal or 
less than 25 dB HL. If participants met audiometric candidacy, a custom ear impression was 
made of one of their ears using a common, clinically used, two-part impression material. 
 
Randomization 
 
Each participant was made three earmolds for a single ear. The main difference between 
participants was the material-type of earmold that they received first. All participants were 
eventually fit with and underwent testing with each earmold material-type. Participants were 
randomly assigned to one of three arms, using a 1:1 allocation ratio, each with a different initial 
material type. The three material-type groups included a control group (EMCTRL) made by a 
professional manufacturer, and two in-house study groups that were 3D printed using Resin 
(EMRES) and PLA (EMPLA ). See Figure 4.3. Randomization was completed a priori via a list 
generated by a custom Microsoft Excel script. This script randomly sequenced three blocks of 
ten numbers equally containing values from 1 to 3. Once participants were deemed eligible, they 
were automatically assigned the next value on the randomized list, from 1 to 3, indicating which 
arm of the study they were allocated to.   
 
 
 
 
 
 
Figure 4. 2 Workflow study diagram across material-type groups 

 
 
 
Earmold Fabrication Period 
 
After completing Listening Session #01, ear impressions were digitally scanned and 
edited using commercially available 3D editing software. The physical ear canal impression was 
then sent to a third-party earmold manufacturer. Each participant was made three earmolds, for 
an overall total of 90 earmolds. For each individual, one earmold was created using a third- party 
manufacturer with the traditional service delivery pathway and two earmolds were created in-
house with the novel service-delivery pathway using local 3D printers. The third-party earmold 
served as the control earmold. The in-house earmolds were made from two different material-
types and served as the study earmolds. To control for style of earmolds, all earmolds were made 
in a skeleton style with a sound bore that accommodates size #13T tubing and a separate select-
a-vent (SAV).   
 
Listening Session #02 
 
Once all earmolds were fabricated and received, participants were scheduled for 
Listening Session #02. This stage involved collecting objective acoustic measurements and 
subjective perceptual ratings while wearing each of the earmolds. A stock Unitron T-stride M 
behind-the-ear hearing aid was programmed to simulate a flat, mild, sensorineural hearing loss at 

40 dB HL from octave frequencies between 250 to 8000Hz. The hearing aid was programmed 
and fit to NAL-NL2 targets for these threshold values. All advanced hearing aid programming 
and features were disabled. The same hearing aid was used across all participants. Participants 
underwent objective and subjective measures three times, once for the third-party control 
earmold and twice for each in-house study earmold. Each material-type condition was separated 
by a short 10 minute washout period, during which participants completed a self-assessment 
questionnaire.   
ANALYSIS PLAN 
 
The alpha level of statistical significance was set at .05 for all statistical analyses. The 
main statistical analysis included a one-way, within group, repeated measures analysis of 
variance (RM-ANOVA) to compare the effect of 3D printed material across outcome measures. 
Assumption testing for normality, outliers, and sphericity were utilized. Outliers were assessed 
on an individual basis, using Cook’s D and a strict cutoff of 0.5. Sphericity was evaluated using 
Mauchly's test for Sphericity with a criteria of .05. If sphericity was violated, then both Geisser 
& Greenhouse and Huynh Feldt  correction factors were used, with the latter being used when 
epsilon was greater than .075. Pairwise t-tests with Bonferroni correction were used for planned 
comparisons.