Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT00438334 |
| Other study ID # |
000170 |
| Secondary ID |
|
| Status |
Completed |
| Phase |
N/A
|
| First received |
December 5, 2006 |
| Last updated |
November 18, 2016 |
| Start date |
April 2001 |
| Est. completion date |
March 2004 |
Study information
| Verified date |
November 2016 |
| Source |
Vanderbilt University |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
United States: Institutional Review Board |
| Study type |
Interventional
|
Clinical Trial Summary
Directional microphone hearing aids have been shown to provide benefit for individuals with
hearing loss in a number of laboratory experiments. However, few studies have investigated
the real-world, subject-reported benefit from these hearing aids, and even fewer have
examined directional hearing aid benefit across varying degrees of hearing loss. This study
will summarize data from a three-year, multi-faceted study of directional hearing aid
benefit. Ninety four subjects were divided into three hearing loss groups
(normal-to-moderate, mild-to-moderately-severe, and moderate-to-profound). These subjects
were then fit with experimental hearing aids set to either directional or omnidirectional
mode to determine if significant differences were present in hearing aid outcomes (both
subjective and objective). Both subject and experimenter were blinded to the hearing aid
settings. Following one month of use in each experimental setting, subjects completed: probe
microphone measurements, speech understanding in noise testing, use questionnaires,
subjective benefit scales, and satisfaction scales. At the conclusion of the study, subjects
rated their preferences for the experimental settings in quiet, noise and overall. Both
objective measures, as well as subjective data, were analyzed across hearing aid and hearing
loss conditions.
Description:
Subjects- 105 subjects were recruited for participation in this study, thirty-five in each
of three hearing loss groups. Subjects were assigned to the three groups according to the
severity of their hearing losses. Group 1 (mild) subjects exhibited normal sloping to
moderately severe SNHL, with Pure Tone Averages (PTAs) at 500, 1000, and 2000 Hz of less
than 35 dB HL. Group 2 (moderate) consisted of subjects with mild sloping to moderately
severe SNHL with PTAs of 35 to 50 dB HL. Group 3 (severe) subjects exhibited
moderately-severe, sloping to severe-profound SNHL, with PTAs of greater than 50. All
subjects had sloping hearing loss defined as at least a 20 dB average difference between
3000 Hz and 500 Hz. (Due to subject drop-out, the final data consisted of 32 subjects in the
mild group, 33 in moderate group, and 29 in the severe group)
Hearing status was assessed by means of audiometric pure-tone and speech recognition testing
in a group of previous hearing aid users. Normal middle ear function was verified by means
of immittance measures. All subjects exhibited absence of significant air-bone gap at any
frequency (<10 dB) and normal tympanograms defined as compensated static admittance between
0.25 and 2.5 mmho measured from the positive tail with tympanometric peak pressure between
-150 and +100 daPa. All subjects were service-connected veterans who are eligible for care
and amplification through the VA Audiology service. All subjects were previous wearers of
binaural hearing aids, with a minimum daily usage requirement of 4 hours/day. All subjects
were previous users of output compression hearing aids from the same manufacturer.
All subjects participated in approximately eight to ten hours of testing over the course of
four visits. At the first visit, subjects received a hearing test, unaided speech
understanding in noise measures, and aided speech understanding in noise with their current
hearing aids. Additionally, earmold impressions were obtained for the experimental hearing
aids. At the second visit, subjects completed the first set of subjective measures for the
unaided and current (own) hearing aid conditions. Subjects were then fit with digitally
programmable user-selectable directional/omnidirectional hearing aids in the first of two
experimental settings (randomly selected between directional/omnidirectional and
omnidirectional only), which they used for approximately one month before returning for the
next test session. At the third visit, subjects again completed the entire test battery for
the experimental hearing aid worn during the last month. The experimental hearing aid was
then programmed for the other condition (directional/omnidirectional or omnidirectional
only). At the fourth and final visit, subjects completed the entire test battery for this
final hearing aid condition. Additionally, at the final visit, subjects completed a
preference questionnaire.
Speech understanding in noise tests:
The Connected Sentence Test (CST) and the Hearing In Noise Test (HINT) were administered to
all subjects. An investigator in the room with the subject scored the test. The investigator
was blinded to the experimental settings of the hearing aids to control for experimenter
bias. The CST is a test of speech intelligibility for everyday speech presented at a fixed
SNR. The test consisted of 24 pairs of speech passages produced conversationally. The
subject's task was to repeat all words of each test sentence. Each passage included 25 key
words that were scored correct or incorrect. Subject scores from 1 pair of passages were
averaged to obtain an intelligibility score for each experimental condition. Data from
Pearsons et al. indicate that real-world SNRs in relatively noisy environments range from
approximately +4 dB to -1 dB. Consequently, the tests were administered at a +3 dB SNR,
which represented a relatively difficult real-world listening situation. This SNR was chosen
to minimize floor and ceiling effects for all subject groups based on a previous
investigation in our laboratory, given the steep performance-intensity function that has
been reported for the CST.
The HINT was administered as a second test of sentence intelligibility in noise. For this
investigation, two blocks of ten sentences were used for each condition. Listeners were
required to repeat sentences spoken by a male talker in the presence of a speech-shaped
noise, which was presented at a fixed level of 65 dBA. The level of the speech stimuli was
adjusted adaptively until a Speech Reception Threshold (SRT) was determined. The SRT was
defined as the SNR necessary for a listener to recognize the speech materials correctly 50 %
of the time. Correct identification of each sentence was based on proper repetition of all
words of the sentence, with minor exceptions. These exceptions related to the fact that
small substitutions in verb tense and the articles "a" and "the" were allowed without
scoring a sentence as incorrect. Presentation level of the sentences was adjusted based on
the subjects' responses (an incorrect response raised the level; a correct response lowered
the level for the next sentence). The level was varied in 4 dB steps for the first 5 trials,
and 2 dB steps for the final 15 trials.
Speech in noise test environment:
The arrangement of the speakers for the speech-in-noise testing is shown in figure 1. Both
of the speech-in-noise tests were administered in a conference room (5.05 X 4.71 X 2.60
meters) with moderate reverberation (average reverberation time Rt60: 482 ms, measured for
octave frequencies from 250 through 4000 Hz, under experimental conditions with 2 people in
the room). Each subject was seated in the center of the room with an eight-speaker
configuration for the presentation of the speech and noise stimuli. Speech will be presented
from a point-source loudspeaker (Tannoy System 600, fused-concentric driver) at a 0ยบ
azimuth. Uncorrelated noise was delivered from the seven bipolar loudspeakers (Definitive
Technologies BP-2X) spaced equally about the listener [approximately 25, 76, 128, 180, 232,
284, 335]. The use of bipolar loudspeakers allowed for a more diffuse source position in
comparison to standard, front-firing loudspeakers. All speakers were equidistant (1.5m) from
the subject's head. Speech and noise levels were controlled using a Pentium IV class
computer and an eight-channel level controller (Ashly VCM-88).
Hearing aid fitting protocol:
Hearing aid gain was determined using the National Acoustics Laboratory-Revised (NAL-R)
prescriptive targets and verified using real-ear (Fonix 6500) measurements. Hearing aid
frequency-gain parameters were adjusted so that the measured real ear aided response matched
the target response as closely as possible for octave frequencies from 500 to 4000 Hz for
both omnidirectional and directional modes. The matches to target are reported in the
results. The processing strategy of the experimental hearing aids was set as output
compression to match each subject's previous hearing aids. Targets were matched for a 65 dB
SPL composite noise input. A real ear saturation response was obtained with a 90 dB SPL
broadband input to ensure that high-level stimuli did not exceed listener discomfort levels,
and the hearing aid output was adjusted accordingly. In order to maintain a double-blind
experiment, the hearing aid programming, fitting, and real ear measurements were performed
by one investigator who recorded how the hearing aid was set (omnidirectional or
directional) for each visit. This investigator kept these data until the subject completed
all aspects of the study. Furthermore, the investigator who programmed and fit the hearing
aids was not involved in further data collection with that subject.
Since all subjects were previous users of binaural amplification, a brief orientation to the
use of the experimental hearing aids should be sufficient. Subjects were issued a remote
control with a volume control and three program buttons. Program 1 was set with the default
setting (directional or omnidirectional). In order to ensure subject safety, an
omnidirectional program was included in program two across both conditions; however,
subjects were instructed only to use program two in situations where it was necessary to
hear sounds from all angles equally (e.g. crossing the street in traffic, etc.). Program
three on the remote control was set to mute, so that subjects could use only the first two
programs. Subjects were be given identical instructions for both settings (omnidirectional
and directional) and the investigator who gave the instructions did not know which setting
was currently in the subject's hearing aids. Subjects were told that the hearing aids are
likely to work best in noise if they could position themselves so that the signal of
interest is in front of them and the interfering noise behind. Subjects were instructed on
cleaning, care, battery usage, and volume control adjustment. Subjects were asked to wear
the experimental hearing aids as much as possible during waking hours, minimally 6
hours/day. Subjects were asked to log their daily hearing aid use on a log sheet that will
be provided to verify that they met the 6 hour/day. Additionally, subjects recorded how much
time each day was spent in each of the two programs.
Subjective measures:
PHAB- The investigator who administered the subjective measures was masked as to the
experimental settings of the hearing aids. All subjects completed the Profile of Hearing Aid
Benefit (PHAB) questionnaire for each condition: unaided, previous aid, experimental
directional, and experimental omnidirectional. The PHAB is a 66-item inventory that was
developed for research usage to generate a measure of hearing aid benefit. Subjects
completed the 66 items once for unaided listening and once for each aided condition. The
test instrument was scored based on the benefit provided for aided versus unaided
conditions.
SADL- All subjects completed the Satisfaction with Amplification in Daily Living (SADL)
questionnaire for each of the three aided conditions. The SADL was designed to quantify
satisfaction with hearing aids. This scale consists of 15 items in four subscales: positive
effects of amplification, service and costs, negative features, and personal image. Subjects
respond to questions about their general opinions of wearing hearing aids. For the current
study, the 3 questions on cost and service were omitted, because the subjects did not pay
for the hearing aids, only wore the experimental hearing aids for one month before
completing the survey.
Preference questionnaire- At the conclusion of a subject's involvement in the study, he/she
was asked which hearing aid was preferred for quiet and noisy environments as well as if
she/he had an overall preference for any of the three hearing aid conditions.
