ABSTRACT
Technological limitations have restricted the capability of older generation in-the-ear (ITE) hearing aids to closely match prescribed real ear gain/frequency responses. Newer technology, widely available in currently marketed ITE hearing aids, has considerably improved this capability. Data for 60 ears are presented comparing the real ear insertion gain (REIG) actually achieved to the target REIG, using ITE hearing aids having: 1) older generation narrow-band receivers, and amplifiers with single-pole-filter low frequency tone control and a class A amplifier output stage (n = 30), and 2) newer generation amplifiers with a two- or four-pole-filter low frequency tone control, and wide band receivers, containing a class D amplifier output stage (n = 30). With the newer technology ITE hearing aids, the means and ranges of deviation from target gain were reduced. Capability for achieving prescription REIG with ITE hearing aids can be further improved with multichannel amplifiers. Examples of the latter are shown for several difficult-to-fit audiograms.
Subject(s)
Hearing Aids/standards , Amplifiers, Electronic , Equipment Design , Humans , Retrospective StudiesABSTRACT
Custom in-the-ear (ITE) hearing aids (standard linear amplifiers with single-pole-filter low-frequency tone control and a class A amplifier output stage) were fit to 90 ears using the revised National Acoustics Laboratories' formula (NAL-R), and to 20 ears each using Prescription of Gain/Output II (POGO II) and Memphis State University (MSU) formulas. Both real-ear insertion gain and 2-cc coupler gain were evaluated. Examination of differences between prescribed gain and that actually achieved in the fittings revealed that too much gain was often given in the low- and mid-frequency range and insufficient gain in the high frequencies. There was little difference among the formulas in the degree of deviation from target. For some fittings, the deviation resulted in poorer predicted speech recognition scores (modified Speech Transmission Index). For the POGO II and MSU methods, underfitting of prescribed SSPL-90 values was far more common than overfitting.
Subject(s)
Hearing Aids , Hearing Loss, Sensorineural/diagnosis , Adult , Amplifiers, Electronic , Audiometry , Ear/physiopathology , Female , Hearing Loss, Sensorineural/physiopathology , Hearing Loss, Sensorineural/rehabilitation , Humans , Loudness Perception , Male , Speech IntelligibilityABSTRACT
There are few systematic comparisons of Etymotic ER-3A insert earphones versus supra-aural earphones in auditory brainstem response (ABR) measurement. We compared ER-3A insert earphones and two types of supra-aural earphones (TDH-39P and TDH-49P) in a group of normal hearing adults. Acoustic analyses revealed spectral and temporal differences among earphones. Behavioral and ABR thresholds to click stimuli were slightly elevated with the ER-3A compared to the TDH earphones. The ER-3A earphones produced a latency delay, relative to the TDH earphones, that varied from about 0.8 to 1.0 msec, and increased at lower stimulus intensity levels. In addition, ABR wave I amplitude was significantly reduced with the ER-3A earphone. Based on these data, we recommend collection of normative data with the ER-3A earphones prior to their use in ABR measurement.
Subject(s)
Audiometry, Evoked Response/instrumentation , Evoked Potentials, Auditory, Brain Stem , Hearing/physiology , Acoustic Stimulation , Adult , Audiometry, Evoked Response/methods , Auditory Threshold , Equipment Design , Female , Humans , Male , TransducersABSTRACT
Click interaural attenuation (IA) was measured behaviorally and with the auditory brain stem response (ABR) in two unilaterally deaf adults with Etymotic ER-3A insert earphones, and TDH-39P and TDH-49P supraaural earphones. Stimulus crossover for each set of earphones was also determined with pure-tone audiometry. Pure-tone results agreed with previous research, showing that the ER-3A provided substantially greater IA than the supraaural earphones, particularly for low frequencies. For click stimuli, behavioral and ABR results revealed only modest, if any, improvement in IA with the ER-3A relative to the supraaural earphones. The results of this study suggest that while the ER-3A earphones provide a clear IA advantage for behavioral pure-tone audiometry, they do not eliminate the need for contralateral masking of click stimuli in ABR testing.
Subject(s)
Audiometry, Evoked Response/instrumentation , Audiometry, Pure-Tone/instrumentation , Audiometry/instrumentation , Brain Stem/physiology , Adult , Audiometry, Evoked Response/methods , Deafness/diagnosis , Female , Humans , MaleABSTRACT
The purpose of this study was to conduct an acoustic analysis of incubator noise under two conditions: when the incubator was associated with different types of life-support equipment; and when impulse noise was created by striking the side of the incubator or by opening and closing the doors of the storage unit. It was found that the life-support equipment increased the overall noise levels of incubators by as much as 15 to 20 dB. Much of this increased energy was in the high frequency region. Impulse signals created by striking the side of the incubator ranged from 130 to 140 dB. A representative impulse for opening the incubator was 92.8 dB, whereas closing the door produced a peak amplitude of 114 dB.
