Publication Abstracts - 2001

Crandell, C. & Lewis, M.S. (2001). Coupling strategies for FM systems. ADVANCE for Speech-Language Pathologists and Audiologists, 11(19), 5.

A well-accepted procedure for improving speech perception in noisy or reverberant rooms, such as classrooms, is the utilization of a personal FM system.  With this type of system, the speaker's voice is picked up via an FM wireless microphone located near the person's mouth, where the deleterious effects of reverberation and noise are minimal.  The acoustic signal is then converted to an electrical waveform and transmitted via an FM signal to a receiver tuned to the same frequency.  The electrical signal is then amplified, converted back to an acoustical waveform, and conveyed to the listener.

There are several ways to couple an FM system to listeners with hearing impairment.  The signal can be presented through headphones, earbuds, or directly to the hearing aids via induction loop or Direct Auditory Input (DAI) technology.  The FM unit can also be coupled directly to the ear via a button or a behind-the-ear (BTE) transducer.

For individuals with conductive or mixed hearing losses, the FM system can be coupled to a bone-conduction transducer.  A recent advancement in FM technology allows a personal FM receiver to be added via an audio boot to a regular BTE hearing aid.  This technology allows the user to convert his or her personal hearing aid into an FM system simply by attaching the audio boot.

Personal FM systems also are available in ear-level models.  For listeners with hearing loss, this type of system provides the user with a combination of both a hearing aid and an FM system in the same ear-level device.  Both the audio boot and the ear-level device allow the user the freedom of not having to utilize body-worn receivers as required with more traditional FM systems.  Certainly, if these prove as effective in augmenting communication as more traditional systems, they may be particularly advantageous for individuals who may not want to utilize personal FM systems due to the stigma associated with them.

It should be noted that the listener's personal hearing aid should be incorporated with the FM system whenever possible. This allows the personal hearing aid, which is often more electroacoustically flexible than the FM system, to more accurately meet the child's pure tone sensitivity requirements.

The addition of an FM system to the individual's hearing aid(s) offers the individual an improved signal-to-noise ratio (SNR) for the listening environment.  It is often best to allow the hearing aid to do what it does best- improve hearing sensitivity- and let the FM system accomplish what it does best, which is to improve to SNR of the listening environment.  Of course, one concern with this recommendation is that it assumes the listener has a completely functioning hearing aid with the option of switching between various transmission modes:

·     FM only, for the purpose of focusing primarily on the talker;

·   Environmental microphone (EM) only, for the purpose of listening to all individuals in the immediate listening environment as well as monitoring his or her own voice; and

·     FM+EM, for listening to the speaker as well as other individuals in that listening environment.

For people with normal hearing, such as children with central auditory processing deficits, there are a number of methods of coupling the FM signal to the listener's ear(s).  For example, the signal can be presented through earbuds or Walkman-style earphones.  When recommending these devices, it is imperative that attenuated headphones are recommended.  An attenuated headphone will reduce the gain/output of the unit by approximately 10 to 20 dB, thus reducing the potential for over-amplification.

Personal FM systems for individuals with normal hearing also are available in ear-level models. In this configuration the FM system is located in  BTE configuration, often in conjunction with an open earmold.  These systems allow the user the freedom of not having to utilize body-worn receivers as required with the more traditional FM systems.

A final form of FM technology is sound field FM amplification. A sound field FM system is similar to a personal FM system.  However, with sound field the speaker's voice is conveyed to listeners in the room via one or more strategically placed loudspeakers.  The objectives when placing a sound field FM system in a classroom are twofold: to amplify the speaker's voice by approximately 8 to 10 dB, thus improving the SNR of the listening environment; and to provide amplification uniformly throughout the classroom regardless of teacher or student position.

Sound field systems vary from compact, portable, battery-powered single-speaker units to more permanently placed, AC-powered speaker systems that utilize multiple (usually four) loudspeakers.  While loudspeakers typically are place don stands and strategically placed within the classroom, several companies now sell loudspeakers that can be placed in ceiling mounts.  In addition, portable sound field FM amplification systems, which can be placed on the child's desk, also are available.

Although numerous studies have demonstrated the benefits of FM amplification systems, it is unclear which commercially available coupling system provides the best performance for augmenting speech perception and sound quality.

We have begun several investigations examining speech perception and quality via various FM coupling systems for listeners with normal hearing and hearing impairment.  Coupling strategies have included Walkman-style headphones, attenuated Walkman-style headphones, earbuds with hearing protection (earmuffs) attached, BTE, audio boots and stetoclips.

In these investigations speech perception ability as been assessed using the Hearing in Noise Test (HINT) sentences with speech noise as the competition.  All subjects chose a desired volume control setting for each strategy prior to testing.  At the completion of each condition, subjects were asked to rate each device in terms of quality, comfort and appearance.

Preliminary results suggest that individuals with hearing loss obtained significantly higher speech-recognition scores in noise when utilizing any of the FM coupling strategies.  BTE coupling strategies, such s the utilization of an audio boot technology, offered the highest speech-recognition improvements.  In addition, individuals with hearing loss preferred the quality, comfort and appearance of BTE technologies.

For individuals with normal hearing, each of the coupling options provided a significant improvement in speech perception.  Interesting, no significant differences, in terms of speech perception and sound quality, between the different coupling strategies have been noted.  In terms of comfort and appearance, only binaural earbuds with hearing protection and the stetoclip were rated significantly poorer than the other coupling strategies.  Many individuals favored BTE systems.

It is well recognized that personal FM amplification systems can provide a significant improvement in SNR within adverse listening environments, such as classrooms and restaurants.  At present a number of coupling options are commercially available for listeners with normal hearing and hearing loss.  It is essential that audiologists acquaint themselves with FM technologies and coupling strategies so t hey can meet their patients' communicative, emotional and social needs more effectively.

We have found it particularly beneficial to demonstrate and discuss each coupling strategy, including their advantages and potential limitations, with patients-particularly children and parents- prior to making specific recommendations.  With this counseling strategy we often are able to determine the best match of FM technology, coupling strategy, and the patients' emotional and social needs.

Doolittle, N. D., Muldoon, L. L., Brummett, R. E., Tyson, R. M., Lacy, C., Bubalo, J. S. Kraemer, D. F., Heinrich, M. C., Henry, J. A., & Neuwelt, E. A. (2001).  Delayed sodium thiosulfate as an otoprotectant against carboplatin induced hearing loss in patients with malignant brain tumors.  Clinical Cancer Research, 7:493-500. 

Department of Neurology, Oregon Health Sciences University, Portland 97201, USA.

Carboplatin is effective in the treatment of malignant brain tumors. However, when administered in conjunction with osmotic opening of the blood-brain barrier (BBB), carboplatin is ototoxic. The purpose of this study was to determine whether delayed administration of sodium thiosulfate (STS), given after BBB closure, provided protection against carboplatin ototoxicity. Patients underwent monthly treatment with intra-arterial carboplatin (200 mg/m2/day x 2) in conjunction with osmotic opening of the BBB, for up to 1 year. Audiological assessment was conducted at baseline and within 24 h before each monthly treatment. STS was administered i.v. as one (20 g/m2) or two (20 g/m2 and 16 g/m2) 15-min doses, depending on baseline hearing status. The initial group received the first STS dose 2 h (or 2 and 6 h) after carboplatin (STS2) and a subsequent group received STS 4 h (or 4 and 8 h) after carboplatin (STS4). Audiological data were compared with a historical comparison group (HCG) treated with carboplatin without STS. Spearman correlation coefficients comparing STS 2 (n = 24), STS4 (n = 17), and HCG (n = 19) indicated significantly lower rates of ototoxicity with increased delay in STS (P = 0.0006). On the basis of the analysis of hearing levels, there were significant differences among the two STS groups and HCG at 8000 Hz (P = 0.0010) and at 4000 Hz (P = 0.0075). The log-rank test for time to ototoxicity indicated a significant difference between STS4 and HCG (P = 0.0018). Delayed STS was effective in protecting against carboplatin-induced hearing loss. STS delayed to 4 h after carboplatin significantly decreased time to development of ototoxicity and rate of ototoxicity when compared with HCG.

Dorn, P., Konrad-Martin, D., Neely, S., Keefe, D., Cyr, E., and Gorga, M. (2001). Distortion product otoacoustic emission input/output functions in normal and hearing-impaired human ears. J. Acoust. Soc. Am. 110, 3119-3131.

Boys Town National Research Hospital, Omaha, Nebraska 68131, USA. dornp@boystown.org

DPOAE input/output (I/O) functions were measured at 7f2 frequencies (1 to 8 kHz; f2/f1 = 1.22) over a range of levels (-5 to 95 dB SPL) in normal-hearing and hearing-impaired human ears. L1-L2 was level dependent in order to produce the largest 2f1-f2 responses in normal ears. System distortion was determined by collecting DP data in six different acoustic cavities. These data were used to derive a multiple linear regression model to predict system distortion levels. The model was tested on cochlear-implant users and used to estimate system distortion in all other ears. At most but not all f2's, measurements in cochlear implant ears were consistent with model predictions. At all f2 frequencies, the ears with normal auditory thresholds produced I/O functions characterized by compressive nonlinear regions at moderate levels, with more rapid growth at low and high stimulus levels. As auditory threshold increased, DPOAE threshold increased, accompanied by DPOAE amplitude reductions, notably over the range of levels where normal ears showed compression. The slope of the I/O function was steeper in impaired ears. The data from normal-hearing ears resembled direct measurements of basilar membrane displacement in lower animals. Data from ears with hearing loss showed that the compressive region was affected by cochlear damage; however, responses at high levels of stimulation resembled those observed in normal ears.

Folmer, R. L., & Griest, S. E. (2001). Chronic tinnitus as phantom auditory pain. Otolaryngology Head and Neck Surgery, 124:414-20. 

Tinnitus Clinic, Oregon Hearing Research Center, Department of Otolaryngology, Oregon Health Sciences University, Portland, 97201-3098, USA. folmerr@ohsu.edu

OBJECTIVES: To investigate similarities between patients who experience chronic tinnitus or pain and to formulate treatment strategies that are likely to be effective for patients who experience phantom auditory pain. STUDY DESIGN: A total of 160 patients rated the severity and loudness of their tinnitus and completed the State-Trait Anxiety Inventory (STAI) and an abbreviated version of the Beck Depression Inventory (aBDI). Patients received counseling, audiometric testing, and matched the loudness of their tinnitus to sounds played through headphones. SETTING: A specialized tinnitus clinic within an urban medical center. RESULTS: Tinnitus severity was highly correlated with patients' degree of sleep disturbance, STAI, and aBDI scores. The self-rated (on a 1-to-10 scale)--but not the matched--loudness of tinnitus was correlated with tinnitus severity, sleep disturbance, STAI, and aBDI scores. CONCLUSIONS: The severity of chronic tinnitus is correlated with the severity of insomnia, anxiety, and depression. These relationships are the same for many patients with chronic pain. Treatment recommendations are discussed in reference to these results.

Ford JD, Campbell KA, Storzbach, D., Anger WK, Binder LM, Rohlman DS: Posttraumatic stress symptomatology is associated with unexplained illness attributed to Persian Gulf war military service. Psychosomatic Medicine, 63, 842-849.

Department of Psychiatry, University of Connecticut School of Medicine, Farmington, Connecticut 06030, USA. Ford@Psychiatry.UCHC.edu

OBJECTIVE: Controversy exists concerning unexplained illness in Persian Gulf War veterans, especially regarding the contribution of psychological trauma. We sought to determine if war zone trauma or posttraumatic stress symptomatology (PTSS) are associated with illnesses reported by Gulf War veterans that were documented by medical examination but not attributable to a medical diagnosis. METHODS: A total of 1119 (55% response rate) of 2022 randomly sampled veterans of the United States Persian Gulf War were screened and 237 cases and 113 controls were identified by medical examination for a case-control study comparing Persian Gulf War military veterans with or without medically documented, but unexplained, symptoms. Multivariate logistic regression and cross-validation analyses examined self-report measures of demographics, subjective physical symptoms and functioning, psychiatric symptoms, stressors, war zone trauma, and PTSS, to identify correlates of case-control status. RESULTS: Posttraumatic stress symptomatology and somatic complaints were independently associated with case status, as were (although less consistently) war zone trauma and depression. Age, education, and self-reported health, stress-related somatization, pain, energy/fatigue, illness-related functional impairment, recent stressors, and anxiety were univariate (but not multivariate) correlates of case status. CONCLUSIONS: PTSS related to war zone trauma warrants additional prospective research study and attention in clinical screening and assessment as a potential contributor to the often debilitating physical health problems experienced by Persian Gulf War veterans.

Kaylie, D. M., Hefeneider, S. H., Kempton, J. B., Siess, C. T., Vedder, C. T., Merkens, L. S., & Trune, D. R. (2001). Decreased cochlear DNA receptor staining in MRL.  Mpj-Fas autoimmune mice with hearing loss. Laryngoscope, 111:1275-1280 

Department of Otolaryngology-Head and Neck Surgery, Oregon Hearing Research Center, Oregon Health Sciences University, Portland, Oregon 97201-3998, USA.

OBJECTIVES: Previous studies of decreased cochlear DNA binding in autoimmune mice suggested that antibodies against a cochlear cell surface DNA receptor cause autoimmune hearing loss. However, the presence of a cochlear DNA receptor has not been determined. Therefore, immunohistochemistry with an anti-DNA receptor antibody was performed on MRL.MpJ-Fas(lpr) (MRL/lpr) autoimmune mice to determine 1) which inner ear structures contain DNA receptors and 2) whether the receptor staining pattern changes as autoimmune disease progresses and hearing thresholds increase. STUDY DESIGN: A prospective study of the progression of hearing loss in autoimmune mice and correlated alterations in immunostaining for the inner ear DNA receptor. METHODS: One group of MRL/lpr mice (n = 10) was allowed to develop autoimmune disease, and auditory brainstem response (ABR) audiometry was performed at 4, 6, and 9 months of age to measure the progression of hearing loss. A second group (n = 5) was tested for ABR thresholds at 2 months of age and immediately killed to assess receptor staining before the onset of autoimmune disease and hearing loss. The inner ears from all mice were immunohistochemically stained with an anti-DNA receptor antibody, and a qualitative analysis of the staining of cochlear structures was performed. RESULTS: Auditory brainstem response audiometry revealed a significant 20- to 30-dB elevation of thresholds as systemic disease progressed. Anti-DNA receptor staining was heaviest in the spiral ligament and less intense in the spiral ganglion and cochlear nerve. Both groups showed a similar pattern of staining in these structures. The stria vascularis and hair cells also stained in both groups. However, the stria cells of normal-hearing mice showed diffuse intracellular immunoreactivity, whereas older mice displayed less staining that was confined to the cell membranes. CONCLUSIONS: The inner ears of MRL/lpr mice contain DNA receptors. Autoimmune hearing loss was correlated with weaker overall intracellular staining in the stria vascularis and hair cells but increased staining of the cell membranes. This suggested DNA receptors have impaired endocytosis and more receptors remain on the cell membrane, possibly as a result of binding by circulating autoantibodies.

Konrad-Martin, D.>, Norton, S.J., Mascher, K.E., and Tempel, B.L. (2001). Effects of PMCA2 mutation on DPOAE amplitudes and latencies in deafwaddler mice. Hear. Res. 151, 205-220.

Department of Speech and Hearing Sciences, University of Washington, Seattle 98195, USA. konradd@boystown.org

The deafwaddler (dfw) mouse mutant is caused by a spontaneous mutation in the gene that encodes a plasma membrane Ca(2+) ATPase (type 2), PMCA2 (Street et al., 1998. Nat. Genet. 19, 390-394), which is expressed in cochlear and vestibular hair cells. Distortion product otoacoustic emission (DPOAE) amplitudes and latencies were examined in control mice, deafwaddler mutants, and controls treated with the drug furosemide. Furosemide causes a transient reduction of DPOAEs (Mills et al., 1993. J. Acoust. Soc. Am. 94, 2108-2122). We wanted to determine whether DPOAEs obtained in furosemide-treated mice were similar or different from results obtained in +/dfw mice. DPOAE amplitude and phase were measured as a function of f(2)/f(1) ratio. These data were converted into waveforms using inverse fast Fourier transform, and their average latency was used to estimate DPOAE group delay. Homozygous deafwaddlers did not produce DPOAEs. Heterozygous deafwaddlers (+/dfw) had increased DPOAE thresholds and reduced amplitudes at high frequencies, compared to controls. To the extent that DPOAEs depend on functional outer hair cells (OHCs), abnormal DPOAEs in +/dfw mice suggest that PMCA2 is important for OHC function at high frequencies. Similar to the effects of furosemide, the mutation reduced DPOAEs for low-level stimuli; in contrast to furosemide, the mutation altered DPOAEs elicited by high levels.

Konrad-Martin, D., Neely, S.T., Keefe, D.H., Dorn, P.A., and Gorga, M.P. (2001). Sources of DPOAEs revealed by suppression experiments and IFFTs in normal ears. J. Acoust. Soc. Am. 109, 2862-2879.

Boys Town National Research Hospital, Omaha, Nebraska 68131, USA. konradd@boystown.org

Primary and secondary sources combine to produce the 2f1-f2 distortion product otoacoustic emission (DPOAE) measured in the ear canals of humans. DPOAEs were obtained in nine normal-hearing subjects using a fixed-f2 paradigm in which f1 was varied. The f2 was 2 or 4 kHz, and absolute and relative primary levels were varied. Data were obtained with and without a third tone (f3) placed 15.6 Hz below 2f1-f2. The level of f3 was varied in order to suppress the stimulus frequency otoacoustic emission (SFOAE) coming from the 2f1-f2 place. These data were converted from the complex frequency domain into an equivalent time representation using an inverse fast Fourier transform (IFFT). IFFTs of unsuppressed DPOAE data were characterized by two or more peaks. Relative amplitudes of these peaks depended on overall primary level and on primary-level differences. The suppressor eliminated later peaks, but early peaks remained relatively unaltered. Results are interpreted to mean that the DPOAE measured in humans includes components from the f2 place (intermodulation distortion) and DP place (in the form of a SFOAE). These findings build on previous work by providing evidence that multiple peaks in the IFFT are due to a secondary source at the DP place.

Ren, T., & Nuttall, A. L. (2001). Basilar Membrane Vibration in the Basal Turns of the Sensitive Gerbil Cochlea. Hearing Research, 151:48-60. 

Oregon Hearing Research Center (NRC04), Department of Otolaryngology and Head and Neck Surgery, Oregon Health Sciences University, Portland 97201-3098, USA. rent@ohsu.edu

The basal membrane (BM) velocity responses to pure tones were measured using a newly developed laser interferometer microscope that does not require placing a reflecting object on the BM. It was demonstrated that the instrument is able to measure sub-nanometer vibration from the cochlear partition in the basal turn of the gerbil. The overall shape of the amplitude spectra shows typical tuning features. The 'best' frequencies (BFs) for the BM locations studied were between 14 kHz and 27 kHz, depending on the longitudinal position. For a given BM location, tuning sharpness was input level dependent, indicated by the Q(10dB), which varied from approximately 3 at low stimulus levels to near 1.5 at high input levels. At frequencies below BF, parallel amplitude/frequency curves across stimulus levels indicate a linear growth function. However, at frequencies near BF, the velocity increased linearly at low levels (<40 dB SPL) and became compressed between 40 and 50 dB SPL. Although the velocity gain for the frequency range below BF was a function of frequency, for a given frequency the gains were approximately constant across different levels. At frequencies near BF, the velocity gain at low sound pressure level was greater than that at a high sound pressure level, indicating a nonlinear negative relationship to stimulus level. The data also showed that the BF shifts toward the low frequencies with stimulus intensity increase. The phase spectra showed two important features: (1) at frequencies about half octave below the BF, phase slope is very small, indicating an extremely short delay; (2) the greatest phase lag occurs at frequencies near the BF, indicating a significant delay near this frequency range.

Ren, T., & Nuttall, A. (2001). Recording depth of the heterodyne laser interferometer for cochlear vibration measurement. Journal of the Acoustical Society of America, 109:826-829. 

Measurement of the cochlear partition vibration as a function of the optical-axis (z-axis) position in the gerbil cochlea showed that the velocity distributes over a range of more than 300 microm, which is larger than the thickness of the cochlear partition. This finding suggests that the recording depth (RD) of the heterodyne interferometer probably is not as small as reported in the literature. In the current experiment, the RD of the heterodyne laser interferometer was studied by measuring the velocity of a vibrating mirror as a function of the z-axis position. Results demonstrate that the optical sectioning characteristic, measured by the intensity of the reflected laser beam as a function of the z-axis position, is not able to correctly estimate the RD of the heterodyne interferometer: the RD is much larger than optical sectioning, indicating a poor spatial resolution along the z axis.

Salinsky M, Storzbach, D., Dodrill CB, Binder LM: Test-retest bias, reliability, and regression equations for neuropsychological measures repeated over a 12-16 week period. Journal of the International Neuropsychological Society, 7, 597-605, 2001.

Department of Neurology, Oregon Health Sciences University Epilepsy Center, Portland 97201, USA. Salinsky@OHSU.edu

The interpretation of neurobehavioral change over time requires knowledge of the test-retest characteristics of the measures. Without this information it is not possible to distinguish a true change (i.e., one reflecting the occurrence or resolution of an intervening process) from that occurring on the basis of chance or systematic bias. We tested a group of 72 healthy young to middle aged adults twice over a 12-to-16-week interval in order to observe the change in scores over time when there was no known intervention. The test battery consisted of seven commonly used cognitive measures and the Profile of Mood States (POMS). Test-retest regression equations were calculated for each measure using initial performance, age, education, and a measure of general intellectual function (Wonderlic Personnel Test) as regressors. Test-retest correlations ranged from .39 (POMS Fatigue) to .89 (Digit Symbol). Cognitive measures generally yielded higher correlations than did the POMS. Univariate regressions based only on initial performance adequately predicted retest performance for the majority of measures. Age and education had a relatively minor influence. Practice effects and regression to the mean were common. These test-retest regression equations can be used to predict retest scores when there has been no known intervention. They can also be used to generate statistical statements regarding the significance of change in an individual's performance over a 12-to-16-week interval.

Spencer PS, McCauley LA, Joos SK, Lapidus JA, Lasarev MR, Joos SK, Storzbach, D.: Self-reported exposures and their association with unexplained illness in a population-based case-control study of Gulf War veterans. Journal of Occupational Medicine 43:1041-1056.

Center for Research on Occupational and Environmental Toxicology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, CROET Mailcode L606, Portland, OR 97201, USA. spencer@ohsu.edu

Many factors have been considered as possible causes of the unexplained illness reported by veterans of the Gulf War (GW). In this study, we report an analysis of risk factors and unexplained illness in a population-based sample of GW veterans who underwent clinical evaluation. Multiple risk factors were compared in 241 veterans who met criteria for unexplained illness and 113 healthy controls. Results suggest that GW unexplained illness is most highly associated with combat conditions, heat stress, and having sought medical attention during the GW. When controlling for multiple simultaneous exposures during the GW, interactions around pyridostigmine bromide, insecticides and repellents, and stress were not significant. These results indicate that most unexplained illness in GW veterans cannot be explained by neurotoxic effects of exposures to chemicals that inhibit cholinesterase activity.