Publication Abstracts - 2002

Crandell, C., Smaldino, J., Lewis, M.S., & Kriesman, B. (2002). Auditory rehabilitation: Improving communication for individuals with hearing impairment. In M. Valente (ed.), Hearing aids: Standards, options, and limitations (2nd edition). New York, NY: Theime.

It has been amply demonstrated that the major sequela of hearing loss is difficulty understanding speech, particularly in difficult listening environments.  Due to the adverse effects of hearing loss on speech recognition, the literature has demonstrated that individuals with hearing loss may exhibit reduced psychosocial, emotional, and physical health status.  Because of the communicative, psychosocial, and physical health deficits that can be related t hearing loss, it is imperative that audiologists not limit rehabilitative strategies to hearing aids alone.  This is particularly critical as traditional amplification technology may provide little or no improvement to the signal-to-noise ratio (SNR) in everyday listening environments.  Even SNR enhancing strategies, such as directional microphones, may provide limited communicative benefit in real0world listening environments that contain not only background noise but also reverberation (see Chapters 2 and 7 for discussions on directional microphone technologies).  Unfortunately, assistive technologies to augment communication in listeners with hearing loss account for less than 2% of gross sales revenues for audiologists.  With these considerations in mind, this chapter addresses rehabilitative technologies and communication strategies that have been demonstrated to improve communication in listeners with sensorineural hearing loss (SNHL) within a number of listening environments, such as houses of worship, restaurants, classrooms, meeting/conference rooms, and theaters.  In addition, this chapter provides information on how to improve perception of the telephone, radio, and television, and discusses alerting/signaling technologies that can assist individuals with hearing loss in the awareness of various sounds within their listening environment.  The terms auditory rehabilitative technology and auditory assistive technology, rather than assistive listening devices (ALDs), are used to discuss technologies that improve communicative status through the transmission of an amplified auditory, tactile, kinesthetic, or visual signal to the listener.  These terms were selected over the more commonly used ALD because many of these technologies are not limited to improving listening per se.  In addition, although this chapter focuses on individuals with bilateral SNHL, it must be remembered that the technologies that are discussed here are also often applicable to individuals with conductive, mixed, and unilateral hearing losses.  Moreover, these technologies are often beneficial for adults and children with central auditory processing deficits.

Gorga, M.P., Neely, S.T., Dorn, P.A., and Konrad-Martin, D. (2002). The use of DPOAE suppression as an estimate of response growth. Journal of the Acoustical Society of America, 111, 271-284.

Distortion product otoacoustic emission (DPOAE) levels in response to primary pairs (f2=2 or 4 kHz, L2 ranging from 20 to 60 dB SPL, L1=0.4L2 + 39 dB) were measured with and without suppressor tones (f3), which varied from 1 octave below to 1/2 octave above f2, in normal-hearing subjects.  Suppressor level (L3) varied from -5 to 85 dB SPL.  DPOAE levels were converted into decrements by subtracting the level in the presence of the suppressor from the level in the absence of a suppressor.  DPOAE decrement vs L3 functions showed steeper slopes when f3<f2 and shallower slopes when f3>f2.  This pattern is similar to other measurements of response growth, such as direct measures of basilar-membrane motion, single-unit rate-level functions, suppression of basilar-membrane motion, and discharge-rate suppression from lower animals.  As L2 increased, the L3 necessary to maintain 3 dB of suppression increased at a rate of about 1 dB/dB when f3 was approximately equal to f2, but increased more slowly when f3<f2. Functions relating L3 to L2 in order to maintain a constant 3-dB reduction in DPOAE level were compared for f3<f2 and for f3»f2 in order to derive an estimate related to "cochlear-amplifier gain." These results were consistent with the view that "cochlear gain" is greater at lower input levels, decreasing as level increases.

Hall, J.W. & Lewis, M.S. (2002). Diagnostic audiology and hearing aids. In J.B. Snow, Jr, (ed.), Ballenger's diseases of the nose, throat, ear, head, and neck (16th edition). Baltimore, MD: Williams & Wilkins.

This synopsis presents current techniques and strategies for hearing assessment, with an emphasis on the application of a test battery approach that maximizes diagnostic accuracy and efficiency while minimizing test time and costs. It also includes a review of current hearing aid technology for none-medical management of hearing impairment and a précis of pediatric habilitation approaches.

Hodoshima, N., Arai T., Kusumoto K. (2002). Enhancing temporal dynamics of speech to improve intelligibility in reverberant environments, Proc. Forum Acusticum Sevilla.

Hodoshima, N., Inoue, T., Arai, T. and Kusumoto, A., (2002). Suppressing steady-state portions of speech for improving intelligibility in various reverberant environments, Proc. China-Japan Joint Conference on Acoustics, pp. 199-202.

Konrad-Martin, D., Neely, S.T., Keefe, D.H., Dorn, P.A., and Gorga, M.P. (2002). Sources of DPOAEs revealed by suppression experiments, IFFTs, and SFOAEs in impaired ears. Journal of the Acoustical Society of America, 111,1800-9.

Boys Town National Research Hospital, Omaha, Nebraska 68131, USA. Dawn_Konrad-Martin@rush.edu

DPOAE sources are modeled by intermodulation distortion generated near the f2 place and a reflection of this distortion near the DP place. In a previous paper, inverse fast Fourier transforms (IFFTs) of DPOAE filter functions in normal ears were consistent with this model [Konrad-Martin et al., J. Acoust. Soc. Am. 109, 2862-2879 (2001)]. In the present article, similar measurements were made in ears with specific hearing-loss configurations. It was hypothesized that hearing loss at f2 or DP frequencies would influence the relative contributions to the DPOAE from the corresponding basilar membrane places, and would affect the relative magnitudes of SFOAEs at frequencies equal to f2 and fDP. DPOAEs were measured with f2 = 4 kHz, f1 varied, and a suppressor near fDP. L2 was 25-55 dB SPL (L1 = L2 + 10 dB). SFOAEs were measured at f2 and at 2.7 kHz (the average fDP produced by the f1 sweep) for stimulus levels of 20-60 dB SPL. SFOAE results supported predictions of the pattern of amplitude differences between SFOAEs at 4 and 2.7 kHz for sloping losses, but did not support predictions for the rising- and flat-loss categories. Unsuppressed IFFTs for rising losses typically had one peak. IFFTs for flat or sloping losses typically have two or more peaks; later peaks were more prominent in ears with sloping losses compared to normal ears. Specific predictions were unambiguously supported by the results for only four of ten cases, and were generally supported in two additional cases. Therefore, the relative contributions of the two DPOAE sources often were abnormal in impaired ears, but not always in the predicted manner.

Lewis, M.S., Crandell, C., Valente, M., Enrietto, J., & Kriesman, N. (2002, October). Improving speech perception in noise with directional microphones and frequency modulation (FM) technology. Available on-line at http://www.audiologyonline.com.

Individuals with sensorineural hearing loss (SNHL) often exhibit difficulty understanding speech, particularly in noise (Dubno, Dirks & Morgan, 1984; Suter, 1985; Helfer & Wilber, 1990; Crandell, 1991; Helfer & Huntley, 1991; Killion, 1997). Unfortunately, traditional amplification strategies may provide little or no improvement in adverse listening environments. To date, however, there are several noise reduction technologies that have been shown to improve speech intelligibility (Crandell and Smaldino, 2000). These technologies include directional microphones and personal frequency modulation (FM) systems (Hawkins, 1984; Fabry, 1994; Valente, Fabry, & Potts, 1995; Kuk, Kollofski, Brown, Melum & Rosenthal, 1999; Preves, Sammeth & Wynne, 1999; Pumford, Seewald, Scollie, & Jenstad, 2000; Ricketts, 2000; Valente, Schuchman, Potts, & Beck, 2000).

Directional microphones typically use a cardiod polar plot sensitivity pattern. That is, they reduce signals originating from the rear and the sides and only amplify signals arriving from the front - where the speaker will often be located. For discussions on other polar plot sensitivity patterns the reader is directed to Valente et al. (2000). Numerous investigations have demonstrated that directional microphone technology can enhance speech intelligibility in noisy listening environments (Valente et al., 1995; Gravel, Fausel, Liskow, & Chobot, 1999; Kuk et al., 1999; Preves et al., 1999; Ricketts & Dhar, 1999; Pumford et al., 2000; Ricketts, 2000; Valente et al., 2000; Ricketts et al., 2001). In fact, recent investigations have demonstrated that the utilization of directional microphone technology can improve speech intelligibility in noise by as much as 6 to 8 dB as compared to typical omnidirectional microphone technology (Valente et al., 1995; Gravel et al., 1999; Ricketts & Dhar, 1999; Pumford et al., 2000; Valente et al., 2000). It should be noted, however, that benefits in signal-to noise ratio (SNR) might decrease significantly in reverberant listening conditions.

Personal FM systems have also been shown to improve speech intelligibility in noise (Hawkins, 1984; Fabry, 1994; Crandell & Smaldino, 2000). Past investigations have demonstrated that the utilization of FM technology can improve speech intelligibility in noise by as much as 20-25 dB (see Crandell and Smaldino, 2000). With a personal FM system, the speaker's voice is picked-up via FM wireless microphone located near the speaker's mouth - where the effects of reverberation, distance, and noise are minimal. The FM system converts the acoustic signal to an electrical waveform at the microphone, and the signal is transmitted via FM signal, from the transmitter to the receiver. Both the transmitter and the receiver are tuned to the same transmitting and receiving frequency. At the receiver end, the electrical signal is amplified, converted back to an acoustical waveform and conveyed to the listener.

A recent and popular method for coupling FM systems to the listener with hearing impairment is through an "audio boot" coupled to a BTE hearing aid. This type of technology, such as the Phonak Microlink (see Figure 1), allows the user to convert his/her personal hearing aid into a FM system simply by attaching the audio boot. Typically, such FM systems enable the user to have three FM settings: (1) FM only; for the purpose of focusing primarily on the talker, (2) environmental microphone (EM) only; for the purpose of listening to all individuals in the immediate listening environment as well as monitoring his/her own voice, and (3) FM + EM for listening to both the speaker as well as other individuals in that listening environment.

Despite the documented enhancement in speech intelligibility with directional microphone and FM technologies, only one investigation has attempted to directly compare these two (Hawkins, 1984). In this study, Hawkins (1984) evaluated the speech intelligibility of children utilizing these two types of technologies. Results demonstrated that FM technology, when utilized in the FM only mode, provided significantly better speech recognition in noise when compared to directional microphone technology.

We (the authors of this article) recently began an investigation to examine the speech-perception ability of adults with slight to severe SNHL, in a noisy background, utilizing directional microphone and FM technology. Specifically, speech perception was assessed with the Hearing in Noise Test (HINT) (Nilsson, Soli & Sullivan, 1994). Speech spectrum noise was utilized as the noise source, in the following listening conditions: (1) binaural BTE hearing aids in omnidirectional mode; (2) binaural BTE hearing aids in the directional mode; and (3) binaural BTE hearing aids utilized with two FM receivers in the FM only mode. The speech spectrum noise was presented from four loudspeakers positioned at 45°, 135°, 225°, and 315° azimuths. All loudspeakers were located one meter from the subject and the noise was held constant at 65 dB(A).

Forty-six subjects (recruited from the University of Florida and the Washington University School of Medicine) were evaluated in this study. Subjects ranged in age from 24 to 84 years, with a median age of 73 years. All subjects were fit with Phonak Claro 311 dAZ digital, BTE hearing aids bilaterally. The Phonak Microlink ML8 was used as the FM receiver. All FM receivers were evaluated in the FM only mode. All subjects used the Phonak TX3 HandyMic FM transmitter.

These devices were fit via the Desired Sensation Level (DSL) prescriptive fitting formula on the Phonak Fitting Guideline (PFG) Version 7.3 software. All hearing aid fittings were verified via probe-microphone measures.

Preliminary data from this investigation indicated the following results:

The mean reception threshold for sentences (RTS) for the directional microphone condition (-0.54 dB) yielded significantly better performance than the omnidirectional microphone condition (2.9 dB). That is, on average, the directional microphones improved the RTS by 3.44 dB.< The mean RTS for the condition with two FM receivers in the FM only mode (-19.84 dB) yielded significantly better scores than the directional microphone condition (-0.54 dB). Stated otherwise, the binaural FM improved the RTS by 19.3 dB.

Lewis, M.S., Crandell, C., Valente, M., Enrietto, J., & Kreisman, N. (2002, September). Improving speech perception in noise with directional microphones and frequency modulation (FM) technology. Available on-line at http://www.healthyhearing.com.

Same As Above Article

Salinsky M, Storzbach, D., Binder L, Arons C, Dodrill C. Effects of Gabapentin and Carbamazepine on the EEG, Alertness, and Cognition in Healthy Volunteers. Epilepsia 43:482-490.

Purpose: Antiepileptic drug (AED) therapy can be associated with neurotoxic side effects including cognitive dysfunction.  Objective methods for detection of neurotoxicity in individual patients would be useful.  We studied the effects of gabapentin (GBP) and carbamazepine (CBZ) on neurophysiologic and cognitive/behavioral measures in healthy volunteers.

Methods: In a 12-week, randomized, double-blind, parallel-group study of CBZ and GBP in healthy volunteers, 23 subjects completed the protocol.  All achieved the target dose of 1,200 mg CBZ or 3,600 mg GBP.  A structured EEG for quantitative analysis and a cognitive test battery were administered before AED therapy and againa fter 12 weeks of therapy.  Test-retest differences were compared with those of 72 untreated control subjects.

Results: Both CBZ and GBP significantly decreased the peak frequency of the posterior (alpha) rhythm, with CBZ exerting a greater effect.  Ten CBZ and six GBP subjects exceeded the 95% confidence interval (CI) for an individual.  Cognitive tests revealed AED vs. control group effects for two of seven measures (Digit Symbol, Stroop) and all subjective measures. However, few subjects exceeded the 95% CI for any objective test.  Differences between CBZ and GBP were not significant.  Greater EEG slowing was associated with greater subjective neurotoxicity and poorer test-retest performance on a cognitive test summary measure.

Conclusions: Prolonged CBZ and GBP therapy induced EEG slowing that correlated with cognitive complaints and often exceeded the confidence interval for individual subjects.  Quantitative EEG measures may be useful in the objective determination of AED-related neurotoxicity.

Saunders, G.H. and Cienkowski, K.M. (2002) A test to measure subjective and objective speech intelligibility. Journal of the American Academy of Audiology,13:38-49.

National Center for Rehabilitative Auditory Research, Portland, Oregon 97207, USA.

Measurement of hearing aid outcome is particularly difficult because there are numerous dimensions to consider (e.g., performance, satisfaction, benefit). Often there are discrepancies between scores in these dimensions. It is difficult to reconcile these discrepancies because the materials and formats used to measure each dimension are so very different. We report data obtained with an outcome measure that examines both objective and subjective dimensions with the same test format and materials and gives results in the same unit of measurement (signal-to-noise ratio). Two variables are measured: a "performance" speech reception threshold and a "perceptual" speech reception threshold. The signal-to-noise ratio difference between these is computed to determine the perceptual-performance discrepancy (PPDIS). The results showed that, on average, 48 percent of the variance in subjective ratings of a hearing aid could be explained by a combination of the performance speech reception threshold and the PPDIS. These findings suggest that the measure is potentially a valuable clinical tool.

Binder LM, Storzbach, D., Campbell K, Rohlman D, Anger WK, Members of the Portland Environmental Hazards Research Center: Neurobehavioral deficits in Gulf War veterans with chronic fatigue. Journal of the International Neuropsychological Society, 7, 835-839.

Gulf War unexplained illnesses (GWUI) are a heterogeneous collection of symptoms of unknown origin known to be more common among veterans of the Gulf War than among nonveterans.  In the present study we focused on one of these unexplained illnesses.  We tested the hypothesis that in a sample of Persian Gulf war veterans chronic fatigue syndrome (CFS) was associated with cofnitive deficits on computerized cognitive testing after controlling for the effects of premorbid cognitive differences.  We obtained Armed Forces Qualification Test (AFQT) data acquired around the date of induction into the military on 94 veterans of the Gulf War, 32 with CFS and 62 healthy controls. Controls performed better than participants diagnosed with CFS on the AFQT.  Cognitive deficits were associated with CFS on 3 of 8 variables after the  effect of premorbid AFQT scores was removed with ANCOVA.

Bourdette DN, McCauley LA, Barkhuizen A, Johnston W, Wynn M., Joos SK, Storzbach, D., Shuell MS, Sticker 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 43:1026-1040.