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When combining a multicode CDMA system with convolutional coding, two methods have been considered in the literature. In one method, coding is across time in each multicode channel while in the other the coding is across both multicodes and time. In this paper, a performance/complexity analysis of decoding metrics and trellis structures for the two schemes is carried out. It is shown that the latter scheme can exploit the multicode diversity inherent in convolutionally coded direct sequence code division multiple access (DS-CDMA) systems which employ minimum mean squared error (MMSE) multiuser detectors. In particular, when the MMSE detector provides sufficiently different signal-to-interference ratios (SIRs) for the multicode channels, coding across multicodes and time can obtain significant performance gain over coding across time, with nearly the same decoding complexity.

When combining a multicode CDMA system with convolutional coding, two methods have been considered in the literature. In one method, coding is across time in each multicode channel while in the other the coding is across both multicodes and time. In this paper, a performance/complexity analysis of decoding metrics and trellis structures for the two schemes is carried out. It is shown that the latter scheme can exploit the multicode diversity inherent in convolutionally coded direct sequence code division multiple access (DS-CDMA) systems which employ minimum mean squared error (MMSE) multiuser detectors. In particular, when the MMSE detector provides sufficiently different signal-to-interference ratios (SIRs) for the multicode channels, coding across multicodes and time can obtain significant performance gain over coding across time, with nearly the same decoding complexity.

Purpose: Speech recognition may be analyzed in terms of recognition probabilities for perceptual wholes (e.g., words) and parts (e.g., phonemes), where j or the j-factor reveals the number of independent perceptual units required for recognition of the whole (Boothroyd, 1968b; Boothroyd & Nittrouer, 1988; Nittrouer & Boothroyd, 1990). For consonant-vowel-consonant (CVC) nonsense syllables, j ∼ 3 because all 3 phonemes are needed to identify the syllable, but j ∼ 2.5 for real-word CVCs (revealing ∼2.5 independent perceptual units) because higher level contributions such as lexical knowledge enable word recognition even if less than 3 phonemes are accurately received. These findings were almost exclusively determined with the 120-word corpus of the isophonemic word lists (Boothroyd, 1968a; Boothroyd & Nittrouer, 1988), presented one word at a time. It is therefore possible that its generality or applicability may be limited. This study thus determined j by using a much larger and less restricted corpus of real-word CVCs presented in 3-word groups as well as whether j is influenced by test size., Method: The j-factor for real-word CVCs was derived from the recognition performance of 223 individuals with a broad range of hearing sensitivity by using the Tri-Word Test (Gelfand, 1998), which involves 50 three-word presentations and a corpus of 450 words. The influence of test size was determined from a subsample of 96 participants with separate scores for the first 10, 20, and 25 (and all 50) presentation sets of the full test., Results: The mean value of j was 2.48 with a 95% confidence interval of 2.44-2.53, which is in good agreement with values obtained with isophonemic word lists, although its value varies among individuals. A significant correlation was found between percent-correct scores and j, but it was small and accounted for only 12.4% of the variance in j for phoneme scores ≥60%. Mean j-factors for the 10-, 20-, 25-, and 50-set test sizes were between 2.49 and 2.53 and were not significantly different from one another., Conclusions: The j-factor based on a 450-word corpus and tri-word testing confirms and expands on findings from single-word presentations of isophonemic lists and a 120-word corpus. This enhances the generality (external validity) of the notions that j ∼ 2.5 for real-word CVCs, and lexical knowledge enables CVC word recognition based on ∼2.5 independent perceptual units. The robust nature of isophonemic word test outcomes is confirmed by close agreement with those provided by the high-reliability Tri-Word Test. Percent-correct performance was correlated with j but appeared to account for less than 13% of j-factor variance for most scores likely to be encountered in practice. Variability in the size of j suggests individual differences in the ability to take advantage of lexical knowledge in word recognition. The j-factor may be useful to inform rehabilitation needs, intervention content, and outcome assessment, as well as for other clinical applications.

Method: Complete psychometric functions for phoneme and word recognition scores at 8 signal-to-noise ratios from -15 dB to 20 dB were generated for the first 10, 20, and 25, as well as all 50, three-word presentations of the Tri-Word or Computer Assisted Speech Recognition Assessment (CASRA) Test (Gelfand, 1998) based on the results of 12 normal-hearing young adult participants from the original study., Results: The psychometric functions for both phoneme and word scores were very similar and essentially overlapping for all set sizes. Performance on the shortened tests accounted for 98.8% to 99.5% of the full (50-set) test variance with phoneme scoring, and 95.8% to 99.2% of the full test variance with word scoring. Shortening the tests accounted for little if any of the variance in the slopes of the functions., Conclusions: The psychometric functions for abbreviated versions of the Tri-Word speech recognition test using 10, 20, and 25 presentation sets were described and are comparable to those of the original 50-presentation approach for both phoneme and word scoring in healthy, normal-hearing, young adult participants.

Speech recognition test reliability is optimized with 450 test items, and the Computer Assisted Speech Recognition Assessment (CASRA) test is a practical approach for achieving this goal by combining 50 presentations of 3 consonant-vowel nucleus-consonant (CNC) words each with phonemic scoring (S. A. Gelfand, 1998). However, optimized reliability might not be essential if reliability is as high as possible in light of practical constraints and what the clinician is trying to do with the results. The CASRA paradigm addresses these compromise goals with a reduced number of 3-word sets: 25 sets yield 25 (groups) x 3 (words) x 3 (phonemes) = 225 test items, 20 sets give 20 x 3 x 3 = 180 items, and 10 sets provide 10 x 3 x 3 = 90 items. This study addressed the empirical reliability of such an approach, and the extent to which results on shortened versions predict full-test scores. Test and retest scores were obtained for 10-, 20-, and 25-set versions of the CASRA for 144 participants with a wide range of hearing ability. For group data, first and second scores were highly correlated and not significantly different from each other for all 3 test sizes. Performance based on 20 and 25 sets accounted for roughly 97% of the variance of full (50-set) test scores, and scores based on 10 sets accounted for about 88% of the full-test variance. Individual test-retest reliability agreed with theoretical expectations based on 95% binomial confidence intervals. Cases outside the 95% confidence limits were 7.6% for 10 sets, and 3.5% for 20 and 25 sets with phoneme scoring, and 4.9% for 10 and 20 sets and 3.5% for 25 sets with word scoring. The shortened CASRA is a practical way to achieve improvements in reliability over traditional word tests. The 20-set version may approximate the strongest compromise when trying to shorten test size without appreciably reducing reliability for clinical purposes. However, the 10-set version is probably a more practical approach for routine use because it accounts for 88% of full-test variance, is more reliable than a traditional 75-word test, and does not appear to be subject to significant short-term learning effects.

Speech recognition assessment involves a dilemma because clinicians want a test that is short and reliable, but statistical principles dictate that a short test is unreliable. Curves representing the variability of test scores based on the binomial model reveal that approximately 450 scorable items are needed in order to optimize the reliability of a speech recognition test. A testing approach was developed to achieve this sample size while retaining the principal features of the most commonly accepted speech recognition tests (i.e., monosyllabic words presented in an open-set format, verbal responses, and right/wrong scoring). It involves the use of an interactive computer program to present CNC words in 50 three-word groups, which are scored phonemically, resulting in 450 scorable items. Normal performance is described as a function of both presentation level and signal-to-noise ratio. Comparisons of test and retest scores for 100 individuals with normal hearing and 100 persons with sensorineural losses revealed that the approach achieves the degree of reliability predicted by the binomial model for both groups. Phoneme scores accounted for 99% of the variance of word scores for most of the performance range encountered in clinical practice, making it possible for test outcomes based on phonemic scoring to be expressed in terms of equivalent word recognition scores.

Six subjects who developed individually significant auditory deprivation effects associated with monaural amplification were tracked for 6.2 to 15.1 years from the time of their initial hearing aid fitting. Each subject received binaural hearing aids after the auditory deprivation effect became apparent and used binaural amplification for at least 4 years. The findings corroborate and expand upon existing case reports. Several general configurations of recovery and no recovery following the introduction of binaural amplification were identified: (1) cases in which auditory deprivation effects developed within about 2 years and recovered completely within about 2 years of binaural use; (2) cases with significant but incomplete recovery; and (3) cases in which the auditory deprivation effect took several years to develop and did not recover following several years of binaural amplification. Clinical implications of the results are proposed.

This study addressed the issue of whether functional impairments can be identified or confirmed using tonal acoustic reflex thresholds (ARTs). Tonal ARTs from 74 ears with functional impairments were compared to 10th percentiles of the ARTs for normal and cochlear-impaired ears at 500 to 2000 Hz (Gelfand, Schwander, and Silman, 1990). Only one ear (5.3%) was correctly identified among the 19 ears in which all of the voluntary thresholds at 500 to 2000 Hz were < or = 55 dB HL. Acoustic reflex thresholds correctly identified functional losses in 70.9 percent, 78.6 percent, and 85.7 percent of the ears with voluntary thresholds > or = 60 dB HL at one, two, or three of these frequencies, respectively. The false positive rate was only 5 to 7 percent for a control group of 50 ears with genuine sensorineural hearing losses. The results indicate that tonal ARTs are an effective nonbehavioral tool for identifying or substantiating the presence of functional losses when thresholds are > or = 60 dB HL; however, ARTs cannot identify functional components when thresholds are < or = 55 dB HL.

This study investigated the effects of monaural versus binaural amplification upon the speech recognition scores (SRSs) of children with bilateral moderate sensorineural hearing loss after more than 4 years of hearing aid use. There was a significant decrease in SRSs for the unaided ears of the monaural hearing aid users, but there were no significant differences between initial and retest SRSs for their aided ears, or for both ears of those using binaural amplification. The SRS reduction was found to be large enough to be significant on an individual ear basis (by exceeding 95% confidence limits of the binomial model) in five of the ten unaided ears of the monaurally fitted children, but this did not occur for any of the initial-retest SRS differences in the aided ears of either group. These findings demonstrate that the auditory deprivation effect, which has been reported for adults using monaural hearing aids, is also found in children.

Previous studies on the relationship between functional overlays and underlying organic hearing levels in nonorganic hearing loss (NOHL) have relied upon the clinical resolution of the nonorganic portion of the loss. This study involved the first use of subjects with sensorineural losses in a simulated NOHL experiment. This is important because most adults with NOHLs have underlying sensorineural losses. Different configurations of the experimentally simulated functional components (the difference between the exaggerated and real thresholds) as a function of frequency were associated with (a) normal hearing; (b) losses becoming abruptly worse at 4000 Hz, and (c) sloping losses, respectively. Thus, the simulation data corroborate the observations made using clinical patients with resolved NOHLs, and provide further support for the notion that these patients typically employ a strategy involving the use of an internalized loudness-based anchor on a within-ear basis to generate their exaggerated audiograms. Moreover, the outcome of this study reveals the limitations of restricting the subjects used in simulated NOHL experiments to normal hearing individuals, and highlights the importance of using hearing impaired groups in future experimental simulations of nonorganic hearing losses.

This study expanded upon previous work (Gelfand & Silman, 1985) on the relationship between functional components (the difference between the nonorganic and resolved thresholds) and the underlying organic hearing levels. The nature of nonorganic hearing loss (NOHL) was studied with respect to hearing sensitivity after resolution of the nonorganic components in 25 patients with unilateral NOHLs. Most of the subjects had an organic hearing loss underlying the functional components. The configuration of the functional components as a function of frequency was related to that of the resolved hearing levels in a manner similar to that reported for bilateral NOHLs. The strategy employed to exaggerate the loss in the ear with the nonorganic overlay appeared to be unrelated to the nature of the loss in the opposite ear, but the perception of an interaural difference might in some way bias the patient to 'choose' a unilateral NOHL as opposed to a bilateral one. The findings confirm and expand upon the prior ones, suggesting the use of an internalized loudness-based anchor by patients with NOHLs. Thus, the pure tone configuration of NOHL is consistently accounted for on the basis of known and explainable auditory factors regardless of whether the hearing levels are exaggerated in one or both ears.

The purposes of this investigation were two-fold: 1) to prospectively investigate the effect of prolonged lack of binaural amplification in the unaided ears of adults with bilaterally symmetrical sensorineural hearing impairment (BSSHI) fitted monaurally; and, 2) to prospectively investigate the effects of amplification on speech-recognition performance in the aided ears of monaurally and binaurally fitted subjects. Subjects consisted of 19 monaurally aided adults, 28 binaurally aided adults, and 19 control adults. Both ears of the experimental subjects (binaurally and monaurally aided adults) had BSSHI. The speech measures included the W-22 CID suprathreshold speech-recognition test, nonsense syllable test, and speech-perception-in-noise test. Initial testing was done between 6 and 12 weeks following hearing-aid fitting. Retests were performed approximately 1 year following the initial test. The results revealed that the mean aided minus unaided ear score for the nonsense syllable and W-22 tests increased significantly from the initial test to retest, reflecting a slight improvement in speech performance in the aided ear and a slightly greater decrement in the unaided ear. The findings were interpreted with respect to the theories of auditory deprivation and acclimatization.

A modification of the City University of New York nonsense syllable test (CUNY NST) has been developed in which (a) the several subtests of the original test are replaced with a 22-item consonant-vowel (CV) subtest and a 16-item vowel-consonant (VC) subtest; and, (b) the response choices for each target syllable include all 22 initial and all 16 final consonants, respectively. In addition, the test tokens are presented as isolated syllables without a carrier phrase. These changes enable the resolution of confusions not possible on the original NST, and also the construction of a single confusion matrix each for CVs and VCs, respectively. The modified nonsense syllable test (MNST) provides results that compare favorably to those of the original NST.

Adult-onset auditory deprivation following prolonged lack of amplification in the unaided ears of persons with bilaterally symmetrical sensorineural hearing impairment was first reported in 1984. This article on the phenomenon includes a review of the literature on adult-onset auditory deprivation in relation to etiology, pathophysiology, hearing-loss manifestations, typical audiologic profile, amplification strategies, contraindications or challenges to conventional hearing-aid fitting, and future research. A case study illustrates the phenomenon of auditory deprivation from monaural amplification with recovery following binaural amplification. The results of a complete audiologic and acoustic-immittance evaluation are presented for a bilaterally sensorineural hearing-impaired male with adult-onset auditory deprivation who initially was fit monaurally and later was fit binaurally. A significant decrement in the suprathreshold word-recognition scores occurred only in the unaided ear following monaural amplification, illustrating the phenomenon of adult-onset auditory deprivation. Following binaural amplification, the suprathreshold word-recognition scores for the formerly unaided ear improved significantly, illustrating the phenomenon of recovery from the adult-onset auditory deprivation with binaural amplification.

Ninetieth percentile cutoffs for acoustic reflex thresholds (ARTs) were determined for a sample of 2,748 ears of 1,374 subjects with normal hearing and sensorineural loss of cochlear origin. All subjects had measurable hearing (less than or equal to 110 dB HL, ANSI-1969) at all three activator frequencies (500, 1000, and 2000 Hz). Cutoff values including "no responses" ("absent" reflexes at 125 dB HL) were higher than those excluding no responses when hearing losses were greater than about 55 dB. The 90th percentiles including the effects of no responses identified ears with retrocochlear involvement for hearing losses as great as about 756 dB. For greater hearing losses at the activator frequency, the no-response rate for both cochlear and retrocochlear cases is too high to enable them to be differentiated by acoustic reflex thresholds. The 90th percentiles are derived at each activator frequency collapsed across ears. It is therefore necessary to determine the probabilities that normal or cochlear-impaired ears will have one, two, or three frequencies at which the ARTs exceed their respective 90th percentiles. It was found that among normal and cochlear-impaired ears, 12.2% have one ART elevated above the 90th percentile, but only 5.6% have two or three elevated ARTs. Clinical implications are discussed.

The effect of sensorineural hearing loss upon stapedius reflex growth functions was studied in the elderly. The reflex activators were pure tones (500, 1000, and 2000 Hz) and broadband noise; reflex magnitude was expressed in decibels relative to static acoustic impedance. When expressed in decibels relative to reflex threshold, the mean growth functions of the elderly were reduced compared to previous data for young subjects [Silman, Popelka, and Gelfand, J. Acoust. Soc. Am. 64, 1406--1411 (1978)] and the noise functions differed in terms of both shape and magnitude. When expressed in SPL, the mean growth functions of the normal hearing elderly demonstrated saturation at high activator levels, whereas saturation was not observed in the mean growth functions of the hearing loss subjects. In the normal elderly, saturation was found to be frequency dependent. The saturation effect is discussed in terms of energy integration of the reflex response in the aging ear.

This study expands upon our earlier work by comparing initial PB scores and audiometric thresholds with results obtained 4-17 years later for subjects with bilateral sensorineural hearing losses who were monaurally aided (n = 48), binaurally aided (n = 19), or unaided (n = 19). Thresholds decreased slightly for all groups, but aided and unaided ears did not differ significantly in this respect, revealing no acoustic trauma effect due to hearing aid use. PB scores decreased significantly only for the unaided ear of the monaurally aided subjects, but not for their aided ear, or for the binaurally aided or unaided groups. These findings suggest an auditory deprivation effect for the unaided ear of those wearing a monaural hearing aid. Changes in PB scores were not correlated with duration between the two test dates. Changes in PB scores were correlated with degree of hearing loss only for the unaided group.

Acoustic reflex thresholds (ARTs) at 500, 1000, and 2000 Hz from 1833 ears were subjected to multiple linear regression analyses using a stepwise inclusion model to determine the effects of hearing losses in the 500- to 4000-Hz range for each of the activators. Although statistically significant regression equations were developed, these accounted for only 1 to 47% of the variance of ART levels. In light of the wide variance of ARTs unexplainable directly from audiometric data, it was deemed more appropriate to consider the range of ARTs from the standpoint of the sampling distribution of ARTs as a function of hearing level. Deciles were calculated in the 10th through 90th percentile ranges. These data corroborate and expand upon previously reported material on the distributions of ARTs among ears with normal hearing and cochlear impairment.

Consonant recognition in quiet using the Nonsense Syllable Test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)] was investigated in 62 normal hearing subjects 20 to 65 years of age at their most comfortable listening levels (MCLs) and at 8 dB above and below MCL. Although overall consonant recognition performance was high (as expected for normal listeners), the effects of age decade, relative presentation level, and NST subsets were all significant, as was the interaction of age X level. The interactions of age X NST subset, and age X subset X level were nonsignificant. These findings suggest that consonant recognition decreases with normal aging, particularly below MCL. However, the relative perceptual difficulty of the seven subtests is the same across age groups. Confusion matrices were similar across levels and age groups. Percent information transmitted for several consonant features was calculated from the confusion matrices. Older subjects showed decrements in performance primarily for the features recognized relatively less accurately by the younger subjects. The results suggest that normal hearing older individuals listening in quiet have decreased consonant recognition ability, but that their confusions are similar to those of younger persons.

Responses to a hearing aid usage questionnaire were received from 128 patients with high-frequency sensorineural hearing loss fitted monaurally with contralateral routing of signals (CROS) or ipsilateral routing of signals (IROS) hearing aids. Functional benefits were demonstrated by wearing the instruments 8 to 9 hr/day, use of the aids about 60% of the time in communicative situations, subjective benefit judgements of 5 to 9 on a 10-point scale, improved subjective sound localization, and improved clarity of speech with the hearing aids. Although CROS and IROS fittings could not be separated on the basis of these factors, considerably more complaints were reported by the CROS wearers, and many of these related to auditory factors. Both CROS and IROS fittings appear to be effective approaches to the patient with high-frequency hearing loss. However in light of the fewer complaints by the IROS group, and the fact that a large proportion of the CROS complaints related to the amplified signal, IROS appears to be the preferable of the two. The exception involves cases requiring high gain so that CROS might be employed to reduce acoustic feedback.

Fifty (58%) unilaterally deaf patients responded to a contralateral routing of signals (CROS) hearing aid usage questionnaire. Their actual usage in communicative environments was quite variable, with 50% to 60% of the time being the avarage in most of these situations. Mean communicative usage was essentially similar when the ambient nature of the environment could be described as quiet, speech competition, noise and/or speech babble, and reverberant/noisy. It is extremely difficult to determine who will be a successful CROS wearer on the basis of diagnostic results that are obtained with the use of earphones. Not every unilateral listener is a CROS candidate. The importance of a sound-field evaluation in a controlled environment, a trial period, and follow-up consultations cannot be overemphasized.

The nature of functional hearing loss was retrospectively studied with respect to hearing sensitivity after resolution of the nonorganic components in 63 adults with bilateral exaggerated losses (126 ears). The configuration of the functional components (difference between the functional and resolved thresholds) was found to be related to that of the resolved hearing levels. The size of the functional overlay was essentially the same across the audiometric frequency range when the hearing was actually normal or if there was only mild loss. In cases of precipitously sloping high-frequency losses, the magnitude of the functional overlay became dramatically smaller for the impaired frequencies than for lower frequencies where hearing was normal or only mildly impaired. Moderate and severe losses represented a transitional situation, in which the functional components became gradually smaller with increasing frequency. Subjects with different resolved hearing in each ear (e.g., mild loss in one ear and a precipitous loss in the other) demonstrated nonorganic overlays that were consistent with the actual hearing levels for each respective ear. The findings suggest the use of an internalized, loudness level-based anchor by subjects with functional losses: the test signal must sound as loud as the anchor at each frequency in order for an exaggerated threshold response to be volunteered at that respective frequency. The pure-tone audiometric configuration and amount of functional loss at least in bilateral cases is thus consistently accounted for on the basis of known and explainable auditory factors.

This study investigated the effects of reverberation upon the speech discrimination performance of 30 normally hearing subjects and 30 persons with bilateral sensorineural hearing loss. Following preliminary tests, the Modified Rhyme Test was administered monaurally and binaurally at reverberation times of 0, 1, 2 and 3 sec. All stimuli were administered under earphones. The lists and conditions were appropriately randomized and counterbalanced so that each subject heard a test list at each reverberation time (RT) monaurally and binaurally. The expected gain due to binaural summation of loudness was simulated in order to test the possibility that any binaural enhancement of intelligibility might be due to binaural loudness summation. For all conditions, the normally hearing subjects performed significantly better than the hearing-impaired group. However, in relative terms, the two groups were remarkably similar. Binaural scores were significantly higher than monaural scores at each RT for both groups (in spite of homophasic conditions). For both groups, monaural and binaural scores decreased with increasing RT. Monaural scores decreased at a significantly faster rate with RT than did the binaural scores (the binaural advantage, however, was larger for the normal group). Increasing the monaural presentation levels to simulate the binaural loudness gain did not result in higher scores. It was concluded that speech discrimination under reverberation is better binaurally than monaurally for both normally hearing and hearing-impaired persons. This is due, at least partly, to the ability of the binaural auditory system to squelch the effects of reverberation. A tentative model is suggested for the binaural squelch of reverberation. The current findings are compared with existing data; and suggestions are offered for clinical application.

Performance on tests of pure-tone thresholds, speech-recognition thresholds, and speech-recognition scores for the two ears of each subject were evaluated in two groups of adults with bilateral hearing losses. One group was composed of individuals fitted with binaural hearing aids, and the other group included persons with monaural hearing aids. Performance prior to the use of hearing aids was compared to performance after 4-5 years of hearing aid use in order to determine whether the unaided ear would show effects of auditory deprivation. There were no differences over time for pure-tone thresholds or speech-recognition thresholds for both ears of both groups. Nevertheless, the results revealed that the speech-recognition difference scores of the binaurally fitted subjects remained stable over time whereas they increased for the monaurally fitted subjects. The findings reveal an auditory deprivation effect for the unfitted ears of the subjects with monaural hearing aids.

Dichotic CV recognition at interaural temporal onset asynchronies (lag times) of 0, 30, 60, and 90 ms was investigated in normal hearing young and elderly subjects. The results for the young group were consistent with those reported in previous studies (Studdert-Kennedy et al., 1970; Berlin et al., 1973a). The older group demonstrated a mean right ear advantage (REA) at simultaneity of 12.7%, which was not significantly different from that of the young group (12.4%). This suggests that the processes subserving the REA are not affected by age. However, there was a significant reduction in the total (right ear plus left ear) dichotic scores of the elderly group compared to the young; suggesting an age-associated reduction in the channel capacity of the aging auditory system. Further, there were striking aberrations of the dictotic lag effect in the elderly group compared to the young subjects, consistent with age-related changes in auditory temporal processing. The findings are discussed with respect to the aging auditory system and the nature of dichotic speech processing.

The subject was a 47-year-old male with a moderate asymmetrical sensorineural hearing loss that initially presented cochlear signs except for positive stapedius reflex results. Over the course of only five weeks, he developed the audiological constellation of retrocochlear involvement. The retrocochlear results were confirmed by the removal of an acoustic tumour. The results highlight the importance of audiological monitoring and reflex measures in the identification of acoustic neuromas. Several observations provide insight into the apparent relationship between loudness and the stapedius reflex. The findings are discussed with reference to a proposed extension of Borg's recent theory that elevated reflex thresholds and reflex decay reflect differing degrees of the eighth nerve destruction.

The acoustic reflex threshold (ART) was studied in 544 ears having hearing levels (ANSI-1969) ranging from 0 to 110 dB HL. The activating signals were pure tones (500, 1000, and 2000 Hz) presented at levels up to 125 dB HL. The results indicated that the ART increased with hearing loss beyond certain levels. The proportion of absence of reflex responses depends upon the degree of hearing loss, test frequency, and the limits imposed by the instrumentation. Absence of reflex responses is rare for hearing losses of less than about 80 dB HL when the hearing loss is attributable to cochlear involvement.

The precision of the Rinne test at 128-2048 Hz was studied in 100 ears with confirmed conductive pathologies. The number of negative (diagnostic) Rinnes decreased significantly with fall in frequency. While there were significantly more negative than positive Rinnes at 128 and 256 Hz, there were significantly more positive results at higher frequencies; indicating that the Rinne is not reliably diagnostic above 256 Hz. However, the possibility of vibrotactile responses must be remembered with low frequency tuning forks. Also, conductive lesions manifested as high tone air-bone gaps will not be identified with low frequency Rinne tests. Air-bone gaps of 25 to 40 dB, depending on frequency, are necessary for the Rinne to identify the presence of conductive components in most cases. Gaps of 25-30 dB for 128 Hz; 35-40 dB for 256 Hz; 55-60 dB for 512 Hz; and 45-50 dB for 1024 Hz, are necessary for the Rinne to meet a 75% correct detection criterion. The 2o48 Hz Rinne does not attain even chance detection. The Rinne test cannot be validly employed as a criterion against which other measures can be evaluated.

Abnormal acoustic-reflex adaptation monitored in the same ear for both contralaterally and ipsilaterally presented tonal activators is reported in three cases. One case had Bell's palsy, whereas the other two cases had no clinically observable evidence of seventh-nerve involvement. These cases show that the existence of abnormal acoustic-reflex adaptation in the absence of Bell's palsy does not necessarily implicate the presence of eighth-nerve pathology.

Consonant recognition in quiet and in noise was investigated as a function of age for essentially normal hearing listeners 21-68 years old, using the nonsense syllable test (NST) [Resnick et al., J. Acoust. Soc. Am. Suppl. 1 58, S114 (1975)]. The subjects audited the materials in quiet and at S/N ratios of +10 and +5 dB at their most comfortable listening levels (MCLs). The MCLs approximated conversational speech levels and were not significantly different between the age groups. The effects of age group, S/N condition (quiet, S/N +10, S/N +5) and NST subsets, and the S/N condition X subset interaction were all significant. Interactions involving the age factor were nonsignificant. Confusion matrices were similar across age groups, including the directions of errors between the most frequently confused phonemes. Also, the older subjects experienced performance decrements on the same features that were least accurately recognized by the younger subjects. The findings suggest that essentially normal older persons listening in quiet and in noise experience decreased consonant recognition ability, but that the nature of their phoneme confusions is similar to that of younger individuals. Even though the older subjects met the same selection criteria as did younger ones, there was an expected shift upward in auditory thresholds with age within these limits. Sensitivity at 8000 Hz was correlated with NST scores in noise when controlling for age, but the correlation between performance in noise and age was nonsignificant when controlling for the 8000-Hz threshold. These associations seem to implicate the phenomena underlying the increased 8000-Hz thresholds in the speech recognition problems of the elderly, and appear to support the concept of peripheral auditory deterioration with aging even among those with essentially normal hearing.

This study examined the precision of the bivariate method in subjects with high-frequency sensorineural hearing loss. The current bivariate data effectively separated normal hearing subjects from those with pure tone averages of greater than 32 dB HL, in a manner consistent with the results of Popelka and Trumpf (1976) and Margolis and Fox (1977b). However, for persons with high-frequency losses the prediction of hearing levels from acoustic reflex thresholds (ARTs) appears to be complicated. Moderate hearing losses involving 500, 1000 and 2000 Hz ("speech frequencies") as well as higher frequencies were identified on the basis of elevated average ARTs for 500, 1000 and 2000 Hz. Normal ears (pure tone averages of less than 30 dB HL) were isolated from others on the basis of position on the bivariate graph. Those with (1) normal hearing in the "speech frequencies" and a high-frequency loss and (2) a mild loss in the "speech frequencies" and a high-frequency loss, could be separated from those with normal hearing by location on the bivariate graph, and from those with moderate (or worse) losses on the basis of average ART for tones. Consideration of these findings is useful in the evaluation of patients at risk for high-frequency loss, such as patients with noise exposure, and is particularly useful in cases of suspected functional impairment within this population. A modification of the bivariate method is suggested which extends its application to patient populations with a large incidence of high frequency sensorineural hearing loss.

Multiple linear regression equations were derived to define the expected levels of acoustic reflex thresholds (ARTs) at 500, 1000, and 2000 Hz predictable from hearing levels at 500-4000 Hz in 646 ears. When the hearing level at the activator frequency is less than or equal to 50 dB HL, ARTs tend to be best defined by a constant value of 86-90 dB HL with small adjustments due to the loss at the activator or higher frequencies. When the hearing level at the activator frequency is 55-90 dB HL, the ART is best predicted by a constant plus the degree of loss at that frequency plus the loss at 4000 Hz. These data present the clinician with empirically derived bases for determining the effects of other frequencies on a given ART. Application of these findings permits the clinician to apply known relationships in determining whether a particular ART is representative of those expected for normal and/or cochlear impaired ears, elevated or depressed, without having to rely on vague intuitions of such relationships. Clinical applications are discussed.

The effect of age on accuracy of prediction of hearing impairment with the bivariate-plotting procedure was investigated in 72 normal-hearing subjects aged 20-69 years and in 86 sensorineural hearing-impaired subjects aged 20-83 years. The predictive accuracy with the bivariate-plotting procedure improved markedly when the data from subjects over 44 years of age were excluded from the bivariate plot. The predictive accuracy improved further when the construction of the line segments in the traditional bivariate plot was modified.

The growth function of the acoustic stapedius reflex was measured in subjects with normal hearing and sensorineural hearing loss of cochlear origin. The effects of age and magnitude of hearing loss were controlled. Activating stimuli were 500, 1000, and 2000 Hz tones and broadband noise. Stapedius muscle activity was inferred from acoustic impedance measures in the contralateral ear. The mean growth functions for tones were essentially linear in log-log plots with the rate of growth equal for the two groups. The mean growth function for the noise signal was curvilinear for the normal hearing groud had linear for the hearing loss group. Comparison of slope functions derived from the fitted data indicated that the rate of reflex growth for the noise signal, over a limited range above reflex threshold, is greater in ears with cochlear lesions than normal ears. For higher level noise signals, however, the rate of reflex growth is similar for normal and pathological ears. The effect of a cochlear lesion on the input-output function of the cochlea for both tonal and noise stimuli is to maintain the rate of reflex growth but shift the function along the intensity axis of a tonal signal and the response axis for a noise signal.

Acoustic reflex growth functions for pure tone activators of 500, 1000 and 2000 Hz and a broad-band noise (BBN) were obtained with activator durations of 20, 200 and 1000 msec (10 msec rise/decay) in four young, normal subjects. The lowest reflex thresholds were obtained for the 1000 msec activators, followed by 200 msec and then 20 msec. The reflex growth functions revealed lower reflex magnitudes for the shorter duration activators. When normalized to account for temporal summation at reflex threshold, reflex magnitude growth was similar among the three durations at 500 Hz, slower for 20 msec than for 200 and 1000 msec at 1000 Hz, and became progressively slower with decreasing duration from 1000 to 200 to 20 msec at 2000 Hz. When expressed in SPL, the BBN growth functions reasonably resembled those at 2000 Hz. No particular pattern was revealed for the normalized BBN growth functions.

This study examined the utility of the bivariate plotting approach to reflex-based hearing loss prediction, and introduced a modification to the method which accounts for the effects of mild and high frequency hearing losses. The effect of pure tone sensitivity at 3,000 Hz was found to be of particular importance in the predictive accuracy of the method. When 3,000 Hz is considered, the original concept of the bivariate graph can be further refined into three regions. Here, normal ears and those with substantial hearing loss can be identified with considerable success. A "grey area" between these correctly identifies some degree of loss with 89% accuracy.

This study replicated Silman's [J. Acoust. Soc. Am. 66 (1979a)] experiment comparing acoustic reflex thresholds in normal hearing young and elderly subjects. The original study was modified so that the criterion for normal hearing was extended through 8000 Hz, and the range of auditory thresholds among the younger group was selected to approximate those of the elderly subjects as closely as possible. The data confirmed those reported by Silman, showing an elevation of the ART for broadband noise, but nor for tonal activators in the elderly group.

Sentence reception thresholds (SRTs) and babble detection thresholds (BDTs) were measured for signals presented from loudspeakers located at 0 deg and 90 deg azimuth. In addition, the S/B ratios necessary to achieve SRT in the presence of a 12-talker babble were determined under three conditions in which the speech and babble were presented from the same or spatially separated loudspeakers. In the first experiment, normal-hearing subjects were tested on two occasions. The results were highly reliable, with standard errors of the test-retest differences of less than 1dB for all conditions. In the second experiment, SRTs, BDTs, and S/B ratios were measured for three normal-hearing groups (less than or equal to 39, 40-54, and greater than or equal to 55 years) and for a fourth group with presbycusis (greater than or equal to 55 years). Presbycusics had higher SRTs and BDTs than all other groups regardless of age, and the oldest normals had higher thresholds than younger subjects. Presbycusics required higher S/B ratios than any of the normal groups, and the oldest normal group needed a higher S/B ratio compared to the youngest group. All groups demonstrated a significant advantage in S/B ratio when the sentences and babble sources were spatially separated compared to when they were presented from the same loudspeaker. There was no significant difference in the magnitude of advantage due to spatial separation of speech and noise between the normal groups regardless of age, but the presbycusics had significantly smaller advantages than all normals.(ABSTRACT TRUNCATED AT 250 WORDS)