A Critique of the National Academies of Sciences, Engineering, and Medicine Report (2021) and the Diagnostic Accuracy of Measurements of Functional Hearing Ability.

PURPOSE: The Social Security Administration (SSA) asked the National Academies of Sciences, Engineering, and Medicine (NASEM, 2021) to make recommendations for tests of functional hearing ability. These tests include speech perception measures administered in quiet and in background noise. Such tests are required to make disability determinations for adults and children following cochlear implantation. The test review required an evaluation of the diagnostic accuracy of the speech perception measures. Following a review of the literature, NASEM wrote that the evidence needed to support such a recommendation was lacking. They resorted to "professional judgment" and recommended a monosyllabic word recognition test, presumably in quiet, along with a measure of self-report or parent report. The primary purpose of this article was to critically review the committee's report. The secondary purpose was to critique the committee's recommendation of a monosyllabic word test as a measure of functional hearing ability for disability determinations. The third purpose was to provide a review of diagnostic accuracy studies not included in NASEM (2021) with an emphasis on speech recognition in noise (SRN) tests. CONCLUSIONS: In contrast to the committee's recommendation, studies have shown that a monosyllabic word test is a poor predictor of SRN ability. Contrary to the conclusion of NASEM (2021), diagnostic accuracy studies have been conducted for a few SRN tests. The Hearing in Noise Test and the AzBio SRN test have published data demonstrating their ability to correctly identify the presence and absence of an SRN disorder.

The World Health Organization (WHO) hearing impairment guidelines and a speech recognition in noise (SRN) disorder.

OBJECTIVE: The WHO uses the better ear PTA(0.5, 1.0, 2.0, 4.0 kHz) to infer speech recognition in noise (SRN) ability. The purpose of this study was to determine the ability of this measure to detect an SRN disorder. DESIGN: The reference standard was the Hearing in Noise Test (HINT). The index test was better ear PTA(0.5, 1.0, 2.0, 4.0 kHz). Diagnostic accuracy was determined with receiver operating characteristic curves and the area under the curve (AUC) for data sets with and without complete audibility of the HINT stimuli. STUDY SAMPLE: Data from previously published studies (n = 381) were retrospectively divided into disordered and control groups. RESULTS: For the All Data analysis, better ear PTA(0.5, 1.0, 2.0, 4.0 kHz) was a significant predictor of an SRN disorder, however, the AUC was just above chance (AUC = 0.59, p < 0.001). For the Partial Audibility analysis, better ear PTA(0.5, 1.0, 2.0, 4.0 kHz) was a significant predictor of the target disorder (AUC = 0.85, p = 0.001). CONCLUSIONS: The utilization of better ear PTA(0.5, 1.0, 2.0, 4.0 kHz) to infer SRN ability is questionable for individuals with complete audibility of the reference test speech and noise stimuli.

Diagnostic Accuracy of the AzBio Speech Recognition in Noise Test.

Purpose The goal of this study was to determine the ability of the AzBio speech recognition in noise (SRN) test to distinguish between groups of participants with and without a self-reported SRN disorder and a self-reported signal-to-noise ratio (SNR) loss. Method Fifty-four native English-speaking young adults with normal pure-tone thresholds (≤ 25 dB HL, 0.25-6.0 kHz) participated. Individuals who reported hearing difficulty in a noisy restaurant (Reference Standard 1) were placed in the SRN disorder group. SNR loss groups were created based on the self-report of the ability to hear Hearing in Noise Test (HINT) sentences in steady-state speech-shaped noise, four-talker babble, and 20-talker babble in a controlled listening environment (Reference Standard 2). Participants with HINT thresholds poorer than or equal to the median were assigned to the SNR loss group. Results The area under the curve from the receiver operating characteristics curves revealed that the AzBio test was not a significant predictor of an SRN disorder, or an SNR loss using the steady-state noise Reference Standard 2 condition. However, the AzBio was a significant predictor of an SNR loss using the four-talker babble and 20-talker babble Reference Standard 2 conditions (p < .05). The AzBio was a significant predictor of an SNR loss when using the average HINT thresholds across the three Reference Standard 2 masker conditions (area under the curve = .79, p = .001). Conclusions The AzBio test was not a significant predictor of a self-reported SRN disorder or a self-reported SNR loss in steady-state noise. However, it was a significant predictor of a self-reported SNR loss in babble noise and the average across all noise conditions. A battery of reference standard tests with a range of maskers in a controlled listening environment is recommended for diagnostic accuracy evaluations of SRN tests.

A convergent validity study: Listening in Spatialized Noise-Sentences (LiSN-S) test and the Hearing in Noise Test (HINT).

OBJECTIVES: The primary purpose of this study was to compare Listening in Spatialized Noise - Sentence (LiSN-S) test and the Hearing in Noise Test (HINT) thresholds in order to determine if the two tests measure the same construct (convergent validity). The secondary purpose was to determine performance differences between the two test protocols. The third purpose was to determine the relationships between quiet measures (pure-tone average [PTA] and HINT Quiet thresholds) vs. speech-in-noise performances. DESIGN: Statistical analyses included descriptive statistics, Spearman rho statistic, repeated measures analysis of variance (ANOVA) and linear mixed model analyses. Study sample: Fifty-six young adults with normal PTAs (≤15 dB HL for 0.5-4.0 kHz) participated in this study. RESULTS: No statistically significant relationships were found between LiSN-S and HINT measures (poor convergent validity). However, statistically significant relationships were found between the quiet measures (HINT Quiet thresholds and average PTA(0.5-4.0 kHz)) vs. the LiSN-S (same and different voices) ±90° performances. CONCLUSION: LiSN-S performances in two-talker babble cannot be generalized to the ability to recognise HINT sentences in steady-state speech-shaped noise, and vice versa. The results imply that LiSN-S ± 90° thresholds were influenced by hearing sensitivity or by supra-threshold distortions that co-vary with hearing sensitivity.

The Effect of Stimulus Audibility on the Relationship between Pure-Tone Average and Speech Recognition in Noise Ability.

BACKGROUND: The literature presents conflicting reports on the relationship between pure-tone threshold average and speech recognition in noise ability. PURPOSE: The purpose of this retrospective study and meta-analysis was to determine the effect of stimulus audibility on the relationship between speech recognition in noise ability and bilateral pure-tone average (BPTA). RESEARCH DESIGN: Pure-tone threshold and Hearing in Noise Test (HINT) data from two data sets were evaluated. The HINT data from both data sets were divided into groups with complete and partial audibility of the HINT stimuli delivered at 65 dBA. STUDY SAMPLE: Normal and hearing-impaired participants were included in this retrospective study. For data set 1 (n = 215), a relatively weak relationship had been found between HINT thresholds and BPTA. For data set 2 (n = 55), a relatively strong relationship had been found between HINT thresholds and BPTA. For data set 1, only 10% of the participants had partial audibility of the HINT stimuli. For data set 2, 16% of the participants had partial audibility of the HINT stimuli. DATA COLLECTION AND ANALYSIS: Pure-tone thresholds and HINT data were obtained from published and unpublished studies. HINT data were collected in a simulated soundfield environment under headphones using the standard HINT protocol. Statistical analyses included descriptive statistics, correlations, and a two-way analysis of variance (ANOVA), and multiple regression. RESULTS: A two-way ANOVA followed by post hoc analyses revealed a greater difference between the data sets for the Noise Front thresholds obtained with partial rather than complete audibility of the stimuli. A weak and nonsignificant relationship was found between BPTA(0.5, 1.0, 2.0, 3.0, 6.0 kHz) versus HINT Noise Front thresholds for complete audibility data (r = 0.060, p = 0.356) and a strong relationship was found for the partial audibility data (r = 0.863, p < 0.001). CONCLUSIONS: The proportion of partial audibility data in a given data set may influence the relative strength of the relationship between BPTA and HINT Noise Front thresholds. This brings into question the convention of using pure-tone average as a predictor of speech recognition in noise ability.

Sentence Recognition in Steady-State Speech-Shaped Noise versus Four-Talker Babble.

BACKGROUND: Speech recognition in noise (SRN) evaluations reveal information about listening ability that is unavailable from pure-tone thresholds. Unfortunately, SRN evaluations are not commonly used in the clinic. A lack of standardization may be an explanation for the lack of widespread acceptance of SRN testing. Arguments have been made for the utilization of steady-state speech-shaped noise vs. multi-talker babble. Previous investigations into the effect of masker type have used a monaural presentation of the stimuli. However, results of monaural SRN tests cannot be generalized to binaural listening conditions. PURPOSE: The purpose of this study was to investigate the effect of masker type on SRN thresholds under binaural listening conditions. RESEARCH DESIGN: The Hearing in Noise Test (HINT) protocol was selected in order to measure SRN thresholds in steady-state speech-shaped noise (HINT noise) and four-talker babble with and without the spatial separation of the target speech and masker stimuli. STUDY SAMPLE: Fifty native speakers of English with normal pure-tone thresholds (≤ 25 dB HL, 250-4000 Hz) participated in the study. The mean age was 20.5 years (SD 1.01). DATA COLLECTION AND ANALYSIS: All participants were tested using the standard protocol for the HINT in a simulated soundfield environment under TDH-50P headphones. Thresholds were measured for the Noise Front, Noise Left, and Noise Right listening conditions with HINT noise and four-talker babble. The HINT composite score was determined for each noise condition. The spatial advantage was calculated from the HINT thresholds. Pure-tone threshold data were collected using the modified Hughson-Westlake procedure. Statistical analyses include descriptive statistics, effect size, correlations, and repeated measures ANOVA followed by matched-pairs t-tests. RESULTS: Repeated measures ANOVA was conducted to investigate the effects of masker type and noise location on HINT thresholds. Both main effects and their interaction were statistically significant (p < 0.01). No significant differences were found between masker conditions for the Noise Front thresholds. However, for the Noise Side conditions the four-talker babble thresholds were significantly better than the HINT noise thresholds. Overall, greater spatial advantage was found for the four-talker babble as opposed to the HINT noise conditions (p < 0.01). Pearson correlation analysis revealed no significant relationships between four-talker babble and HINT noise speech recognition performances for the Noise Front, Noise Right conditions, and the spatial advantage measures. Significant relationships (p < 0.05) were found between masking noise performances for the Noise Left condition and the Noise Composite scores. CONCLUSIONS: One cannot assume that a patient who performs within normal limits on a speech in four-talker babble test will also perform within normal limits on a speech in steady-state speech-shaped noise test, and vice-versa. Additionally, performances for the Noise Front condition cannot be used to predict performances for the Noise Side conditions. The utilization of both HINT noise and four-talker babble maskers, with and without the spatial separation of the stimuli, may be useful when determining the range of speech recognition in noise abilities found in everyday listening conditions.

The relationship between speech recognition in noise and non-speech recognition in noise test performances: Implications for central auditory processing disorders testing.

BACKGROUND: According to the American Academy of Audiology, a recommendation for frequency-modulation systems may be based upon performances on speech perception tests that do not include background noise. PURPOSE: The primary purpose of this study was to evaluate the presumption that non-speech recognition in noise test results are related to speech recognition in noise ability for a group of young adults. RESEARCH DESIGN: Performances on the non-speech recognition in noise tests included in the SCAN-3:A test battery were compared to speech recognition in noise performances as measured with the auditory figure ground subtest of the SCAN-3:A and the Hearing in Noise Test. STUDY SAMPLE: Fifty-four young, native speakers of American English with normal pure-tone thresholds participated in the study. DATA COLLECTION AND ANALYSIS: For the purposes of this study, the SCAN-3:A raw scores were used. The Hearing in Noise Test was administered in a simulated soundfield environment under headphones. The Spearman rho statistic was used to determine the relationships between non-speech recognition in noise vs. speech recognition in noise test results. RESULTS: No significant relationships were found between the auditory figure-ground results and any of the non-speech recognition in noise subtest performances. Modest but statistically significant relationships were found between the Hearing in Noise Test Composite scores vs. the competing words-directed ear and the time compressed sentences subtests of the SCAN-3:A. CONCLUSION: Of the four non-speech recognition in noise subtests that were evaluated, only the competing words-directed ear and the time-compressed sentences performances were significantly correlated to the Composite scores of the Hearing in Noise Test. The results demonstrated a limited external validity for two of the four non-SRN tests for the determination of SRN ability.

The Relationship between Random Gap Detection and Hearing in Noise Test Performances.

BACKGROUND: Temporal acoustic cues are particularly important for speech understanding, and past research has inferred a relationship between temporal resolution and speech recognition in noise ability. A temporal resolution disorder is thought to affect speech understanding abilities because persons would not be able to accurately encode these frequency transitions, creating speech discrimination errors even in the presence of normal pure-tone hearing. PURPOSE: The primary purpose was to investigate the relationship between temporal resolution as measured by the Random Gap Detection Test (RGDT) and speech recognition in noise performance as measured by the Hearing in Noise Test (HINT) in adults with normal audiometric thresholds. The second purpose was to examine the relationship between temporal resolution and spatial release from masking. RESEARCH DESIGN: The HINT and RGDT protocols were administered under headphones according to the guidelines specified by the developers. The HINT uses an adaptive protocol to determine the signal-to-noise ratio where the participant recognizes 50% of the sentences. For HINT conditions, the target sentences were presented at 0° and the steady-state speech-shaped noise and a four-talker babble (4TB) was presented at 0°, +90°, or -90° for noise front, noise right, and noise left conditions, respectively. The RGDT is used to evaluate temporal resolution by determining the smallest time interval between two matching stimuli that can be detected by the participant. The RGDT threshold is the shortest time interval where the participant detects a gap. Tonal (0.5, 1, 2, and 4 kHz) and click stimuli random gap subtests were presented at 60 dB HL. Tonal subtests were presented in a random order to minimize presentation order effects. STUDY SAMPLE: Twenty-one young, native English-speaking participants with normal pure-tone thresholds (≤25 dB HL for 500-4000 Hz) participated in this study. The average age of the participants was 20.2 years (SD = 0.66). DATA COLLECTION AND ANALYSIS: Spearman rho correlation coefficients were conducted using SPSS 22 (IBM Corp., Armonk, NY) to determine the relationships between HINT and RGDT thresholds and derived measures (spatial advantage and composite scores). Nonparametric testing was used because of the ordinal nature of RGDT data. RESULTS: Moderate negative correlations (p < 0.05) were found between eight RGDT and HINT threshold measures and a moderate positive correlation (p < 0.05) was found between RGDT click thresholds and HINT 4TB spatial advantage. This suggests that as temporal resolution abilities worsened, speech recognition in noise performance improved. These correlations were not statistically significant after the p value reflected the Bonferroni correction for multiple comparisons. CONCLUSION: The results of the present study imply that the RGDT and HINT use different temporal processes. Performance on the RGDT cannot be predicted from HINT thresholds or vice versa.

An Evaluation of the World Health Organization and American Medical Association Ratings of Hearing Impairment and Simulated Single-Sided Deafness.

BACKGROUND: According to the World Health Organization (WHO), a pure-tone threshold average (PTA) ≤25 dB HL for the better ear represents "no impairment." This implies that patients with single-sided deafness (SSD) would have "no or very slight hearing problems." According to the American Medical Association (AMA), a patient with SSD would receive a binaural hearing impairment rating of 16.7%. The premise of the WHO and AMA methods is that PTA is related to the ability to perceive speech in everyday environments. PURPOSE: The overall goal of the study was to evaluate the WHO and AMA criteria for the rating of hearing impairment. The purpose of this study was to quantify the impact of simulated SSD on the ability to recognize speech in the presence of background noise in terms of binaural and spatial advantage measures. RESEARCH DESIGN: Study participants were tested using the standard protocol for the Hearing in Noise Test (HINT) in both binaural and monaural conditions using a simulated soundfield environment under headphones. The target sentences were presented at 0°. Binaural thresholds were obtained for the Noise Front (0°), Noise Left (270°), and Noise Right (90°) listening conditions. Monaural thresholds were collected for each ear for the Noise Front condition and for the unshadowed ear for the Noise Left and Noise Right conditions. Binaural advantage was determined by subtracting the binaural from the monaural thresholds. Spatial advantage was determined by subtracting the Noise Side from the Noise Front thresholds. STUDY SAMPLE: Twenty-five young native speakers of English with normal pure-tone thresholds (≤25 dB HL, 250-8000 Hz) participated in the study. DATA COLLECTION AND ANALYSIS: Pure-tone threshold data were collected using the modified Hughson-Westlake procedure. Speech recognition in noise data were collected using a Windows-based HINT software system. The binaural and spatial advantage measures were calculated from the HINT thresholds. Statistical analyses included descriptive statistics, correlation coefficients, and matched-pairs t-tests. RESULTS: The average binaural advantage for the Noise Front conditions was 1.21 dB (p < 0.01) or a maximum estimated intelligibility improvement of 12.01% when the speech and noise were presented at 0°. The average binaural advantage across the Noise Side conditions was 11.25 dB (p < 0.01) or a maximum estimated intelligibility improvement of 84.09% when the noise was spatially separated from the speech. The average spatial advantage for the binaural conditions was 6.72 dB (p < 0.01) or a maximum estimated intelligibility improvement of 60.03%. The average spatial advantage for the monaural conditions was -3.32 dB or a maximum estimated decrease in intelligibility of 32.27%. CONCLUSIONS: The results do not support the WHO or AMA hearing impairment ratings for SSD. The WHO and AMA criteria for the determination of hearing impairment should be updated to include speech recognition in noise testing with and without the spatial separation of the speech and noise stimuli. In this way actual, as opposed to inferred perceptions of speech in noisy environments, may be determined. This will provide a much-needed improvement in the ratings of hearing impairment.

An Argument for Self-Report as a Reference Standard in Audiology.

BACKGROUND: The primary components of a diagnostic accuracy study are an index test, the target condition (or disorder), and a reference standard. According to the Standards for Reporting Diagnostic Accuracy statement, the reference standard should be the best method available to independently determine if the results of an index test are correct. Pure-tone thresholds have been used as the "gold standard" for the validation of some tests used in audiology. Many studies, however, have shown a lack of agreement between the audiogram and the patient's perception of hearing ability. For example, patients with normal audiograms may report difficulty understanding speech in the presence of background noise. PURPOSE: The primary purpose of this article is to present an argument for the use of self-report as a reference standard for diagnostic studies in the field of audiology. This will be in the form of a literature review on pure-tone threshold measures and self-report as reference standards. The secondary purpose is to determine the diagnostic accuracy of pure-tone threshold and Hearing-in-Noise Test (HINT) measures for the detection of a speech-recognition-in-noise disorder. RESEARCH DESIGN: Two groups of participants with normal pure-tone thresholds were evaluated. The King-Kopetzky syndrome (KKS) group was made up of participants with the self-report of speech-recognition-in-noise difficulties. The control group was made up of participants with no reports of speech-recognition-in-noise problems. The reference standard was self-report. Diagnostic accuracy of HINT and pure-tone threshold measures was determined by measuring group differences, sensitivity and specificity, and the area under the curve (AUC) for receiver-operating characteristic (ROC) curves. STUDY SAMPLE: Forty-seven participants were tested. All participants were native speakers of American English. Twenty-two participants were in the control group and 25 in the KKS group. The groups were matched for age. DATA COLLECTION AND ANALYSIS: Pure-tone threshold data were collected using the Hughson-Westlake procedure. Speech-recognition-in-noise data was collected using a software system and the standard HINT protocol. Statistical analyses were conducted using descriptive, correlational, two-sample t tests, and logistic regression. RESULTS: The literature review revealed that self-report has been used as a reference standard in investigations of patients with normal audiograms and the perception of difficulty understanding speech in the presence of background noise. Self-report may be a better indicator of hearing ability than pure-tone thresholds in some situations. The diagnostic accuracy investigation revealed statistically significant differences between control and KKS groups for HINT performance (p < 0.01), but not for pure-tone threshold measures. Better sensitivity was found for the HINT Composite score (88%) than pure-tone average (PTA; 28%). The specificities for the HINT Composite score and PTA were 77% and 95%, respectively. ROC curves revealed a greater AUC for the HINT Composite score (AUC = 0.87) than for PTA (AUC = 0.51). CONCLUSION: Self-report is a reasonable reference standard for studies on the diagnostic accuracy of speech-recognition-in-noise tests. For individuals with normal pure-tone thresholds, the HINT demonstrated a higher degree of diagnostic accuracy than pure-tone thresholds for the detection of speech-recognition-in-noise disorder.

On Diagnostic Accuracy in Audiology: Central Site of Lesion and Central Auditory Processing Disorder Studies.

BACKGROUND: In the field of audiology a test protocol (index test) is used to determine the presence or absence of a target condition. The value of an index test rests in its diagnostic accuracy. Results from an index test must be verified through the use of a reference standard. The clinician and researcher should determine the quality and applicability of diagnostic accuracy studies. The Standards for Reporting of Diagnostic Accuracy (STARD) statement was published in response to the low quality of research conducted across many fields of study. It provides guidelines for the development and interpretation of diagnostic accuracy studies. PURPOSE: The primary purpose of this article is to assess the degree to which the main principles of diagnostic accuracy studies are used for the detection of central auditory nervous system lesions and a central auditory processing disorder (CAPD). The secondary purpose is to compare the design of these studies to select key guidelines from the STARD statement. The third purpose of this article is to present an argument against the reassignment of diagnostic accuracy values of a particular index test for one target condition (e.g., a central site of lesion) to a different target condition (e.g., a CAPD). RESULTS: A review of diagnostic accuracy literature on the detection of a central site of lesion reveals the use of a reference standard for the independent verification of the index test results. However, diagnostic accuracy studies involving index tests for the detection of a CAPD show that independent verification of index test results is nonexistent or at best questionable. CONCLUSION: For a particular index test, while the diagnostic accuracy for detection of a central site of lesion may have been determined appropriately, it is inappropriate to reassign these diagnostic accuracy values to a different diagnostic target such as a CAPD.

On the clinical entity in audiology: (central) auditory processing and speech recognition in noise disorders.

BACKGROUND: The area of (central) auditory processing disorder [(C)APD] is highly controversial. This controversy is fueled in part by multiple ambiguous descriptions of this condition. The American Speech-Language and Hearing Association and the American Academy of Audiology state that (C)APD is a clinical entity, but other sources say that this is questionable. The clinical entity is a concept used to define the nature of a disorder in order to facilitate diagnosis and intervention. Nosography is the study of the systematic description of diseases and disorders. The work in the field of nosography by physicians Thomas Sydenham and Otto Guttentag is reviewed. PURPOSE: The Sydenham-Guttentag criteria for the clinical entity are presented as a framework for the conceptualization of disorders in the field of audiology. This paper discusses central auditory processing and speech recognition-in-noise disorders in reference to these criteria.

The relationship between high-frequency pure-tone hearing loss, hearing in noise test (HINT) thresholds, and the articulation index.

BACKGROUND: Speech recognition in noise testing has been conducted at least since the 1940s (Dickson et al, 1946). The ability to recognize speech in noise is a distinct function of the auditory system (Plomp, 1978). According to Kochkin (2002), difficulty recognizing speech in noise is the primary complaint of hearing aid users. However, speech recognition in noise testing has not found widespread use in the field of audiology (Mueller, 2003; Strom, 2003; Tannenbaum and Rosenfeld, 1996). The audiogram has been used as the "gold standard" for hearing ability. However, the audiogram is a poor indicator of speech recognition in noise ability. PURPOSE: This study investigates the relationship between pure-tone thresholds, the articulation index, and the ability to recognize speech in quiet and in noise. RESEARCH DESIGN: Pure-tone thresholds were measured for audiometric frequencies 250-6000 Hz. Pure-tone threshold groups were created. These included a normal threshold group and slight, mild, severe, and profound high-frequency pure-tone threshold groups. Speech recognition thresholds in quiet and in noise were obtained using the Hearing in Noise Test (HINT) (Nilsson et al, 1994; Vermiglio, 2008). The articulation index was determined by using Pavlovic's method with pure-tone thresholds (Pavlovic, 1989, 1991). STUDY SAMPLE: Two hundred seventy-eight participants were tested. All participants were native speakers of American English. Sixty-three of the original participants were removed in order to create groups of participants with normal low-frequency pure-tone thresholds and relatively symmetrical high-frequency pure-tone threshold groups. The final set of 215 participants had a mean age of 33 yr with a range of 17-59 yr. DATA COLLECTION AND ANALYSIS: Pure-tone threshold data were collected using the Hughson-Weslake procedure. Speech recognition data were collected using a Windows-based HINT software system. Statistical analyses were conducted using descriptive, correlational, and multivariate analysis of covariance (MANCOVA) statistics. RESULTS: The MANCOVA analysis (where the effect of age was statistically removed) indicated that there were no significant differences in HINT performances between groups of participants with normal audiograms and those groups with slight, mild, moderate, or severe high-frequency hearing losses. With all of the data combined across groups, correlational analyses revealed significant correlations between pure-tone averages and speech recognition in quiet performance. Nonsignificant or significant but weak correlations were found between pure-tone averages and HINT thresholds. CONCLUSIONS: The ability to recognize speech in steady-state noise cannot be predicted from the audiogram. A new classification scheme of hearing impairment based on the audiogram and the speech reception in noise thresholds, as measured with the HINT, may be useful for the characterization of the hearing ability in the global sense. This classification scheme is consistent with Plomp's two aspects of hearing ability (Plomp, 1978).

The use of interaural time and level difference cues by bilateral cochlear implant users.

While considerable evidence suggests that bilateral cochlear implant (CI) users' sound localization abilities rely primarily on interaural level difference (ILD) cues, and only secondarily, if at all, on interaural time difference (ITD) cues, this evidence has largely been indirect. This study used head-related transfer functions (HRTFs) to independently manipulate ITD and ILD cues and directly measure their contribution to bilateral CI users' localization abilities. The results revealed a strong reliance on ILD cues, but some CI users also made use of ITD cues. The results also suggest a complex interaction between ITD and ILD cues.

Evaluation of binaural functions in bilateral cochlear implant users.

Binaural abilities are difficult to assess, yet important to understand, in the course of rehabilitating bilateral cochlear implantees. One purpose of this research was to develop a binaural assessment methodology using direct electrical input to the cochlear implant, ''direct connect assessment'', pre-processed by appropriate headrelated transfer functions (HRTFs) to simulate the binaural cues for spatial release from masking and sound localization. A second purpose was to create and evaluate new, modified rules for adaptively measuring the speech reception threshold in noise with the Hearing In Noise Test (HINT) for use with cochlear implant subjects. A third purpose was to develop a new sound localization protocol whose difficulty is adjusted to the sound localization ability of the individual cochlear implant subject. These new protocols were combined with the direct connect method and evaluated in acoustic hearing subjects and cochlear implant subjects. HINT thresholds and sound localization scores measured in the sound field and with the direct connect method did not differ significantly and were highly correlated in both groups. Measures of spatial release from masking, head shadow effects, binaural squelch, and binaural summation derived from the thresholds also were comparable for both methods. The alternative adaptive rules for HINT were found to measure different points on the same performance-intensity function. These rules allowed all cochlear implant subjects in the study to be tested adaptively and their thresholds to be compared to norms. Sound localization was measured successfully in all subjects with a sector localization protocol whose difficulty is to be adjusted to the localization ability of the subject. This protocol reduced by one-third to one-half the time required to complete the assessment of the localization ability.