School-Age Hearing Screening Based on Speech-in-Noise Perception Using the Digit Triplet Test.

OBJECTIVES: This study aims to investigate the large-scale applicability of the Digit Triplet test (DTT) for school-age hearing screening in fifth grade elementary (5E) (9 to 12 years old) and third grade secondary (3S) (13 to 16 years old) school children. The reliability of the test is investigated as well as whether pass/fail criteria need to be corrected for training and/or age, and whether these criteria have to be refined with respect to referral rates and pure-tone audiometry results. DESIGN: Eleven school health service centers participated in the region of Flanders (the Northern part of Belgium). Pure-tone screening tests, which are commonly used for hearing screening in school children, were replaced by the DTT. Initial pass/fail criteria were determined. Children with speech reception thresholds (SRT) of -7.2 dB signal to noise ratio (SNR) (5E) and -8.3 dB SNR (3S) or worse were referred for an audiogram and follow-up. In total, n = 3412 (5E) and n = 3617 (3S) children participated. RESULTS: Population SRTs (±2 SD) were -9.8 (±1.8) dB SNR (5E) and -10.5 (±1.6) dB SNR (3S), and do not need correction for training and/or age. Whereas grade-specific pass/fail criteria are more appropriate, a linear regression analysis showed an improvement of 0.2 dB per year of the SRT until late adolescence. SRTs could be estimated with a within-measurement reliability of 0.6 dB. Test duration was also grade-dependent, and was 6 min 50 sec (SD = 61 sec) (5E) and 5 min 45 sec (SD = 49 sec) (3S) on average for both ears. The SRT, test reliability, and test duration were comparable across centers. With initial cut-off values, 2.9% (5E) and 3.5% (3S) of children were referred. Based on audiograms of n = 39 (5E) and n = 59 (3S) children, the diagnostic accuracy of the DTT was assessed. A peripheral hearing loss was detected in 31% (5E) and 53% (3S) of the referred children. Hearing losses found were mild. Less strict pass/fail criteria increased the diagnostic accuracy. Optimal pass/fail criteria were determined at -6.5 dB SNR (5E) and -8.1 dB SNR (3S). With these criteria, referral rates dropped to 1.3% (5E) and 2.4% (3S). CONCLUSIONS: The DTT has been implemented as the new hearing screening methodology in the Flemish school-age hearing screening program. Based on the results of this study, pass/fail criteria were determined and optimized to be used for systematic hearing screening of 5E and 3S school children. Furthermore, this study provides reference values for the DTT in children 9 to 16 years of age. Reliable SRTs can be obtained with the test, allowing accurate monitoring of hearing over time. This is important in the context of a screening guideline, which aims to identify children with noise-induced hearing loss. Validation of the screening result should go beyond taking an audiogram, as a peripheral hearing impairment cannot always be found in children with a failed test.

Prevalence and Nature of Hearing Loss in 22q11.2 Deletion Syndrome.

PURPOSE: The purpose of this study was to clarify the prevalence, type, severity, and age-dependency of hearing loss in 22q11.2 deletion syndrome. METHOD: Extensive audiological measurements were conducted in 40 persons with proven 22q11.2 deletion (aged 6-36 years). Besides air and bone conduction thresholds in the frequency range between 0.125 and 8.000 kHz, high-frequency thresholds up to 16.000 kHz were determined and tympanometry, acoustic reflex (AR) measurement, and distortion product otoacoustic emission (DPOAE) testing were performed. RESULTS: Hearing loss was identified in 59% of the tested ears and was mainly conductive in nature. In addition, a high-frequency sensorineural hearing loss with down-sloping curve was found in the majority of patients. Aberrant tympanometric results were recorded in 39% of the ears. In 85% of ears with a Type A or C tympanometric peak, ARs were absent. A DPOAE response in at least 6 frequencies was present in only 23% of the ears with a hearing threshold ≤30 dB HL. In patients above 14 years of age, there was a significantly lower percentage of measurable DPOAEs. CONCLUSION: Hearing loss in 22q11.2 deletion syndrome is highly prevalent and both conductive and high-frequency sensorineural in nature. The age-dependent absence of DPOAEs in 22q11.2 deletion syndrome suggests cochlear damage underlying the high-frequency hearing loss.

Development of a Dutch matrix sentence test to assess speech intelligibility in noise.

OBJECTIVE: A Dutch matrix sentence test was developed and evaluated. A matrix test is a speech-in-noise test based on a closed speech corpus of sentences derived from words from fixed categories. An example is "Mark gives five large flowers." DESIGN: This report consists of the development of the speech test and a multi-center evaluation. STUDY SAMPLE: Forty-five normal-hearing participants. RESULTS: The developed matrix test has a speech reception threshold in stationary noise of - 8.4 dB with an inter-list standard deviation of 0.2 dB. The slope of the intelligibility function is 10.2 %/dB and this is slightly lower than that of similar tests in other languages (12.6 to 17.1 %/dB). CONCLUSIONS: The matrix test is now also available in Dutch and can be used in both Flanders and the Netherlands.

Exploring the sensitivity of speech-in-noise tests for noise-induced hearing loss.

OBJECTIVE: Recently, the digit triplet test was shown to be a sensitive speech-in-noise test for early high-frequency hearing loss in noise-exposed workers. This study investigates if a further improvement is achieved when using a closed set of consonant-vowel-consonant (CVC) speech items with the same vowel, and/or a low-pass (LP) filtered version of the standard speech-shaped noise. DESIGN: Speech reception thresholds in noise were gathered for the digit triplet, CVC, and CVC_LP test and compared to the high-frequency pure-tone average (PTA). STUDY SAMPLE: 118 noise-exposed workers showing a wide range of high-frequency hearing losses. RESULTS: For the 84 Dutch-speaking participants, the CVC test showed an increased measurement error and a decreased between-subject variation, leading to a weaker correlation with the PTA2,3,4,6 (R = 0.64) and thus a lower sensitivity compared to the digit triplet test (R = 0.86). However, the use of LP-filtered noise resulted in a sensitivity improvement (R = 0.79 versus R = 0.64) due to the large increase in between-subject spread. Similar trends were found for the 34 French-speaking workers. CONCLUSIONS: Using CVC words with the same vowel could not increase the sensitivity to detect isolated high-frequency hearing loss. With LP-filtered noise, test sensitivity improved, but it did not surpass the original digit triplet test.

Efficient hearing screening in noise-exposed listeners using the digit triplet test.

OBJECTIVES: Hearing screening in occupational medicine is generally based on pure-tone threshold audiometry. However, reliable and valid thresholds can only be obtained in a sound-proof room, using a high-quality, well-calibrated audiometer, and by a well-trained administrator. Thresholds also need to be determined for several audiometric frequencies. This makes the test time-consuming and expensive, which is not ideal for the screening of large populations. A Speech-In-Noise test (SPIN), by contrast, does not have the abovementioned requirements. Because it can be implemented as a quick automated self-test, possibly over the Internet, a SPIN test is highly advantageous for screening purposes. However, its sensitivity for (isolated) high-frequency hearing loss, as typically seen in noise-exposed listeners, was unclear up to present. In this study, the authors investigated the sensitivity and specificity of the Digit Triplet SPIN test for detecting and monitoring (early-stage) high-frequency hearing loss, and its similarity across two different language versions. DESIGN: One-hundred eighteen noise-exposed workers, representing a wide range from no to severe high-frequency hearing loss, completed the French or Dutch version of the broadband Digit Triplet self-test in an office-like room. Pure-tone thresholds, collected by a professional audiologist in favorable settings, served as the reference. RESULTS: The 84 Dutch-speaking participants showed a very strong linear relation between the reference and the Digit Triplet test, with the pure-tone average at 2, 3, 4, and 6 kHz as a strong predictor (R = 0.86) for the speech-reception threshold. The sensitivity and specificity to detect mild high-frequency hearing loss were 92% (61 of 66) and 89% (16 of 18), respectively. The area under the receiver operating characteristic (ROC) curve was very high (≥0.91) for several degrees of high-frequency hearing loss. With a within-subject standard deviation of only 0.8 dB, the Digit Triplet test also had a low measurement error. The results of the 34 French-speaking subjects showed a highly similar trend. CONCLUSIONS: The Digit Triplet test proves to have a high sensitivity and specificity for detecting different degrees of high-frequency hearing loss. Given its ease of use, this test is very suitable for screening purposes in occupational medicine, and potentially for the screening of adolescents at risk of recreational noise-induced hearing loss.

Hemispheric asymmetry of auditory steady-state responses to monaural and diotic stimulation.

Amplitude modulations in the speech envelope are crucial elements for speech perception. These modulations comprise the processing rate at which syllabic (~3-7 Hz), and phonemic transitions occur in speech. Theories about speech perception hypothesize that each hemisphere in the auditory cortex is specialized in analyzing modulations at different timescales, and that phonemic-rate modulations of the speech envelope lateralize to the left hemisphere, whereas right lateralization occurs for slow, syllabic-rate modulations. In the present study, neural processing of phonemic- and syllabic-rate modulations was investigated with auditory steady-state responses (ASSRs). ASSRs to speech-weighted noise stimuli, amplitude modulated at 4, 20, and 80 Hz, were recorded in 30 normal-hearing adults. The 80 Hz ASSR is primarily generated by the brainstem, whereas 20 and 4 Hz ASSRs are mainly cortically evoked and relate to speech perception. Stimuli were presented diotically (same signal to both ears) and monaurally (one signal to the left or right ear). For 80 Hz, diotic ASSRs were larger than monaural responses. This binaural advantage decreased with decreasing modulation frequency. For 20 Hz, diotic ASSRs were equal to monaural responses, while for 4 Hz, diotic responses were smaller than monaural responses. Comparison of left and right ear stimulation demonstrated that, with decreasing modulation rate, a gradual change from ipsilateral to right lateralization occurred. Together, these results (1) suggest that ASSR enhancement to binaural stimulation decreases in the ascending auditory system and (2) indicate that right lateralization is more prominent for low-frequency ASSRs. These findings may have important consequences for electrode placement in clinical settings, as well as for the understanding of low-frequency ASSR generation.

Investigation of a significant increase in referrals during neonatal hearing screening: a comparison of Natus ALGO Portable and ALGO 3i.

OBJECTIVE: Neonatal hearing screening programs in Flanders and the Netherlands use Natus ALGO screening devices. Since 2006 in Flanders and 2009 in the Netherlands, both programs have replaced the older ALGO Portable devices with the newer ALGO 3i devices. However, in both countries, ALGO 3i devices have a significantly higher rate of referrals than ALGO Portable devices. In Flanders, the refer rate has more than doubled with the switch to ALGO 3i devices. In the Netherlands, screening centers which used ALGO 3i devices also showed a significant increase in referrals. In both countries, the percentage of children diagnosed with permanent hearing loss remained approximately the same. DESIGN: A technical comparison of both device types was carried out to identify possible causes for the increase in referrals. The stimulus output of two ALGO Portable and three ALGO 3i devices was recorded and analysed for stimulus level, spectral properties, and stimulus irregularities. RESULTS: ALGO 3i devices stimulate at a peak level 4.6 dB lower than ALGO Portable devices, have a different stimulus spectrum and show unexplained stimulus irregularities during 4% of the stimulation time. CONCLUSIONS: A number of technical differences were found between both device types which could explain the increase in referrals.

Comparison of three types of French speech-in-noise tests: a multi-center study.

OBJECTIVE: To compare results on the everyday sentence test 'FIST', the new closed-set sentence test 'FrMatrix', and the digit triplet screening test 'FrDigit3'. DESIGN: First, the FrMatrix was developed and normative values were obtained. Subsequently, speech reception thresholds (SRTs) for the three types of tests were gathered at four study centers representing different geographic regions in Belgium and France. STUDY SAMPLE: Fifty-seven normal-hearing listeners took part in the normative study of the FrMatrix, and 118 subjects, with a wide range of hearing thresholds, participated in the comparative study. RESULTS: Homogenizing the individual words of the FrMatrix with regard to their intelligibility resulted in a reference SRT of -6.0 (±0.6) dB SNR and slope at the SRT of 14.0 %/dB. The within-subject variability was only 0.4 dB. Comparison of the three tests showed high correlations between the SRTs mutually (>0.81). The FrMatrix had the highest discriminative power, both in stationary and in fluctuating noise. For all three tests, differences across the participating study centers were small and not significant. CONCLUSIONS: The FIST, the FrMatrix, and the FrDigit3 provide similar results and reliably evaluate speech recognition performance in noise both in normal-hearing and hearing-impaired listeners.

Auditory steady state cortical responses indicate deviant phonemic-rate processing in adults with dyslexia.

OBJECTIVES: Speech intelligibility is strongly influenced by the ability to process temporal modulations. It is hypothesized that in dyslexia, deficient processing of rapidly changing auditory information underlies a deficient development of phonological representations, causing reading and spelling problems. Low-frequency modulations between 4 and 20 Hz correspond to the processing rate of important phonological segments (syllables and phonemes, respectively) in speech and therefore provide a bridge between low-level auditory and phonological processing. In the present study, temporal modulation processing was investigated by auditory steady state responses (ASSRs) in normal-reading and dyslexic adults. DESIGN: Multichannel ASSRs were recorded in normal-reading and dyslexic adults in response to speech-weighted noise stimuli amplitude modulated at 80, 20, and 4 Hz. The 80 Hz modulation is known to be primarily generated by the brainstem, whereas the 20 and 4 Hz modulations are mainly generated in the cortex. Furthermore, the 20 and 4 Hz modulations provide an objective auditory performance measure related to phonemic- and syllabic-rate processing. In addition to neurophysiological measures, psychophysical tests of speech-in-noise perception and phonological awareness were assessed. RESULTS: On the basis of response strength and phase coherence measures, normal-reading and dyslexic participants showed similar processing at the brainstem level. At the cortical level of the auditory system, dyslexic subjects demonstrated deviant phonemic-rate responses compared with normal readers, whereas no group differences were found for the syllabic rate. Furthermore, a relationship between phonemic-rate ASSRs and psychophysical tests of speech-in-noise perception and phonological awareness was obtained. CONCLUSIONS: The results suggest reduced cortical processing for phonemic-rate modulations in dyslexic adults, presumably resulting in limited integration of temporal information in the dorsal phonological pathway.

Reduced sensitivity to slow-rate dynamic auditory information in children with dyslexia.

The etiology of developmental dyslexia remains widely debated. An appealing theory postulates that the reading and spelling problems in individuals with dyslexia originate from reduced sensitivity to slow-rate dynamic auditory cues. This low-level auditory deficit is thought to provoke a cascade of effects, including inaccurate speech perception and eventually unspecified phoneme representations. The present study investigated sensitivity to frequency modulation and amplitude rise time, speech-in-noise perception and phonological awareness in 11-year-old children with dyslexia and a matched normal-reading control children. Group comparisons demonstrated that children with dyslexia were less sensitive than normal-reading children to slow-rate dynamic auditory processing, speech-in-noise perception, phonological awareness and literacy abilities. Correlations were found between slow-rate dynamic auditory processing and phonological awareness, and speech-in-noise perception and reading. Yet, no significant correlation between slow-rate dynamic auditory processing and speech-in-noise perception was obtained. Together, these results indicate that children with dyslexia have difficulties with slow-rate dynamic auditory processing and speech-in-noise perception and that these problems persist until sixth grade.

Preschool impairments in auditory processing and speech perception uniquely predict future reading problems.

Developmental dyslexia is characterized by severe reading and spelling difficulties that are persistent and resistant to the usual didactic measures and remedial efforts. It is well established that a major cause of these problems lies in poorly specified phonological representations. Many individuals with dyslexia also present impairments in auditory temporal processing and speech perception, but it remains debated whether these more basic perceptual impairments play a role in causing the reading problem. Longitudinal studies may help clarifying this issue by assessing preschool children before they receive reading instruction and by following them up through literacy development. The current longitudinal study shows impairments in auditory frequency modulation (FM) detection, speech perception and phonological awareness in kindergarten and in grade 1 in children who receive a dyslexia diagnosis in grade 3. FM sensitivity and speech-in-noise perception in kindergarten uniquely contribute to growth in reading ability, even after controlling for letter knowledge and phonological awareness. These findings indicate that impairments in auditory processing and speech perception are not merely an epiphenomenon of reading failure. Although no specific directional relations were observed between auditory processing, speech perception and phonological awareness, the highly significant concurrent and predictive correlations between all these variables suggest a reciprocal association and corroborate the evidence for the auditory deficit theory of dyslexia.

Impairments in speech and nonspeech sound categorization in children with dyslexia are driven by temporal processing difficulties.

Auditory processing problems in persons with dyslexia are still subject to debate, and one central issue concerns the specific nature of the deficit. In particular, it is questioned whether the deficit is specific to speech and/or specific to temporal processing. To resolve this issue, a categorical perception identification task was administered in thirteen 11-year old dyslexic readers and 25 matched normal readers using 4 sound continua: (1) a speech contrast exploiting temporal cues (/bA/-/dA/), (2) a speech contrast defined by nontemporal spectral cues (/u/-/y/), (3) a nonspeech temporal contrast (spectrally rotated/bA/-/da/), and (4) a nonspeech nontemporal contrast (spectrally rotated/u/-/y/). Results indicate that children with dyslexia are less consistent in classifying speech and nonspeech sounds on the basis of rapidly changing (i.e., temporal) information whereas they are unimpaired in steady-state speech and nonspeech sounds. The deficit is thus restricted to categorizing sounds on the basis of temporal cues and is independent of the speech status of the stimuli. The finding of a temporal-specific but not speech-specific deficit in children with dyslexia is in line with findings obtained in adults using the same paradigm (Vandermosten et al., 2010, Proceedings of the National Academy of Sciences of the United States of America, 107: 10389-10394). Comparison of the child and adult data indicates that the consistency of categorization considerably improves between late childhood and adulthood, particularly for the continua with temporal cues. Dyslexic and normal readers show a similar developmental progress with the dyslexic readers lagging behind both in late childhood and in adulthood.

Adults with dyslexia are impaired in categorizing speech and nonspeech sounds on the basis of temporal cues.

Developmental dyslexia is characterized by severe reading and spelling difficulties that are persistent and resistant to the usual didactic measures and remedial efforts. It is well established that a major cause of these problems lies in poorly specified representations of speech sounds. One hypothesis states that this phonological deficit results from a more fundamental deficit in auditory processing. Despite substantial research effort, the specific nature of these auditory problems remains debated. A first controversy concerns the speech specificity of the auditory processing problems: Can they be reduced to more basic auditory processing, or are they specific to the perception of speech sounds? A second topic of debate concerns the extent to which the auditory problems are specific to the processing of rapidly changing temporal information or whether they encompass a broader range of complex spectro-temporal processing. By applying a balanced design with stimuli that were adequately controlled for acoustic complexity, we show that adults with dyslexia are specifically impaired at categorizing speech and nonspeech sounds that differ in terms of rapidly changing acoustic cues (i.e., temporal cues), but that they perform adequately when categorizing steady-state speech and nonspeech sounds. Thus, we show that individuals with dyslexia have an auditory temporal processing deficit that is not speech-specific.

The French digit triplet test: a hearing screening tool for speech intelligibility in noise.

A French speech intelligibility screening test in noise that applies digit triplets as stimuli has been developed and evaluated for both telephone and broadband headphone use. After optimizing the speech material based on the intelligibility of the individual digits, norms for normal-hearing subjects were established. speech reception thresholds (SRTs) of -6.4 +/- 0.4 and -10.5 +/- 0.3 dB SNR, and slopes of 17.1 and 27.1 %/dB were obtained for telephone and broadband headphone presentation, respectively. The French digit triplet test by telephone was then implemented as an automatic self-screening test by home telephone, and further evaluated in normal-hearing and hearing-impaired listeners. A test-retest variability of 0.7 dB was found and the correlation between SRT and pure-tone average (PTA(0.5,1,2,4)) was 0.77. One month after launching the test, 20,000 calls were registered. It can be concluded that both versions of the newly developed test have steep slopes and small SRT differences across normal-hearing listeners. The screening test by telephone is highly reliable and proves to fulfill the need for an easily accessible and objective hearing screening.

Detection and identification of monaural and binaural pitch contours in dyslexic listeners.

The use of binaural pitch stimuli to test for the presence of binaural auditory impairment in reading-disabled subjects has so far led to contradictory outcomes. While some studies found that a majority of dyslexic subjects was unable to perceive binaural pitch, others obtained a clear response of dyslexic listeners to Huggins' pitch (HP). The present study clarified whether impaired binaural pitch perception is found in dyslexia. Results from a pitch contour identification test, performed in 31 dyslexic listeners and 31 matched controls, clearly showed that dyslexics perceived HP as well as the controls. Both groups also showed comparable results with a similar-sounding, but monaurally detectable, pitch-evoking stimulus. However, nine of the dyslexic subjects were found to have difficulty identifying pitch contours both in the binaural and the monaural conditions. The ability of subjects to correctly identify pitch contours was found to be significantly correlated to measures of frequency discrimination. This correlation may be attributed to the similarity of the experimental tasks and probably reflects impaired cognitive mechanisms related to auditory memory or auditory attention rather than impaired low-level auditory processing per se.

Multicenter evaluation of signal enhancement algorithms for hearing aids.

In the framework of the European HearCom project, promising signal enhancement algorithms were developed and evaluated for future use in hearing instruments. To assess the algorithms' performance, five of the algorithms were selected and implemented on a common real-time hardware/software platform. Four test centers in Belgium, The Netherlands, Germany, and Switzerland perceptually evaluated the algorithms. Listening tests were performed with large numbers of normal-hearing and hearing-impaired subjects. Three perceptual measures were used: speech reception threshold (SRT), listening effort scaling, and preference rating. Tests were carried out in two types of rooms. Speech was presented in multitalker babble arriving from one or three loudspeakers. In a pseudo-diffuse noise scenario, only one algorithm, the spatially preprocessed speech-distortion-weighted multi-channel Wiener filtering, provided a SRT improvement relative to the unprocessed condition. Despite the general lack of improvement in SRT, some algorithms were preferred over the unprocessed condition at all tested signal-to-noise ratios (SNRs). These effects were found across different subject groups and test sites. The listening effort scores were less consistent over test sites. For the algorithms that did not affect speech intelligibility, a reduction in listening effort was observed at 0 dB SNR.

Latencies of auditory steady-state responses recorded in early infancy.

Multiple-stimulus auditory steady-state responses (ASSRs) were assessed in 111 ears of 70 infants between -4 and 19 weeks of age at risk for hearing loss. ASSR thresholds obtained in infants with normal hearing (n = 69 ears) were compared with normal adult ASSR thresholds (n = 32 ears), and the linear relation between ASSR thresholds and behavioral thresholds (BHTs) was investigated in normal-hearing and hearing-impaired infants (n = 79 ears). Furthermore, latency estimates of significant responses to stimuli of 50 dB SPL were compared between the normal-hearing infants (n = 171 data points) and adults (n = 124 data points) and developmental changes in latency were evaluated within the infant group. Normal ASSR thresholds were on average 12 dB higher in infants compared with adults. Correlations between ASSR thresholds and BHTs were 0.75, 0.87, 0.87 and 0.79 for 500, 1000, 2000 and 4000 Hz, respectively. There was a significant effect of carrier frequency on ASSR latency, with higher carrier frequencies evoking shorter latencies in both infants and adults. Mean latencies in adults were 24.3 +/- 1.5, 22.3 +/- 1.1, 19.4 +/- 1.0 and 18.0 +/- 1.1 ms for 500, 1000, 2000 and 4000 Hz, respectively. Depending on the data fit of the infant latency estimates, mean latencies were 1.0 ms shorter or 9.5 ms longer in infants compared with adults. In infants, latencies were on average 2.0 ms longer in the youngest infant group (< or =0 weeks) relative to the oldest infant group (3-8 weeks). These age-related trends, together with other arguments, point to longer latencies in infants compared with adults. The results of this study are valuable as a clinical reference for interpreting ASSR results obtained in high-risk infants within their first months of life and indicate that developmental changes occur regarding ASSR latency.

Cortical auditory steady-state responses to low modulation rates.

This paper describes low-frequency auditory steady-state responses (ASSRs) to speech-weighted noise stimuli. The effect of modulation frequency was evaluated within the frequency range below 40 Hz. Furthermore, objective ASSR measures were related to speech understanding performance in normal-hearing and hearing-impaired listeners. The variability in ASSR recordings over independent test sessions was larger between subjects than within. Trends of increased responses around 10 and/or 20 Hz were found in all subjects. Obtained latency estimates of the responses pointed to primarily cortical sources involved in ASSR generation at low frequencies. Furthermore, significant differences between normal-hearing and hearing-impaired adults were found for ASSRs to stimuli related to the temporal envelope of speech. Comparing these responses with phoneme identification scores over different stimulus levels showed both measures increased with stimulus level in a similar way (rho=0.82). At a fixed stimulus level, ASSRs were significantly correlated with speech reception thresholds for phonemes and sentences in noise (rho from -0.45 to -0.53). These results indicate that objective low-frequency ASSRs are related to behavioral speech understanding, independently of level.

The influence of the detection paradigm in recording auditory steady-state responses.

OBJECTIVES: The purpose of this study was to evaluate the risks of uncontrolled use of an objective detection criterion in recording auditory steady-state responses (ASSRs). The influence of decisions such as when to accept a response and stop the recording was assessed by analyzing the number of false- and true-detected responses. DESIGN: A large sample of 500 multiple-stimulus ASSR recordings of normal-hearing and hearing-impaired adults and babies was processed offline. Three types of detection paradigms were evaluated. A first type had a fixed recording length with significance testing after the last sweep. A second type allowed a variable recording length and implied sequential application of the statistical decision criterion. The recording was stopped after significance was reached for y consecutive sweeps. The third type was analogous to the second, with the additional requirement of a minimum of eight recorded sweeps. Furthermore, the effect of significance level and averaging procedure were assessed. Error rates were calculated for the different detection paradigms at eight control frequencies. At the signal frequencies, detection rates and recording times were determined, keeping the error rates fixed. Moreover, ASSR thresholds were compared for a selection of detection paradigms. RESULTS: When a variable recording length was allowed and a significance level of p = 0.05 was applied, the error rate increased to unacceptable levels because of the effect of repeated testing. The error rate decreased as the required number of consecutive significant sweeps increased and approximated 5% only when eight consecutive significant sweeps were required (with a maximum of 32 recorded sweeps). With an error rate of 5%, the highest detection rate was associated with a fixed recording length of 32 sweeps combined with weighted averaging. A substantial decrease in detection rate was noted when less than 24 sweeps were recorded per intensity. All paradigms with a variable recording length had rather comparable detection rates and recording times. With an error rate of only 1%, small responses could not be distinguished from the noise. The reduction in recording time using a variable instead of a fixed recording length was very limited when a conventional multiple-stimulus approach was used. Test duration would be reduced considerably when the test set-up would allow an independent presentation and recording of the eight signals and responses. Differences in overall detection rate had a small effect on the ASSR thresholds. CONCLUSIONS: The error rate, detection rate, and recording time can improve or deteriorate significantly, even with small adaptations of the detection protocol. When a variable recording length is allowed, the acceptance criterion of the statistical test needs to be adjusted to ensure a tolerable error rate. However, most commercial devices do not offer this option. Then, it is advisable to use a fixed recording length and to judge the significance of the responses at the end of the recording. Although response detection is objective, the measurement protocol has to be well-considered and a critical approach is required when interpreting the responses.