How does the sound pressure generated by circumaural, supra-aural, and insert earphones differ for adult and infant ears?

Lumped element models of sound conduction in the human ear: A systematic review

Lumped element models facilitate investigating the fundamental mechanisms of human ear sound conduction. This systematic review aims to guide researchers to the optimal model for the investigated parameters. For this purpose, the literature was reviewed up to 12 July 2023, according to the PRISMA guidelines. Seven models are included via database searching, and another 19 via cross-referencing. The quality of the models is assessed by comparing the predicted middle ear transfer function, the tympanic membrane impedance, the energy reflectance, and the intracochlear pressures (ICPs) (scala vestibuli, scala tympani, and differential) with experimental data. Regarding air conduction (AC), the models characterize the pathway from the outer to the inner ear and accurately predict all six aforementioned parameters. This contrasts with the few existing bone conduction (BC) models that simulate only a part of the ear. In addition, these models excel at predicting one observable parameter, namely, ICP. Thus, a model that simulates BC from the coupling site to the inner ear is still lacking and would increase insights into the human ear sound conduction. Last, this review provides insights and recommendations to determine the appropriate model for AC and BC implants, which is highly relevant for future clinical applications.

Predicting wideband real-ear-to-coupler differences in children using wideband acoustic immittance

Individual differences in ear-canal acoustics introduce variability into hearing aid output that can affect speech audibility. Measuring ear-canal acoustics in young children can be challenging, and relying on normative real-ear-to-coupler difference (RECD) transforms can lead to large fitting errors. Acoustic immittance measures characterize the impedance of the ear and are more easily measured than RECD. Using 226 Hz tympanometry to predict the RECD is more accurate than using age-based average RECD values. The current study sought to determine whether wideband acoustic immittance measurements could improve predictions of wideband real-ear-to-coupler difference (wRECD). 150 children ages 2-10 years with intact tympanic membranes underwent wRECD and wideband acoustic immittance measures in each ear. Three models were constructed to predict each child's measured wRECD: the age-based average wRECD, 226 Hz admittance wRECD, and wideband absorbance wRECD. The average age-based wRECD model predicted the child's measured wRECD within 3 dB in 62% of cases, but both the 226 Hz admittance and wideband absorbance wRECD were within 3 dB in 90% of cases. Using individual 226 Hz or wideband absorbance to predict wRECD improved the accuracy and precision of transforms used for pediatric hearing aid fitting.

Hearing Thresholds, Speech Recognition, and Audibility as Indicators for Modifying Intervention in Children With Hearing Aids

OBJECTIVES

The purpose of this study was to determine if traditional audiologic measures (e.g., pure-tone average, speech recognition) and audibility-based measures predict risk for spoken language delay in children who are hard of hearing (CHH) who use hearing aids (HAs). Audibility-based measures included the Speech Intelligibility Index (SII), HA use, and auditory dosage, a measure of auditory access that weighs each child's unaided and aided audibility by the average hours of HA use per day. The authors also sought to estimate values of these measures at which CHH would be at greater risk for delayed outcomes compared with a group of children with typical hearing (CTH) matched for age and socioeconomic status, potentially signaling a need to make changes to a child's hearing technology or intervention plan.

DESIGN

The authors compared spoken language outcomes of 182 CHH and 78 CTH and evaluated relationships between language and audiologic measures (e.g., aided SII) in CHH using generalized additive models. They used these models to identify values associated with falling below CTH (by > 1.5 SDs from the mean) on language assessments, putting CHH at risk for language delay.

RESULTS

Risk for language delay was associated with aided speech recognition in noise performance (<59% phonemes correct, 95% confidence interval [55%, 62%]), aided Speech Intelligibility Index (SII < 0.61, 95% confidence internal [.53,.68]), and auditory dosage (dosage < 6.0, 95% confidence internal [5.3, 6.7]) in CHH. The level of speech recognition in quiet, unaided pure-tone average, and unaided SII that placed children at risk for language delay could not be determined due to imprecise estimates with broad confidence intervals.

CONCLUSIONS

Results support using aided SII, aided speech recognition in noise measures, and auditory dosage as tools to facilitate clinical decision-making, such as deciding whether changes to a child's hearing technology are warranted. Values identified in this article can complement other metrics (e.g., unaided hearing thresholds, aided speech recognition testing, language assessment) when considering changes to intervention, such as adding language supports, making HA adjustments, or referring for cochlear implant candidacy evaluation.

Predicting children's real-ear-to-coupler differences based on tympanometric data

OBJECTIVE

Paediatric hearing-aid verification relies on measures of output obtained from the ear canal or in a coupler with the child's real-ear-to-coupler difference (RECD). Measured RECD cannot always be completed in children, leading to fitting inaccuracies. Audiologists often have tympanometry data that characterises the child's ear-canal acoustics. The goal of this study was to determine if tympanometry can be used to improve predictions of measured RECD.

DESIGN

A retrospective analysis of RECD and admittance, tympanometric peak pressure, and equivalent ear-canal volume from 226 Hz tympanometry collected as part of a longitudinal study of children with hearing loss were modelled with Bayesian hierarchical regression.

STUDY SAMPLE

Two-hundred sixty-six children with mild-to-severe hearing loss contributed data.

RESULTS

Age-based average RECD models were within 3 dB of measured RECD values in 54% of cases with normal middle ear status and 50.6% of cases with abnormal middle ear status. Immittance-predicted RECD were within 3 dB in 69.6% of cases with normal middle ear status and 74.4% of cases with abnormal middle ear status.

CONCLUSION

Immittance-predicted RECD was more accurate than age-based average RECD, particularly in children with abnormal middle ear status. The findings suggest that 226 Hz tympanometry could be used clinically to improve predictions of measured RECD when it cannot be measured.

Descriptions of Hearing Loss Severity Differentially Influence Parental Concern about the Impact of Childhood Hearing Loss

PURPOSE

The purpose of this study was to measure how parent concern about childhood hearing loss varies under different description conditions: classification-based, audibility-based, and simulation-based descriptions.

METHOD

We randomly allocated study participants (n = 143) to complete an online survey about expected child difficulties with listening situations with hearing loss. Our participants were parents of children with typical hearing in the 0- to 12-month age range. Participants were exposed to one type of description (classification-based, audibility-based, or simulation-based) and one level of hearing loss (slight, mild, and moderate or their audibility and simulation equivalents), producing nine total groups. Participants rated the level of expected difficulty their child would experience performing age-appropriate listening tasks with the given hearing loss. They also selected what they perceived as the most appropriate intervention from a list of increasingly intense options.

RESULTS

Our findings revealed that audibility-based descriptions elicited significantly higher levels of parent concerns about hearing loss than classification-based strategies, but that simulation-based descriptions elicited the highest levels of concern. Those assigned to simulation-based and audibility-based groups also judged relatively more intense intervention options as appropriate compared to those assigned to classification-based groups.

CONCLUSIONS

This study expands our knowledge base about descriptive factors that impact levels of parent concern about hearing loss after diagnosis. This has potentially cascading effects on later intervention actions such as fitting hearing technology. It also provides a foundation for developing and testing clinical applications of audibility-based counseling strategies.

Quantifying Access to Speech in Children with Hearing Loss: The Influence of the Work of Pat Stelmachowicz on Measures of Audibility

This article reviews the research of Pat Stelmachowicz on traditional and novel measures for quantifying speech audibility (i.e., pure-tone average [PTA], the articulation/audibility index [AI], the speech intelligibility index, and auditory dosage) as predictors of speech perception and language outcomes in children. We discuss the limitations of using audiometric PTA as a predictor of perceptual outcomes in children and how Pat's research shed light on the importance of measures that characterize high-frequency audibility. We also discuss the AI, Pat's work on the calculation of the AI as a hearing aid outcome measure, and how this work led to the application of the speech intelligibility index as a clinically utilized measure of unaided and aided audibility. Finally, we describe a novel measure of audibility-auditory dosage-that was developed based on Pat's work on audibility and hearing aid use for children who are hard of hearing.

Comprehensive Audiological Management of Hearing Loss in Children, Including Mild and Unilateral Hearing Loss

Management of hearing loss in infants and young children has evolved rapidly with the formation of universal newborn hearing screening and early intervention programs. This review describes the management process for children with hearing loss, including determining candidacy for amplification, selection of amplification devices, electroacoustic verification, and outcomes validation. The importance of a coordinated, evidence-based approach can help to ensure the best communication outcomes for children with hearing loss.

Characteristics of Speech-Evoked Envelope Following Responses in Infancy

Envelope following responses (EFRs) may be a useful tool for evaluating the audibility of speech sounds in infants. The present study aimed to evaluate the characteristics of speech-evoked EFRs in infants with normal hearing, relative to adults, and identify age-dependent changes in EFR characteristics during infancy. In 42 infants and 21 young adults, EFRs were elicited by the first (F1) and the second and higher formants (F2+) of the vowels /u/, /a/, and /i/, dominant in low and mid frequencies, respectively, and by amplitude-modulated fricatives /s/ and /∫/, dominant in high frequencies. In a subset of 20 infants, the in-ear stimulus level was adjusted to match that of an average adult ear (65 dB sound pressure level [SPL]). We found that (a) adult-infant differences in EFR amplitude, signal-to-noise ratio, and intertrial phase coherence were larger and spread across the frequency range when in-ear stimulus level was adjusted in infants, (b) adult-infant differences in EFR characteristics were the largest for low-frequency stimuli, (c) infants demonstrated adult-like phase coherence when they received a higher (i.e., unadjusted) stimulus level, and (d) EFR phase coherence and signal-to-noise ratio changed with age in the first year of life for a few F2+ vowel stimuli in a level-specific manner. Together, our findings reveal that development-related changes in EFRs during infancy likely vary by stimulus frequency, with low-frequency stimuli demonstrating the largest adult-infant differences. Consistent with previous research, our findings emphasize the significant role of stimulus level calibration methods while investigating developmental trends in EFRs.

The accuracy of standard audiometric hearing level thresholds in pediatric patients

OBJECTIVES

Standard audiograms provide decibels Hearing Level (dB HL) thresholds, which are referenced to normative values specified in decibels Sound Pressure Level in an acoustic coupler. Due to variability in external ear acoustics, the actual sound levels reaching the eardrum can vary across individuals. The real-ear to coupler difference (RECD) is a frequency-specific measurement of the difference between sound levels measured at the eardrum and in a coupler. Here, we compare the standard audiogram dB HL levels to RECD corrected hearing thresholds (dB RECHL) in children.

METHODS

Children who underwent standard audiometric and RECD testing were included. The dB RECHL was established and the differences between dB HL and dB RECHL (threshold error) was calculated. A threshold error >5 dB was considered significant.

RESULTS

A total of 166 children were included (mean age 12 years). Overall, 14% had normal hearing, 52% had conductive hearing loss and 27% had sensorineural hearing loss. Hearing threshold levels were overestimated by the standard audiogram compared to dB RECHL, at all frequencies (250-6000 Hz). In the lower frequencies and at 6000 Hz, 33-59% of patients were overestimated, with a threshold error up to 25 dB. In the mid frequencies, 33% were overestimated with a similar threshold error.

CONCLUSION

Standard audiogram thresholds overestimated hearing levels in children which may have clinical implications. This problem can be addressed by correcting thresholds with RECD. More studies are needed to assess the effect of correcting thresholds on hearing outcomes in children.

Automated Audiometry: A Review of the Implementation and Evaluation Methods

Objectives

Automated audiometry provides an opportunity to do audiometry when there is no direct access to a clinical audiologist. This approach will help to use hearing services and resources efficiently. The purpose of this study was to review studies related to automated audiometry by focusing on the implementation of an audiometer, the use of transducers and evaluation methods.

Methods

This review study was conducted in 2017. The papers related to the design and implementation of automated audiometry were searched in the following databases: Science Direct, Web of Science, PubMed, and Scopus. The time frame for the papers was between January 1, 2010 and August 31, 2017. Initially, 143 papers were found, and after screening, the number of papers was reduced to 16.

Results

The findings showed that the implementation methods were categorized into the use of software (7 papers), hardware (3 papers) and smartphones/tablets (6 papers). The used transducers were a variety of earphones and bone vibrators. Different evaluation methods were used to evaluate the accuracy and the reliability of the diagnoses. However, in most studies, no significant difference was found between automated and traditional audiometry.

Conclusions

It seems that automated audiometry produces the same results compared with traditional audiometry. However, the main advantages of this method; namely, saving costs and increased accessibility to hearing services, can lead to a faster diagnosis of hearing impairment, especially in poor areas.

Effects of Self-Generated Noise on Estimates of Detection Threshold in Quiet for School-Age Children and Adults

OBJECTIVES

Detection thresholds in quiet become adult-like earlier in childhood for high than low frequencies. When adults listen for sounds near threshold, they tend to engage in behaviors that reduce physiologic noise (e.g., quiet breathing), which is predominantly low frequency. Children may not suppress self-generated noise to the same extent as adults, such that low-frequency self-generated noise elevates thresholds in the associated frequency regions. This possibility was evaluated by measuring noise levels in the ear canal simultaneous with adaptive threshold estimation.

DESIGN

Listeners were normal-hearing children (4.3 to 16.0 years) and adults. Detection thresholds were measured adaptively for 250-, 1000-, and 4000-Hz pure tones using a three-alternative forced-choice procedure. Recordings of noise in the ear canal were made while the listeners performed this task, with the earphone and microphone routed through a single foam insert. Levels of self-generated noise were computed in octave-wide bands. Age effects were evaluated for four groups: 4- to 6-year olds, 7- to 10-year olds, 11- to 16-year olds, and adults.

RESULTS

Consistent with previous data, the effect of child age on thresholds was robust at 250 Hz and fell off at higher frequencies; thresholds of even the youngest listeners were similar to adults' at 4000 Hz. Self-generated noise had a similar low-pass spectral shape for all age groups, although the magnitude of self-generated noise was higher in younger listeners. If self-generated noise impairs detection, then noise levels should be higher for trials associated with the wrong answer than the right answer. This association was observed for all listener groups at the 250-Hz signal frequency. For adults and older children, this association was limited to the noise band centered on the 250-Hz signal. For the two younger groups of children, this association was strongest at the signal frequency, but extended to bands spectrally remote from the 250-Hz signal. For the 1000-Hz signal frequency, there was a broadly tuned association between noise and response only for the two younger groups of children. For the 4000-Hz signal frequency, only the youngest group of children demonstrated an association between responses and noise levels, and this association was particularly pronounced for bands below the signal frequency.

CONCLUSIONS

These results provide evidence that self-generated noise plays a role in the prolonged development of low-frequency detection thresholds in quiet. Some aspects of the results are consistent with the possibility that self-generated noise elevates thresholds via energetic masking, particularly at 250 Hz. The association between behavioral responses and noise spectrally remote from the signal frequency is also consistent with the idea that self-generated noise may also reflect contributions of more central factors (e.g., inattention to the task). Evaluation of self-generated noise could improve diagnosis of minimal or mild hearing loss.

Improving newborn hearing screening: Are automated auditory brainstem response ear inserts an effective option?

OBJECTIVE

Universal newborn hearing screening is an established practice among Hong Kong public hospitals using a 2-stage automated auditory brainstem response (AABR) screening protocol. To enhance overall efficiency without sacrificing program accuracy, cost reduction in terms of replacing the initial ear coupler-based screening with a more economical ear insert-based screening procedure was considered. This study examined the utility of an insert-based AABR initial screening approach and the projected cost-effectiveness of a combined probe-based plus follow-up ear coupler AABR screening procedure.

METHODS

Following prenatal maternal consent, newborn hearing screening was conducted with 167 healthy neonates using a cross-sectional, repeated measures study design. The neonates were screened with AABR sequentially; using ear coupler and ear probe (insert) procedures, in both ears, with two different but comparable AABR instruments. Testing took place in the antenatal ward of a department of obstetrics and gynaecology, at a large public hospital.

RESULTS

With the specific combination of instruments deployed for this study insert-based AABR screening generated a five-fold higher rescreen rate and took an additional 50% screening time compared to coupler-based AABR screening. Although the cost of consumables used in a 2-stage AABR screening protocol would reduce by 9.87% if the combined procedure was implemented, the findings indicated AABR screening when conducted with an ear probe has reduced utility compared with conventional ear coupler screening.

CONCLUSIONS

Significant differences may occur in screening outcomes when changes are made to coupler method. Initiating a 2-stage AABR screening protocol with an ear insert technique may be impracticable in newborn nurseries given the greater number of false positive cases generated by this approach in the present study and the increased time required to carry out an insert-based procedure.

Preliminary evaluation of a light-based contact hearing device for the hearing impaired

OBJECTIVE

To assess the safety, stability, and performance of the broad-spectrum, light-based contact hearing device (CHD) on listeners with hearing impairment.

STUDY DESIGN

Feasibility study.

SETTING

Single-site research and development facility.

PARTICIPANTS

Thirteen participants with symmetric mild-to-severe sensorineural hearing impairment had the CHD placed bilaterally.

INTERVENTION

A custom-molded light-activated tympanic contact actuator (TCA) was placed into each ear by a physician, where it stayed in contact with the umbo and a portion of the medial wall of the ear canal for 4 months. Each CHD was calibrated and programmed to provide appropriate broad-spectrum amplification.

MAIN OUTCOME MEASURES

Safety was determined through routine otologic examinations. Aided and pre-TCA-insertion unaided audiometric thresholds (functional gain), maximum gain before feedback, tympanic membrane damping, Reception Threshold for Sentences (RTS), and Abbreviated Profile of Hearing Aid Benefit (APHAB) measurements were made to characterize system performance as well as the benefits of amplification via the CHD.

RESULTS

The TCAs remained on participants' ears for an average total of 122 days, without causing signs of inflammation or infection, and there were no serious device-related adverse events. Measured average maximum output of 90 to 110 dB SPL in the range of 0.25 to 10 kHz, average maximum gain before feedback of 40 dB, and functional gain through 10 kHz show extended-bandwidth broad-spectrum output and gain. RTS results showed significant aided improvements of up to 2.8 dB, and APHAB results showed clinically significant aided benefits in 92% of participants (11/12).

CONCLUSION

The safety, stability, and performance demonstrated in this initial 4-month study suggest that the CHD may offer a feasible way of providing broad-spectrum amplification appropriate to treat listeners with mild-to-severe hearing impairment.

Provisional stimulus level corrections for low frequency bone-conduction ABR in babies under three months corrected age

OBJECTIVE

To estimate bone-conduction stimulus level corrections by testing the auditory brainstem response (ABR) of normally-hearing newborns. The stimuli used were low frequency tone pips calibrated to reference levels derived from ISO 389 values.

DESIGN

Tone pips were presented via supra-aural earphones and a B71 Radioear bone vibrator at 0.5 or 1 kHz. ABR thresholds from both transducers were compared at each frequency.

STUDY SAMPLE

twenty-seven newborn hearing screening referrals (33 ears) who passed an ABR discharge criterion at 4 kHz.

RESULTS

Median air- and bone-conduction ABR threshold differences were 30 dB at 0.5 kHz and 20 dB at 1 kHz.

CONCLUSION

The 0.5 kHz data from this study and previous studies were compared. Previous studies suggested lower figures for the bone-conduction stimulus level correction. Likely sources of this discrepancy are discussed. The average 0.5 kHz bone-conduction correction value for infants < 3 months old is about 28 dB. The correction for 1 kHz is 20 dB. We recommend that calibration reference levels used in this study be adopted and that appropriate corrections be applied to bone conduction ABR thresholds in infants < 3 months old before calculation of any air-bone gap and subsequent clinical interpretation.

Behavioral hearing thresholds between 0.125 and 20 kHz using depth-compensated ear simulator calibration

OBJECTIVES

The purpose of this study was to obtain behavioral hearing thresholds for frequencies between 0.125 and 20 kHz from a large population between 10 and 65 yr old using a clinically feasible calibration method expected to compensate well for variations in the distance between the eardrum and an insert-type sound source. Previous reports of hearing thresholds in the extended high frequencies (>8 kHz) have either used calibration techniques known to be inaccurate or specialized equipment not suitable for clinical use.

DESIGN

Hearing thresholds were measured from 352 human subjects between 10 and 65 yr old having clinically normal-hearing thresholds (<20 dB HL) up to 4 kHz. An otoacoustic emission probe fitted with custom sound sources was used, and the stimulus levels individually tailored on the basis of an estimate of the insertion depth of the measurement probe. The calibrated stimulus levels were determined on the basis of measurements made at various depths of insertion in a standard ear simulator. Threshold values were obtained for 21 frequencies between 0.125 and 20 kHz using a modified Békésy technique. Forty-six of the subjects returned for a second measurement months later from the initial evaluation.

RESULTS

In agreement with previous reports, hearing thresholds at extended high frequencies were found to be sensitive to age-related changes in auditory function. In contrast with previous reports, no gender differences were found in average hearing thresholds at most evaluated frequencies. Two aging processes, one faster than the other in time scale, seem to influence hearing thresholds in different frequency ranges. The standard deviation (SD) of test-retest threshold difference for all evaluated frequencies was 5 to 10 dB, comparable to that reported in the literature for similar measurement techniques but smaller than that observed for data obtained using the standard clinical procedure.

CONCLUSIONS

The depth-compensated ear simulator-based calibration method and the modified Békésy technique allow reliable measurement of hearing thresholds over the entire frequency range of human hearing. Hearing thresholds at the extended high frequencies are sensitive to aging and reveal subtle differences, which are not evident in the frequency range evaluated regularly (≤8 kHz). Previously reported gender-related differences in hearing thresholds may be related to ear-canal acoustics and the calibration procedure and not because of differences in hearing sensitivity.

Further assessment of forward pressure level for in situ calibration

Quantifying ear-canal sound level in forward pressure has been suggested as a more accurate and practical alternative to sound pressure level (SPL) calibrations used in clinical settings. The mathematical isolation of forward (and reverse) pressure requires defining the Thévenin-equivalent impedance and pressure of the sound source and characteristic impedance of the load; however, the extent to which inaccuracies in characterizing the source and/or load impact forward pressure level (FPL) calibrations has not been specifically evaluated. This study examined how commercially available probe tips and estimates of characteristic impedance impact the calculation of forward and reverse pressure in a number of test cavities with dimensions chosen to reflect human ear-canal dimensions. Results demonstrate that FPL calibration, which has already been shown to be more accurate than in situ SPL calibration, can be improved particularly around standing-wave null frequencies by refining estimates of characteristic impedance. Better estimates allow FPL to be accurately calculated at least through 10 kHz using a variety of probe tips in test cavities of different sizes, suggesting that FPL calibration can be performed in ear canals of all sizes. Additionally, FPL calibration appears a reasonable option when quantifying the levels of extended high-frequency (10-18 kHz) stimuli.

The efficiency of the single- versus multiple-stimulus auditory steady state responses in infants

OBJECTIVES

Multiple auditory steady state responses (ASSRs) will likely be included in the diagnostic test battery for estimating infant auditory thresholds in the near future; however, the effects of single- versus multiple-stimulus presentation in infants has never been investigated. In adults, there are no interactions (reduced amplitudes) between responses to multiple simultaneous stimuli presented at 60 dB SPL or lower. Maturational differences, however, may lead to greater interactions in infants; thus, it is unknown whether the single-stimulus technique or the multiple-stimulus technique is more efficient for testing infants. Two studies were carried out to address this issue.

DESIGN

All infants in study A participated in three stimulus conditions, which differed in the number of stimuli presented simultaneously. The monotic single (MS) condition consisted of 500, 1000, 2000, and 4000 Hz tones, which were presented singly to one ear. The monotic multiple (MM) condition was composed of four tones (500, 1000, 2000, and 4000 Hz) presented to one ear simultaneously. The dichotic multiple (DM) condition consisted of eight tones presented simultaneously to both ears (four tones to each ear). ASSR amplitudes were obtained from 15 normal infants (mean age: 23.1 wks) in response to multiple (MM, DM) and single (MS) air conduction amplitude-modulated (AM) tones (77 to 105 Hz modulation rates; 60 dB SPL). In study B, ASSR thresholds were determined for 500-Hz stimuli in the single- and DM-stimulus conditions (14 infants; mean age: 20.2 wks).

RESULTS

Mean single-stimulus ASSR amplitudes for 500, 1000, 2000, and 4000 Hz were 30, 39, 45 and 43 nV, respectively. Presentation of multiple AM tones (i.e., four octave-spaced frequencies) to one ear resulted in ASSR amplitudes that were 97%, 87%, 82%, and 70% (for 500, 1000, 2000, and 4000 Hz, respectively) of the single-stimulus ASSR amplitudes. Results for the dichotic presentation of eight AM tones show ASSR amplitudes that were 70%, 77%, 67%, and 67% relative to the MS condition. Although decreases in amplitude occurred using multiple stimuli in infants, the multiple ASSR remained more efficient than the single-stimulus ASSR (i.e., multiple-stimulus amplitudes were greater than single-stimulus amplitudes divided by √K, where K is the number of stimuli). Results from study B indicate that ASSR thresholds for 500 Hz presented in the DM condition were elevated 3 dB compared with that obtained in the 500-Hz single-stimulus condition. This statistically nonsignificant difference is within the range of acceptable test-retest variability and is thus not of clinical significance.

CONCLUSIONS

The amplitude reductions seen in the multiple-stimulus conditions in infants, not seen in adults, could be related to maturational differences in the ear canal, middle ear, cochlea, and/or brain stem. Because greater interactions occur in the DM-stimulus condition compared with the monotic multiple-stimulus condition and baseline single-stimulus condition, brain stem origins of these interactions are likely. Study B revealed statistically nonsignificant differences between threshold for 500 Hz when presented in the single- and DM-stimulus conditions. In summary, as with adults, multiple-stimulus presentation in infants is more efficient than single AM tones, at least for 60 dB SPL stimuli.

Pure-tone auditory threshold in school children

To determine pure-tone auditory thresholds, 197 screened children at a typical primary school in a German town (~70,000 inhabitants) were examined. All children underwent a tympanometry and an audiometry at 17 frequencies from 125 to 16 kHz. Regarding age effects, two groups (6-8 and 9-12 years) were analyzed. The cross-sectional research was supplemented by a follow-up study with 35 children of the first graders 3 years later. School children have the poorest hearing sensitivity at low frequencies (below 1 kHz) and the best sensitivity at the extended high frequencies above 8 kHz. Hearing thresholds are rising significantly with age. Through all frequencies, averaged improvements were 3.8 dB (right ear) and 3.7 dB (left ear) at the cross-sectional study and 3.7 dB (right ear) and 5.1 dB (left ear) at the longitudinal study. The overall deviation (left and right) from the standard thresholds for adults were 7.4 and 3.6 dB for the younger and older age groups, respectively. The ear canal volume (ECV) measured by tympanometric tests was at mean with 1.06 cm(3) for the 6- to 8-year age group significantly lower (p < 0.001) in comparison with 1.18 cm(3) for the 9- to 12-year age group. Also, girls had significant (p < 0.001) smaller ECV (mean 1.07 cm(3)) than boys (1.17 cm(3)). Auditory performance improves with rising age in school children.

Impact on hearing of routine ear suctioning at the tympanic membrane

OBJECTIVE

Patient and equipment safety has become increasingly scrutinized in today's medical care. Routine otolaryngologic evaluation often involves suctioning with Frazier-type suction devices in the ear canal for improved visualization, but data are limited on the potential acoustic trauma from ear canal suction devices. This study intends to document the objective and subjective effects of ear canal suctioning to identify any risk for hearing threshold shifts or other potential negative effects.

PATIENTS AND METHODS

Prospective study on 21 healthy volunteers enlisted for evaluation. Presuctioning tympanogram, audiogram, and otoacoustic emissions data were obtained. Spectrum analyses were recorded during ear canal suctioning with a probe microphone placed lateral to the tympanic membrane. Subjective data were recorded, and a follow-up audiogram and otoacoustic emissions were obtained to identify any temporary threshold shifts.

RESULTS

Spectrum analyses revealed a high degree of variability between subjects. A peak intensity of 111 dB sound pressure level was recorded. All patients tolerated suctioning, and none reported hearing loss. No threshold shifts were observed. Subjective data failed to correlate with the objective recorded intensities.

CONCLUSIONS

Clinicians and patients need to be acutely aware of potential risks and benefits from any medical intervention. Routine ear canal suctioning can be extremely loud and uncomfortable for patients. This study failed to document objective proof of hearing detriment from ear canal suctioning, although the possibility exists during office and surgical intervention. Further study and potential alternative suctioning methods deserve attention.

Reference zero for the calibration of air-conduction audiometric equipment using ‘tone bursts’ as test signals

The aim of this study was to determine reference peak-to-peak threshold sound pressure levels for air conduction sound transducers using groups of tone bursts as test signals. For this purpose, threshold measurements with five different earphones and a loudspeaker were carried out on groups of 25 young, otologically normal test subjects in the frequency range between 250 Hz and 8000 Hz, following as closely as possible the ISO Preferred Test Conditions. The dependence of the results on repetition rate, type of sound transducer, gender and age of the test subjects, and on reference pure tone thresholds was investigated. The results mainly depend on the reference equivalent sound pressure levels for pure tones of each sound transducer. Together with the results of another study carried out in Denmark, the data of the present study will form the basis for the International Standard ISO 389 Part 6 on reference hearing thresholds for acoustic test signals of short duration.

Call for calibration standard for newborn screening using auditory brainstem responses

The mode of stimulation employed in newborn screening of the auditory brainstem response has evolved from the clinically standardized supraaural earphone to the tubal insert earphone, to most recently a circumaural earphone developed for this test. Considered here is the need to develop a standard for calibration of such devices for newborn screening applications, in particular. At risk is the prospect of missing the milder degrees of hearing loss, assuming a goal of detecting all clinically-significant congenital hearing losses. Two commercially manufactured test instruments for automated newborn screening were scrutinized via bench testing of sound output from their respective transducers, using a variety of measurements. By convention or design, none of the measurement approaches involved a model of the newborn ear, per se. While it was concluded that the manufacturers' method shows promise, namely as a relatively simple and potentially reliable method of calibration, concerns arose regarding output levels when measured according to both the manufacturers' and the authors' methods. Further work is needed to critically assess calibration methods and to establish, to the extent possible, appropriate norms and validation studies in newborns to provide a better understanding of the actual sound pressure level of the screening stimulus.