Customized acoustic transform functions and their accuracy at predicting real-ear hearing aid performance

OBJECTIVE: The purpose of the study was to evaluate the validity of predicting the real-ear aided response by adding customized acoustic transform functions to the performance of a hearing aid in a 2-cc coupler. DESIGN: The real-ear hearing aid response, the real-ear-to-coupler difference (RECD/HA2), and field to behind-the-ear microphone transfer functions were measured in both ears of 24 normally hearing subjects using probe-tube microphone equipment. The RECD/HA2 transform function was obtained using both insert earphones and with the hearing aid/ pressure comparison method. An RECD/HA2 transfer function was also obtained with a customized earmold, ER-3A foam tip, and an oto-admittance tip. RESULTS: Validity estimates were calculated as the difference between the derived and measured real-ear response. The derived response was generally within 5 dB of the measured real-ear response when it incorporated an RECD/HA2 transform function obtained with a customized earmold for the specific ear in question. Discrepancies increased when the RECD/HA2 transfer function was obtained from the same subject but the opposite ear. There were significant differences between the RECD/HA2 transform function obtained with customized and temporary earmolds. As a result, the derived response incorporating these transforms differed significantly from the measured real-ear response obtained with the customized earmold. The insert earphone and the hearing aid RECD/HA2 transfer function were equally valid. CONCLUSIONS: The derived response may be used as a substitute for in situ hearing aid response procedures when it incorporates acoustic transform functions obtained with a customized earmold from the specific ear in question.     

Deriving the real-ear SPL of audiometric data using the "coupler to dial difference" and the "real ear to coupler difference"

OBJECTIVE: The purpose of the study was to compare the measured real-ear sound pressure level (SPL) of audiometer output with the derived real-ear SPL obtained by adding the coupler to dial difference (CDD) and real-ear to coupler difference (RECD) to the audiometer dial reading. DESIGN: The real-ear SPL and RECD were measured in one ear of 16 normally hearing subjects using a probe-tube microphone. The CDD transform and the RECD transfer function were measured in an HA1 and an HA2 2-cc coupler using an EAR-LINK foam ear-tip or a customized earmold. The RECD transfer function was measured using the EARTone ER 3A and the Audioscan RE770 insert earphone. RESULTS: The procedures were very reliable with mean differences on retest of less than 1 dB. The mean difference between the measured and derived real-ear SPL was generally less than 1 dB and rarely exceeded 3 dB in any subject. CONCLUSIONS: The CDD measured for an individual audiometer and the RECD measured for an individual ear can be used to derive a valid estimate of real-ear SPL when it has not been possible to measure this directly.     

鼓膜穿孔对真耳-耦合腔差的影响

目的:探讨鼓膜穿孔对真耳一耦合腔差(RECD)的影响.方法:34例(34耳)中耳功能及听力正常成人为对照组,30例(34耳)干性鼓膜穿孔患者为实验组,用真耳分析仪测试RECD.结果:实验组与对照组RECD值比较在1 kHz以下(含1 kHz)及4 kHz差异有统计学意义(P＜0.05),实验组比对照组要小;实验组的标准差变化较大,平均为4.4 dB,而对照组为1.4 dB;实验组RECD值与等效外耳道容积大小在0.75 kHz以下呈显著负相关(r=-0.70,P＜0.01),而1 kHz以上无相关性;鼓膜穿孔大小对RECD值无影响.结论:鼓膜穿孔患者RECD值在不同频率变化较大,选配助听器时应进行真耳测量以测试个体RECD,尽量不用平均值,适当增加低频的增益.     

Is the real-ear to coupler difference independent of the measurement earphone?

Direct measurement of real-ear hearing aid performance can be obtained using a probe tube microphone system. Alternatively, it can be derived by adding the real-ear to coupler difference (RECD) to the electroacoustic performance of the hearing instrument measured in a 2-cc coupler. Inherent in this derivation is the assumption that the RECD measured with one transducer can be applied to a coupler measurement performed with a different transducer. For the RECD procedure to be valid, it should be independent of the measurement transducer. The Audioscan RM500 is an example of a commercially available real-ear measurement system that incorporates a clinical protocol for the measurement of the RECD. The RECD can be measured on the Audioscan RM500 using a standard EAR-Tone ER-3A insert earphone or the Audioscan's own RE770 insert earphone. The aim of this study was to compare the RECDs obtained with these two earphones. The Audioscan RM500 was used to measure the RECD from the right ears of 18 adult subjects ranging in age from 22 to 36 years (mean 25 years). Measurements were made with the EAR-Tone ER-3A and RE770 insert earphone and three earmould configurations: (1) the EARLINK foam ear-tip; (2) a hard acrylic shell earmould with the same length of acoustical tubing as the foam ear-tip (25 mm); and (3) the shell ear mould with the appropriate length of tubing for a behind-the-ear (BTE) hearing aid fitting (approximately 35-45 mm). The results show that the mean RECD was around 3 dB higher at 1.5 kHz with the foam ear-tip when measured with the RE770 earphone than when measured with the ER-3A earphone. The same magnitude of difference was obtained with the shell earmould and 25-mm tubing; however, this increased to 9 dB when the tubing was increased to around 40 mm for a BTE fitting. The difference in mean RECD with the two earphones was statistically significant on a repeated-measures ANOVA for every earmould configuration (p<0.001). The results of this study demonstrate that the RECD procedure that uses an HA2 coupler and earmould is not independent of the measurement earphone. This has important implications for clinical practice.     

Real-Ear to coupler difference in patients with ear drum perforation.

The aim of this study is to investigate the effects of ear drum perforation on real-ear to coupler difference (RECD) in adults. RECD was measured using a probe tube microphone system in 22 patients with ear drum perforations. Twenty-two normal subjects served as controls. For normal subjects, RECD was in good agreement with the values reported in the literature. For the perforated ears, the RECD was up to 8 dB smaller in the frequency range from 0.5 to 1 kHz. There was no significant difference at frequencies below 0.25 kHz and above 1 kHz. A much larger intersubject variability was found in the experimental group. The mean intersubject standard deviation was 4.4 dB in the experimental group as contrasted with 2.2 dB in the control group. Neither the equivalent ear canal volume nor the perforation size appeared to be correlated with the degree of RECD reduction over lower frequencies. These results strongly suggest the need for individual RECD measurements, rather than using the average normal RECD, to appropriately compensate for the reduced transmission of lower-frequency sounds in fitting hearing aids for patients with ear drum perforations.     

Effect of earmold fit on predicted real ear SPL using a real ear to coupler difference procedure

OBJECTIVES: The goal of Experiment I was to quantify the SPL entering the ear canal via a secondary pathway created by a vent in the earmold and/or a slit leak around the earmold. The goal of Experiment II was to determine the validity of a real ear to coupler difference (RECD) procedure under conditions that are likely to produce errors (e.g., when hearing aid gain in the low frequencies is minimal and large negative RECD values occur as a result of venting or a loosely fitting earmold). DESIGN: In Experiment I, the SPL entering the ear via the secondary pathway was measured in 61 hearing-impaired children and 13 normal-hearing adults. In Experiment II, traditional probe microphone measures of real ear SPL were compared to the SPL predicted using the RECD procedure in five normal-hearing adults with loosely fitting earmolds. RESULTS: Results of Experiment I indicated that sound entered the ear canal unattenuated at 250 and 500 Hz, regardless of earmold fit, vent size, or subject age. In Experiment II, the largest differences between traditional probe microphone measures of SPL and predicted measures were noted when hearing aid gain was 0 dB and large negative RECD values were present. When hearing aid gain was minimal and the RECD was in the -10 to -22 dB range, predicted values underestimated the real ear SPL by an average of 14 dB. CONCLUSIONS: Although the results of this study apply only to a limited range of conditions found in clinical practice, in those cases, the errors may influence clinical decisions about the type of hearing aid fitted and the amount of gain provided. Potential solutions to this problem are discussed.     

The influence of RECD transducer when deriving real-ear sound pressure level

OBJECTIVE: The main aim of the present study was to compare the derived and directly measured real-ear hearing instrument performance for a range of commonly used hearing instruments. A secondary aim was to compare the real-ear to coupler difference (RECD) measured using the ER-3A insert earphone and a selection of hearing instruments. DESIGN: The real-ear SPL was measured for four models of hearing instrument in 20 adult participants using an Audioscan RM500 real-ear system. This was compared with the derived real-ear SPL obtained by adding the RECD (measured using the ER-3A insert earphone) to the 2-cc coupler response of each hearing instrument. Measurements were made at 1/12 octave intervals from 0.2 to 6 kHz, using both the HA1 and HA2 2-cc coupler. In addition, the RECD was measured using four models of hearing instrument for comparison with the ER-3A insert earphone values. RESULTS: The procedures were very reliable with mean differences on retest of less than 1 dB. Repeated-measures analysis of variance revealed statistically significant differences between the measured and derived real-ear SPL (p < 0.001) for several models of hearing instrument. The derived responses using the HA1 coupler yielded good accuracy, whereas the HA2 yielded less accuracy. For three models of hearing instrument, the maximum difference was between 5 and 10 dB when using the HA2 coupler. The mean RECD measured with the ER-3A insert earphone and HA2 coupler was not always equivalent to the RECD measured with the hearing instruments. CONCLUSIONS: The accuracy of the derived real-ear response obtained using an RECD, measured with an ER-3A insert earphone, is very good when an HA1 is used for the coupler component of the RECD. The accuracy diminishes somewhat with the HA2 coupler, especially for undamped hearing instruments. The accuracy of the derived real-ear response is very good when the RECD is measured using the hearing instrument and the HA1 or the HA2 coupler.     

Measuring the real-ear to coupler difference transfer function with an insert earphone and a hearing instrument: are they the same?

OBJECTIVE: The purpose of the study was to compare the real-ear to coupler difference (RECD) measured with an insert earphone and two models of hearing instrument. DESIGN: The RECD was obtained from one ear of 18 normal-hearing subjects by subtracting the 2-cc coupler (HA1 and HA2) response from a real-ear aided response, using a conventional probe-tube microphone system. The measurements were made with a conventional ER-3A earphone and two models of behind-the-ear hearing instrument (Unitron US80, Unitron, Kitchener, Canada; and Widex Diva, Widex, Vaerloese, Denmark). RESULTS: The procedures were very reliable, with mean differences on retest of less than 1 dB. There were statistically significant differences between the mean RECDs obtained using an insert earphone compared with those obtained with each hearing instrument (p < 0.05). The differences were greatest when using the HA2 2-cc coupler. For example, the maximum difference in mean RECD between the insert earphone and the Widex Diva was 6 dB and 11 dB when using the HA1 and the HA2 2-cc coupler, respectively. CONCLUSIONS: The RECD is dependent on the acoustic impedance of the sound source, the coupling system, and the coupler and ear. The acoustic impedance may be different for an insert earphone and a given hearing instrument. Therefore, the RECD measured with an insert earphone may not always accurately represent the difference in performance of a hearing instrument measured in the real ear and the 2-cc coupler.     

四川地区成年人真耳-耦合腔差值分析

目的：了解四川地区成年人真耳耦合腔差值（RECD）的平均值。方法：对95例四川地区成年人进行双耳RECD测定．并进行性别及左右耳间的比较及与欧美地区成年人的RECD平均值比较。结果：四川地区与欧美地区成年人的RECD平均值差异有统计学意义。结论：在助听器验配过程中,使用RECD值时不能盲目采用欧美地区成年人的平均值标准。     

Perforation of the tympanic membrane and its effect on the real-ear-to-coupler difference acoustic transform function.

It is not always possible to undertake extensive real-ear measurements, especially in infants and young children. An alternative approach is to estimate the real-ear SPL by use of an acoustic transform function such as the real-ear-to-coupler difference (RECD). This may be used to estimate the real-ear sound pressure level (SPL) obtained from an insert transducer or a hearing instrument. The aim of the present study was to investigate the effects of tympanic membrane perforation on the RECD transform function. Subjects in the study comprised two groups of 12 individuals aged between nine and 65 years. One group of subjects had a tympanic membrane perforation and was recruited to the study before admission for myringoplasty. There was no evidence of middle ear pathology in the remaining subjects who comprised the control group. An RECD transform function for an insert transducer was measured on each subject using the standard clinical protocol on the Audioscan RM500 real-ear measurement system. There was a statistically significant difference between the two groups; mean RECD transform value of the perforation group was 9-12 dB lower than the corresponding value in the control group at audiometric frequencies below 1.5 kHz. This difference is probably due to the perforation acting as a vent and allowing low-frequency acoustic energy to escape into the middle ear cavity. Use of an average RECD transform function to estimate real-ear SPL in subjects with a perforation will overestimate the SPL reaching the tympanic membrane. As a result, the derived real-ear SPL obtained by use of either an insert transducer or a hearing instrument will be overestimated. This has implications for the selection and verification of a hearing instrument. The difference in the mean RECD transform function between the control group and subjects with a tympanic membrane perforation supports the use of individually measured RECD values wherever possible.     

Impact on hearing aid targets of measuring thresholds in dB HL versus dB SPL

Audiometric measurements are traditionally made in dB HL, which by definition are specified relative to the sound pressure level (SPL) in a coupler. Real-ear dB SPL is then estimated by applying an average ear transform to the coupler value. However, individual variation in ear canal acoustics and variations in transducer placement strongly influence the dB SPL of signals arriving at the eardrum. In this paper, data from 1814 ears are presented, showing that the distribution of eardrum dB SPL for a fixed signal level varies across ears and across frequency by as much as 40 dB. The impact of this variance upon hearing aid targets computed with the NAL-NL1 fitting algorithm is examined by comparing the targets obtained from using an average transform with those obtained when audiometric data in dB SPL are obtained by applying individually measured real-ear-to-coupler difference (RECD) values to dB HL thresholds. The impact can be considerable.     

单、双耳阈上不同给声强度对言语识别率的影响

目的研究阈上不同强度测试声对双耳及左、右耳言语识别率的影响方法在隔声环境中，测试听力正常青年左右耳的听阈，以阈上10dB，20dB，30dB的言语声测试言语识别率，比较双耳及左．右单耳在阈上不同强度测试声分别获得的富语识别率。结果单耳阈上10dB，20dB，30dB测试声之间的言语识别率差异有显著性；阈上10dB，20dB，30dB给声，左、右单耳之间富语识别率差异无显著性；双耳阈上20．30dB给声与阈上10dB给声的富语识别率差异有显著性；阈上10dB，20dB的测试声，双耳与左．右单耳的言语识别率差异有显著性，阈上30dB测试声双耳与左．右单耳的言语识别率差异无显著性（p〉0．05）。结论随着声音强度的增加，左．右单耳，双耳的言语识别率均显著提高。在阈上10dB，20dB时，双耳聆听的富语识别率较单耳有明显优势。而在阈上30dB时，双耳聆听的言语识别率优势不明显，未发现有双耳聆听干扰现象。     

Evaluation of a probe-tube insertion technique for measuring the real-ear-to-coupler difference (RECD) in young infants

A common strategy for measuring the real-ear response of the real-ear-to-coupler difference (RECD) in the pediatric population is to insert a probe-tube separately from the eartip. This strategy is at times difficult to implement while attempting to obtain the measurement from a young infant. An RECD probe-tube insertion technique that involves connecting the probe-tube to an eartip with plastic film for simultaneous insertion was examined on 30 infants. Repeated measurements were completed on each infant to obtain within-session test-retest reliability data. Probe-tube insertion depth was also examined across participants to provide a guideline for the infant population. Findings indicate that reliable RECD values can be obtained in infants when the probe-tube is extended approximately two to four millimeters (mm) beyond the eartip or 11 mm from the entrance to the ear canal. Clinical implications of this work are discussed.     

The order of testing effect in otoacoustic emissions and its consequences for sex and ear differences in neonates

The amplitude values of transient-evoked otoacoustic emissions, recorded from a large sample of neonates, were used to examine the asymmetry between ears tested and the differences due to the sex of the subject. Whilst the sex difference, with females having larger responses than males, has been a consistent finding in previous reports, the right/left ear difference, with the right ear giving a larger response than the left, has produced variable results that differed between laboratories. In this study, the sex difference was confirmed with females giving a 1.2 dB greater response than males. It was not affected by the age of the neonate. A significant effect of test order was found. The measured right/left difference was enhanced when the right ear was tested first but was diminished when the left ear was tested first. If the left ear is tested first then the measured right/left difference would be about 0.5 dB whereas, if the right ear is tested first, the measured right/left difference would be about 1.5 dB. When male/female comparisons were made for right and left ears separately and for the same ear tested first, the sex differences were the same for all four conditions. The sex and right/left differences have been confirmed as statistically significant effects and the order effect could explain the discrepancies and variability of the right/left differences reported in the literature.     

Probe-tube microphone measures in patients with open-mastoid surgery: real-ear-to-coupler differences and real-ear unaided responses

Real-ear-to-coupler differences (RECDs) and real-ear unaided responses (REURs) were measured using a probe-tube microphone system in 15 patients who underwent open mastoid surgery. The results show that RECDs are significantly smaller at higher frequencies (1.5, 2.0, 3.0, 4.0 and 6.0 kHz) in mastoid ears. The intrasubject variability of RECDs measures in these patients is on average 2.6 dB larger than for controls. For REURs, mastoid surgery significantly reduced the mean peak resonant frequency without affecting the amplitude and bandwidth. In operated ears, mean resonant frequency is by a factor of 1.4 lower than that for normal ears. Reduced responses (negative gains) at frequencies above the resonance peak occurred in 7 out of the 15 patients. These reduced responses corresponded to the smaller RECD at the middle and high frequencies. The results support the need for individual RECD measures to be made in operated ears instead of using average values from normal subjects. Otherwise, real-ear measures of the aided response should be made for each patient with open-mastoid cavity and the fitting should be done in terms of the target response at the eardrum rather than by defining a target insertion gain.     

Use of the 'real-ear to dial difference' to derive real-ear SPL from hearing level obtained with insert earphones

The electroacoustic characteristics of a hearing instrument are normally selected for individuals using data obtained during audiological assessment. The precise inter-relationship between the electroacoustic and audiometric variables is most readily appreciated when they have been measured at the same reference point, such as the tympanic membrane. However, it is not always possible to obtain the real-ear sound pressure level (SPL) directly if this is below the noise floor of the probe-tube microphone system or if the subject is unco-operative. The real-ear SPL may be derived by adding the subject's real-ear to dial difference (REDD) acoustic transform to the audiometer dial setting. The aim of the present study was to confirm the validity of the Audioscan RM500 to measure the REDD with the ER-3A insert earphone. A probe-tube microphone was used to measure the real-ear SPL and REDD from the right ears of 16 adult subjects ranging in age from 22 to 41 years (mean age 27 years). Measurements were made from 0.25 kHz to 6 kHz at a dial setting of 70 dB with an ER-3A insert earphone and two earmould configurations: the EAR-LINK foam ear-tip and the subjects' customized skeleton earmoulds. Mean REDD varied as a function of frequency but was typically approximately 12 dB with a standard deviation (SD) of +/- 1.7 dB and +/- 2.7 dB for the foam ear-tip and customized earmould, respectively. The mean test-retest difference of the REDD varied with frequency but was typically 0.5 dB (SD 1 dB). Over the frequency range 0.5-4 kHz, the derived values were found to be within 5 dB of the measured values in 95% of subjects when using the EAR-LINK foam ear-tip and within 4 dB when using the skeleton earmould. The individually measured REDD transform can be used in clinical practice to derive a valid estimate of real-ear SPL when it has not been possible to measure this directly.     

Dichotic sentence identification test in Portuguese: a study in young adults

IntroductionAmong the currently-applied auditory processing tests, dichotic listening tests have been widely used, since they allow investigating the hemispheric and inter-hemispheric function and their respective skills to process the received auditory information.ObjectiveTo obtain normality reference measures with the new dichotic sentence identification test in right-handed adults with normal hearing.MethodsQuantitative, observational, cross-sectional study. 72 subjects were assessed, aged 19–44 years, right-handed, with normal hearing, without hearing complaints. The dichotic sentence identification test consists of different lists of sentences, which were combined two by two and presented at the same time, using earphones in both ears, at 50 dB Sensation Level. The test was applied in four stages: training of the 3 stages, free attention, right and left directed attention, thus evaluating different auditory skills.ResultsIn the free attention task, the average percentage of correct answers in the right ear was 93.59% and in the left ear 86.06%, with a statistically significant difference between the ears, with an advantage for the right ear. In the directed attention task, the average percentage of correct answers was 99.37% in the right ear and 98.8% in the left ear, with no statistical difference between the ears.ConclusionIt is suggested, as a normality reference for the stage of free attention, 90%–100% for correct answers for the right ear and for the left ear, from 80% to 100%. When there is asymmetry between the ears, differences of up to 20% are expected, with an advantage for the right ear For the directed attention stage, the expected normality reference values ??are 100% for the right ear and for the left ear, with no asymmetry between the ears; however, if it occurs, a difference of 10% is expected between the ears, with an advantage for the right ear.     

Performance of custom-fit versus fixed-format hearing aids for precipitously sloping high-frequency hearing loss

This study compared the real-ear response provided by custom-fit hearing aids to the closest matching fixed-format disposable hearing aids in patients with precipitous high-frequency hearing loss. Laboratory and field measures of aided performance were obtained to compare patient performance with the custom-fit and fixed-format hearing aids. In addition, coupler versus real-ear response differences were compared for the two hearing aid types. The results revealed that relatively close approximations to the real-ear aided responses of the custom-fit instruments were possible for most participants using seven fixed acoustic formats. No significant differences in mean performance between the two instrument types were observed for aided speech recognition or field ratings of aided performance, although mean patient satisfaction was lower for the disposable hearing aids. The real-ear to coupler difference was greater for the disposable hearing aid than for the custom-fit instruments, presumably owing to its deeper insertion into the ear canal.     

Transient evoked otoacoustic emissions (TEOAEs) in new-borns: normative data.

OBJECTIVE: Early diagnosis and rehabilitation of congenital hearing loss are mandatory in order to achieve a satisfactory linguistic and cognitive development. A universal hearing screening in order to identify congenital hearing losses before 3 months of age is required. METHODS: TEOAEs are an easy to perform, short lasting, not invasive and low-cost test with a high sensitivity. 320 at term new-borns (640 ears) without any risk factor for hearing loss underwent TEOAEs. The new-borns were screened 3 days after birth. Those who failed the first test were retested when possible before the discharge from the hospital. ABR was performed 3 months later in cases who failed TEOAE. RESULTS: The median TEOAE sampling time was 98 s, the median test duration was 14 min. The mean stimulus amplitude was 80 dB peSPL in the left ear and 81 dB peSPL in the right ear, noise levels within the external meatus during sampling were 44 dB SPL on the right ear and 43 dB SPL on the left one, noise contained within the response (A-B difference) was 8.65 dB SPL in the left ear and 8.74 dB SPL in the right ear, mean TEOAEs amplitudes were 21.49 dB SPL and 21.78 dB SPL in the right and left ear respectively, the mean lower and upper limit of the spectrum being 678 and 5720 Hz. According to these criteria 494/640 ears (77.2%) passed the test at the first recording, while TEOAEs resulted to be absent in 146/640 ears (22.8%). A retest was performed successfully before the discharge from the Hospital in 30/640 ears (4.7%). An ABR recording within the third month of life was scheduled as out-patient in the 58 new-borns (116 ears, 18.2%) who failed the test. 18 of them (36 ears, 5.6%) did not complete the program, 19 new-borns (38 ears, 11.8%) showed a normal ABR, while two new-borns (four ears, 0.6%) failed ABR after 3 months. A second ABR performed after 6 months was normal. CONCLUSIONS: TEOAEs recording seems at now the test of choice for a universal hearing screening. However, a greater standardization of criteria both in performing the test and in evaluating the results is needed.