Normal-hearing Subjects Research Articles

Improved Music Perception after Music Therapy following Cochlear Implantation in the Elderly Population.

Background: Cochlear implantation (CI) and the accompanying rehabilitation has become a routine procedure in hearing restoration. Literature is sparse on elderly CI recipients focusing on the issue of age and their inclined auditory resolution, taking their diminished cognitive function into account, which requires adaptation of rehabilitation programs to overcome habituation. Objective: This study aims to show that a few adjustments in the therapy program towards age, mental, physical and auditory condition significantly improve music perception and overall auditory benefit, hence normal communication and social interactions can be found. Methods: Subjects implanted with a CI 65 years or older were compared to age-matched normal hearing subjects. Questionnaires were administered before and after ten music therapy sessions, to evaluate the participant’s music habits, the perception of sound quality and self-awareness and hearing implant satisfaction. Results: The greatest benefit was seen in participants’ gain in self-confidence and enjoyable music perception. Not only did the amount of listening to music increase, but also the impression of sound quality changed from poor up to good/very good sound quality. Conclusions: The music therapy was well accepted and resulted in beneficial subjective as well as objective outcomes towards hearing and music impression, hence improved quality of life.

Impact of Hearing Loss on Cognitive Abilities in Subjects with Tinnitus.

This study aimed to delineate the underlying pathophysiology of tinnitus between normal hearing and hearing loss subjects. The study aimed to characterize the neuropsychological aspects of two types of groups with tinnitus having variable hearing thresholds. The study sample comprises 75 subjects in a group with tinnitus and normal hearing, and 100 subjects in the tinnitus and hearing loss group. Subjects were matched to their respective controls for age, gender, and education levels. Subjects underwent verbal learning and memory tasks, visual learning, memory, listening attention, sustained visual attention, work memory, category control, phonemic mastery, response inhibition, and data processing velocity. Subjects having hearing loss with bilateral tinnitus showed significantly reduced performance on total learning capacity (P = 0.02) and recognition (P = 0.05) (Rey's auditory verbal learning test), auditory attention tasks, digit forward span test (DFST) (P = 0.03), digit span test score (P = 0.01), and working memory (P = 0.02) (digit backward span test). For response inhibition tasks and Stroop interference (P = 0.03), subjects with normal hearing with bilateral tinnitus displayed lower performance. This study proves a relationship between poor working memory, auditory memory, total learning capacity, and recognition due to hearing impairment in bilateral Tinnitus subjects. The study has substantial implications for effective assessment and treatment recommendations in hearing loss with bilateral tinnitus subjects.

A model of speech recognition for hearing-impaired listeners based on deep learning

Automatic speech recognition (ASR) has made major progress based on deep machine learning, which motivated the use of deep neural networks (DNNs) as perception models and specifically to predict human speech recognition (HSR). This study investigates if a modeling approach based on a DNN that serves as phoneme classifier [Spille, Ewert, Kollmeier, and Meyer (2018). Comput. Speech Lang. 48, 51-66] can predict HSR for subjects with different degrees of hearing loss when listening to speech embedded in different complex noises. The eight noise signals range from simple stationary noise to a single competing talker and are added to matrix sentences, which are presented to 20 hearing-impaired (HI) listeners (categorized into three groups with different types of age-related hearing loss) to measure their speech recognition threshold (SRT), i.e., the signal-to-noise ratio with 50% word recognition rate. These are compared to responses obtained from the ASR-based model using degraded feature representations that take into account the individual hearing loss of the participants captured by a pure-tone audiogram. Additionally, SRTs obtained from eight normal-hearing (NH) listeners are analyzed. For NH subjects and three groups of HI listeners, the average SRT prediction error is below 2 dB, which is lower than the errors of the baseline models.

Extended high-frequency bone conduction audiometry Calibration of bone conductor transducers in the conventional and extended high-frequency range

Objective To monitor ototoxicity, air conduction (AC) extended high frequency (EHF) thresholds can be measured up to 16 kHz. However, conductive hearing loss might influence these results. This is unfortunate because the EHF thresholds are important to follow the impact of ototoxic medication during therapy. Therefore a suitable bone conduction (BC) transducer and norm values for EHF BC measurements are needed. Design In this study three different BC transducers were used: the B71 (Radioear), the KH70 (Präcitronic), and the KLH96 (Westra). Hearing thresholds were measured from 0.125 to 16 kHz using AC transducers (Telephonics TDH39, Sennheiser HDA200), and BC thresholds from 0.25 to 8 kHz with the B71, and from 0.25 to 16 kHz with the KLH96 and KH70. Study sample 60 ears of 30 normal hearing subjects were measured. Results The KLH96 showed the highest output for the high frequencies, and distortion measurements were similar to the KH70. The results show that EHF measurements are possible using the KLH96 and KH70 bone conductors. Conclusion EHF BC measurements are reliable when using the KLH96 and KH70 bone conductors. The extended force sensitivity of the used artificial mastoid should be determined for a proper EHF BC calibration.

Investigating Bilateral Cochlear Implant Users' Localization of Amplitude- and Time-Panned Stimuli Produced Over a Limited Loudspeaker Arrangement.

The objective of this study was to investigate the localization ability of bilateral cochlear implant (BiCI) users for virtual sound sources produced over a limited loudspeaker arrangement. Ten BiCI users and 10 normal-hearing subjects participated in listening tests in which amplitude- and time-panned virtual sound sources were produced over a limited loudspeaker setup with varying azimuth angles. Three stimuli were utilized: speech, bandpassed pink noise between 20 Hz and 1 kHz, and bandpassed pink noise between 1 kHz and 8 kHz. The data were collected via a two-alternative forced-choice procedure and used to calculate the minimum audible angle (MAA) of each subject, which was subsequently compared to the results of previous studies in which real sound sources were employed. The median MAAs of the amplitude-panned speech, low-frequency pink noise, and high-frequency pink noise stimuli for the BiCI group were calculated to be 20°, 38°, and 12°, respectively. For the time-panned stimuli, the MAAs of the BiCI group for all three stimuli were calculated to be close to the upper limit of the listening test. The computed MAAs of the BiCI group for amplitude-panned speech were marginally larger than BiCI users' previously reported MAAs for real sound sources, whereas their computed MAAs for the time-panned stimuli were significantly larger. Subsequent statistical analysis indicated a statistically significant difference in the performances of the BiCI group in localizing the amplitude-panned sources and the time-panned sources. It follows that time-panning over limited loudspeaker arrangements may not be a useful clinical tool, whereas amplitude-panning utilizing such a setup may be further explored as such. Additionally, a comparison with the patient demographics indicated correlations between the results and the patients' age at time of diagnoses and the time passed between date of diagnosis and their implant surgeries.

Digits-in-noise test in Brazilian Portuguese: how demographic and socioeconomic variables influence normal-hearing subjects.

Verify how demographic and socioeconomic variables on the in-noise speech recognition threshold (SRT) from the digits-in-noise test (DIN) in Brazilian Portuguese influence normal-hearing subjects. Cross-sectional, prospective study. The convenience sample had 151 normal-hearing subjects between 12 and 79 years (mean=34.66) who underwent pure tone audiometry and digits-in-noise test with white noise using a sequence of three numbers in diotic stimulus (in-phase) on the same day. The DIN was performed using a Motorola Z3 Play smartphone with internet access and in-ear headphones. In-noise digit speech recognition threshold (SRT) was analyzed for gender, age, educational levels, and socioeconomic status. We used the non-parametric version of the Kruskal-Wallis and Mann-Whitney U tests to compare independent samples adopting a significance level of 5%. The mean SRT was -8.47 dBNA (SD -3.89) with a median of -9.6 dBNA. The SRT was proportionally inverse to educational levels and socioeconomic status and more negative (better) with lower age groups. Gender did not influence the DIN SRT. Age, educational levels, and socioeconomic status influenced the DIN threshold. These variables must be considered when analyzing DIN performance in Brazilian Portuguese in normal-hearing subjects.

Measuring and Modeling Cue Dependent Spatial Release from Masking in the Presence of Typical Delays in the Treatment of Hearing Loss.

In asymmetric treatment of hearing loss, processing latencies of the modalities typically differ. This often alters the reference interaural time difference (ITD) (i.e., the ITD at 0° azimuth) by several milliseconds. Such changes in reference ITD have shown to influence sound source localization in bimodal listeners provided with a hearing aid (HA) in one and a cochlear implant (CI) in the contralateral ear. In this study, the effect of changes in reference ITD on speech understanding, especially spatial release from masking (SRM) in normal-hearing subjects was explored. Speech reception thresholds (SRT) were measured in ten normal-hearing subjects for reference ITDs of 0, 1.75, 3.5, 5.25 and 7 ms with spatially collocated (S0N0) and spatially separated (S0N90) sound sources. Further, the cues for separation of target and masker were manipulated to measure the effect of a reference ITD on unmasking by A) ITDs and interaural level differences (ILDs), B) ITDs only and C) ILDs only. A blind equalization-cancellation (EC) model was applied to simulate all measured conditions. SRM decreased significantly in conditions A) and B) when the reference ITD was increased: In condition A) from 8.8 dB SNR on average at 0 ms reference ITD to 4.6 dB at 7 ms, in condition B) from 5.5 dB to 1.1 dB. In condition C) no significant effect was found. These results were accurately predicted by the applied EC-model. The outcomes show that interaural processing latency differences should be considered in asymmetric treatment of hearing loss.

Development and Psychometric Evaluation of Persian Dynamic Spatial Quick Speech-in-Noise Test in Adults with Normal Hearing

Background and Aim: Spatial hearing is a prerequisite for the proper function of the listener in complex auditory environments. In the present study, a Persian version of the dynamic spatial-quick speech in noise (DS-QSIN) has been developed with respect to all possible factors affecting the test and to run five lists for normal hearing subjects and assessment of reliability.
 Methods: To construct five new lists according to the original quick speech in noise (QSIN) test, we used frequent, familiar, and difficult words to construct unpredictable sentences. After determining the content and face validity of the sentences, 30 selected sentences were played using a DS-QSIN software for 35 subjects aged 18–25 years. The reliability of the test was assessed after repeating the test after two weeks.
 Results: According to expert judges, these 30 sentences showed acceptable content and face validity with the changes. The average signal-to-noise ratio (SNR) loss of five lists was –5.2 dB. No significant difference was seen between men and women in all lists. The results indicate no difference in the average SNR loss between the five lists. Regarding the reliability assessment, the test-retest correlation coefficient was 0.5 to 0.7 (p<0.05). The intra-class correlation coefficient between test-retest was statistically significant (p>0.001) and confirmed that the lists have high reliability and repeatability.
 Conclusion: DS-QSIN test showed good validity and reliability and can be helpful in diagnosis and selecting the best method for rehabilitation of people with a spatial hearing disorder.

ACOUSTIC STAPEDIAL REFLEX THRESHOLD IN NORMAL HEARING PARTICIPANTS IN SULAIMANI CITY

Background Acoustic stapedial reflex threshold (ASRT) is an objective, important test that can be included in a test battery along with behavioural pure tone audiometry and otoacoustic emissions to differentiate among middle ear, cochlear, and retro cochlear sites of the lesion. It can be used as a cross-check with a behavioural audiogram to increase confidence in the diagnosis. In most people with normal hearing thresholds and middle ear function, the acoustic stapedial reflex will be present at all frequencies and within an intensity range of 70-90 dB HL above the behavioural hearing threshold. Objectives To measure ASRT in participants with normal hearing thresholds in Sulaymaniyah city and to observe the effect of different parameters on the threshold. Patients and Methods The study was conducted on 200 participants (400 ears) who met inclusion criteria (110 males and 90 females); data were collected through visiting five different places with different age groups within three months duration. Participants were divided into three age groups (6-12 years), (13-18 years), (19 years and above).Only participants with normal otoscopic examination, normal pure tone audiometry, normal tympanogram, undergone through stapedial reflex threshold measurement, and the reflexes were elicited and recorded bilaterally by using tympanometer (Impedance meter) MAICO MI34 brand, single frequency 226 Hz of German-made model 2011. Results Mean ASRT measured in both ears was within the normal range of 70-90 dB HL above hearing threshold in both ipsilateral and contralateral pathways as Right ipsilateral (74.5 dB HL), right contralateral (76.9 dB HL), left ipsilateral (74.6 dB HL), and left contralateral (76.8 dB HL) above hearing thresholds. There was no significant difference between right and left ears according to ASRT (P-values > 0.05). There was no gender effect on ASRT (P-values > 0.05), while there was a significant effect of age on ASRT, especially in the adult population (P-values < 0.05). Conclusion A stapedial reflex threshold in normal hearing subjects was within normal range, different parameters as the side of ear and gender did not affect the threshold. In contrast, with advancing age amount of intensity needed to elicit the reflex increased.

Executive Functions and Deafness: Results in a Group of Cochlear Implanted Children

Objects: This study aimed to evaluate the Executive Function (EF) domains in a group of profoundly deaf children treated with cochlear implant (CI) in comparison to normal hearing (NH) children. The secondary aim was to evaluate the influence exerted by the age at cochlear implant activation on EFs. Materials and Methods: 32 children were enrolled into two groups: group A of 17 CI users with a mean age of 8.78 years and group B of 15 NH subjects with a mean age of 7.99 years (SD + 2.3). All subjects were tested using the following tests: the subtests for working memory of the neuropsychological evaluation battery for the developmental age (Batteria di valutazione neuropsicologica per l’età evolutive), inhibition and control of the impulsive response—CAF, and the tower of London test. Results: No children with CIs scored within the normal range in the tests administered for the evaluation of EF domains. The same scores were significantly lower when compared with scores obtained by NH children. Children with younger age at CI activation showed better executive performances in planning, working memory (backward digit span), and cognitive flexibility (categorical fluency). Conclusion: The results of this study highlight that cochlear implantation plays a role in improving hearing and consequently influences the development of EFs in deaf children.

Cerebral Representation of Sound Localization Using Functional Near-Infrared Spectroscopy.

Sound localization is an essential part of auditory processing. However, the cortical representation of identifying the direction of sound sources presented in the sound field using functional near-infrared spectroscopy (fNIRS) is currently unknown. Therefore, in this study, we used fNIRS to investigate the cerebral representation of different sound sources. Twenty-five normal-hearing subjects (aged 26 ± 2.7, male 11, female 14) were included and actively took part in a block design task. The test setup for sound localization was composed of a seven-speaker array spanning a horizontal arc of 180° in front of the participants. Pink noise bursts with two intensity levels (48 dB/58 dB) were randomly applied via five loudspeakers (–90°/–30°/–0°/+30°/+90°). Sound localization task performances were collected, and simultaneous signals from auditory processing cortical fields were recorded for analysis by using a support vector machine (SVM). The results showed a classification accuracy of 73.60, 75.60, and 77.40% on average at –90°/0°, 0°/+90°, and –90°/+90° with high intensity, and 70.60, 73.6, and 78.6% with low intensity. The increase of oxyhemoglobin was observed in the bilateral non-primary auditory cortex (AC) and dorsolateral prefrontal cortex (dlPFC). In conclusion, the oxyhemoglobin (oxy-Hb) response showed different neural activity patterns between the lateral and front sources in the AC and dlPFC. Our results may serve as a basic contribution for further research on the use of fNIRS in spatial auditory studies.

Cortical Processing of Binaural Cues as Shown by EEG Responses to Random-Chord Stereograms

Spatial hearing facilitates the perceptual organization of complex soundscapes into accurate mental representations of sound sources in the environment. Yet, the role of binaural cues in auditory scene analysis (ASA) has received relatively little attention in recent neuroscientific studies employing novel, spectro-temporally complex stimuli. This may be because a stimulation paradigm that provides binaurally derived grouping cues of sufficient spectro-temporal complexity has not yet been established for neuroscientific ASA experiments. Random-chord stereograms (RCS) are a class of auditory stimuli that exploit spectro-temporal variations in the interaural envelope correlation of noise-like sounds with interaurally coherent fine structure; they evoke salient auditory percepts that emerge only under binaural listening. Here, our aim was to assess the usability of the RCS paradigm for indexing binaural processing in the human brain. To this end, we recorded EEG responses to RCS stimuli from 12 normal-hearing subjects. The stimuli consisted of an initial 3-s noise segment with interaurally uncorrelated envelopes, followed by another 3-s segment, where envelope correlation was modulated periodically according to the RCS paradigm. Modulations were applied either across the entire stimulus bandwidth (wideband stimuli) or in temporally shifting frequency bands (ripple stimulus). Event-related potentials and inter-trial phase coherence analyses of the EEG responses showed that the introduction of the 3- or 5-Hz wideband modulations produced a prominent change-onset complex and ongoing synchronized responses to the RCS modulations. In contrast, the ripple stimulus elicited a change-onset response but no response to ongoing RCS modulation. Frequency-domain analyses revealed increased spectral power at the fundamental frequency and the first harmonic of wideband RCS modulations. RCS stimulation yields robust EEG measures of binaurally driven auditory reorganization and has potential to provide a flexible stimulation paradigm suitable for isolating binaural effects in ASA experiments.

Relative Weights of Temporal Envelope Cues in Different Frequency Regions for Mandarin Vowel, Consonant, and Lexical Tone Recognition.

Objectives: Mandarin-speaking users of cochlear implants (CI) perform poorer than their English counterpart. This may be because present CI speech coding schemes are largely based on English. This study aims to evaluate the relative contributions of temporal envelope (E) cues to Mandarin phoneme (including vowel, and consonant) and lexical tone recognition to provide information for speech coding schemes specific to Mandarin.Design: Eleven normal hearing subjects were studied using acoustic temporal E cues that were extracted from 30 continuous frequency bands between 80 and 7,562 Hz using the Hilbert transform and divided into five frequency regions. Percent-correct recognition scores were obtained with acoustic E cues presented in three, four, and five frequency regions and their relative weights calculated using the least-square approach.Results: For stimuli with three, four, and five frequency regions, percent-correct scores for vowel recognition using E cues were 50.43–84.82%, 76.27–95.24%, and 96.58%, respectively; for consonant recognition 35.49–63.77%, 67.75–78.87%, and 87.87%; for lexical tone recognition 60.80–97.15%, 73.16–96.87%, and 96.73%. For frequency region 1 to frequency region 5, the mean weights in vowel recognition were 0.17, 0.31, 0.22, 0.18, and 0.12, respectively; in consonant recognition 0.10, 0.16, 0.18, 0.23, and 0.33; in lexical tone recognition 0.38, 0.18, 0.14, 0.16, and 0.14.Conclusion: Regions that contributed most for vowel recognition was Region 2 (502–1,022 Hz) that contains first formant (F1) information; Region 5 (3,856–7,562 Hz) contributed most to consonant recognition; Region 1 (80–502 Hz) that contains fundamental frequency (F0) information contributed most to lexical tone recognition.

The development of linguistic stimuli for the Swedish Situated Phoneme test

AbstractThe speech perception ability of people with hearing loss can be efficiently measured using phonemic-level scoring. We aimed to develop linguistic stimuli suitable for a closed-set phonemic discrimination test in the Swedish language called the Situated Phoneme (SiP) test. The SiP test stimuli that we developed consisted of real monosyllabic words with minimal phonemic contrast, realised by phonetically similar phones. The lexical and sublexical factors of word frequency, phonological neighbourhood density, phonotactic probability, and orthographic transparency were similar between all contrasting words. Each test word was recorded five times by two different speakers, including one male and one female. The accuracy of the test-word recordings was evaluated by 28 normal-hearing subjects in a listening experiment with a silent background using a closed-set design. With a few exceptions, all test words could be correctly discriminated. We discuss the results in terms of content- and construct-validity implications for the Swedish SiP test.

ADHEAR device in bone conduction audiometry.

ADHEAR is a bone conduction hearing aid that uses an adhesive skin adapter. In the current study, the use of ADHEAR as an audiometric bone stimulator was investigated in normal-hearing subjects by comparing it to the standard Radio-Ear B71. Bone conduction thresholds of 15 normal-hearing subjects (aged 21-36 years) were measured four times in a randomized order, twice with the B71 and twice with the ADHEAR. There were no significant differences in test-retest reliability between the two devices. Subjectively rated comfort was better for the ADHEAR. The development of a specific audiometric adhesive bone stimulator may be warranted.

Cortical Auditory Evoked Potential in Adults With Cochlear Implants: A Comparison With Adults With Normal Hearing.

Background and ObjectivesTo examine the maturational status of the auditory cortex in adults with cochlear implants (CIs) using the latencies of the P1, N1, and P2 components of cortical auditory-evoked potentials (CAEPs).Subjects and MethodsA total of 25 adults with CIs and 25 age-matched, normal-hearing control subjects participated in this study. Specifically, patients with CIs were divided into three groups depending on their age of deafness onset: Group A comprised patients with prelingual deafness who had received CI during early childhood (n=7), Group B comprised patients with early childhood-onset, progressive deafness who had received CI during childhood (n=6), and Group C comprised patients with adult-onset deafness (n=12). The P1, N1, and P2 latencies of their CAEPs were then compared between CI patients and normal-hearing subjects.ResultsAll participants showed clear CAEP responses. P1 and N1 latencies in Group A and Group C patients were significantly longer than those in the control group. Meanwhile, Group B patients had significantly longer N1 and P2 latencies, as compared with those in the control group.ConclusionsPatients with prelingual deafness and those with early-childhood onset, progressive deafness who received CI developed primary and higher-order auditory areas postoperatively when they became adults. However, their auditory cortex maturational statuses seemed to be worse than that of normal-hearing individuals. Furthermore, adult patients with late-onset deafness might experience degenerative auditory cortex changes during the auditory deprivation period between deafness onset and cochlear implantation.

Pure tone discrimination with cochlear implants and filter-band spread

For many cochlear implant (CI) users, frequency discrimination is still challenging. We studied the effect of frequency differences relative to the electrode frequency bands on pure tone discrimination. A single-center, prospective, controlled, psychoacoustic exploratory study was conducted in a tertiary university referral center. Thirty-four patients with Cochlear Ltd. and MED-EL CIs and 19 age-matched normal-hearing control subjects were included. Two sinusoidal tones were presented with varying frequency differences. The reference tone frequency was chosen according to the center frequency of basal or apical electrodes. Discrimination abilities were psychophysically measured in a three-interval, two-alternative, forced-choice procedure (3I-2AFC) for various CI electrodes. Hit rates were measured, particularly with respect to discrimination abilities at the corner frequency of the electrode frequency-bands. The mean rate of correct decision concerning pitch difference was about 60% for CI users and about 90% for the normal-hearing control group. In CI users, the difference limen was two semitones, while normal-hearing participants detected the difference of one semitone. No influence of the corner frequency of the CI electrodes was found. In CI users, pure tone discrimination seems to be independent of tone positions relative to the corner frequency of the electrode frequency-band. Differences of 2 semitones can be distinguished within one electrode.

Energetic/informational masking and listening effort, as measured by electroencephalography and pupillometry

Measuring the listening effort exerted by an individual to understand speech under auditory masking conditions can provide vital information that is not available from accuracy scores alone. The goal of this study was to compare the amount of listening effort elicited in young, normal-hearing subjects during a noise masking condition producing primarily energetic masking (due to spectrotemporal overlap between target and maskers) versus during an intelligible speech masking condition producing a high degree of informational masking (additional masking due to listener uncertainty; e.g., target-masker confusions). Listening effort was measured simultaneously using two physiological metrics: alpha power (via electroencephalography) and pupil dilation. The target speech comprised 5-word matrix-style sentences in both conditions. The target was presented at 0 deg azimuth, and the maskers were presented at ± 45 deg azimuth. In each condition, the target-to-masker ratio was set at each subject’s 75% correct point on the psychometric function. Preliminary results suggest that the intelligible speech masking condition elicits a higher degree of listening effort than the noise condition. This finding is consistent with the view that greater effort is involved in ignoring acoustically and linguistically similar sources than highly dissimilar, low-information value sources. [Work supported by NIH K99DC018829.]

Effects of entropy in real-world noise on speech perception

Traditional tests of speech-in-noise perception use artificial background noise, leading to results that do not generalize to real-world scenarios. There is a significant need for improved ecological validity in laboratory and clinic speech-in-noise tests, particularly with respect to the types of noise used. However, the acoustic complexity and random nature of real-world noise poses challenges to its use and the interpretation of results. In this study, the complexity of real-world noise from 8 environments was systematically quantified in the time and frequency domains using entropy. Then, segments of noise distributed in entropy from low to high were extracted and combined with target sentences at fixed signal-to-noise ratios. Ten normal-hearing subjects were tested on 200 sentences-in-noise across the entropy distribution in both the time and frequency domains in a trial-by-trial design. Linear mixed effect models showed a significant effect of entropy in the time and frequency domains on number of words correct per trial. There was a systematic improvement in speech perception with increases in entropy variance in both time and frequency domains. Entropy in real-world noise affects speech perception even when the overall signal-to-noise ratio is fixed. Experiments using real-world noise should consider this effect in their design and interpretation.

Performance evaluation on three-forced choice pure tone audiometry in open space environment

In this report, we investigated the performance comparison of Three-Forced Choice (3AFC) with a pair of Bluetooth-connected active noise cancelling headphones and Two-Forced Choice (2AFC) in an audiological booth for audiometry examination. The procedure was essentially to generate mono pure tone on six different frequencies with adaptive loudness level to both left and right ear, respectively. The subject presented the pure tone, then he or she pressed a button. If it is right than the loudness level will be lowered until it is inaudible. This level was marked as the hearing threshold of the subject. We recruited 38 normal-hearing subjects who underwent to an audiology clinic for audiometry examination (using the gold standard, 2AFC technique). The recorded responses were statistically analyzed using non-parametric Wilcoxon test with Bonferroni correction. The audiometry results using the outdoor 3AFC method on 2000 Hz and 4000 Hz have mean-differences closer to ISO 226 accuracy reference for all 38 participants. These results suggested that the proposed technique may replace the gold standard.