Directional Microphone Research Articles

Electroacoustic analysis of a directional moving-coil microphone using combined lumped-parameter models and BEM

This article presents a lumped-parameter model combined with external sound pressure field simulation, based on the boundary element method (BEM) for utilization in a directional microphone. A study about microphone capsule of a typical handheld moving-coil microphone with hyper-cardioid pattern has been conducted. In the BEM simulation, a simplified 3D model of the capsule that met sound waves which radiated from a point sound source has been taken into account. The blocked average pressure at the openings of the capsule is used to drive the lumped element equivalent circuit model. Through the model, the sensitivity, directivity, and impedance of the microphone were analyzed. Hence, the proximity effect is observed and discussed. To verify our simulation, the microphone characteristics were experimentally measured by B&K devices with SoundCheck software in an anechoic chamber. The simulation data are in good agreement with the measurement data at low and medium frequencies below 13 kHz, and there were larger errors at higher frequencies, which may indicate that the lumped parameters is less applicable at higher frequencies. The proposed method gains more precise and comprehensive prediction for the microphone characteristics, which therefore could be utilized in optimizing the choice of materials and size of the microphone capsule design.

A bio-inspired optical directional microphone with cavity-coupled diaphragms.

A bio-inspired acoustic sensor for sound source localization is presented, mimicking the internally coupled ears found in many terrestrial vertebrates and insects. It consists of two aluminum diaphragms coupled by a U-shaped cavity and detected by a low-coherence fiber optic interferometer system. A large-scale prototype with a center-to-center separation of 1″ is fabricated and experimentally demonstrated to amplify the interaural phase difference by a factor of 2 to 4 for a wide frequency range (0.5-2 kHz), which agrees well with simulation. This work presents a mechanism of using cavity-coupled diaphragms to develop acoustic sensors for sound source localization.

Influence of Material Properties on Tire/Road Noise for Non-destructive Pavement Condition Assessment

With the purpose of using tire/road noise for pavement condition assessment as a non-destructive test method, an investigation on the influence of pavement material characteristics on tire/road noise is conducted. The acoustic data is collected by a directional microphone mounted behind the rear tire on the passenger’s side of a test vehicle, driving over different sections of pavements with different material properties. The tire/road noise under 2000 Hz is extracted to investigate how it is influenced by the pavement features, such as macrotexture, porosity, top-layer thickness, and top-layer stiffness. The macrotexture, which mainly reflects pavement friction, exhibits high relevance to the tire/road noise below 1000 Hz. The top-layer stiffness of pavement could be distinguished from the sound pressure level at peak frequency between 700 ∼ 1300 Hz, the larger stiffness coming with higher amplitude of sound pressure level (SPL) at peak frequency. The results show high potential to assess pavement friction by the tire/road noise starting from macrotexture measurement. Moreover, the consistency of paving quality or sudden change of pavement subsurface structure can be recognized by looking into the spectrum features at peak frequency area of tire/road noise.

EXPERIMENTAL INVESTIGATIONS OF THE INFLUENCE OF SCREENS AND PROTECTIVE EQUIPMENT ON THE LEVEL OF ACOUSTIC SIGNAL IN A ROOM WITH GLASS AND METAL PLASTIC

In the digital stage of world development, information is constantly expanding its facets. That is why the exchange of information is a leading component of constant change in life. Although humanity is gradually moving to the use of electronic technology, acoustic information still plays a key role in information circulation. This applies to official communication in public institutions up to the highest level, business contacts in commercial structures and private communication between people. The process of transmitting information in acoustic form has dangerous consequences. The use of appropriate devices, such as directional acoustic microphones or technical intelligence acoustic antennas, which may be outside the scope of the information activity, makes it possible to obtain unauthorized information that should not reach third parties. Therefore, the task of detecting and protecting information leakage channels, including acoustic ones, is gaining a new degree of importance every day. The protection of the premises or building, where acoustic information regularly circulates, provides a set of organizational and technical measures and means of protection of information circulation, taking into account the peculiarities of the location and arrangement of the object. This study involves the study of the dependence of the level of the acoustic signal on ways to prevent leakage of information through the acoustic channel, which includes vibration noise by means of technical protection and coverage of improvised materials (shielding) of enclosing structures of information activities (OID). The experiment determines the degree of influence of density, sound-absorbing properties of materials and their combinations on acoustic oscillations, the source of which is in the OID. The object of the study was a basic room, where the enclosing structures are walls with windows and doors, ceiling and floor. It is also worth noting that the acoustic signal measurements were not performed in complete silence, which directly affected the accuracy of the results. This step was taken in order to best reproduce the conditions in which criminals often work.

Symmetrical and asymmetrical directional benefits are present for talkers at the front and side

Objective The purpose of the study was to examine the effects of symmetrical and asymmetrical directional microphone settings on speech recognition, localisation and microphone preference in listening conditions with on- and off-axis talkers. Design A within-subjects repeated-measure evaluation of three hearing aid microphone settings (bilateral omnidirectional, bilateral directional, asymmetrical directional) was completed in a moderately reverberant laboratory. An exploratory analysis of the potential relationship between microphone preference and unaided measures was also completed. Study Sample Twenty adult listeners with mild to moderately severe bilateral hearing loss participated. Results The directional and asymmetric microphone settings resulted in equivalent benefits for sentence recognition in noise, word recall, and localisation speed regardless of the speech loudspeaker location (on- or off-axis). However, localisation accuracy was significantly worse with the asymmetric fitting than the directional setting when speech was presented from the rear hemisphere. Listeners who always preferred directional microphones had significantly poorer unaided speech recognition than those who preferred the omnidirectional setting for one or more listening condition. Conclusions Benefits from directional and asymmetric processing were small in the current study, but generally similar to each other. Unaided speech recognition in noise performance may have utility as a clinical predictor of preference for directional processing.

METHODS OF COUNTERING INTELLIGENCE USING SMALL-SIZED UNMANNED AERIAL VEHICLES

Small-sized aircrafts are increasingly used for espionage or intelligence. This is due to their small size, which gives them the advantage of being unnoticed. Easily carried in a backpack or bag, they can be launched almost anywhere in the world. Drones easily provide the collection of useful information with the help of technical means installed on them, it can be both cameras that have high resolution, and directional microphones that collect the recording of confidential information for tens of meters from the object of intelligence. All this poses a threat to the inhabitants of all countries of the world. In this article, a study is conducted on possible methods for detecting small-sized aircrafts, general effectiveness of these methods is evaluated, and it’s concluded that passive radar is a promising method of countering and detecting unmanned aerial vehicles.

Directional Sound Sensor With Consistent Directivity and Sensitivity in the Audible Range

Inspired by the human cochlea, we propose a directional sound sensor using a resonator array to overcome the limitations of existing directional microphones. The proposed sensor consists of multiple cantilevers that respond to different resonance frequencies and separately acquire signals to then combine them for sound sensing. The directionality of the cantilevers is bipolar (figure-of-8) because a signal proportional to the input sound’s pressure gradient is generated. We adopt multimode resonance to cover the wide frequency range of 100-8,000 Hz using few resonators. A wide-bandwidth (low-quality-factor) trenched cantilever is used to obtain a flat frequency response. Bidirectional sound sensors are tapered to achieve acoustic beamforming by simple signal processing. The directional characteristics can be easily changed according to the weighted sum of the signals acquired from a pair of sensors. We demonstrate that ambient noise can be effectively suppressed through beamforming to acquire the desired signal using the proposed sensor. [2021-0012]

Tracking mass removal of portable laser ablation sampling by its acoustic response

If the sample cannot be brought to the lab for sampling, then the sampling needs to be done at the sample location. The portable laser ablation (pLA) system is one of the candidates to address this challenge, as it is a powerful tool for field deployable sampling of solids with the benefits of laser based analysis methods. However, sampling in the field is not always as convenient as in a defined laboratory setting and requires a neat prior method development. In the field, the evaluation of the sampling performance is not straightforward with current hardware. During mass removal by (p)LA, an acoustic pressure wave is formed for every individual LA event. In order to track these signals, a directional microphone was integrated into the handheld pLA-module. This allowed the monitoring of the acoustic signal close to the ablation site to count and quantify LA events from each individual pulse. In order to monitor mass removal and acoustic response quasi-simultaneously, the pLA sampling device was coupled to an ICPMS via a gas-exchange device (GED). Performance was investigated using various samples. Discrepancies were observed between samples with low and high ablation thresholds. For samples with low ablation thresholds, e.g. metals, the acoustic signal was mainly influenced by the laser fluence at the ablation site and not by the amount of mass removal. Comparatively, when ablating samples with high ablation thresholds, such as glasses and minerals, these variations were less pronounced, resulting in the observation of a linear relationship. Consequently, this allows the use of the acoustic energy as a measure of the amount of mass removal. In summary, results show that this approach enables a straightforward way to track all actual ablation events during on-site sampling and allows an instant evaluation of the ablation performance, thereby reducing unsuccessful sampling sessions.

Coupled D33 Mode-Based High Performing Bio-Inspired Piezoelectric MEMS Directional Microphone

Microelectromechanical system (MEMS) directional microphones have been identified as having use in multi-projected virtual reality applications such as virtual meetings for projecting cameras. In these applications, the acoustic sensitivity plays a vital role as it biases the directional sensing, signal-to-noise ratio (SNR) and self-noise. The acoustic sensitivity is the multiplied outcome of the mechanical sensitivity and the electrical sensitivity. As the dimensions are limited in MEMS technology, the improvement of the acoustic sensitivity by reflecting the mechanical as well as electrical domains is a challenge. This paper reports on a new formation of the D33 mode, the coupled D33 mode, based on piezoelectric sensing to improve the acoustic functionalities. The unique advancement of the proposed D33 mode is that it allows multiple spans of the regular D33 mode to perform together, despite this increasing the diaphragm’s dimensions. At a reduced diaphragm size, the orientation of the coupled D33 mode realizes the maximum conversion of the mechanical deflection into electrical sensitivity. The significance of the proposed D33 mode in comparison to the regular D33 mode is simulated using COMSOL Multiphysics. Then, for a proof–of–concept, the experimental validation is carried out using a piezoelectric MEMS directional microphone inspired by the ears of the fly Ormia ochracea. In both ways, the results are found to be substantially improved in comparison with the regular approach of the D33 mode, showing the novelty of this work.

The Effect of Cognition on the Aided Benefit in Terms of Speech Understanding and Listening Effort Obtained With Digital Hearing Aids: A Systematic Review.

Purpose Hearing aids are the primary rehabilitation devices used to compensate for presbycusis, though large intersubject variability in hearing aid benefit has been reported. This systematic review aimed to investigate how intersubject differences in cognition could influence the aided benefit for speech understanding and listening effort with bilateral digital hearing aids. Method Articles were selected through systematic searches in MEDLINE, Embase, Central, and reference lists. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Results The initial search resulted in 1,092 unique hits, of which 16 were included. The effect of cognition on the aided benefit in terms of speech understanding and listening effort was examined in 12 and four studies, respectively. The aided speech and listening effort benefit obtained from hearing aid use in general or from a specific digital feature (i.e., microphone directionality, noise reduction, amplitude compression, and frequency compression) was associated with four cognitive functions (i.e., working memory, processing speed, selective attention, and executive functions). Conclusions Hearing aid users with poorer cognitive functioning derived more aided benefit in terms of speech understanding from hearing aid settings facilitating the matching process between the incoming auditory signal and representations stored in long-term memory. However, since the number of included studies was limited, this trend should be interpreted with caution. Supplemental Material https://doi.org/10.23641/asha.13626509.

Individual Differences Offer Insight Into Clinical Recommendations for Directional and Remote Microphone Technology Use in Children.

Purpose This study sought to evaluate the effects of common hearing aid microphone technologies on speech recognition and listening effort, and to evaluate potential predictive factors related to microphone benefits for school-age children with hearing loss in a realistic listening situation. Method Children (n = 17, ages 10-17 years) with bilateral, sensorineural hearing loss were fitted with hearing aids set to include three programs: omnidirectional, adaptive directional, and omnidirectional + remote microphone. Children completed a dual-task paradigm in a moderately reverberant room. The primary task included monosyllabic word recognition, with target speech presented at 60 dB A from 0° (front) or 180° (back) azimuth. The secondary task was a "go/no-go," visual shape-recognition task. Multitalker babble noise created a +5 dB SNR. Children were evaluated in two speaker conditions (front, back) using all three hearing aid programs. The remote microphone transmitter remained at the front speaker throughout testing. Speech recognition performance was calculated from the primary task while listening effort was measured as response time during the secondary task. Results Speech presented from the back significantly increased listening effort and caused a reduction in speech perception when directional and remote microphones were used. Considerable variability was found in pattern of benefit across microphones and source location. Clinical measures did not predict benefit patterns with directional or remote microphones; however, child age and performance with omnidirectional microphones did. Conclusions When compared to a traditional omnidirectional setting, the directional and remote microphone configurations evaluated in this study have the potential to provide benefit for some children and increase difficulty for others when used in dynamic environments. A child's performance with omnidirectional hearing aids could be used to better inform clinical recommendations for these technologies.

Hammering Sound Frequency Analysis to Fix an Acetabular Cup during Total Hip Arthroplasty: Clinical Trials and Biomechanical Studies

Failure during total hip arthroplasty may lead to bedridden of the elderly. Since the acetabulum cup fix in an anatomically deep region, failures, such as loosening and fracture, occur three times more frequently compared with failures of the stem fix in the femur. We investigated the possibility of evaluating whether fixation was acquired by frequency analysis of the hammering sound of implanting a cup into the acetabulum. The subjects were 11 patients (11 joints) who underwent total hip arthroplasty, biomechanical test materials, and orthopedic models. Surgeries and experiments were performed by orthopedists specialized in the hip. A system was constructed with a tablet PC and directional microphone, the peak frequency at which the amplitude reached the maximum was determined, and judgment processing (stable, unstable) of cup fixability was performed in real time. The stable maximum peak frequency observed in the clinical trials was 4.42 ± 4.02 kHz. The mean stable maximum peak frequency in the biomechanical tests was 4.46 ± 1.19 kHz in biomechanical test materials and 4.56 ± 2.02 kHz in orthopaedicmodels. When hammering was continued, the frequency leading to fracture decreased in both biomechanical test materials and orthopaedicmodels. In conclusion, in clinical trials and biomechanical studies, variation of the maximum peak frequency decreased when fixation was acquired and the frequency stabilized. It was suggested that this method can serve as a fixability evaluation method of acetabular cups because analysis can be performed in real time during surgery, for which prevention of intraoperative fracture can be expected.

Assessing Real-Life Benefit From Hearing-Aid Noise Management: SSQ12 Questionnaire Versus Ecological Momentary Assessment With Acoustic Data-Logging.

Purpose The purpose of this study was to investigate real-life benefit from directional microphone and noise reduction ("noise management" [NM]) processing using retrospective self-reports and smartphone-based ecological momentary assessments (EMAs) combined with logging of the acoustic environments. Method A single-blinded, counterbalanced crossover design was used. Eleven hearing-impaired adults were bilaterally fitted with behind-the-ear devices with NM either activated (NMON) or deactivated. For the retrospective self-reports, the short scale of the Speech, Spatial, and Qualities Hearing Scale questionnaire (SSQ12) was applied. For the EMAs, smartphone-based self-reports combined with hearing aid (HA)-based classifications of the listening environments ("soundscapes") experienced by the participants was used. To explore potential associations with the real-life data, two laboratory measures of aided speech recognition in noise were administered. Results The soundscapes in which the participants submitted their EMAs were representative of the soundscapes they experienced during normal HA use and of the soundscapes reported in the literature for older HA users. The SSQ12 and EMA scores both showed an overall benefit from NMON. The EMA scores, together with the logged acoustic data, revealed that this benefit was driven by NMON being preferred particularly in listening environments classified as "speech" or "speech in noise." The laboratory measures of aided speech recognition in noise were unable to predict the real-life data. Conclusions EMA combined with acoustic data-logging is suited for more targeted evaluations of real-life HA benefit. Advanced NM settings can provide subjective user benefits in specific listening situations.

Contactless diagnostics of the technical state of the valve mechanism of the internal combustion engine

The aim of the study is to analyze the possibilities of developing a contactless diagnostics system of the technical state of the valve mechanism, which excludes mounting sensors on the body of the diagnosed equipment, by using a directional microphone as a sensitive element. In order to test the proposed hypothesis, a directional microphone designed to measure the level of acoustic noise, sound pressure level and to obtain amplitude-frequency characteristics in the range of 10-10 kHz has been used. In the work, an experimental determination of the spectrum of the valve mechanism acoustic vibration and its comparison with the spectrum obtained from an accelerometer has been carried out; the principle of building an automated diagnostic system using a directional microphone has been formulated.

Why Ecological Momentary Assessment Surveys Go Incomplete: When It Happens and How It Impacts Data.

Ecological momentary assessment (EMA) often requires respondents to complete surveys in the moment to report real-time experiences. Because EMA may seem disruptive or intrusive, respondents may not complete surveys as directed in certain circumstances. This article aims to determine the effect of environmental characteristics on the likelihood of instances where respondents do not complete EMA surveys (referred to as survey incompletion), and to estimate the impact of survey incompletion on EMA self-report data. An observational study. Ten adults hearing aid (HA) users. Experienced, bilateral HA users were recruited and fit with study HAs. The study HAs were equipped with real-time data loggers, an algorithm that logged the data generated by HAs (e.g., overall sound level, environment classification, and feature status including microphone mode and amount of gain reduction). The study HAs were also connected via Bluetooth to a smartphone app, which collected the real-time data logging data as well as presented the participants with EMA surveys about their listening environments and experiences. The participants were sent out to wear the HAs and complete surveys for 1 week. Real-time data logging was triggered when participants completed surveys and when participants ignored or snoozed surveys. Data logging data were used to estimate the effect of environmental characteristics on the likelihood of survey incompletion, and to predict participants' responses to survey questions in the instances of survey incompletion. Across the 10 participants, 715 surveys were completed and survey incompletion occurred 228 times. Mixed effects logistic regression models indicated that survey incompletion was more likely to happen in the environments that were less quiet and contained more speech, noise, and machine sounds, and in the environments wherein directional microphones and noise reduction algorithms were enabled. The results of survey response prediction further indicated that the participants could have reported more challenging environments and more listening difficulty in the instances of survey incompletion. However, the difference in the distribution of survey responses between the observed responses and the combined observed and predicted responses was small. The present study indicates that EMA survey incompletion occurs systematically. Although survey incompletion could bias EMA self-report data, the impact is likely to be small.

The Benefit of Remote and On-Ear Directional Microphone Technology Persists in the Presence of Visual Information.

Both the Roger remote microphone and on-ear, adaptive beamforming technologies (e.g., Phonak UltraZoom) have been shown to improve speech understanding in noise for cochlear implant (CI) listeners when tested in audio-only (A-only) test environments. Our aim was to determine if adult and pediatric CI recipients benefited from these technologies in a more common environment-one in which both audio and visual cues were available and when overall performance was high. Ten adult CI listeners (Experiment 1) and seven pediatric CI listeners (Experiment 2) were tested. Adults were tested in quiet and in two levels of noise (level 1 and level 2) in A-only and audio-visual (AV) environments. There were four device conditions: (1) an ear canal-level, omnidirectional microphone (T-mic) in quiet, (2) the T-mic in noise, (3) an adaptive directional mic (UltraZoom) in noise, and (4) a wireless, remote mic (Roger Pen) in noise. Pediatric listeners were tested in quiet and in level 1 noise in A-only and AV environments. The test conditions were: (1) a behind-the-ear level omnidirectional mic (processor mic) in quiet, (2) the processor mic in noise, (3) the T-mic in noise, and (4) the Roger Pen in noise. In each test condition, sentence understanding was assessed (percent correct) and ease of listening ratings were obtained. The sentence understanding data were entered into repeated-measures analyses of variance. For both adult and pediatric listeners in the AV test conditions in level 1 noise, performance with the Roger Pen was significantly higher than with the T-mic. For both populations, performance in level 1 noise with the Roger Pen approached the level of baseline performance in quiet. Ease of listening in noise was rated higher in the Roger Pen conditions than in the T-mic or processor mic conditions in both A-only and AV test conditions. The Roger remote mic and on-ear directional mic technologies benefit both speech understanding and ease of listening in a realistic laboratory test environment and are likely do the same in real-world listening environments.

The impact of cochlear implant microphone settings on the binaural hearing of experienced cochlear implant users with single-sided deafness

ObjectiveCochlear implantation has become a well-accepted treatment option for people with single-sided deafness (SSD) and has become a clinical standard in many countries. A cochlear implant (CI) is the only device which restores binaural hearing. The effect of microphone directionality (MD) settings has been investigated in other CI indication groups, but its impact on speech perception in noise has not been established in CI users with SSD. The focus of this investigation was, therefore, to assess binaural hearing effects using different MD settings in CI users with SSD.MethodsTwenty-nine experienced CI users with SSD were recruited to determine speech reception thresholds with varying target and noise sources to define binaural effects (head shadow, squelch, summation, and spatial release from masking), sound localization, and sound quality using the SSQ12 and HISQUI19 questionnaires. Outcome measures included the MD settings “natural”, “adaptive”, and “omnidirectional”.ResultsThe 29 participants involved in the study were divided into two groups: 11 SONNET users and 18 OPUS 2/RONDO users. In both groups, a significant head shadow effect of 7.4–9.2 dB was achieved with the CI. The MD setting “adaptive” provided a significant head shadow effect of 9.2 dB, a squelch effect of 0.9 dB, and spatial release from masking of 7.6 dB in the SONNET group. No significant summation effect could be determined in either group with CI. Outcomes with the omnidirectional setting were not significantly different between groups. For both groups, localization improved significantly when the CI was activated and was best when the omnidirectional setting was used. The groups’ sound quality scores did not significantly differ.ConclusionsAdaptive directional microphone settings improve speech perception and binaural hearing abilities in CI users with SSD. Binaural effect measures are valuable to quantify the benefit of CI use, especially in this indication group.

Using the Repeat-Recall Test to Examine Factors Affecting Context Use.

The effect of context on speech processing has been studied using different speech materials and response criteria. The Repeat-Recall Test (RRT) evaluates listener performance using high context (HC) and low context (LC) sentences; this may offer another platform for studying context use (CU). This article aims to evaluate if the RRT may be used to study how different signal-to-noise ratios (SNRs), hearing aid technologies (directional microphone and noise reduction), and listener working memory capacities (WMCs) interact to affect CU on the different measures of the RRT. Double-blind, within-subject repeated measures design. Nineteen listeners with a mild-to-moderately severe hearing loss. The RRT was administered with participants wearing the study hearing aids under two microphone (omnidirectional vs. directional) by two noise reduction (on vs. off) conditions. Speech was presented from 0 degree at 75 dB sound pressure level and a continuous speech-shaped noise from 180 degrees at SNRs of 0, 5, 10, and 15 dB. The order of SNR and hearing aid conditions was counterbalanced across listeners. Each test condition was completed twice in two 2-hour sessions separated by 1 month. CU was calculated as the difference between HC and LC sentence scores for each outcome measure (i.e., repeat, recall, listening effort, and tolerable time). For all outcome measures, repeated measures analyses of variance revealed that CU was significantly affected by the SNR of the test conditions. For repeat, recall, and listening effort measures, these effects were qualified by significant two-way interactions between SNR and microphone mode. In addition, the WMC group significantly affected CU during recall and rating of listening effort, the latter of which was qualified by an interaction between the WMC group and SNR. Listener WMC affected CU on estimates of tolerable time as qualified by significant two-way interactions between SNR and microphone mode. The study supports use of the RRT as a tool for measuring how listeners use sentence context to aid in speech processing. The degree to which context influenced scores on each outcome measure of the RRT was found to depend on complex interactions between the SNR of the listening environment, hearing aid features, and the WMC of the listeners.

Application of Wireless Contralateral Routing of Signal (CROS) Technology in Unilateral Cochlear Implant Users

IntrodutionSingle cochlear implantation usually provides substantial speech intelligibility benefits but bilaterally deaf, unilaterally implanted subjects will continue to experience limitations due to the head shadow effect, like single-sided deaf individuals. In the treatment of individuals with single-sided deafness one option is contralateral routing of signal (CROS) devices, which constitute a non-surgical intervention of the second ear in unilaterally implanted individuals. MethodTwelve experienced adult cochlear implant (CI) users with Naída Q70 processor and the CROS device used in combination participated in the study. For the study three conditions were provided: CI only, omnidirectional microphone mode (CROS deactivated); CI plus CROS activated, omnidirectional microphone mode and CI plus CROS activated, UltraZoom mode. Speech reception thresholds were determined in quiet and noise. Subjective feedback regarding the practical usability of the CROS device and the perceived benefit were collected. ResultsThere was a 27.6% improvement in speech understanding in quiet and 32.5% improvement in noise when CROS device was activated. Using advanced directional microphones, a statistically significant benefit of 35% was obtained. The responses to the questionnaires revealed that the subjects perceived benefit in their everyday lives when using the CROS device with their CI. ConclusionThe investigated CROS device used by unilateral CI recipients in cases where bilateral implantation is not an option provides both subjective and objective speech recognition benefit when the signal is directed to the CROS device. Unfavourable conditions where speech is presented from the CI side and noise from the CROS side or diffusely were not included in this evaluation since the CROS device adds additional noise and performance is expected to decrease as has previously been shown.

Review of Self-Motion in the Context of Hearing and Hearing Device Research.

The benefit from directional hearing devices predicted in the lab often differs from reported user experience, suggesting that laboratory findings lack ecological validity. This difference may be partly caused by differences in self-motion between the lab and real-life environments. This literature review aims to provide an overview of the methods used to measure and quantify self-motion, the test environments, and the measurement paradigms. Self-motion is the rotation and translation of the head and torso and movement of the eyes. Studies were considered which explicitly assessed or controlled self-motion within the scope of hearing and hearing device research. The methods and outcomes of the reviewed studies are compared and discussed in relation to ecological validity. The reviewed studies demonstrate interactions between hearing device benefit and self-motion, such as a decreased benefit from directional microphones due to a more natural head movement when the test environment and task include realistic complexity. Identified factors associated with these interactions include the presence of audiovisual cues in the environment, interaction with conversation partners, and the nature of the tasks being performed. This review indicates that although some aspects of the interactions between self-motion and hearing device benefit have been shown and many methods for assessment and analysis of self-motion are available, it is still unclear to what extent individual factors affect the ecological validity of the findings. Further research is required to relate lab-based measures of self-motion to the individual's real-life hearing ability.