Cardioid Microphones Research Articles

Validation of an absorption coefficient measurement technique using two cardioid microphones in any impedance tube

We have proposed a technique for measuring sound pressure and particle velocity using a combination of cardioid microphones and then applied it to obtain the acoustic absorption coefficient in a tube. So far, we have revealed that either using one cardioid microphone measured twice or using a pair of cardioid microphones measured once are both suitable for the measurement and that the calibration of the cardioid microphones is required. If the technique works correctly, this technique holds promise for measuring the acoustic absorption coefficient of various specimens in any tube and with any cardioid microphones. To validate the technique's effectiveness, we conducted experiments in multiple square-section wooden or round-section steel tubes, with specimens of glass wool and polyester terephthalate (PET) wool. As a result, this technique can provide accurate absorption coefficient measurements in any tube configuration.

Basic examinations of the sound transmission loss measurement using two cardioid microphones

This paper reports results of an experiment on sound transmission loss measurement using the C-C method. This method is an inexpensive and stable method for measuring the sound pressure, the particle velocity, and the sound intensity. The measurements are carried out in accordance with JIS A 1441-1:2007 based on ISO 15186-1:2000, and the C-C method is applied for measuring the sound intensity. Comparing the measured results with those of the sound pressure level difference method, comparable results are obtained above 250 Hz. Naturally, the precision of the measurements depends on the microphone calibration used in the C-C method. In this report, we employ two calibration methods using an acoustic tube and an anechoic chamber, and also exhibit comparison of the results obtained by these methods.

Performance bounds for source localization using tetrahedral microphones

The Cramér-Rao Bound (CRB) quantifies the minimum variance on a given unbiased estimation parameter. It can be used to derive a lower bound on source localization error for arrays, of which there are several probabilistic models in the literature. However, existing work only considers source localization using arrays of omnidirectional sensors. This presentation describes a model of the CRB as a minimum variance estimation of localization using multiple tetrahedral microphones which have cardioid microphones. Tetrahedral microphones are commonly used to record soundfields for virtual audio reproduction. The proposed method uses the cross spectral density of signals in order to calculate the CRB. This allows for more signal parameters to be included in the model. The model of the CRB was validated with an experiment in an anechoic room with a single sound source. Experimental results show the CRB forms a lower bound at low signal-to-noise ratios.

Calibration of a cardioid microphone for improving accuracy of normal impedance measurement in a tube

This paper presents a method for obtaining the complex amplitudes of both the sound pressure and the particle velocity of a cardioid microphone. These values are used as calibration values in a new technique for measuring the impedance of materials using a combination of two cardioid microphones placed in a tube. The previous technique, which utilized a single cardioid microphone placed in a tube, required two separate measurements to be taken - one with the microphone facing the specimen and one with the microphone facing away. This new method provides a more efficient approach to impedance measurement.

Spherical-sector harmonics domain processing for wideband source localization using spherical-sector array of directional microphones

The spherical microphone array can be uneconomical for applications where the sources arrive only from a known section of the sphere. For this reason, the spherical-sector harmonics was developed for processing spherical sector array. The orthonormal spherical sector harmonics (SSH) basis functions which accounts for the discontinuity arising from sectioning the sphere have been developed and shown to work for the array of omnidirectional microphones. In this work, the SSH basis functions are applied to far-field wideband sound source localization using spherical-sector array of first-order directional microphones (cardioid microphones). The array manifold interpolation method is used to produce the steered covariance matrix and the MUSIC algorithm applied for the direction of arrival estimation. The root-mean-square error performance of this spherical-sector array of the first-order cardioid microphones is compared against that of the omnidirectional microphones for different directions and signal-to-noise ratio.

Livestreamed cross-institutional hybrid simulations on healthcare inequality: a time, cost and environmentally friendly opportunity for large group learning?

Students intercalating in BSc Urgent and Emergency Care/BSc Critical Care degrees undertake placements in 32 NHS Trusts across the UK. A collaborative simulation day was planned between the University and a geographically distant hospital, aiming to explore bias within healthcare. Inequality has been examined through simulation previously and recommendations exist on maximising simulation effectiveness [1]. A hybrid simulation day took place with 11 students present ‘in-situ’ and 49 remote students across the UK joining a livestream. High-definition cameras provided multi-angle simulation views plus a patient monitor with separate audio from ceiling-mounted boundary microphones. A webcam and cardioid microphone captured the debriefing. The free programme OBS Studio controlled the livestream as a single ‘virtual camera’, with test results overlaid as appropriate. Scenarios involved an atypical myocardial infarction, sickle cell crisis, and female genital mutilation/trauma in pregnancy. Feedback from learners (n=21) rated the content most useful for ‘trauma in pregnancy’ (2.95/5) and ‘teamworking’ (2.90/5), whilst ‘networking with peers’ was lowest rated (2.21/5). Scenarios were realistic (75%) and appropriate for training level (86%). However, the audio-visual system was rated adequate by only 57%. Comments described difficulty with simultaneous speech during the simulation. Satisfaction with reflective debriefing was 76%, however free-text comments revealed verbal feedback delivered to simulation teams by ‘remote’ peers was perceived more critically than feedback received from local faculty. A novel technological setup with OBS Studio was used for a collaborative simulation event viewed across the UK. Scenarios were rated positively. There was difficulty discerning multiple audio streams during the simulation. We plan to provide team leaders with dedicated microphones for overall commentary. We recognised the lack of diversity in simulation manikins within the host hospital and, as recommended [1], are now arranging representative manikins that can be used routinely and not for stereotypical scenarios. Feedback from a remote group to a smaller ‘in-situ’ participant group can feel daunting and direct. This may reflect the challenging topics explored, but also difficulties recognising the nuances of nonverbal cues in a virtual space. As such, care must be taken with ground rules, and facilitating appropriate exploration of learning points. Although feedback has identified areas for improvement, hybrid simulation can deliver immersive experiences to geographically-dispersed learners which are time- and cost-effective, with reduced environmental impact from travel. Alongside allowing physical-distancing, it may support distance-learning and facilitate cross-institutional collaborations. We recommend exploring OBS Studio for livestreaming simulations [2]. 1. Vora S, Dahlen B, Adler M, Kessler DO, Jones VF, Kimble S, Calhoun A. Recommendations and Guidelines for the Use of Simulation to Address Structural Racism and Implicit Bias. Simulation in Healthcare. 2021;16(4):275–294. 2. Gumble E. Setting up for remote simulation using OBS Studio. 2021.

Longitudinal Assessment of Singing Students

Singers have unique vocal demands, and if the voice is impaired there can be a negative impact on their quality of life. While a variety of options exist to assess vocal health, the utilization of cepstral peak prominence (CPP) has increased due to his reliability in some situations. However, it has not been utilized commonly in the singing population. This study sought to assess vocal health in singing students using noninvasive measures such as singing voice handicap index (SVHI) and consensus auditory perceptual evaluation of voice (CAPE-V) as well as CPP to provide preliminary information on this measure. A prospective longitudinal study of singing students independent of year of training enrolled in a 2-credit voice lesson at an undergraduate School of Music was conducted. Non-invasive measures were used to evaluate the voice. All participants recorded the same spoken sentence at four equally spaced intervals throughout the semester using a ZOOM H4n Pro (two cardioid input microphone, Hauppauge, New Year). Participants completed SVHI at the time of each recording, and CAPE-V conducted by two speech language pathologists trained in voice. CPP was determined using running speech samples. A total of 23 singers completed the study (11 male, 12 female). There was a significant difference in SVHI at the first recording compared to the final recording (10.6 ± 4.6 vs 9.3 ± 5.9, P= 0.008). Similarly, there was a significant difference in CPP at the first recording compared to the final recording (9 ± 3 vs 9.4 ± 1.1, P < 0.001). However, no significant difference was seen with CAPE-V. Our results are similar to previous studies. There was no evidence in decline in objective and subjective vocal quality utilizing the measure included in our study.

Fully Steerable Collocated First-Order Cardioid Microphone Array Acoustic Beam-Pattern

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Fully Steerable Collocated First-Order Cardioid Microphone Array Acoustic Beam-Pattern

Fully Steerable Collocated First-Order Cardioid Microphone Array Acoustic Beam-Pattern

On the Performance of L- and V-Shaped Arrays of Cardioid Microphones for Direction Finding

The L-shaped and V-shaped arrays of first-order cardioid microphones for direction finding are presented in this paper. A comparative study of the direction of arrival estimation performance of the arrays was carried out by analytically deriving, in closed-form, and comparing the Cramér-Rao bounds of an incident signal's direction-of-arrival (DoA) azimuth and polar angles for these arrays. The maximum-likelihood estimator is used to verify the correctness of derived bounds. This investigation reveals that for direction finding, the L-shaped array of cardioid microphones would generally outperform the V-shaped array of cardioid microphones in more sub-regions of the DoA polar-azimuth angle space. However, in regions where the V-shaped array of cardioid microphones outperforms the L-shaped array of cardioid microphone, the variance ratios are usually higher in favor of the V-shaped array.

Retraction to: M111. QUANTITATIVE ASSESSMENT OF MANIA AND PSYCHOSIS DURING HOSPITALIZATION USING AUTOMATED ANALYSIS OF FACE, VOICE, AND LANGUAGE

Abstract Background A major challenge for reliable and effective mental health care is the lack of objective markers of illness. Computational approaches to measuring naturalistic behavior in clinical settings could therefore provide an objective backstop for mental health assessment and disease monitoring. This study aimed to train machine-learning (ML) classifiers to estimate conventional clinical measures of severe mental illness using quantitative metrics derived from computational analysis of facial and vocal behaviors. Methods Individuals hospitalized for any active psychotic condition were recruited to participate in up to ten recorded study visits, comprised of three segments. Each visit was captured using two synchronized HD webcams and cardioid microphones, to obtain high quality audiovisual (AV) data from both patient and interviewer. We performed automated facial action coding, vocal analysis, and speech transcription using publicly available software (e.g., openFace, openSmile, TranscribeMe). Results A total of 34 participants, participated in 66 sessions between 2015 and 2018, resulting in over 40 hours of AV recordings. In our visual and vocal analysis, we found that several features derived from face, voice, and use of language (i.e. eyebrow furrowing, eye widening, smile variability, characteristics of vowels) were both robustly measured using our approach, and allowed us to accurately estimate multiple symptom domains (i.e. mania, depression, psychosis) with (R= &amp;gt;0.7, p = &amp;lt;0.05). In our linguistic analysis, we found that abundance of power words (i.e. superiority, important) and lack of contextual language (i.e. yesterday, nearby) are highly indicative of positive psychotic symptoms with (R= +0.417, p = 0.002) and (R= -0.302, p = 0.028) respectively. Discussion Automated analysis of face, voice, and speech provides a number of robust behavioral markers sensitive enough to detect changes in psychopathology within individuals over time. Therefore, naturalistic, quantitative assessments can yield objective markers of mood and cognition that can be used to optimize both access and quality of treatments for a wide range of psychiatric conditions.

Practical open-concentric spherical microphone array design

The problem of higher order sound field capture is considered. First-order microphone arrays, such as tetrahedral A-format designs, are commonplace, while interest remains in the increased spatial resolution delivered by higher order arrays. Such arrays typically consist of pressure microphones mounted on a solid spherical baffle, with which higher-order spatial components are estimated algorithmically. This produces a design trade-off, with small arrays being preferred for spatial aliasing performance and large arrays being preferred for reduced amplification of microphone capsule noise at low frequencies. A practical open sphere design is proposed that contains microphones mounted at multiple radii to fulfill both criteria. Coupled with the use of cardioid microphones, such an array captures higher order soundfields over a wider audio bandwidth than baffled spherical designs of fixed radius.

Wind noise reduction for a closely spaced microphone array in a car environment

This work studies a wind noise reduction approach for communication applications in a car environment. An endfire array consisting of two microphones is considered as a substitute for an ordinary cardioid microphone capsule of the same size. Using the decomposition of the multichannel Wiener filter (MWF), a suitable beamformer and a single-channel post filter are derived. Due to the known array geometry and the location of the speech source, assumptions about the signal properties can be made to simplify the MWF beamformer and to estimate the speech and noise power spectral densities required for the post filter. Even for closely spaced microphones, the different signal properties at the microphones can be exploited to achieve a significant reduction of wind noise. The proposed beamformer approach results in an improved speech signal regarding the signal-to-noise-ratio and keeps the linear speech distortion low. The derived post filter shows equal performance compared to known approaches but reduces the effort for noise estimation.

Small aperture acoustic methods to locate transients

Acoustic microphone arrays have been used in battlefield environments to detect and locate continuous wave targets like helicopters and ground vehicles, and for transient events like gunshots, mortars, rockets and explosions. Depending on the application, source bandwidth, propagation distance, and required localization accuracy, these arrays can vary their sensor separation greatly. Unattended ground sensors, manned- and unmanned-platforms, and Soldier-worn systems can all benefit from very small apertures if performance can be maintained. A commercially available acoustic particle velocity sensor, approximately one-half an inch in diameter, showed good transient localization at a field experiment. Data will also be presented from a small cluster-array of cardioid microphones.

Perceptual thresholds for non-ideal diffuse field reverberation.

The objective of this study is to understand listeners' sensitivity to directional variations in non-ideal diffuse field reverberation. An ABX discrimination test was conducted using a semi-spherical 28-loudspeaker array; perceptual thresholds were estimated by systematically varying the level of a segment of loudspeakers for lateral, height, and frontal conditions. The overall energy was held constant using a gain compensation scheme. When compared to an ideal diffuse field, the perceptual threshold for detection is -2.5 dB for the lateral condition, -6.8 dB for the height condition, and -3.2 dB for the frontal condition. Measurements of the experimental stimuli were analyzed using a Head and Torso Simulator as well as with opposing cardioid microphones aligned on the three Cartesian axes. Additionally, opposing cardioid measurements made in an acoustic space demonstrate that level differences corresponding to the perceptual thresholds can be found in practice. These results suggest that non-ideal diffuse field reverberation may be a previously unrecognized component of spatial impression.

Elucidation of a mechanism of acoustic impedance technique using two cardioid microphones and ensemble averaging method

Recently, there is growing need for in-situ impedance measurement of several materials. We propose using two cardioid microphones (called C-C sensor) for it. C-C sensor has many advantages against two omnidirectional microphones (called P-P sensor) and one omnidirectional microphone and sound velocity (called P-U sensor). I reported the possibility of using C-C sensor for measuring acoustic impedance on 12th Western Pacific Acoustics Conference 2015 (WESPAC2015) and International Congress on Acoustics 2016 (ICA2016). When measuring some porous materials, C-C method can measure acoustic impedance as same as using P-P method, and C-C method can do it from 100 Hz to over 10 kHz. Next, we tried to elucidate the mechanism of using C-C sensor and Ensemble Averaging (EA) method using numerical experiments. As a result, the range in application of C-C sensor for measuring acoustic impedance was clarified. In this presentation, we'll introduce the measuring technique and mechanism.

Low frequency sound spatial encoding within an enclosure using spherical microphone arrays.

In a spherical coordinate system, interior sound field can be expressed in terms of a series of Fourier-Bessel expansions. The process that obtains the expansion coefficients by use of a microphone array (e.g., a spherical microphone array) is called spatial encoding. Until now spatial encoding has mainly been examined in a free field or a diffuse field which can be modeled as a sum of plane waves. For spatial encoding within an enclosure at low frequencies, special challenges would be encountered in two aspects. First, the expansions are influenced by array configurations. Second, an acoustic mode based model instead of a plane wave based one should be considered. This study focuses on these challenges. Different kinds of array configurations were compared specifically at low frequencies, and the spatial encoding for the cylindrical cavity modes was investigated. It was found that the spherical array with cardioid microphones was optimal when kr<1, the cavity modes can be effectively represented by only a sparse subset of expansion coefficients and a good reproduction can be achieved even outside the spherical valid region, which demonstrates an effective alternative way to describe the cylindrical cavity modes and can be implemented efficiently in practice.

Relating hearing loss and executive functions to hearing aid users' preference for, and speech recognition with, different combinations of binaural noise reduction and microphone directionality.

Knowledge of how executive functions relate to preferred hearing aid (HA) processing is sparse and seemingly inconsistent with related knowledge for speech recognition outcomes. This study thus aimed to find out if (1) performance on a measure of reading span (RS) is related to preferred binaural noise reduction (NR) strength, (2) similar relations exist for two different, non-verbal measures of executive function, (3) pure-tone average hearing loss (PTA), signal-to-noise ratio (SNR), and microphone directionality (DIR) also influence preferred NR strength, and (4) preference and speech recognition outcomes are similar. Sixty elderly HA users took part. Six HA conditions consisting of omnidirectional or cardioid microphones followed by inactive, moderate, or strong binaural NR as well as linear amplification were tested. Outcome was assessed at fixed SNRs using headphone simulations of a frontal target talker in a busy cafeteria. Analyses showed positive effects of active NR and DIR on preference, and negative and positive effects of, respectively, strong NR and DIR on speech recognition. Also, while moderate NR was the most preferred NR setting overall, preference for strong NR increased with SNR. No relation between RS and preference was found. However, larger PTA was related to weaker preference for inactive NR and stronger preference for strong NR for both microphone modes. Equivalent (but weaker) relations between worse performance on one non-verbal measure of executive function and the HA conditions without DIR were found. For speech recognition, there were relations between HA condition, PTA, and RS, but their pattern differed from that for preference. Altogether, these results indicate that, while moderate NR works well in general, a notable proportion of HA users prefer stronger NR. Furthermore, PTA and executive functions can account for some of the variability in preference for, and speech recognition with, different binaural NR and DIR settings.

Evaluating microphones and microphone placement for signal processing and automatic speech recognition of teacher-student dialog

We evaluate a variety of audio recording techniques for a project on the automatic analysis of speech dialog in middle school and high school classrooms. In our scenario, the teacher wears a headset microphone or a lapel microphone. A second microphone is then used to collect speech and related sounds from students in the classroom. Various boundary microphones, omni-directional microphones, and cardioid microphones are tested as this second classroom microphone. A commercial microphone array [Microsoft Xbox Kinect] is also tested. We report on how well digital source-separation techniques work for segregating the teacher and student speech signals from one another based on these various microphones and placements. We also test the recordings using various automatic speech recognition engines for word recognition error rates under different levels of background noise. Preliminary results indicate one boundary microphone, the Crown PZM-30, to be superior for the classroom recordings. This is based on its performance at capturing near and distant student signals for ASR in noisy conditions, as measured by ASR error rates across different ASR engines.

Multi-channel audio recording based on superdirective beamforming for portable multimedia recording devices

In this paper, an audio recording method using a near-coincident microphone array is proposed for a multichannel audio system. A coincident or near-coincident microphone recording method attempts to capture spatial images in a multi-channel audio system depending on directional-level differences or directivities. Thus, high directivity is required for good spatial quality in the multichannel audio system, and it is usually obtained using a directional microphone. However, the currently available microphones such as cardioid, hyper-cardioid, and figure-8 directional microphones have lower directivities. To overcome this problem, the proposed method forms a superdirective sound beam in each steered direction using closely spaced omni-microphones. It is shown from subjective listening tests that the proposed method provides higher spatial quality with lower timbral distortions than other conventional recording methods for stereo and 5.1-channel audio systems.