Direction Of Sound Source Research Articles

Three-dimensional sound source diagnostic using a spherical microphone array from multiple capture positions

Most sound source diagnosis systems based on acoustic images are spatially stationary and unable to combine information from multiple capture positions, resulting in unreliable and partial diagnostics. In this paper it is proposed, developed and validated a measurement method based on a mobile spherical microphone array that generates acoustic images using beamforming from multiple capture positions, called Acoustic Imaging Structure From Motion (AISFM). The tridimensional localization, magnitude and directivity of multiple sound sources may be recovered with or without knowledge of the capture positions. An automatic and unsupervised acoustic image processing algorithm is deployed to facilitate the measurement workflow. An acoustic image correspondence problem is solved in order to eliminate false-positives and false-negatives from the diagnostic and render the AISFM feasible. Sound sources localization uncertainties estimates related to the sources’ magnitude, directivity and extension projected on the acoustic images are used in order to improve the diagnosis. The method and its effectiveness are experimentally validated with a measurement setup comprising five simultaneous sound sources on an anechoic environment.

Efficient representation of head-related transfer functions in continuous space–frequency domains

Utilizing spherical harmonic (SH) domain has been established as the default method of obtaining continuity over space in head-related transfer functions (HRTFs). This paper concerns different variants of extending this solution by replacing SHs with four-dimensional (4D) continuous functional models in which frequency is imagined as another physical dimension. Recently developed hyperspherical harmonic (HSH) representation is compared with models defined in spherindrical coordinate system by merging SHs with one-dimensional basis functions. The efficiency of both approaches is evaluated based on the reproduction errors for individual HRTFs from HUTUBS database, including detailed analysis of its dependency on chosen orders of approximation in frequency and space. Employing continuous functional models defined in 4D coordinate systems allows HRTF magnitude spectra to be expressed as a small set of coefficients which can be decoded back into values at any direction and frequency. The best performance was noted for HSHs and SHs merged with reverse Fourier–Bessel series, with the former featuring better compression abilities, achieving slightly higher accuracy for low number of coefficients. The presented models can serve multiple purposes, such as interpolation, compression or parametrization for machine learning applications, and can be applied not only to HRTFs but also to other types of directivity functions, e.g. sound source directivity.

The Accuracy of Dynamic Sound Source Localization and Recognition Ability of Individual Head-Related Transfer Functions in Binaural Audio Systems with Head Tracking

The use of audio systems that employ binaural synthesis with head tracking has become increasingly popular, particularly in virtual reality gaming systems. The binaural synthesis process uses the Head-Related Transfer Functions (HRTF) as an input required to assign the directions of arrival to sounds coming from virtual sound sources in the created virtual environments. Generic HRTFs are often used for this purpose to accommodate all potential listeners. The hypothesis of the research is that the use of individual HRTF in binaural synthesis instead of generic HRTF leads to improved accuracy and quality of virtual sound source localization, thus enhancing the user experience. A novel methodology is proposed that involves the use of dynamic virtual sound sources. In the experiments, the test participants were asked to determine the direction of a dynamic virtual sound source in both the horizontal and vertical planes using both generic and individual HRTFs. The gathered data are statistically analyzed, and the accuracy of localization is assessed with respect to the type of HRTF used. The individual HRTFs of the test participants are measured using a novel and efficient method that is accessible to a broad range of users.

Real-time TDOA-based stationary sound source direction finding

Real-time TDOA-based stationary sound source direction finding

Vision‐audio fusion SLAM in dynamic environments

AbstractMoving humans, agents, and subjects bring many challenges to robot self‐localisation and environment perception. To adapt to dynamic environments, SLAM researchers typically apply several deep learning image segmentation models to eliminate these moving obstacles. However, these moving obstacle segmentation methods cost too much computation resource for the onboard processing of mobile robots. In the current industrial environment, mobile robot collaboration scenario, the noise of mobile robots could be easily found by on‐board audio‐sensing processors and the direction of sound sources can be effectively acquired by sound source estimation algorithms, but the distance estimation of sound sources is difficult. However, in the field of visual perception, the 3D structure information of the scene is relatively easy to obtain, but the recognition and segmentation of moving objects is more difficult. To address these problems, a novel vision‐audio fusion method that combines sound source localisation methods with a visual SLAM scheme is proposed, thereby eliminating the effect of dynamic obstacles on multi‐agent systems. Several heterogeneous robots experiments in different dynamic scenes indicate very stable self‐localisation and environment reconstruction performance of our method.

Speech directivity patterns generated from a high-fidelity speech corpus

Human talkers are directional sound sources—a phenomenon that has consequences for speech perception in multi-talker environments. Directivity patterns for speech showing frequency- and angle-dependent radiation reveal that speech generally becomes more directional toward the front of the talker as frequency increases. Differences in physical attributes can lead to individual variability in directivity patterns across talkers. Here, we examine individual variability in speech directivity using frequency-dependentdirectivity indices and directivity maps. Speech directivity was examined in the horizontal plane using a corpus of simultaneous multi-channelfull-bandwidth (48-kHz sampling rate) recordings of the Bamford-Kowal-Bench (BKB) sentences recorded in an anechoic chamber. Thirty subjects (15 female) were recorded. The long-term average speech spectrum was utilized to calculate directivity indices in 1-ERB (equivalent rectangular bandwidth) bands. Gender differences in directivity indices were evaluated using a linear mixed-effects model. There was no main effect of gender. There was a main effect of ERB band with higher-frequency bands tending to have higher (i.e., more directional) directivity indices, however there was a nonmonotonic relationship between average directivity indices and frequency. Directivity maps demonstrated individual differences in speech radiation. [Work supported by NIH under Grant No. R01-DC019745.]

Program assessment in undergraduate acoustics at Kettering University

Kettering University has been teaching acoustics as part of undergraduate engineering for decades, and the senior-level acoustics laboratory course has assumed a critical role in the continuous improvement process for our ABET-accredited programs in Applied Physics and Engineering Physics. This project-based course addresses learning objectives focused on transferable skills in test and measurement, literature and theoretical foundations, and computational modeling. These are set in the context of two modules, on sound source directivity and modal testing. The assessment structure is built around rubrics, used for both formative and summative evaluation of student performance on authentic tasks including recording activity in lab notebooks and scientific writing. A 32-question multiple choice instrument is deployed as a pre-test and post-test to assess gains in content knowledge from the course. Finally, we discuss specific examples of assessment for effective teamwork (ABET EAC Outcome 5) and developing and conducting experiments and analyzing and interpreting data (ABET EAC Outcome 6).

Spatial location from running binaural signals using cepstral analysis and logarithmic filtering

This paper proposes an acoustic model for predicting the acoustical room characteristics from a running binaural signal. This is accomplished via training a convolutional neural network on a precedence effect model to extract the spatial locations of the direct sound source and its early reflections. The precedence effect model extends and modifies the BICAM algorithm with cepstral analysis [Tyler, J., Si, M., \& Braasch, J. Acoust. Soc. Am. 151] and a logarithmic filter. The logarithmic filter takes human perception into account and provides better separation at higher frequencies. A synthetic dataset of binaural signals was generated using anechoic orchestral recordings with added reflections and reverberations. The binaural model generates binaural activity maps from binaural input signals, which are then used to train a convolutional neural network. The ability to predict the traits of a direct sound source and its reflections has applications in academic areas like perceptual modeling and room acoustical analysis. It can also be applied to industrial areas such as television and movies, video games, and augmented and virtual reality, to name a few. [Work supported by the National Science Foundation: HCC-1909229.]

Sound source directivity considering source movement

When the source moves, frequency modulation (Doppler effect) occurs in the radiated sound, and the directivity of source changes. In addition, the source can be not located in a direction from the direction of arrival of radiated sound. Therefore, the sound pressure directivity may differ depending on whether the source is static or moving. There are two types of wave equations, one that describes sound pressure as a variable and one that describes velocity potential as a variable. When the sound source moves at a constant velocity and the equation is solved assuming that the source strength is constant with respect to the velocity, the sound pressure directivity of the radiated sound changes depending on the description method of the wave equation. The sound pressure was obtained by solving the wave equations where a single monopole source and a dipole source are moving at a constant velocity. From the results, we showed the difference of sound pressure directivity when source is moving from the directivity of static source.

Virtual sound source perception challenges of binaural audio systems with head-tracking

With the recent leaps in spatial audio technology, the use of binaural head-tracking for spatial audio can revolutionize the way how music and audio are experienced. Moreover, to research noise-related perception in laboratories, binaural head-tracking is frequently used as an audio reproduction system. Although this technology is getting significantly better in recent years, signal processing of binaural audio is often experiencing problems such as non-adequate sound source externalization and unacceptably high values of system response time since it influences the usability of the technology at fast head rotation. In this paper, the results of an experiment are presented, in which test subjects are determining the direction of a virtual sound source in the horizontal plane with multiple parameter changes. The experiment is done in a controlled environment in a listening room with known acoustical properties. Parameter variation includes: hardware head-tracker variation (commercial one and head-tracker based on simple embedded system), various software solutions for real-time binaural synthesis, and variation in the used Head-Related Transfer Functions. The problem of externalization of a virtual sound source via headphones is discussed, and possible solutions to the problem are given. Results of the experiment and recorded data are presented.

Investigation of the influence of the torso, lips and vocal tract configuration on speech directivity using measurements from a custom head and torso simulator

The human voice is a directional sound source. This property has been explored for more than 200 years, mainly using measurements of human participants. Some efforts have been made to understand the anatomical parameters that influence speech directivity, e.g., the mouth opening, diffraction and reflections due to the head and torso, the lips and the vocal tract. However, these parameters have mostly been studied separately, without being integrated into a complete model or replica. The aim of this work was to study the combined influence of the torso, the lips and the vocal tract geometry on speech directivity. For this purpose, a simplified head and torso simulator was built; this simulator made it possible to vary these parameters independently. It consisted of two spheres representing the head and the torso into which vocal tract replicas with or without lips could be inserted. The directivity patterns were measured in an anechoic room with a turntable and a microphone that could be placed at different angular positions. Different effects such as torso diffraction and reflections, the correlation of the mouth dimensions with directionality, the higher-order modes and the increase in directionality due to the lips were confirmed and further documented. Interactions between the different parameters were found. It was observed that torso diffraction and reflections were enhanced by the presence of the lips, that they could be modified or masked by the effect of higher-order modes and that the lips tend to attenuate the effect of higher-order modes.

A Bayesian model for human directional localization of broadband static sound sources

Humans estimate sound-source directions by combining prior beliefs with sensory evidence. Prior beliefs represent statistical knowledge about the environment, and the sensory evidence consists of auditory features such as interaural disparities and monaural spectral shapes. Models of directional sound localization often impose constraints on the contribution of these features to either the horizontal or vertical dimension. Instead, we propose a Bayesian model that flexibly incorporates each feature according to its spatial precision and integrates prior beliefs in the inference process. The model estimates the direction of a single, broadband, stationary sound source presented to a static human listener in an anechoic environment. We simplified interaural features to be broadband and compared two model variants, each considering a different type of monaural spectral features: magnitude profiles and gradient profiles. Both model variants were fitted to the baseline performance of five listeners and evaluated on the effects of localizing with non-individual head-related transfer functions (HRTFs) and sounds with rippled spectrum. We found that the variant equipped with spectral gradient profiles outperformed other localization models. The proposed model appears particularly useful for the evaluation of HRTFs and may serve as a basis for future extensions towards modeling dynamic listening conditions.

Are frog calls relatively difficult to locate by mammalian predators?

Frogs call in acoustically dense choruses to attract conspecific females. Their calls can potentially reveal their location to predators, many of which are mammals. However, frogs and mammals have very different acoustic receivers and mechanisms for determining sound source direction. We argue that frog calls may have been selected so that they are harder to locate with the direction-finding mechanisms of mammals. We focus on interaural time delay (ITD) estimation using delay-line coincidence detection (place code), and a binaural excitatory/inhibitory (E/I) ITD mechanism found in mammals with small heads (population code). We identify four "strategies" which frogs may employ to exploit the weaknesses of either mechanism. The first two strategies used by the frog confound delay estimation to increase direction ambiguity using highly periodic calls or narrowband calls. The third strategy relies on using short pulses. The E/I mechanism is susceptible to noise with sounds being pulled to the medial plane when signal-to-noise ratio is low. Together, these three strategies compromise both ongoing and onset determination of location using either mechanism. Finally, frogs call in dense choruses using various means for controlling synchrony, maintaining chorus tenure, and abruptly switching off calling, all of which serve to confound location finding. Of these strategies, only chorusing adversely impacts the localization performance of frogs' acoustic receivers. We illustrate these strategies with an analysis of calls from three different frog species.

Sound field of a traditional Chinese Palace courtyard theatre

Chinese Palace theatres mostly adopt a semi-open courtyard layout, where sound field quality is crucial for the performance of Chinese dramas. This study conducted field measurements and a simulation of the Jiayintang Theatre sound field in the Shenyang Imperial Palace to determine the basic parameters of traditional courtyard theatre sound fields. Moreover, the effects of sound source directivity and the spatial elements on the sound field of the theatre were analysed. The results indicate that the acoustic parameters of the Jiayintang Theatre meet the performance requirements of traditional Beijing Operas, as the acoustic conditions are similar to those of modern Beijing Opera theatres with good listening features. Removing the roof and sidewalls reduces the sound intensity and reverberation time in the aisles. Changing the stage position from the current projecting style to the embedded style would result in a 1.6 and 2.6 dB decrease in the sound intensity in mid-frequency in the main hall and aisles, respectively, while the musical clarity (C80) as well as the speech transition index (STI) in the main hall would decrease, which would negatively affect the audience perception of acoustic quality. The pavilion roof primarily serves to support the actors considering acoustics. If the singing direction of the actors changes from the main hall to the aisles, the sound intensity in the main hall would decrease by 1.8 dB, and the STI and C80 values would also significantly decrease.

Influence of sound source directivity on finite element simulation of small-room acoustics

Numerical simulation is a flexible and effective method for room acoustic design. Full-range simulation of room acoustics requires a combination of different numerical methods, in which wave acoustic methods (WAM) and geometric acoustic methods (GAM) are used for the low and high frequency region, respectively. In the general low-frequency WAM simulation, a sound source is often assumed to be a point source or loudspeakers are usually approximated by circular planar pistons. However, compared to a large room, the critical frequency between WAM and GAM should be higher in acoustic simulation of small rooms because of relative size between the wavelength and the room, and thus, the above simplifications of actual sound sources, typically loudspeakers, may lead to errors in terms of directivity in the frequency range that the WAM is applied for. Further errors in the desired room impulse responses or other room acoustic parameters caused by directivity errors needs quantitative analysis, and then evaluation can be made on whether it is necessary to consider a more accurate sound source directivity in the WAM simulation of small room acoustics.

Holographic signal processing for estimation of sound source direction by a vector receiver in shallow water

A holographic signal processing method for estimation of sound source direction of broadband moving sound source is proposed in the paper. The holographic estimation of sound source direction is based on signal processing of single vector receiver (VR) channels: x-th and y-th components of the oscillatory velocity. The sound field of a moving sound source creates a stable interference pattern of the intensity distribution (interferogram) in the frequency-time domain on VR channels. The two-dimensional Fourier transformation (2D-FT) is applied to analyze the channels interferograms. The result of the 2D-FT are holograms of the x-th and y-th oscillatory velocity components. The angle distributions of channels holograms are calculated. The offered holographic method is based on the ratio of the absolute values of the holograms angle distributions maxima. The expressions for VR channels holograms are derived. The results of the numerical experiment for source direction reconstruction are presented. A significant advantage of the proposed holographic method that there is no need for information about noise signal source, the additive noise obstacle and waveguide transfer function. [This study was supported by Russian Science Foundation grant no. 22-79-10233. Tkachenko’s numerical experiment was supported by grant no. МК-4846.2022.4.]

Human-mimetic binaural ear design and sound source direction estimation for task realization of musculoskeletal humanoids

Human-like environment recognition by musculoskeletal humanoids is important for task realization in real complex environments and for use as dummies for test subjects. Humans integrate various sensory information to perceive their surroundings, and hearing is particularly useful for recognizing objects out of view or out of touch. In this research, we aim to realize human-like auditory environmental recognition and task realization for musculoskeletal humanoids by equipping them with a human-like auditory processing system. Humans realize sound-based environmental recognition by estimating directions of the sound sources and detecting environmental sounds based on changes in the time and frequency domain of incoming sounds and the integration of auditory information in the central nervous system. We propose a human mimetic auditory information processing system, which consists of three components: the human mimetic binaural ear unit, which mimics human ear structure and characteristics, the sound source direction estimation system, and the environmental sound detection system, which mimics processing in the central nervous system. We apply it to Musashi, a human mimetic musculoskeletal humanoid, and have it perform tasks that require sound information outside of view in real noisy environments to confirm the usefulness of the proposed methods.

Two-dimensional acoustic manipulation in air using interference of standing wave field by three sound waves

A number of small ultrasonic transducers were placed on a flat surface to form a directional ultrasonic sound source. A standing wave field with a hexagonal distribution of sound pressure like a honeycomb was formed when ultrasonic waves were superimposed from three directions using three of these sources. Small objects could be trapped at the nodes of the sound pressure in the sound field. When the phase of the three sources was changed, the sound pressure distribution shifted in the direction of the sound axis of the sources, and the objects trapped at the pressure nodes also shifted. For more stable object trapping, the ultrasonic transducers were placed on the inner wall of a semicylinder and the ultrasonic waves were focused to form a thin two-dimensional planar standing wave field. Three of these sources were used in the experiment, and it was possible to manipulate the objects more stably.

Distance estimation in the spherical harmonic domain using the spherical wave model

Compact spherical microphone arrays are often used to record 3D sound scenes and are well suited to estimate the directions of sound sources. However, estimating the distance of a sound source is a challenging task due to the small dimensions of compact microphone arrays. In this work, different spherical harmonic domain distance estimation methods that utilize the spherical wave propagation model are investigated. Two existing methods are discussed and a new distance estimation method is proposed, which utilizes recurrence relations of spherical Hankel functions. The proposed estimator is related to the ratio between the real and imaginary components of the intensity vector for first-order spherical harmonic domain signals. In addition, a frequency averaging method is proposed and investigated for broadband distance estimation. Finally, the existing and proposed methods are evaluated using simulated anechoic and reverberant scenarios, as well as spherical microphone array recordings in outdoor and indoor environments.

Subjective evaluation of auralization using a directional sound source that simulates a trumpet

Subjective evaluation of auralization using a directional sound source that simulates a trumpet