Loudspeaker Positions Research Articles

Effect of reverberation chamber volume on result of qualification procedure for loudspeaker and loudspeaker positions for airborne sound insulation measurements

Measurement of sound insulation from airborne sound is carried out by determining the level of sound power radiated by the test item. In laboratory practice, this translates into measuring the sound level in the transmitting and receiving chambers and measuring the reverberation time in the receiving chamber. When performing these measurements, significant fluctuations in the sound level for low frequencies can be observed, which is related to the occurrence of standing waves inside the chambers. To ensure proper level averaging, as well as repeatability and reproducibility of measurements ISO 10140-5 describes a qualification procedure for sources and source positions. This article presents the effect of increasing the volume of the source chamber on the results of the qualification procedure for sources and source positions for floor airborne sound insulation measurements.

Characterization of façade sound insulation by impulse response measurements for various source position formats: a case study

The sound insulation of a building's façade is important for estimating the indoor levels in relation to the outdoor levels. The measurement of the sound insulation (i.e., outdoor-to-indoor level difference) is significantly affected by the methodology employed. In this study, an impulse response measurement methodology is incorporated, alleviating uncertainties associated with the measurement's chain. The effect of loudspeaker position on sound insulation is investigated with respect to three source position formats (horizontal, inclined, and linear), each consisting of three source positions. The appropriate length of the excitation signal is verified using the impulse-to-noise ratio (INR) indicator. Focusing on the outdoor-to-indoor level differences, corresponding to the energy captured in each external receiver (placed very close to windows) and across all the internal receivers per source position, significant differences were found. This indicates the impact of both the distance and angle of incidence between the outdoor receiver and the sound source position. In terms of the average outdoor-to-indoor level difference among the three source formats, the linear format shows slightly lower values compared to the horizontal and inclination source formats, which are similar to each other, but follows the main trend.

Exploring variations to ASTM E336 directional sound source positioning

This paper explores variations to the procedures presented in ASTM E336 Standard Test Method for Measurement of Airborne Sound Attenuation between Rooms in Buildings. Per the Test Standard, directional sound sources must be aimed into corners away from the test partition. For source rooms horizontally adjacent to occupied spaces on all sides, multiple loudspeaker positions are needed to measure noise isolation in all directions. Measurements made in 4 office spaces are presented, each made in two ways: firstly in compliance with the Standard; and secondly, with sound sources orientated and operated differently, to explore whether using a single configuration of directional loudspeakers can produce similar results. Variations in the results are discussed, and suggestions are provided for future work.

Effect of loudspeaker position and model on cognitive load, quality, clarity, and sentence recognition performance

We sought to determine the effects of classroom loudspeaker position, model of loudspeaker, and talker accent on mental effort or cognitive load, word clarity, sound quality, and word recognition. Thirty-one typically-developed university students whose native language is English rated and transcribed recorded sentences produced by a native English talker and a native Dutch talker speaking English. The listeners were seated in acoustically pre-calibrated locations in a classroom and were presented 10 sentences at conversational level in each of four randomized conditions: from a conventional classroom loudspeaker in front or mounted above them, and from a loudspeaker optimized for speech reproduction placed in front or mounted above them. At the front of the classroom was a muted video recording of one of the talkers delivering an online lecture. Results showed front-located speakers yielded less cognitive effort, better sound quality, and better word clarity—showing importance of congruence of loudspeaker/talker position.

Investigation into Ventriloquism Effect Considering Indication of the Loudspeaker Position

In this work, we investigated strength variations of the ventriloquism effect when the loudspeaker's position was indicated to the subject. The ventriloquism effect is an audiovisual cross‐modality in which a sound is heard from the position of an image, even though the sound and image are presented at different locations. Previously, this effect has been studied under conditions where the sound location is not revealed. In contrast, this paper proposes measuring the ventriloquism effect using a single loudspeaker displayed as a 3D scanned image in the background of a virtual reality (VR) image. The angular discrimination threshold (the perceived angle of disparity between the sound and the image shifted horizontally) was employed to evaluate the ventriloquism effect. The resulting ventriloquism effect was compared to the effect noted in a previous study, where measurements were conducted without revealing the loudspeaker's position to the subjects. The results indicate that revealing the loudspeaker's position emphasizes the ventriloquism effect. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

The effect of loudspeaker type and position on field airborne sound isolation measurements

Airborne sound isolation measurement per ASTM E336 uses random noise excitation generated by loudspeakers in the source room. For smaller rooms such as those in residences, loudspeakers are typically located in and pointed into a corner. There is some indication that this loudspeaker position results in systematic reductions in the airborne sound isolation. To investigate the reported reductions and other possible effects due to loudspeaker characteristics, we performed a gauge repeatability and reproducibility study (GRR) on a typical demising wall between units in a multi-family residential building. A GRR uses analysis of variations (ANOVA) on an appropriately designed experiment to separate and quantify the components of the overall uncertainty. This adds to the GRR analyses previously completed (see papers by the authors at Internoise 2018, 2019, and 2021). This study used loudspeaker type, position, and level as the study variables. The results are presented, and the effect on noise isolation testing procedures is discussed.

Estimation of insertion loss for noise barrier with multichannel sound reproduction technology

A method based on the wave field synthesis is proposed to estimate the insertion loss of a noise barrier under the complex diffracted sound field due to the characteristics of the noise source and the transmitted sound through the barrier. This method is equivalent to evaluating the acoustical performance of the noise barrier in a reproduced sound field. There are two advantages of the proposed method. First, by storing the radiated sound of various noise sources as a database in advance, the insertion loss for them can be obtained. Second, the impulse responses from multipoint can be measured by changing one loudspeaker position sequentially, so it does not necessarily require many loudspeakers. In order to validate this method, numerical simulation was performed for a diffracted sound field consisting of a point source and a rigid barrier. Moreover, the insertion loss of simple noise barriers for one loudspeaker was estimated under the primary and synthesized sound field conditions experimentally. As a practical example, the insertion loss of the same noise barriers for a moving automobile was also estimated. The results show that the estimation error is within a few decibels in the frequency band where spatial aliasing does not occur.

Applicability of ISO 16283-3 for field measurement of sound insulation of partially open windows

Façade sound insulation regulations are typically focused on closed windows. However, many people prefer open windows for ventilation purposes, or simply because of the psychological effect of having an open window. As such it is important to be able to correctly quantify the sound insulation, also with open windows. The international standard ISO 16283-3 describes a field method for test of façade sound insulation of facades or façade elements, e.g. a window, which is further explained in the scope: "The element methods aim to estimate the sound reduction index of a façade element, for example, a window. The most accurate element method uses a loudspeaker as an artificial sound source. Other less accurate element methods use available traffic noise". However, the standard is probably primarily meant for closed windows, and not for open windows. The applicability of ISO 16283-3 for open windows is therefore under investigation for such conditions which are included in an additional Danish environmental noise guideline. Generally, it can be concluded that the traffic noise method is applicable, but care should be taken by using the loudspeaker method for partially open windows, since the results depend highly on the window opening position compared to the loudspeaker position.

Optimization of loudspeaker positions for virtual auditory displays in a free-field environment

Virtual acoustic environments are created by mimicking the pressures of real acoustic sources at a listener’s ears. In this way, a listener can perceive virtual acoustic sources as coming from any desired direction. There are multiple methods to accomplish this using headphones or loudspeaker arrays, but not all are practical for everyday use. Some use cases limit the use of headphones or the number and position of loudspeakers, such as automobiles and home theater systems. These limitations also put bounds on the performance of each possible system, such as allowable head movement and the accuracy of localization. An exhaustive-search optimizer was used to find the performance of various sparse loudspeaker arrays, given a limited number of possible loudspeaker positions in a free-field environment for a single stationary listener. The optimizer sought to maximize allowable head rotation and translation and to minimize localization errors. Arrays consisting of two or four loudspeakers were considered using a spherical head model to find the necessary head-related transfer functions and cross-talk cancellation was used to create the virtual acoustic environment. From the results, pareto fronts were created that can be used to find the best loudspeaker array configuration for given design constraints.

Weighted Loudspeaker Placement Method for Sound Field Reproduction

Sound field reproduction aims to reconstruct a desired sound field in a listening area by using multiple loudspeakers. To improve sound field reproduction performance, several loudspeaker placement methods have been proposed to select suitable loudspeaker positions. However, most conventional loudspeaker placement methods do not consider the distribution characteristic of the desired sound fields such as the distribution of directions from where the sound wave emanates, making these methods not optimal when the prior knowledge of the distribution characteristic of the desired sound fields is known. In this paper, a weighted loudspeaker placement method is proposed, which considers optimizing the objective function that depends on a set of desired sound fields with different weights. This paper formulates the optimization problem for weighted loudspeaker placement, presenting three alternative discretization methods to obtain a more practical optimization problem, after which the group greedy method is used to solve the optimization problem to find the near-optimal loudspeaker setup. To validate the proposed method, numerical experiments aiming to reconstruct the desired sound wave from a restricted range are conducted. The results indicate that the proposed method performs well in both narrowband and broadband cases, because it can use prior knowledge of the distribution characteristic of the desired sound fields.

Sound Localization in Single-Sided Deaf Participants Provided With a Cochlear Implant.

Spatial hearing is crucial in real life but deteriorates in participants with severe sensorineural hearing loss or single-sided deafness. This ability can potentially be improved with a unilateral cochlear implant (CI). The present study investigated measures of sound localization in participants with single-sided deafness provided with a CI. Sound localization was measured separately at eight loudspeaker positions (4°, 30°, 60°, and 90°) on the CI side and on the normal-hearing side. Low- and high-frequency noise bursts were used in the tests to investigate possible differences in the processing of interaural time and level differences. Data were compared to normal-hearing adults aged between 20 and 83. In addition, the benefit of the CI in speech understanding in noise was compared to the localization ability. Fifteen out of 18 participants were able to localize signals on the CI side and on the normal-hearing side, although performance was highly variable across participants. Three participants always pointed to the normal-hearing side, irrespective of the location of the signal. The comparison with control data showed that participants had particular difficulties localizing sounds at frontal locations and on the CI side. In contrast to most previous results, participants were able to localize low-frequency signals, although they localized high-frequency signals more accurately. Speech understanding in noise was better with the CI compared to testing without CI, but only at a position where the CI also improved sound localization. Our data suggest that a CI can, to a large extent, restore localization in participants with single-sided deafness. Difficulties may remain at frontal locations and on the CI side. However, speech understanding in noise improves when wearing the CI. The treatment with a CI in these participants might provide real-world benefits, such as improved orientation in traffic and speech understanding in difficult listening situations.

Experimental evaluation of a sound diffuse field in a ordinary room

This paper presents a methodology based on analysis of spatial correlation functions for assessing diffusivity of a sound field in reverberant and ordinary reflective rooms. A set of sound field measurements using a microphone array is performed in a room excited by a broadband signal and for many positions of loudspeakers. Each recorded signal is then broken down with a filter bank and the spatial correlation of each obtained band-limited signal is computed. Theoretical predictions of the spatial correlation function and the measured ones show very good agreement when spatial averaging and frequency conditions are met for producing a diffuse field. Evolution of the spatial correlation functions versus frequency and number of spatial averaging, i.e., number of sources positions, are examined in a reflective room. Results show that the proposed technique allows to determine the minimum number of required source positions and the actual lower frequency bound for considering that the field is diffuse. The latter is analogous to the Schroeder frequency for reverberant room. Interest of the presented methodology is its ability to experimentally assess in any reflective ordinary room the actual frequency range over which the field can be considered as diffuse. [Work funded by the AMIDEX Foundation.]

Comparative study of loudspeaker position optimization techniques for multizone sound field reproduction

Mutlizone sound field reproduction aims to generate personal sound zones in a shared space with multiple loudspeakers. Conventionally, loudspeakers are placed to form a regular pattern such as circular, arc or linear array, which are empirical rather than optimal mainly for the convenience of physical placement. Recently, several algorithms have been proposed to select a fixed number of loudspeaker locations from a large set of candidate positions, such as the sparse regularization (i.e. Lasso and Elastic Net) methods, the Constrained Match Pursuit (CMP) method, the Gram-Schmidt Orthogonalization (GSO) method etc. Most of these methods were investigated for single-zone rather than mulit-zone sound field reproduction based on the pressure matching techniques. This paper compares the performance of the state-of-the-art techniques for loudspeaker position optimization in a multizone sound field reproduction system in terms of reproduction error, acoustic contrast and array effort. Simulation results demonstrate that the CMP-LS method shows the best performance in terms of lower MSE and higher AC while the Lasso method needs the lowest AE.

Gauge repeatability and reproducibility study of airborne sound isolation measurements

A gauge repeatability and reproducibility study (GRR) uses analysis of variations (ANOVA) on an appropriately designed experiment to separate and quantify the components of the overall uncertainty. The authors have previously presented results of GRR studies of the measurement of airborne and impact insulation of floor-ceiling and demising wall assemblies in several apartment buildings, in which the uncertainty in the measurement method and the variability of the nominally-identical assemblies were compared. The results of two additional GRR studies on measurements of airborne noise isolation of wood stud demising walls are presented. The first study, like previous studies, evaluates the components of variance attributable to operator, repeatability, and part. The second study uses a fixed operator and part, and evaluates the variance due to loudspeaker type, position, and level on the measured noise reduction. The measurement standard (ASTM E336) gives limited guidance on the type and location of the loudspeaker used on the source side, and this study can inform whether changes in the standard with regards to the loudspeakers could reduce the uncertainty in measurement.

An iterative approach to optimize loudspeaker placement for multi-zone sound field reproduction

Various array patterns, such as circular, linear, and arc-shaped arrays, have been used in multi-zone sound field reproduction, but most of them are based on empirical rather than judicious selection. This article proposes an iterative optimization method to select the loudspeaker positions from a large set of candidate locations. Both the number and locations of the loudspeakers can be designed with superior performance. Both single-frequency and broadband simulations based on the acoustic contrast control method are performed to validate the proposed scheme, and the performance of the optimized array is compared with that of an arc-shaped array and that of an array optimized with an existing method.

Pinpointing the position of flying songbirds with a wireless microphone array: three-dimensional triangulation of warblers on the wing

ABSTRACT Flight calls, the quiet calls emitted by migratory birds on the wing, offer opportunities to understand the behaviour of birds during migration. We test the effectiveness of an eight-element microphone array for three-dimensional triangulation of the position of calling migratory birds. We constructed a microphone array out of commercially available components and used freely available software to process the recordings, so that this technology might be easily adopted for migration monitoring. In the Great Lakes region of North America, we triangulated the position of loudspeakers broadcasting synthetic tones and flight calls, as well as calls of actual passing migrants. Loudspeakers broadcasting synthetic tones showed a triangulation accuracy of 1.52 ± 0.34 m. Loudspeakers broadcasting flight calls of migratory wood-warblers showed a triangulation accuracy of 2.04 ± 0.37 m. Actual migratory warblers passing over the microphone array showed an estimated accuracy of 2.70 ± 0.48 m. We conclude that wireless microphone arrays accurately triangulate migrant birds, at least under optimal recording conditions. We present this proof-of-concept study to demonstrate the reliability of this underutilized technique which should be of interest as a tool for studying migratory bird behaviour, for quantifying migratory bird populations, and for monitoring the conservation of migratory birds.

Auditory localization accuracy and auditory spatial discrimination in children with auditory processing disorders

The present study investigated spatial hearing in children aged 6–12 years diagnosed with Auditory Processing Disorders (APD) and compared their results to those of a group of control children matched in age. Sound source localization accuracy was quantified using an absolute localization task and sound source discrimination by measuring the minimum audible angle. Low- and high-frequency noise bursts were presented from eight loudspeaker positions in the left and right hemifields (0°, 30, 60°, and 90° azimuth). Median absolute localization accuracy did not differ between children with APD and control children. However, the intra-individual variability of pointing behavior was higher for children with APD. In contrast, children with APD had significantly higher minimum audible angle thresholds than control children. These findings show that APD impairs sound source discrimination, but does not affect the median relationship between actual and judged sound source locations.

Analysis and simulation of acoustic parameter Cak Durasim Surabaya concert hall

In this study discussed the analysis of acoustic parameters of measurement and simulation of loudspeaker position at Cak Durasim Surabaya. Based on ISO-3382-1 acoustic parameters that need to be analyzed are SPL distribution, RT, C50, and C80. To get these parameters result, data retrieval using Impulse Response method was done. Measurements are made in a condition without audiences. Based on the measurement results, SPL distribution was less evenly with the maximum and minimum difference reached 14 dBA. In addition, the value of RT was 1.1 s which showed the impression of a sound was less “alive”. From these measurements, it was necessary to add loudspeaker to improve the SPL distribution and the value of reverberation time. Based on the simulation, the result of the SPL distribution evenly with the maximum and minimum difference of 6 dBA, C50 of 4.5 dB, and C80 of 8.2 dB. For RT there were no significant change that were 0.68 s. It means the sound impression in the room was still less “alive”. Problems in the simulation result can be solved by giving certain effects of the sound system so it doesn’t need to change the material composing of the room.

Loudspeaker triplet selection based on low distortion within head for multichannel conversion of smart 3D home theater

SummaryIn recent years, with the vigorous development of 3D film industry, the demand for 3D Smart Home Theater, based on Internet of Things (IoT), continues to grow. Theaters are populated with a large number of loudspeakers for more realistic 3D sound effects. However the number of loudspeakers in home is limited. Therefore, multichannel conversion is required to achieve theater 3D sound effects in home. Traditionally, the replaced loudspeaker signal of the original system is assigned to a “loudspeaker triplet” of the converted system. A large amount of subjective evaluations is necessary to judge the consistency of the replaced loudspeaker position with the “phantom source” positions reconstructed by loudspeaker triplets. In this study, after calculating the least‐squares errors of the reproduced sound field within a given region, we explore the constraint between the low distortion of the reproduced sound field and the loudspeaker triplet positions. Using this constraint rule, we present a new loudspeaker triplet selection criteria that can greatly reduce the number and time of subjective evaluations for selecting the optimal loudspeaker triplet. Simulation and subjective evaluation experiments indicate that the proposed selection method outperforms the traditional method, and that the proposed method can be successfully applied to multichannel conversion.

3D Room Geometry Inference Based on Room Impulse Response Stacks

Room geometry inference is concerned with the localization of reflective boundaries in an enclosed space. This paper outlines a method for inferring room geometry based on the positions of loudspeakers and real or image microphones, which are computed using sets of times of arrival (TOAs) obtained from room impulse responses (RIRs). These RIRs describe the acoustic propagation between the loudspeakers in an array and a single microphone. First, peaks corresponding to TOAs in these RIRs are detected and labeled using an automated method. Second, the labeled TOA sets are used to estimate the real and image microphone positions, with knowledge of the loudspeaker array geometry. Third, using all these positions, the positions of reflection points on the available reflectors in the room are determined. The reflection points determine the reflectors’ locations and orientations. This approach is largely automated and usable in real-world scenarios.