Sound System Performance Research Articles

Subwoofer array design for optimal performance and minimal noise pollution in the Roman theatre of Italica, Spain

Subwoofer arrays are widely used in live sound events. However, the performance of sound systems and the generated environmental noise pollution in the vicinity of Roman theatres is not well researched and documented. The investigation aimed to determine the most suitable subwoofer array configuration for an outdoor Roman theatre according to their low frequency coverage across the audience area and overspill on nearby residential areas. Performance suitability was determined by measuring the overall sound pressure (dBA) and spectrum levels of the arrays within the audience area at several locations representative of nearby residential areas. The Array Performance Rating (APR) was calculated for each array configuration to complement performance assessments. Results showed a notorious difference between coupled and uncoupled arrays, as well as between ground-based and flown subwoofer configurations. It was proven that the flown point source array offered overall less sound pressure levels and spectral variability in the audience plane and it caused the least environmental noise pollution. The conclusions drawn from this study can provide valuable guidance applicable to future sound system deployments and reconstruction projects of ancient outdoor theatres of similar architectural and environmental characteristics.

Précis of the TC-25CSS Theater Testing Report

In 2014, SMPTE’s B-Chain Study Group Theater Testing Data Report Group released a major report about the acoustical performance of sound systems in four cinemas and two dubbing stages. This paper provides a precis of this B-Chain report, which is probably the most comprehensive in-depth analysis of cinema audio spaces that has ever been undertaken. The report presents numerous frequency and temporal responses for these sound systems, with in depth analysis of the center channel systems. Being based on the measured impulse responses of the systems, the report’s measurement process departed from current SMPTE standardized methods, which are “time blind.” As such, considerable insights have been gained into the behavior of these systems and the way in which frequency responses develop over time. Of particular interest is the minimal contribution that the reverberant sound field makes to the high-frequency responses. The measured responses indicate significant disparity among venues in the responses at low and high frequencies. One of the report’s conclusions is that the commonly-accepted acoustic mechanism for the roll off of high frequencies known as the X curve does not occur. Discussion of the report’s key features such as the analysis methods, trends in the responses, and conclusions is provided in the paper.

Listening to Intergalactic Sounds – Articulation of Rastafarian Livity in Finnish Roots Reggae Sound System Performances

Rastafari is an Afro-Jamaican religious and social movement, which has since the 1970s spread outside of the Caribbean mainly through reggae music. This paper contributes to the academic discussion on the localization processes of Rastafari and reggae with an ethnographic account from the Nordic context, asking how Finnish reggae artists with Rastafarian conviction mobilize this identification in their performance. The paper focuses on one prominent Finnish reggae sound system group, Intergalaktik Sound.The author sees reggae in Finland as divided between contemporary musical innovation and the preservation of musical tradition. In this field, Intergalaktik Sound attempts to preserve what they consider to be the traditional Jamaican form of reggae sound system performance. For the Intergalaktik Sound vocalists, this specific form of performance becomes an enchanted space within a secular Finnish society, where otherwise marginal Rastafarian convictions can be acted out in public. The author connects the aesthetic of this performance to the Jamaican dub-music tradition, and to the concept of a ‘natural life’, which is a central spiritual concept for many Finnish Rastafarians. The article concludes that these sound system performances constitute a polycentric site where events can be experienced and articulated simultaneously as religious and secular by different individuals in the same space.

The efficacy of internal audits in the NOSA management system implementation at ZIMASCO, Shurugwi, Zimbabwe.

SHE performance at ZIMASCO failed to meet the NOSCAR grade since the inception of the NOSA system yet under normal circumstances, performance is expected to achieve continuous improvement. When conducted properly, internal audits are an essential and primary tool to the achievement of a sound system performance. Nonetheless, in spite of regular internal audits, results from NOSA system performance remained below exceptional. ZIMASCO’s internal audit competency was therefore established through an assessment of; employee’s perception towards the audits, the effectiveness of audits instruments used and the general SHE performance of the organization from 2006 to 2011 2012. Data was acquired through interviews with key informants, questionnaires and existing literature from company records. Major findings pointed towards; lack of employees training that was in line with the internal audit processes, inconsistencies in audit instruments and lack of audit finding closure due to financial constraints. The paper therefore advocates for audit oriented training for all employees regardless of level or grade. More financial resources should be sought and channeled towards achieving informative internal audits for effective NOSA implementation.

Measuring and defining the sound quality of audio systems.

“High quality” is a term often employed as a requirement for the performance of an audio or sound system, yet what does it mean and can it be quantified? In particular, bass performance is an important aspect but again is extremely hard to define. Frequency response assessment alone is not enough to characterize sound quality as this does not provide information with regard to the temporal or transient characteristics of the room or system. The paper will look at a number of techniques that potentially can be used to help assess sound system performance including a new measurement method intended to quantify the transient and temporal characteristic of the bass sound in a room, whether this is via a sound system or an assessment of the room itself.

System and method for designing sound systems

The invention is directed to a display and method for conducting sound system design. The display is configured to simultaneously show a sound system model comprising both audio components and sound environment components, a plurality of parameters and a graphic representation of a calculated sound system performance attribute. In response to receiving input from the user and without any additional user intervention, the display re-displays a newly-calculated sound system performance attribute such as, for example, a graphic representation in the sound system model of a sound path associated with a user-selected reflected sound identifier. A processor also simulates, based on the sound system configuration, the sound performance that a user would expect to hear positioned in an identified listening position of the sound system model.

Research opportunities in evaluating sound system performance

Sound reinforcement has been both ubiquitous and indispensable in our society for many years. With such a volume of experience, it would seem that the accompanying body of knowledge should be sufficient to produce a successful design for every situation. However, the quality of actual systems installed today still varies from good to terrible. A few obvious aspects of this problem have been examined, and papers published, but no serious attempt to list or organize all contributors to sound performance quality has ever been made. In addition, no evaluative techniques or analytical strategies have been established to set standards. There are several valid reasons for this. The actual performance of a sound system is surprisingly complex, both in terms of the number of factors contributing to the overall performance and in the complexity within each factor. As a result, each system is quite unique and difficult to describe in precise terms. Few rigorous investigations have been applied. The results have been meager thus far and are essentially unknown to most practitioners. Research opportunities abound, and their results could have a significant impact. In this paper the current situation is summarized and topics for future study are suggested.

Limitations of current sound system intelligibility performance measurement techniques and metrics

The current and increasing trend to employ sound systems for emergency warning and evacuation purposes has led to an increased need to verify and assess the intelligibility performance of such systems. Applications range from passenger cabin PA systems in aircraft through to paging and emergency evacuation systems in industrial complexes, train stations, public buildings, and stadiums. Although a number of methods are available, these have either been borrowed from the fields of architectural and auditorium acoustics or one-dimensional communication networks. The paper shows that such approaches exhibit a number of fundamental inherent limitations that can lead to significantly reduced accuracy when assessing typical sound system performance. Although important factors such as background noise and reverberation can be accounted for, it is shown that the typical, nonlinear amplitude and frequency response characteristics of many systems are not adequately addressed. Furthermore, common temporal distortions such as discrete specular reflections or later arriving echoes are also shown to result in inaccurate assessments. The need for a simple, easy to use, and yet robust measurement technique is highlighted.

Loudspeaker directivity as a function of frequency, and the importance thereof to sound system performance in large and reverberant spaces

Control of a loudspeaker’s directivity, or coverage pattern, at high frequencies can be readily achieved with devices of modest dimensions. Extending directivity control into the vocal midrange and below requires devices of significantly larger size and possibly greater complexity. However, directivity control at lower frequencies can significantly increase musical clarity and vocal intelligibility in large and typically reverberant spaces such as stadiums and arenas. The basic physics behind achieving extended frequency directivity control, including the use of signal processing, will be outlined. Typical existing, practical examples will be presented. A two-channel computer auralization comparing transducers in a reverberant space with and without extended frequency directivity control will be demonstrated.

Comparison of simulation and measured sound system performance in the German Reichstag Debate Hall, Berlin

For the design of the new sound system for the Reichstag Debate Hall, Berlin, the ulysses computer aided acoustic design program has been used. The 3-D model of the room consisted of more than 1000 faces treated with different absorption in octave bands according to the architect’s plans. Simulation of direct sound coverage, RT60, intelligibility, energy decay via ray-tracing, etc., was done to evaluate different solutions of the sound system designs and their interaction with room acoustics. It is intended to compare actual acoustic test results to simulated predictions and to discuss conformity and deviations. The software was also used to predict directivity balloons of the complex speaker arrays located in the debate hall. The balloons were derived from measured balloons of the single devices used in the arrays. Considering relative mechanical locations, acoustic centers, acoustic power, and delays, the predictions showed good conformity with polar measurements of a real cluster.

Verifying the accuracy of audible simulation (auralization) systems

Auralization systems are beginning to appear in the professional sound industry. Each claims the ultimate benefit of ‘‘hearing the sound system before it is installed.’’ But how much work has been done to substantiate these claims? Can the customer always judge the sound system performance based on what he or she hears on the auralization system? Before any auralization system can be used, it must be ‘‘authenticated.’’ Authentication is the process of verifying that what people hear on an auralization system is the same−or almost the same−as what they would hear in the real environment. A systematic approach to authentication of auralization systems will be described. In this approach, the purpose of the auralization system, along with the perceptual parameters to be tested must first be defined. Then subject-based listening tests−typically one for each perceptual parameter−must be designed, conducted, and evaluated. It will be shown that this authentication process, when followed, can be used to characterize any auralization system.

Acoustical requirements for large multiple‐use arenas

Multiple‐use requirements for large arenas have grown over the past two decades. Activities now include such diverse events as rodeos, athletic events, tractor pulls, circuses, ice shows, road company musical performances, and large assemblies for speech reinforcement. The multiple use of these facilities places strict requirements on the acoustical design. Speech reinforcement for large assemblies is probably the most exciting, requiring controlled acoustics, low HVAC noise, and high‐quality sound system performance. In order for the facility to work successfully for all activities, all aspects of the acoustical design must be carefully integrated during the design phase. Several large arenas are considered, discussing the acoustical requirements and the acoustical methods used in each. The Marriott Center, a 22 300 seat arena at Brigham Young University is highlighted as an example of a successful large arena with very demanding multiple‐use requirements. The uses and corresponding acoustical requirements are examined in detail, as well as the measures taken to achieve the desired results. These methods are contrasted with less successful methods.

Microcomputer‐based implementation of the speech transmission index for large spaces

The speech transmission index (STI) has been shown to be an accurate predictor of speech intelligibility over a wide variety of conditions [T. Houtgust and H. Steeneken, J. Acoust. Soc. Am. 77, 1069 (1985)], and the computationally more efficient RASTI method is being considered as an IEC standard. Instruments have been developed by others to measure the STI after room construction is complete and the sound system is operating, but the method has not been implemented in a program for predicting sound system performance. Thus the method has not been used to predict the intelligibility of unbuilt or in‐process designs. A new microcomputer‐based implementation of the STI method will be described along with the results of an experiment designed to verify its accuracy. A database of ten reverberant rooms was used to compare actual intelligibility scores using human subjects to intelligibility scores predicted by the new computer‐based STI program.

Evaluation of Japanese speech intelligibility for the sound system of an auditorium by STI

Subjective hearing tests and STI measurements were carried out in a church and in six auditoriums. The relationship between the intelligibility and the directivity of the loudspeakers was studied for Japanese speech. In the church, the experiment was performed with four types of loudspeakers having different radiation directivity. At the point of 4*Dc (Dc is the critical distance) from the loudspeaker, STI was about 50%, and the intelligibility was found to be “fair.” STI measurements were successively carried out in six auditoriums with clustered loudspeaker systems designed to cover the audience area within 4* Dc. The results showed almost the same relationship between the STI and the ALcons given by T. Houtgast even for Japanese speech. Finally, the validity limits of STI as parameter for evaluating the performance of sound systems in auditoriums is discussed.