Acoustic Requirements Research Articles

Acoustic quality assessment in a classroom through simulations and measurements

The acoustic quality in a classroom directly impacts the educational relationship between the student and the teacher, reducing speech intelligibility. In addition, inadequate acoustic comfort burdens the vocal health of teachers. This study evaluated a classroom at the Federal University of Paraná, Campus Centro Politécnico, to verify its acoustic quality. The measurements of the acoustics descriptors: Reverberation Time (RT), Definition (D50), Central Time (Ts), Early Decay Time (EDT) were performed according to the ISO 3382-2 standard, concerning Noise Curves (NC) and Background Noise (BGN) these were evaluated by the NBR 10152 and S12.2 standards. The Speech Transmission Index (STI) was measured according to IEC 60268-16 and evaluated according to ISO 9921. The useful-detrimental ratio (U50) and the other descriptors were simulated in the ODEON software version 11. Thus, the results showed that the evaluated room did not meet the minimum requirements in terms of acoustic quality, for the descriptors RT, STI, Ts, D50, RF, and NC. Simultaneously, the RT and STI were also outside the limits established by the German and Finnish standards. Therefore, it is concluded that the evaluated classroom did not reach the minimum acoustic quality requirements.

On the Use of Perforated Sound Absorption Systems for Variable Acoustics Room Design

An important challenge for acoustic engineers in room acoustics design is related to the acoustic performance of multi-purpose auditoriums, which are typically designed to suit several performance requirements. With this intent, the analysis of several scenarios is usually performed individually, and then an acceptable solution, that may be adapted to several situations, is selected. One way of providing a more appropriate acoustic performance for each function of the auditorium is using variable sound absorption techniques to control reverberation and other relevant acoustic phenomena associated to sound perception. In this paper, the acoustic behavior of a perforated system that may be suitable for achieving a variable acoustic solution for room acoustic design is addressed. In the design of a cost-effective solution, the surface appearance is kept unchanged, while variable acoustic behavior is achieved either by closing the holes in the back face of the perforated panel or by placing a porous material in varying positions inside the backing cavity, thus accomplishing different acoustic requirements within a multipurpose auditorium. An analytical approach, based on the transfer matrix method is employed for preliminary acoustic sound absorption assessment provided by the system and to develop optimized solutions. Diffuse sound absorption is then computed and used to simulate, by the ray-tracing method, the acoustic behavior of a multipurpose auditorium to demonstrate efficient acoustic performance for different types of use.

Optimizing the use of acoustic materials in office buildings

Office space designers encounter a challenge in identifying the optimal set of noise control materials to improve the acoustic quality while keeping the cost of selected acoustic materials to a minimum. To address this challenge, this paper presents a novel optimization model that provides the capability of minimizing the cost of acoustic materials while satisfying all designer-specified acoustic quality requirements. The model is developed in five main stages that focus on (1) identifying the correlated designer decisions that influence the model objective function; (2) formulating an optimization objective function; (3) identifying the model constraints that are organized into acoustic quality and materials selection constraints; (4) implementing the model using genetic algorithms (GA); and (5) evaluating the performance of the model using an office space design that is under construction to assess and improve the model feasibility and performance. The outcome of the performance evaluation stage illustrates the novel capabilities of the developed model in identifying the optimal selections for the type and area of acoustic material for each surface in the office space that achieve the desired acoustic quality while keeping the cost of selected acoustic materials to a minimum.

Sustainable Passive Design for Building Performance of Healthy Built Environment in the Lingnan Area

Having a healthy built environment becomes increasingly important, especially under the effects of COVID-19. This paper intends to combine sustainable goals based on climate change with passive design principles to achieve a healthy built environment regarding the building performance of residential buildings. The Yuedao Residential Community in the Lingnan area was taken as an example for the research. Based on relevant standards of healthy buildings, the thermal, light, and acoustic environment requirements were determined. The methods of building performance simulation and on-site measurement were used to quantify the research object environments. Then, the outcomes were obtained based on these standards. As observed, the thermal environment’s adaptive thermal comfort level was level III. It was hot indoors, but the light and acoustic environments met the requirements. Building designs based on a built environment optimized by external shading systems aim to solve problems through building performance simulation and qualitative analysis. After optimization, the thermal environment improved. According to the literature review, this research focused on a healthy built environment with a sustainable passive design in terms of building performance. A research workflow was established that could be used for more practical research, with abundant research methods. The problems were solved to varying degrees, and the Lingnan architectural culture was preserved. Moreover, this research filled the gap in interactive research on healthy built environments with sustainable passive design regarding building performance.

An overview of room acoustics requirements in North American, nonresidential, building standards

In the United States and elsewhere in North America, acoustics requirements for nonresidential buildings in Federal acts, codes, official standards and unofficial guidelines and rating systems tend to be voluntary, grass-roots and bottom-up instead of being mandatory, top-down or governmentally mandated. This relates to the governmental viewpoint that noise is merely a nuisance, not a health risk as viewed in other parts of the world. Existing requirements associated with noise control - whether they are related to environmental/community noise, transmission of transportation noise through the building envelope or occupant noise through the interior construction assemblies or minimizing noise from building services - are more prevalent in these standards. Requirements for good room acoustics related to sound absorption, speech intelligibility and distraction-free and comfortable interiors that promote human health and well-being are appearing in more standards and being updated to have more stringent values. Much improvement is still needed in older standards that do not have regular revision cycles and open, public, review periods. An overview of the types of room acoustics metrics used, their evolving values, advantages/disadvantages and the research behind them will be provided. Recommendations for future advancements will be offered.

Brazilian BIM Objects Technical Standard: a first approach on Acoustics parameters

The Building Information Modeling (BIM) has increased worldwide as a new approach on the building design, construction, and facilities management. Given this panorama, the Brazilian Government enforced a regulation in 2019, Decreto 9983, which outlines a roadmap for the BIM implementation in the Brazilian construction ecosystem. As one of its guidelines is to publish the necessary technical standards, a special committee, ABNT CEE 134, was hosted at the Brazilian organization for Technical Standardization with a dedicated WG for establishing BIM objects parameters. In the framework of the WG, a subgroup on Acoustics analysis aimed to deal on how to incorporate acoustic requirements to the BIM Object. In this paper, the authors describe the development of this feature, unprecedented so far. The approach adopted for incorporating acoustic requirements into BIM objects at the Brazilian BIM Standard aimed to facilitate the workflow of acoustic consulting, while adapting it to the limitations imposed by the existing software and the construction market culture in Brazil. This paper also provides some guidelines on how this issue could be addressed in future standards revisions.

Acoustic regulations for hospital bedrooms - Comparison between selected countries in Europe

Regulatory acoustic requirements for hospitals exist in several countries in Europe, but many countries have either insufficient regulatory limits or only recommendations. The main purpose of limit values is to ensure optimal acoustic conditions for patients under treatment and for personnel for the various tasks taking place in many different rooms, e.g. bedrooms, examination and treatment rooms, corridors, stairwells, waiting and reception areas, canteens, offices, all with different acoustic needs. In addition, some rooms require special considerations like psychiatric rooms and noisy MR-scanning rooms. The extent of limit values varies considerably between countries. Some specify a few, others several criteria. The findings from a comparative study carried out in selected countries in various geographical parts of Europe show a diversity of acoustic descriptors and limit values. The paper includes examples of criteria for reverberation time, airborne and impact sound insulation, noise from traffic and from service equipment. The discrepancies between countries are discussed, aiming at potential learning and implementation of optimized limits for more room types. In addition to regulations or guidelines, some countries have hospitals included in national acoustic classification schemes with different acoustic quality levels. Indications of such classification criteria will be included in the paper.

Interlaboratory and proficiency tests for buildings sound insulation field measurements in Brazil - 4th Edition 2020

Since 2013 ABNT NBR 15575:2013 entered into force in Brazil, a national technical standard that establishes acoustic requirements for dwellings, that can be verified by means of field measurements procedures performed according to specific ISO standards. Therefore, those requirements have fostered the acoustic field measurement market, and the number of laboratories has quickly increased across the county. ProAcústica - Brazilian Association for Acoustical Quality, a non-profit entity, aiming to improve the quality of the acoustics business in Brazil has organized in 2020 the fourth edition of the "Interlaboratory program of field measurements for building acoustics laboratories - INTERLAB Program". This consists of a fundamental tool for acoustic field laboratories to evaluate and verify the quality of their measurement results. This paper presents the methodologies and procedures used in the interlaboratory program, as well as the results of both the interlaboratory test and the proficiency carried out in São Paulo (Brazil) during 2017 by ProAcústica - Brazilian Association for Acoustical Quality. In this edition a total number of 25 laboratories have participated (32% more participants than the last edition in 2017) for different type of field tests: airborne sound insulation, airborne facade sound insulation, impact sound level, sound pressure level from service equipment in buildings, and reverberation time). The main objectives are the evaluation of the precision of the field test methods in the Brazilian market, and the analysis of the performance of the participating laboratories as a quality control tool.

Accurate noise modeling for petrochemical plants - impact of compressor Piping

Compressor piping is a dominant noise source in petrochemical plants with large centrifugal compressors. Acoustic insulation is used on compressor suction, discharge and recycle lines as a measure to mitigate noise radiating from compressor piping. This paper will demonstrate using case studies the importance of acoustic insulation on compressor piping as the primary and most cost effective noise control method for both community and in-plant noise. Case studies include the predicted and measured noise levels obtained during post startup noise surveys. This paper will also illustrate that to obtain good agreement with measured noise levels it is imperative to accurately model the piping sources following the actual piping layout and account for distance attenuation. A cost-benefit analysis of using complete compressor houses and/or acoustic blankets will be presented along with the efficacy of various types of acoustic insulation including elastomeric foam and aerogel based insulation systems. Different acoustic requirements for hot and cold insulation systems will also be presented.

The Brazilian performance standard revision. Sumary and next steps

In 2019, the Brazilian Standard NBR 15575: 2013 start a periodical revision process. This standard presents performance criteria for dwellings, such as acoustic, thermal, lighting, durability, etc. During this first enforcement period, some requirements result in divergent interpretations, e.g. difficulties to define the noise class, proposed as a subjective criteria. Technical groups were created to analyze the current text and propose modifications to solve these issues. This article presents an overview of the mains issues related to the acoustic requirements found in the standard. A summary of the proposals is presented, which went through a national ballot.

Structure-acoustic design of floating foundation in high strength steel cabin

Objectives This paper proposes a design for a floating foundation of a high strength steel cabin which simultaneously meets the requirements of impedance adaptation in acoustics and stiffness matching in mechanics. Methods Typical floating foundations which are not connected with the pressure hull are studied by adjusting the structural parameters of the foundation, analyzing the impedance characteristics and intrinsic modes with the finite element method, and calculating the strength of the pressure structure along with the original and improved foundations. A scheme of a floating foundation which satisfies the design requirements is obtained. Results The results show that the amplitude of the improved foundation is increased, the coupling of the intrinsic modes of the foundation with the mechanical equipment is reduced, the strength of the pressure satisfies the specification requirements, and the added weight is within the acceptable range. Conclusions This floating foundation scheme can provide references for the design of large foundations for high strength steel cabins which take into account both acoustic and mechanical requirements.

Acoustic retrofit strategies of windows in facades of residential buildings: Requirements and recommendations to reduce exposure to environmental noise

Achieving an adequate indoor acoustic comfort environment is one of the main priorities to avoid adverse effects caused by noise. Façades are the constructive elements most likely to be retrofitted due to their delimiting function between indoor and outdoor space. This study compares the acoustic façade requirements established for new and existing buildings in current national building regulations. The assessment of regulations and the analysis of a comparison model, examining different techniques for improving sound insulation, conclude that on a global scale there is a lack of consensus on external noise insulation and acoustic requirements worldwide. It is not possible to merely summarize all requirements into a single number as the sound insulation required depends on the performance of the building element, the outdoor noise level or the indoor noise level. Therefore, there is an in-depth discussion on the harmonization of external sound insulation requirements in acoustic regulations. This study also analyses façade wall solutions of existing housing stock and compliance with current regulations, with results showing that upgrading interventions focused on windows can be sufficient to propose suitable constructive systems in compliance with requirements established worldwide when external noise amounts to 60 dB(A) measured 2 m from the façade.

In-situ investigation of the acoustical performance in collective social dwellings

With the lack of mandatory requirements to be observed by construction and building actors, acoustic performance becomes critical when considering overall comfort conditions in collective multistory dwellings alongside other factors such as those related to social and health conditions. However, despite the increasing number of complaints resulting from noise-related conflicts with neighbours, a very limited number of studies have been devoted to evaluating the acoustic performance of social housing. Hence, the aim of this study to assess objectively, through in-situ standardized measurements, the acoustical comfort within a sample of tunnel formwork multistory housing projects in Algeria. Given the lack of local national guidelines in this respect, a review of regulations implemented worldwide has been made to specify the most suitable descriptors for the case at hand. The acoustical performance considered in the present study concerns airborne, impact and façades sound insulation as well as those ratings used in acoustical housing classification schemes. Comparison of the results obtained to recommendations set by regulations, in countries with a long experience in the field, show that such type of housing can offer only poor to very moderate acoustics comfort to their tenant. This study enhances the urgency to develop a local mandatory regulation code setting clear acoustics requirements for coming housing projects for ensuring a minimum quality of the indoor acoustical environment for occupants and for avoiding undesirable noise-related disputes between neighbours.

Indoor Acoustic Requirements for Autism-Friendly Spaces

The architecture of spaces for people on the autistic spectrum is evolving toward inclusive design, which should fit the requirements for independent, autonomous living, and proper support for relatives and caregivers. The use of smart sensor systems represents a valuable support to internal design in order to achieve independent living for impaired people. Accordingly, these devices can monitor or prevent hazardous situations, ensuring security and privacy. Acoustic sensor systems, for instance, could be used in order to realize a passive monitoring system. The correct functioning of such devices needs optimal indoor acoustic criteria. Nevertheless, these criteria should also comply with dedicated acoustic requests that autistic individuals with hearing impairment or hypersensitivity to sound could need. Thus, this research represents the first attempt to balance, integrate, and develop these issues, presenting (i) a wide literature overview related to both topics, (ii) a focused analysis on real facility, and (iii) a final optimization, which takes into account, merges, and elucidates all the presented unsolved issues.

Noise and acoustic conditions of premises for hearing-impaired people in Korea

Hearing-impaired people need more stringent acoustic and noise requirements than normal-hearing people in terms of speech intelligibility and listening effort. Multiple guidelines recommend a maximum reverberation time of 0.4 s in classrooms, signal-to-noise ratios (SNRs) greater than 15 dB, and ambient noise levels lower than 35 dBA. We measured noise levels and room acoustic parameters of 12 classrooms in two schools for hearing-impaired pupils, a dormitory apartment for the hearing-impaired, and a church mainly for the hearing-impaired in the Republic of Korea. Additionally, subjective speech clarity and quality of verbal communication were evaluated through questionnaires and interviews with hearing-impaired students in one school. Large differences in subjective speech perception were found between younger primary school pupils and older pupils. Subjective data from the questionnaire and interview were inconsistent; major challenges in obtaining reliable subjective speech perception and limitations of the results are discussed.

Design of atypical facade architectural elements as noise reduction barriers - case study

The presented work is the result of affirmation of synergistic work of experts dealing with architectural and acoustic design with the aim and purpose of finding an adequate solution for optimal correction of the effect of GHG systems installed on the facade of the subject (case study) office building in Belgrade. Measurements established that the noise of the constructed GHG systems affected the residential building in the immediate vicinity. The effect of the constructed devices (refers to the installed units) of the office building in question in the case when they operate at full capacity was measuring to be about 58 dB (A). The urban zone in which the building is located (Vracar-Belgrade) belongs to the category of "office residential area" in which the outdoor noise level permitted for the period of day is 60 dB (A), and for the night period is 50 dB (A). Taking into account the stated facts, it has been unequivocally established that GHG systems to a certain extent exceed the permitted noise levels and "endanger" the neighboring observed building. The subject of this professional scientific research is the design of atypical facade architectural elements as a barrier reducing noise on the example of an office building in Belgrade. The architectural challenge was reflected in the fact that, in addition to designing the facade element which, at the request of the investor must not compromise the architecture of the building, therefore, should be "atypical in architectural design", it must also provide flexibility in applying different variants of acoustic barriers, which in addition to architectonic requirement must provide an adequate response to acoustic requirements. To the satisfaction of the authors, the designed barrier confirmed a successful synergy solution. The adopted architectural-acoustic configuration of the barrier proved to be effective regardless of the type of installed air conditioners, which in some way justifies the initial idea of strong causality of acoustic and architectural design, as a synergistic principle.

Finite element modeling using carbon epoxy plates for propeller blades applications

Abstract Over past few decades, tremendous innovations have occurred in the aerospace/marine industry because of environmental regulations, rising fuel costs, increase in airline traffic etc. These reasons lead to more usage of composite materials in the primary structural components. These materials are known for their high strength and stiffness to weight ratio and hence used in structural applications where there are stringent weight requirements as in aerospace and marine applications. Because of recent advancements in manufacturing techniques, there is increase in trend of using composite materials in many complex aerospace and marine structures. Since design and analysis of these structures becomes extremely difficult, Finite Element method is used extensively in most of the applications to reduce time and effort. Marine propellers are generally doubly curved and tapered with solid cross sections due to acoustic requirements and hence modelling of these kind of propeller blades becomes extremely difficult in Finite Element Method. In this paper, different FE modelling strategies for a complex shaped 3D composite structure is discussed and marine propeller blade is analysed and compared with metal blade.

Acoustic analysis and identification of smart solutions for the acoustic insulation of a large historical building

The object of the present paper is the acoustic study of Palazzo Borghese, one of the most important buildings of the neoclassical period present in Florence, which occupies the entire block between Via Ghibellina and Via dei Pandolfini. The Palace has been interested by various architectural interventions occurred in different historical periods. In 1437 a series of grandiose works of unification, enlargement and modernization were undertaken by Michelozzo who created a grand palace with a large open loggia much admired at the time. In 1709 a large, still existing, ballroom was built with a stage for the orchestra. The last major renovation was carried out at the beginning of the nineteenth century by Camillo Borghese: on the first floor, the monumental rooms, above all the main hall and the hall of mirrors, stand out for their magnificence, with a great profusion of gilded stuccoes, marble statues, columns, carved chandeliers, paintings.Currently some areas of the building are used for receptions, conferences and events, while others are part of a receptive structure, residences and offices. The contiguity of spaces, characterized by very different acoustic requirements and by the presence of three very silent internal courtyards on which these spaces overlook, led to the emergence of numerous acoustic problems whose solution is made particularly delicate by the historical-artistic constraints present on the building. In order to identify the acoustic criticalities, several campaigns of acoustic measurements have been carried out, both during the reception activities and through the use of a sample source.This investigation allowed to determine the structural weaknesses of the building and to identify the most appropriate technical and smart interventions compatible with the structural constraints and historical-artistic protection of the property.

Noise exposure ‘the new secondhand smoke’ - How is it addressed in building certification schemes

(introduction) Building certification schemes have expanded to include both the environmental impact of the construction and operation of the building, as well as the building’s influence on the occupants. Drawing attention to the indoor environmental quality, thus the well-being of the occupants, means evaluating a building’s impact on all 5 of the human senses. Hearing, acoustics, can easily be overlooked, but distracting sound can affect our bodies in more ways than we may realize.Buildings that provide a pleasant indoor acoustic environment, allow employees to be more productive, students to learn easier and hospital patients to recover quicker. A survey concluded that 75% of office employees list noise as an important workplace feature, yet only 30% are satisfied with the noise levels in their office. In schools, up to 70% of the consonants spoken by teachers cannot be heard by pupils.A survey of the countries in the EU, requested by the EC, showed that 80% of respondents believed that noise affects their health, either to some or to a great extent. Additionally, noisy environments increase physical and mental risks for example hypertension, diabetes, and obesity. As such, it links to SDG 3 “Ensure healthy lives and promote well-being for all at all ages”.(method) An analysis of the specific room acoustic requirements for open offices, which is the biggest building segment for green building schemes, and schools is the key component of the study. The analysis compares the quantitative requirements such as reverberation time and absorption area in 4 schemes (LEED, BREEAM, DGNB and WELL) to 8 national building regulations in Europe. As the building regulations only exist in their national languages these in depth comparisons are not common.(results & conclusions) This comparison shows that several schemes do not require the anyhow legally required thresholds whereas few schemes go beyond.

Detectability of auditory warning signals in the ambient noise of Dutch train cabins

Locomotive engineers need to detect auditory warning signals for safe and effective job performance. We measured the levels and spectra of the warning signals and noises present in Dutch train cabins to evaluate the effectiveness of these signals. Audio-recordings were made in six train types during normal operation. Signal detectability was estimated using the Detectsound software and compared against ISO 7731. Signal detectability was also measured in six normally-hearing individuals in a laboratory setting. Signal levels ranged between 68 and 84 dBA. Noise levels ranged between 53 and 77 dBA. The acoustical requirements for signal detectability were not met in multiple driving conditions, especially at higher speed. Sufficient signal-to-noise ratio’s were achieved in the laboratory measurements, but difficulties can be expected in unfavourable driving situations or when the engineer suffers from hearing loss. Acoustical, environmental, or work modifications might be required to prevent situations with insufficient audibility in hearing-impaired engineers. Practitioner summary: The audibility of the warning signals in Dutch trains was evaluated by comparing signal and noise spectra. The results showed that sufficient audibility is not always guaranteed. Under laboratory conditions, normally-hearing individuals could compensate for the suboptimal acoustic circumstances, but acoustical, environmental, or work modifications might be required to prevent situations with insufficient audibility in hearing-impaired engineers.