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13.12 Case Studies in Building Acoustics

Review of acoustically related design factors for three recent Los Angeles area music studios.
Time: 5:40 pm

Author: Michael Brown

Abstract ID: 1622

The design of a professional-quality music recording studios involves a specific set of challenges, namely the need to provide high levels of sound isolation, rigorous noise and vibration control for building support systems, and the provision of acoustically appropriate room finishes.  The optimization of design solutions for each of these challenges depends upon project-specific requirements, including aesthetic objectives, base building constraints and the musical genres being recorded. This paper reviews how these challenges were successfully addressed in three recent Los Angeles area music recording/broadcast studio projects. Projects reviewed include a recording studio at University of California, Los Angeles, where challenges included the need to accommodate all musical genres, from jazz, to orchestra, to drum ensembles.  The two other studios were both for broadcast organizations: KCRW, an influential NPR-affiliated music-orientated radio station and for the commercial radio broadcaster SiriusXM. The paper includes discussion of why and how various acoustical techniques were utilized, including use of “floating” construction and live room variable acoustics. Solutions for successfully incorporating significant areas of glazing into live rooms and accommodation of audiences are also discussed, along with the various acoustical room finishes that were applied.

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Acoustic study in a main avenue and its effects in classrooms and offices of a university in Mexico City
Time: 5:20 pm

Author: Antonio Bautista Kuri

Abstract ID: 1987

This study presents the results of a detailed acoustic investigation, systematized and with adequate equipment to the current regulations, carried out in an avenue of intense vehicular traffic located in front of a recently built architectural complex, based on concrete, aluminum, glass, and other materials, called the Postgraduate Unit, belonging to the National Autonomous University of Mexico. These measurements show that, in the initial design of the buildings, the most current knowledge about exterior-interior sound insulation through their facades was not considered. The data collected and the interviews conducted reveal that the Sound Pressure Levels rise, altering the Interior Acoustic Comfort, necessary for the performance of daily academic, administrative and research activities, resulting in permanent inconveniences for users, in addition to the saturation of areas, lack of adequate spaces and excessive unscheduled expenses. Paradoxically, empty spaces are observed in areas with high Sound Pressure Levels, which means that there is a certain level of architectural failure.

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“The answer is blowin’ in the wind” – case study of a perforated roof screen
Time: 2:00 pm

Author: Anthony Nash

Abstract ID: 2072

A recently-completed building was fitted with a roof screen fabricated from perforated sheet metal panels having “U”-shaped upturned flanges. When wind impinges on the panels, complex tone clusters are generated, leading to complaints from the occupants. The unusual character of the tonal spectrum is reminiscent of a film sound effect intended to simulate a hovering extraterrestrial spacecraft. After some preliminary (but inconclusive) field investigations, it was decided to test samples of the perforated panel in a large commercial wind tunnel where the speed and angle of the airstream could be controlled. Tones generated in the tunnel were found to occur in groups or clusters — these are most pronounced when the airstream’s angle of incidence is close to grazing. Gradually increasing airspeed caused the frequency of the tones to “jump” from one cluster to the next higher cluster. The physical principles of the tone-generating mechanism are not fully understood; however, it appears that structural resonances in the panel flanges are excited by air flowing over the perforate. Some form of a positive structural-acoustical feedback loop is involved since a) the frequencies within each tone cluster are quite stable and, b) damping the panel flanges extinguishes the tones.

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Are online meetings noisier than conventional meetings?
Time: 7:40 pm

Author: Nicholas Boulter

Abstract ID: 2226

Design of sound insulation in office meeting rooms is typically based on ‘normal’ speech levels, but anecdotal evidence suggests that raised speech levels may be common where video/teleconferencing (VC/TC) is in use. If this is the case, then partitions in meeting rooms may be under-designed. In order to gain an understanding of the real-world occupational noise levels that exist in VC/TC  enabled meeting rooms, long-term noise monitoring was conducted in multiple offices across the globe and matched to records of VC/TC use. Correlations uncovered include a link between VC/TC use and increased Lp, and higher speech Lw in larger meeting rooms.

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Case Study: Floating Jack-Up Slabs for Multi-Story Cinema in Manhattan
Time: 6:00 pm

Author: Bradlay Hunt

Abstract ID: 2391

A review of a uniquely designed floated jack-up concrete slab to isolate fourteen movie theaters on multiple floors within a multi-use building. The jack-up boxes were engineered and custom tailored to increase airborne sound transmission loss performance while achieving a very high vibration isolation efficiency specified. Field test results were obtained to validate the floating jack-up concrete's acoustical performance.

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A case study in the measurement of door sound isolation with ASTM test standards
Time: 6:20 pm

Author: Devin Clausen

Abstract ID: 2425

The use of the door transmission class rating in lieu of the apparent sound transmission class rating has yet to gain traction within building codes and specified project requirements. This paper presents a case study involving performance requirement testing conducted at a university’s media facility, in which sound insulation properties were a critical design and construction focus. Both test methods described in ASTM E2964 and ASTM E336 were performed where a door was the test partition. Door transmission class ratings were presented in comparison to apparent sound transmission class ratings for the same partition. Testing was performed in a variety of situations, including scenarios both inside and outside of the minimum requirements of testing standards. Our analysis considers the effectiveness of the recently adopted ASTM E2964 in comparison to the methods of the ASTM E336. We also consider some of the subtle differences between the two test methods and how they may impact the testing of certain adjacencies.

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Post-occupancy HVAC survey: What can be learned from 1,800 measurements
Time: 11:40 am

Author: Jeff Fullerton

Abstract ID: 2958

After opening a new multi-family residential complex, the association was asked to perform a comprehensive survey of the sound from their HVAC systems. The survey sought to quantify the sound levels from every HVAC diffuser, grille, and register that served the residences and common spaces. The effort required access into over 250 residences typically measuring between 3 and 5 locations in each residence, and as many as 7 to 9 locations in penthouse residences. While the heat pump systems serving the residences were similar models, their capacities varied depending on the square footage and solar exposure of the residence. The variations in the sound levels of these systems and from the central ventilation were significant. This presentation will highlight what was learned from the survey.

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Machining and fabrication equipment in workplaces
Time: 8:20 pm

Author: William Rosentel

Abstract ID: 3102

Increasingly well-developed workplace acoustic standards have resulted in more consistent outcomes across projects and normalized occupant expectations of acoustic quality, enhancing productivity and satisfaction. Yet these standards are often not developed for or applied to R&D and manufacturing spaces that include traditional workplace room types and uses; design criteria is limited to OSHA-assessment for noise-at-work violations. Hybrid office buildings incorporating prototyping and maker spaces are common today and often contain high-noise equipment traditionally found in dedicated machine shops. As these facilities are incorporated alongside traditional offices, noise and vibration levels generated by fabrication equipment should be accurately quantified to avoid compromised workplace acoustics. While sound data is available for most large construction equipment, available data for smaller fabrication machines typically found in machine shops is often non-standardized and difficult to obtain. Field measurement of existing equipment installations can ground an acoustical analysis with real-world data and be highly valuable in evaluating potential noise and vibration impacts and applying cost-effective mitigation during design. This case study will present measurements obtained during a noise and vibration assessment of an existing machine shop located within an office building. The discussion will include limitations of the data and an assessment of potential for disruptions.

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Noise Control design for a Ventilation Fan – Case Study
Time: 6:40 pm

Author: Joe Cuschieri

Abstract ID: 3238

A ventilation system was design and installed for a multi story garage.  The ventilation system system had a vertical concrete shaft with the ventilation fan located on the top floor at street level.  The ventilation fan is separated from the outside by a set of metal louvers.  Adjacent to the louvers is an open pedestrian area.  The exhaust fan as installed had an inline duct silencer but this was insufficient in terms of providing the desired noise mitigation.  The project desire was not to make changes to the fan or its inline silencer or the external louvers so an alternative noise mitigation option had to be explored.  Based on the provided sound power characteristics of the fan, the exterior noise levels as calculated matched the expected levels coming out of the metal louvers.  The interior of the ventilation shaft is bare concrete with the fan installed though a hole in the concrete top floor.  The predominate noise was the very high reverberation inside the ventilation shaft. The owner of the property made an attempt at installing noise absorption but this was not sufficient.  Based on the field data the sound levels with the preliminary absorption solution matched expectation, but further noise reduction was required.  A complete sound absorption on the walls of the concrete ventilation shaft noise mitigation solution was design, and the expected levels predicted to show that significant noise reductions can be obtained by a comprehensive noise absorption solution.  The noise mitigation solution was implemented and exterior sound level measurements performed  at the completion of the project.  The measured sound levels outside of the metal louvers were in very good agreement with the predicted levels.  Based on the success of this first noise mitigation solution, noise mitigation for a second ventilation system is not being considered.

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The measurements of crowd noise in a large waiting hall of Shenyang Station in China
Time: 7:20 pm

Author: Hongshan Liu

Abstract ID: 1336

This study aims to explore the characteristics and distribution of crowd noise in large space and on-site measurements of crowd noise were conducted in the waiting hall in the ShenYang Railway Station, which is the largest station in Northeast China. Photos and videos were also recorded to obtain the number and the status of the passengers. The results showed that the A-weighted crowd noise in ShenYang station was between 55dB and 80dB and the number of passengers was between 2,000 and 3,000 at peak hours. Although passengers rarely talked, it was found that both the noise level and number of passengers fluctuated rapidly in time domain, and there was a strong linear correlation between the crowd noise level and the number of passengers. The spatial distribution of crowd noise was relatively uniform at peak hours, and the crowd noise in the seating area on both sides was slightly higher than that in the central traffic area in other hours. This study is helpful for the noise control and acoustic design in the extra-large space with large crowd.

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Countermeasures against floor impact sound by heavy impact source of a box floor structure in a reinforced concrete wall construction testing device
Time: 7:00 pm

Author: Ryuta Tomita

Abstract ID: 1832

We have performed experimental examinations for the purpose of proposing a floor finishing structure with superior effects in terms of combating heavy-weight floor impact sound. We have developed a box floor with ease of construction and excellent heavy-weight floor impact sound insulation performance and examined its effect with a 1200 × 1200 mm test piece connected to inter-noise 2020. The box floor has a floor finishing structure with anti-vibration and sound insulation measures aimed at improving measures against heavy-weight floor impact sound. We herein report the results of a basic examination on the reduction of the transmitted heavy-weight floor impact sound of a box floor structure in a reinforced concrete wall construction testing device when the area is further expanded to about 10 ?. As a result, with the air layer under the box floor open, the floor impact sound level was reduced by 9 dB in the 63-Hz band compared to the bare surface. In addition, with the air layer at the bottom of the BOX floor sealed, the floor impact sound level was reduced by 5 dB in the 63-Hz band compared to the bare surface.

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