Sound Isolation Research Articles

Use of a micro acoustic chamber for rapid iterative design, teaching, and demonstration in the development of innovative lower-carbon mass timber assemblies

Mass timber construction offers a range of benefits to the design industry, including the potential for sustainability and reduced building embodied carbon, biophilia, speed of assembly, and prefabrication. However, these benefits can create acoustical challenges for sound isolation between spaces. Thus, the University of Oregon’s Institute for Health in the Built Environment, in collaboration with the TallWood Design Institute, has developed a micro acoustic chamber as a conceptual testbed, educational resource, and demonstration tool for design professionals and students, to develop new and innovative mass timber acoustic assemblies, understand acoustic implications of material choices in composite form, and comparatively analyze the performance of acoustic detailing decisions more rapidly at a small scale. The chamber hosts specimens that are 813 mm × 813 mm and up to 300 mm thick, far smaller than a typical laboratory acoustic floor/ceiling assembly test chamber, creating known limitations; however, test samples can be cost and material efficient, allowing relative performance differences between assemblies to be evaluated quickly and easily for initial design feedback. This presentation will share how the use of a micro acoustic chamber has been integrated into design education, student, and industry pilot research to accelerate the development of mass timber acoustic solutions.

Sound transmission loss through steel-framed building partitions

Load-bearing steel-stud walls pose a unique acoustical challenge because both the spacing and the mil thickness of the studs can significantly affect the acoustical performance of these walls. A single wall type in a load-bearing steel building may actually include many acoustically distinct walls as the stud spacing and mil thickness change from floor to floor in the building due to the different loads. This can be especially challenging on delegated design projects where the final selection of the steel studs is left to the framing contractor and may not be included in the project documents supplied to the acoustical consultant, if there even is one on the project. In prior ASA presentations, Ben Shafer has clearly documented the effects of steel stud spacing and mil thickness on acoustical performance. This presentation adds to Ben’s prior work by investigating the effects of resilient sound isolation clips on wall performance. Clips are a unique application because the spacing of both the clips, and the hat channels does not change with changing stud spacing and because the low stiffness of the rubber isolators should reduce the effect of stud stiffness. This presentation will present the results of recent lab tests of walls with resilient sound isolation clips and compare the results to the data previously presented by Mr. Shafer.

G-Fuzz: A Directed Fuzzing Framework for gVisor

gVisor is a Google-published application-level kernel for containers. As gVisor is lightweight and has sound isolation, it has been widely used in many IT enterprises [1],[2],[3]. When a new vulnerability of the upstream gVisor is found, it is important for the downstream developers to test the corresponding code to maintain the security. To achieve this aim, directed fuzzing is promising. Nevertheless, there are many challenges in applying existing directed fuzzing methods for gVisor. The core reason is that existing directed fuzzers are mainly for general C/C++ applications, while gVisor is an OS kernel written in the Go language. To address the above challenges, we propose G-Fuzz, a directed fuzzing framework for gVisor. There are three core methods in G-Fuzz, including lightweight and fine-grained distance calculation, target related syscall inference and utilization, and exploration and exploitation dynamic switch. Note that the methods of G-Fuzz are general and can be transferred to other OS kernels. We conduct extensive experiments to evaluate the performance of G-Fuzz. Compared to Syzkaller, the state-of-the-art kernel fuzzer, G-Fuzz outperforms it significantly. Furthermore, we have rigorously evaluated the importance for each core method of G-Fuzz. G-Fuzz has been deployed in industry and has detected multiple serious vulnerabilities.

Neonatal Intensive Care Unit an Important Subject: Sound and Light Isolation Importance for Premature Babies

Erken doğumla birlikte prematüre bebekler, gelişimi için en iyi ortam olan anne karnından ayrıldıktan sonra genel durumları stabil olana kadar yenidoğan yoğun bakım ünitesinde (YYBÜ) bakılmaktadır. Bu aşamada YYBÜ içerisindeki ses ve ışık uyaranları prematüre bebeklerde nörolojik problemler, öğrenme ve davranış problemleri, motor becerilerde azalma gibi kısa ve uzun vadede birçok sorunu beraberinde getirmektedir. Bu nedenle YYBÜ içerisinde çevresel ortamının prematüre bebeklerin gelişimine uygun olarak düzenlenmesi, bakım ve işlemler sırasında çevresel uyaranların dikkate alınması konusunda bebeğin primer bakım görevini üstlenen yenidoğan hemşirelerinin sorumlulukları bebeğin büyümesi, gelişmesi ve birçok sağlık sorunu açısından önem teşkil etmektedir. Bu derleme, yenidoğan yoğun bakım ünitesindeki prematüre bebeklerde ses ve ışık izolasyonunun sağlanmasının büyüme ve gelişmeleri açısından önemine, bu konuda hemşirelerin önemine ve bakım uygulamalarına ışık tutmak amacı ile yazılmıştır.

The Benefit of Air Conduction Pure-Tone Audiometry as a Screening Method for Hearing Loss over the VAS Score.

Hearing loss is commonly encountered by general practitioners. We aimed to evaluate the screening benefit of air conduction pure-tone audiometry over visual analogue scale (VAS) scores for hearing loss. Moreover, we intended to perform the first cross-sectional study in Greece to assess hearing loss with pure-tone audiometry in young adults of the general population. We evaluated Greeks between 15 and 40 years old in a high school in Karditsa, Greece, and a primary health care unit in a nearby community. Subjects filled out a VAS score sheet and underwent pure-tone audiometry in a room without sound isolation, with air conduction only. We named the latter procedure modified pure-tone audiometry (mPTA). Subjects with pathologic results were examined via otoscopy and standardized pure-tone audiometry (sPTA). Of the 286 subjects evaluated, the VAS score revealed 5 subjects (1.7%) with hearing loss. mPTA (100 s duration) doubled this percentage (in total 3.8%; Pearson Chi-Square test; p < 0.001). Based on sPTA, the sensitivity and positive predictive value of the VAS score were 40% and 13%, respectively. For mPTA, they were 100% and 37%, respectively. mPTA filtered out pathologic cases in a proper, rapid, cheap and simple way and may be considered a proper screening method for hearing loss in primary health care.

Multi-Order Asymmetric Acoustic Metamaterials with Broad Bandgaps at Subwavelength Scales.

Noise manipulation at the subwavelength scale remains a challenging problem. To obtain better broadband sound isolation within the subwavelength range, a class of asymmetric acoustic metamaterials (AAMs) based on rotation is proposed, and this class of AAMs can further improve subwavelength sound isolation performance by introducing multi-orders. The influences of changing the alternate propagation length of the coiled channel and the square cavity in the unit cell on the band frequency distribution and the omnidirectional band structure were investigated. The effective parameters are calculated with the S-parameter retrieval method, and the generation and change mechanisms of the bandgaps were elucidated. The calculation of sound transmission characteristics showed that, in the asymmetric mode, the overall sound isolation performance of the structure was greatly improved, and the relative bandwidth expanded as the alternate propagation length of the coiled channel and square cavity increased. The omnidirectional bandgaps from the first-order to the third-order AAMs occupied 63.6%, 75.96%, and 76.84% of the subwavelength range, respectively. In particular, the first bandgap moves to the low frequency and becomes wider. Both the experimental results and numerical analyses consistently showed that disrupting structural symmetry enhances acoustic metamaterials for superior broadband sound isolation, inspiring broader applications for asymmetry in this field.

Methods to describe acoustic qualities of vehicles in stationary position

Datasheets or brochures of cars or trims generally do not contain any relevant acoustic data. This is odd, because acoustic qualities of cars are getting more important for customers. From engineering point of view, this is even stranger, because a lot of engineers are working hard to understand, control and shape acoustic qualities of cars during product development. After a disappointing purchase, the author decided to explore how acoustic qualities of cars can be measured and compared by simple means. NVH in most cases cares about qualities of cars in motion, but many acoustically relevant features can be looked at in stationary position. The paper presents the motive, suggested methods of measurements and evaluation with suggested practice in the future. Measured attributes include sound isolation of the cabin, noise level of the ventilation system, cabin intimacy and response of the audio system.

Experimental study on the widening of the sound isolation characteristics of light weight sound isolation structure using inflated membrane with air

Light sound insulation structure by using membrane and air pressure (hereinafter refer to as MSI), which consists of meshes and pressurized membranes, exhibits varying sound insulation characteristics and can be effective for the isolation of low-frequency sound even at a lightweight. However, MSI is ineffective for broadband noise owing to the limited valid frequency range of its sound insulation characteristics. Additionally, the stiffness of the frame of MSI, which constrains the meshes and membrane, must be enhanced as the sound insulation performance in the stiffness-law region depends on the stiffness. To resolve these issues, we focused on the specification of the meshes and the constraint condition of MSI. In this study, first, we evaluated the sound reduction index of a MSI combined with meshes of different specification on the surface and rear of the pressurized membrane. The results revealed that the MSI exhibited sound insulation characteristics with less reduction in sound insulation performance compared to the MSI consisting of mesh with the same specification. Second, we evaluated the sound reduction index of MSI divided by glazing bars within the frame that reinforce the stiffness of MSI. The results revealed that the sound insulation performance in the stiffness-law region can be improved by narrowing the space between bars.

Adiabatic sound transport in acoustic waveguides with time-varying Helmholtz resonators

We investigate the dynamics of acoustic waveguides with time-varying Helmholtz resonators and the ensuing wave propagation features. We focus on the numerical modeling of such a system with emphasis on the time-varying dispersion properties and emerging wave phenomena due to slow time modulation. We show that a propagating wave packet experiences a transformation that preserves the wavenumber content, resulting in frequency conversion that follows the time evolution of the dispersion bands. The conditions for such a transformation to be “adiabatic” are derived analytically, which allows the identification of the limiting modulation speed required to avoid undesired reflections or mode conversions. The predictions from the dispersion investigations are confirmed by time-domain numerical simulations, which illustrate the possibilities for frequency conversion and temporal signal compression or decompression of impinging signals. The framework presented herein may open new avenues in the context of time-varying phonic waveguides, with possible applications in communication, sound isolation, and frequency conversion.

Low frequency sound isolation by a metasurface of Helmholtz ping-pong ball resonators

We study both numerically and experimentally an acoustic metasurface based on coupled Helmholtz resonators to obtain broadband low-frequency spectral responses for acoustic insulation. A hierarchical approach is proposed, starting from single and coupled Helmholtz resonators, up to a periodic array of resonators. To this end, we performed numerical simulations using the finite element method, in which the resonators are modeled as drilled rigid spheres in airborne environment and experimental demonstrations based on ping-pong balls as Helmholtz resonators in an acoustic reverberation box. We showed the alteration of the low-frequency response of acoustic insulation resulting from inter-unit coupling in acoustic metasurfaces, and the apparition of additional attenuation by inserting a plexiglass board as support for the structure.

An investigation of the sound transmission class rating system using large-volume, high-variability datasets

From shortly before, ASTM International introduced the E90-61T classification method in 1961 to the present time, the use of the sound transmission class (STC) rating system in North America expanded arguably more than any other building acoustics metric available today. From building codes to architectural specifications, the STC rating continues to connect acoustical engineers to building designers and occupants as a method for conceptualizing sound isolation in buildings, notwithstanding a valid evidence basis for significant flaws in the STC calculation methodology. Modern innovation in acoustic treatment introduces a far greater variety in achievable sound isolation performance than when the STC was first introduced. PABCO Gypsum has performed thousands of standardized sound transmission loss (STL) testing, providing a large and varied sample from which to observe trends. This paper utilizes this large-volume sample to compare tested assemblies with the same or similar STC ratings. STL data will be observed and compared to probable loudness level differences with the hope that this information will motivate further research and change in sound isolation classification methodology.

Changes in heavy-weight impact sound isolation by construction stage in new residential buildings

In Korea, 63% of the population lives in residential buildings. Due to the prevalence of residential buildings, there are constant disputes and complaints related to floor impact sound. To address the floor impact sound problems, the Ministry of Land, Infrastructure, and Transport (MOLIT) announced strong legal regulations from 2022. The law holds construction companies liable for compensation if they fail to meet the minimum sound insulation standard. The existing construction methods for floor structures were unable to meet the required minimum sound insulation standards, leading to the need for improvements. The evaluation process was enhanced by changing the source from bang-machine to impact ball, leading to more accurate assessments of floor impact sound insulation. In response to the challenges faced with existing methods, the research paper developed and applied a composite floor structure using a new material with increased area density. The performance of each construction stage in the new composite floor structure was measured and evaluated according to the ISO 16283-2 (testing) and ISO 717-2 (evaluation) standards. The implementation of the new composite floor structure with increased area density resulted in a noise reduction of up to 10 compared to the bare slab. [Work supported by the Industrial Technology Innovation Program (20023556, Development of personalized noise mitigation technology and service based on noise simulation to solve the noise problem in personal space) funded By MOTIE, Korea.]

Implementation of active noise cancelling for sound isolation box

A quiet room is essential for acoustical instrument calibration, such as the sound level meter. A small acoustic chamber can be utilized to create an environment that is free from noise. Commonly, it is built with a passive noise-blocking system using high-density absorber material such as rock wool or glass wool. However, this approach results in a room that is both heavy and costly. This paper proposes a mini acoustic chamber that utilizes an active noise cancelling (ANC) system to block the noise. A filtered-x least mean square (FxLMS) algorithm was implemented for the ANC system. A simulation of the system with the recorded actual noise data was conducted to find the optimum filter parameter. The results show that the ANC system could reduce the noise up to 2 dB for certain types of noises. The sound outside the chamber was recorded and processed offline to tune the filter parameter. Evaluation of the effectiveness of the proposed noise reduction system was performed by measuring the sound inside the chamber.

Achieving acoustic comfort in the library: a sound masking initiative

Purpose The purpose of this paper is to highlight the sources of noise generation in a library and suggest the implementation of a sound masking system to provide acoustic comfort, maintain speech privacy and create an environment more engaging for the users. Design/methodology/approach Analyzing the existing literature and exploring the existing practices as observed in different libraries, the study gives an overview of the sound masking initiatives in libraries. Findings With practical examples of libraries, the study demonstrates how a sound masking system has been implemented to invoke better acoustic design in the library. The expansion of various activities in the library and a gradual shift from individual attention to a collaborative approach necessitates a strong focus on the acoustic design architecture of the library. The study showcases how the libraries adopt sound masking with the introduction of acoustic panels, dual panel partitions, sound-absorbent false ceilings, sound insulation, sound isolation and noise-dampening measures, installing furniture with sound containment features, adopting vibration control mechanism, mounting of white noise machines, etc., keeping the aesthetic quotient of the library alive. Originality/value The study attempts to show the current practices of the adoption of the sound masking system in libraries and promotes collaborative reading with the creation of an acoustic design-influenced library environment to control noise and reverberation and provide a comfortable reading environment.

Vibration and structure-borne sound isolation properties of silica aerogels

Vibration reduction and structure-borne sound insulation create a healthy environment in housing by reducing the exposure of the habitants from sources outside or inside the building (railway and road traffic, neighbors). Current solutions include textiles, polymer foams, rubber mats and metal springs, but for many applications, highly sought after. Although thermal insulation drives the silica aerogel market, acoustic applications are increasingly gaining attention. Most acoustic studies focus on airborne sound absorption, but structure-borne sound and vibration isolation remain unexplored. In this paper, we compare the vibroacoustic properties of silica aerogel granules to those of recycled rubber and expanded cork to assess the suitability for vibration damping or vibration isolation. With a remarkably low resonance frequency (<12 Hz) and dynamic stiffness (<0.1 N/mm3), silica aerogels provide superior vibration isolation performance compared to recycled rubber (by 8 dB) over a wide range of static loads (0.02–0.12 MPa), and silica aerogel may become a viable solution for vibration isolation in construction.

Sound Isolation Performance Assessment of Traditional and Retrofitted Timber-Framed Dwellings

This study focuses on sound isolation performances of original timber-framed interior wall and floor components in traditional-framed dwellings in Turkey and 19th century mud-brick samples used as infill within the timber frame. The acoustical ramifications of some retrofits proposed in the contexts of minimum intervention and refunctioning the traditional dwellings are assessed in reference to the relevant standards. Field measurements show that sound isolation performances of the original timber-framed wall and floor are ineffective. The results of this study show that acoustical retrofits applied on the original wall keeping its wood lath and mud-brick infill are about 5–7 dB in the weighted sound reduction index (RW) and are more effective than those applied on the reconstructed wall. Sound transmission loss values of 50- and 100-mm-thick authentic mud samples are 22–38 and 30–43 dB, respectively, between 125 and 4,000 Hz. The sound absorption coefficient at mid frequencies and the noise reduction coefficient of 50-mm-thick mud samples are 0.28 and 0.23, respectively. These results signal the importance of keeping traditional construction techniques of wall and floor during retrofits to improve the sound isolation performance. Adobe mixtures similar to the 19th-century mud-bricks can be of guidance for the production of innovative soundproofing earth-based building materials.

Case study of construction issues affecting speech privacy in legal offices

During the design phase of a project, theoretical calculations for how a space will acoustically perform are often used. However, improper construction practices and other factors such as incompatible manufacturer combinations can lead to large discrepancies between theoretical performance and field-tested performance. The project in question consisted of a renovation of an existing legal office suite with a waffle ceiling and wide window spans. The primary acoustical concern was sound isolation from office to office and from private offices to open office space. A confidential level of speech privacy was the design goal as the suite contained multiple legal consultation rooms. Existing exterior glazings spanned the length of multiple offices, so an acoustical mullion was specified. Full perimeter door seals and automatic door bottoms were also installed. This paper details how the measured performance of this suite of offices was significantly lower than the designed Sound Transmission Class (STC) rating due to issues with the acoustic mullion installation as well as different door seal, door frame, and door manufacturer incompatibilities.

A sound isolation case study for Detroit Metro Airport's TSA K-9 unit break room

The renovation of Transportation Security Administration offices at Detroit Metro Airport included a new K-9 break room for handlers to file reports and for their furry partners to decompress between explosives detection sniffing patrols. Post-renovation, the (human) occupants complained of excessive noise due to luggage conveyer belts located in the ceiling plenum. Soundscape Engineering conducted an assessment to determine feasible noise mitigation solutions to increase acoustical comfort in the break room. The primary noise source was the spiral power turn conveyer and its four motors. With the implementation of gypsum-backed ceiling tiles, an insertion loss of 17 dBA was realized. Despite the NC 57 environment in the room, the noise reduction earned rave reviews from its bipedal users. This paper discusses the budgetary, performance, and scheduling considerations for the barrier ceiling solutions and the resulting improvements obtained in the K-9 break room.

Measuring the sound isolation of doors with ASTM test standards: A case study update

At Inter-Noise 2021, a case study was presented involving performance compliance testing conducted at a university's media facility where the test methods of both ASTM E2964 and ASTM E336 were applied to assess the performance of sound-rated door assemblies. This paper provides an update on the application of the described ASTM testing standards through follow-up testing that was conducted after field adjustments were made at the media facility. The paper compares the resulting door transmission class ratings to the apparent sound transmission class ratings and examines the influence of field adjustments on each rating class.

Observation of non-reciprocal harmonic conversion in real sounds

Reciprocity guarantees that in most media, sound transmission is symmetric between two points of space when the location of the source and receiver are interchanged. This fundamental law can be broken in non-linear media, often at the cost of detrimental input power levels, large insertion losses, and ideally prepared single-frequency input signals. Thus, previous observations of non-reciprocal sound transmission have focused on pure tones, and cannot handle real sounds composed of various harmonics of a low-frequency fundamental note, as generated for example by musical instruments. Here, we extend the reach of non-reciprocal acoustics by achieving large, tunable, and timbre-preserved non-reciprocal transmission of sound notes composed of several harmonics, originating from musical instruments. This is achieved in a non-linear, actively reconfigurable, and non-Hermitian isolator that can handle arbitrarily low input power at any audible frequency, while providing isolation levels up to 30dB and a tunable level of non-reciprocal gain. Our findings may find applications in sound isolation, noise control, non-reciprocal and non-Hermitian metamaterials, and analog audio processing.