Acoustic Design Research Articles

An analysis of spatial impulse response measurements and their ability to validate spatial features within an acoustic model

Conventional impulse response measurements are commonly used to validate omnidirectional metrics within ODEON models. ODEON models can also provide further analysis of the spatial properties of spaces. However, the spatial properties of a model cannot be validated using exclusively conventional measuring techniques. Instead, spatial impulse response measurements must be performed to properly validate the spatial components of an ODEON model. Conventional impulse and spatial impulse response measurements performed at the Recital Hall in the Strauss Performing Arts Center at the University of Nebraska at Omaha were used to create and validate acoustic metrics of an ODEON model of the same space. These spatial impulse response measurements contained visualizations of directional energy over time to assess reflections. ODEON produces several graphics comparable to those produced by the measurements. Across both visualization results, early reflections are nearly identical. However, at late energy reflections, larger discrepancies arise. This is likely due to either ODEON, the spatial measurement processing software, or the ambisonics microphone used to capture the spatial measurements. The accuracy of early energy data across both methods allows spatial impulse response measurements to be used in acoustic design, as a method of validating acoustic models or examining the changes in real-world reflections.

Radiant panels and chilled beams for thermal and acoustical design

Radiant panels and chilled beams are becoming more prevalent in projects using open ceilings and low velocity airflow designs. Radiant panels are being considered with open ceiling designs for thermal efficiency and modern appearances. These panels also offer options to include acoustical absorption, however, which brings challenges that must be addressed with the mechanical engineer and the acoustical consultant. Chilled beams promise better thermal regulation and low created noise, but those promises rely heavily on the installation. This lightning presentation will endeavor to give a high-level review of these two products and how to consider them in your design.

Influence of atmospheric state on variability of long-term residual ambient sound level measurements in a subalpine valley.

Two natural influences on the acoustic environments of mountainous parks and communities are flowing water and shifting weather. A central purpose of the acoustic measurement design used by the United States National Park Service is to provide spectral estimates of residual ambient sound level metrics at a seasonal time scale. Acoustic monitoring sampling methodologies are often designed using a sequence of similar measurements. When source and residual ambient spectra overlap, an estimate of variability in the latter is beneficial to successful monitoring design. The observed and modelled effects of atmospheric state on sound level are analyzed to reveal variability due to these effects at a long-term monitoring site in Denali National Park, Alaska. The analysis of variability incorporates a covariate that is otherwise challenging to estimate in remote settings: vertical temperature gradients in the atmospheric boundary layer. Results reveal inversions (positive gradients) in the atmosphere ≥30% between 19:00 and 09:00. Inversion strengths above 0.06 °C/m are associated with 10-15 dB increases in sound level over hourly time scales. Because inversions tend to occur during otherwise quiescent times of day, they ultimately reduce seasonal variability at the site and corresponding uncertainty in noise metrics for transportation noise arriving from varied directions.

Development and Characterization of a Flexible Soundproofing Metapanel for Noise Reduction

This study addresses the critical challenge of developing lightweight, flexible soundproofing materials for contemporary applications by introducing an innovative Flexible Soundproofing Metapanel (FSM). The FSM represents a significant advancement in acoustic metamaterial design, engineered to attenuate noise within the 2000–5000 Hz range—a frequency band associated with significant human auditory discomfort. The FSM’s novel structure, comprising a box-shaped frame and vibrating membrane, was optimized through rigorous finite element analysis and subsequently validated via comprehensive open field tests for enclosure-type soundproofing. Our results demonstrate that the FSM, featuring an optimized configuration of urethane rubber (Young’s modulus 6.5 MPa) and precisely tuned unit cell dimensions, significantly outperforms conventional mass-law-based materials in sound insulation efficacy across target frequencies. The FSM exhibited superior soundproofing performance across a broad spectrum of frequency bands, with particularly remarkable results in the crucial 2000–5000 Hz range. Its inherent flexibility enables applications to diverse surface geometries, substantially enhancing its practical utility. This research contributes substantially to the rapidly evolving field of acoustic metamaterials, offering a promising solution for noise control in applications where weight and spatial constraints are critical factors.

Investigating embodied carbon of common floor ceiling assemblies and low carbon buildups to meet new requirements

The buildings and construction sector is known to be the largest global emitter of greenhouse gasses, representing 37% of all emissions. International building regulations are poised to incorporate embodied carbon targets for new building construction, with restrictions expected to become stricter over time. California became the first state to add embodied carbon emission control as part of the California Green Building Standards Code. Some cities are also enacting policies like Toronto where new city owned buildings must demonstrate less than 350kg/CO2/m2. With this increased focus and requirements, whole building life cycle assessments will become an important tool in the architecture, engineering and construction (AEC) design process. These evolving environmental regulations demand a deeper understanding of the relationship between the acoustic performance and embodied carbon of common assemblies. This work compares this relationship in several construction types, including concrete, mass timber, and wood frame assemblies. This relationship is evaluated by using environmental product declarations (EPDs) and acoustic testing of various assembly types to offer a holistic comparison of the performance metrics. The findings will support development of best practices for selecting materials and acoustic design approaches to balance low embodied carbon with high acoustic performance and support the construction industry to meet future environmental standards.

From playing in a high school band room to designing them

Jessica Clements discovered the field of acoustics as a high school senior when a square concrete box was constructed for their new band room. Watching the acousticians moving panels around the room to get the sound the band director wanted illustrated what she’d been looking for in a career – one that captured both music and math. She started her consulting career at Merck & Hill Consultants, with the very acousticians who fixed that HS band room. Over 10 years at Merck & Hill, she performed numerous field measurements and noise control investigations as well as architectural acoustics designs. In 2013, she moved to Newcomb & Boyd, LLP where she spent most of her initial time on mechanical system noise and vibration control design, eventually moving into larger noise control projects related to transportation noise, vibration control, and building acoustic occupant comfort in addition to architectural acoustic design, project management, and business development. She is currently a Principal and the Acoustics Discipline Lead for The Smith Group. This presentation will briefly discuss the trajectory of her career and a few of the key lessons she’s learned.

Viscoelastic material enhancement of underwater sound absorption in higher-order resonators: From low-frequency to ultra-broadband

Underwater noise control is crucial for improving the marine acoustic environment. This study introduces a novel underwater acoustic absorber design that integrates viscoelastic materials with higher-order resonance structures to enhance the absorption efficiency of low-frequency sound waves. By embedding a thin layer of rubber within a conventional second-order Helmholtz resonator, the rubber's viscoelastic and damping properties significantly improve this structure's underwater low-frequency acoustic performance. Theoretical and simulation calculations have shown that the structure has two perfect absorption peaks in the low-frequency range. The simulation results show that in the frequency range of 415–1848 Hz (Simulation), only four units are needed to effectively absorb up to 90 % of noise energy, and the total volume is only. Moreover, the absorber maintains excellent absorption performance over a wide range of incidence angles from 0 to 60 degrees. This work is helpful to design ultra-thin low-frequency underwater absorbers.

Akustisch optimierte Arbeitswelten

Acoustically optimized working environments: Strategies to increase productivity, comfort and attractiveness In open office structures, noise is still a widespread source of dissatisfaction, annoyance, disruption and stress. The well-documented effects of noise in research, such as the “irrelevant speech effect”, i.e. the disruption of cognitive performance due to irrelevant background speech, can be found in practice as central challenges of acoustic design. Five aspects are presented below that should definitely be considered when planning and optimizing acoustics – for greater satisfaction, well-being and productivity in the office.

Optimization of acoustic porous material absorbers modeled as rigid multiple microducts networks: Metamaterial design using additive manufacturing

This research presents a strategy to enhancing sound absorption in porous acoustic metamaterials through the optimization of micro-duct networks. The study employs a combination of analytical and numerical methods, systematically adjusting micro-duct diameters within a 2D grid to optimize absorption coefficients at specific frequency bands. The Finite Element Transfer Method (FETM) is utilized for modeling, supported by a multi-objective function influenced by the surface impedance of the network. This approach ensures practical applicability and manufacturability of the designed metamaterial. A significant aspect of the study is the development of an analytical mobility matrix for each microduct, integrated through the Transfer Matrix Method using the visco-thermal dissipation theory. This integration results in a physically coherent model, for which a semi-analytical sensitivity analysis related to the microduct diameters can be directly performed. The optimization employs the Method of Moving Asymptotes (MMA), effectively managing the complexity associated with a large number of design variables. Subsequently, the optimized structure is adapted into a 3D grid, facilitating prototype creation using Additive Manufacturing Technology (AMT) with a specific polymer material. The research methodology is validated through four distinct test cases, each demonstrating the efficacy and adaptability of the optimization tools and techniques. Experimental validation, conducted using an impedance tube, indicates a significant shift in the first absorption maximum from 2500 Hz to 1000 Hz, achieved without altering the material thickness. Additional validation through 3D Finite Element Method (FEM) modeling, which includes visco-thermal effects, further confirms the acoustic efficiency of the final designs. While the potential for achieving lower sub-wavelength conditions is recognized, the study opts for simpler structures, considering the current limitations of 3D printing technology. This study contributes to both theoretical understanding and practical application in acoustic material design, emphasizing the potential for customizing materials to specific frequency ranges. The integration of FETM modeling with MMA provides a systematic and effective approach for optimizing acoustic materials, particularly in enhancing absorption at lower frequencies.

Acoustic optimization design for the laying schemes on the composite roof structure of high-speed train

ABSTRACT If the weak sound insulation in the roof during high-speed train travel through tunnels can be addressed by adjusting the order of materials, this will meet design requirements for both economy and lightweight construction. This paper studies this problem. First, a prediction model for sound transmission loss (STL) of the roof was established to investigate the impact of different material placement schemes and optimize their arrangement. Then, the optimal placement schemes between the roof and floor were compared using STL tests. Finally, this study also examined how an optimal scheme mitigates power radiation from the roof into the train interior under typical mechanical excitations. The results indicate that the optimal laying scheme for the roof differs from that of the floor. By placing sound absorption materials on the inner side of aluminium extrusion and sound insulation materials on decorative plate, it effectively enhances vibro-acoustic characteristics of the roof.

Acoustic capsule: A structure that can carry different objects but obtain the same acoustic radiation force

An acoustic capsule is designed utilizing equivalent anisotropy of density and of sound speed. The designed capsule can carry any object with dimensions smaller than those of its inner cavity. The capsule achieves internal shielding of the sound field, thus ensuring that the capsule and its contents experience the same acoustic radiation force (ARF), regardless of any changes in the contents. An acoustic capsule design method is proposed and its feasibility is verified using a combination of theoretical analysis and finite element simulations. Additionally, optimization strategies to enhance the ARF and enable selection of appropriate material parameters are discussed, and these strategies pave the way toward practical applications of the ARF in life sciences and other fields.

Acoustic properties and attenuation of coupled shaft-submarine hull system under various excitation transfer paths

Pump-jet propulsor excitation transfers to submarine hull along rotor-shaft and duct-stator paths simultaneously. The investigations on the effects of excitation transfer paths on structural vibration and acoustic radiation of submarine are limited. The present work aims to investigate vibro-acoustic characteristics of coupled shaft-submarine hull system utilizing a theoretical wavenumber analysis method and conduct acoustic design. The energy functional of the coupled structure-fluid system of the research object is first developed, and the displacement components of the jointed shell and the acoustic pressure are expanded by the Fourier series along circumferential direction. This allows for obtaining vibro-acoustic responses in the circumferential wavenumber-frequency domain, by which the predominant wavenumbers contributing to acoustic radiation are identified. The discussions reveal that the modes n = 0 and n = 1 respectively dominate the acoustic radiation under axial and vertical rotor loads. The acoustic radiations under duct-stator load are mainly contributed by mode n = 0, and the higher order modes n = 1 and n = 2 determine several acoustic peaks. Furthermore, two acoustic design schemes are proposed to suppress the wavenumbers with high radiation efficiency. It is proven that the design of the symmetric inner foundation and the application of new material are two efficient ways to improve acoustic performance of the submarine.

Optimal ultra-broadband sound-absorption performance design for coiled up space structures with nonlinear robustness

In this paper, based on a high- sound-pressure microperforated plate model, a nonlinear sound-absorption model for multi-unit couplings based on coiled-up space structures is proposed. The sound absorption performance and relative impedance of two-unit coupled structures (TUCSs) were studied. The results show that the TUCS sound-absorption performance, which is good at low sound pressures, decreases significantly as the incident sound pressure increases owing to impedance mismatch. Furthermore, the influence of parameters such as aperture size, plate thickness, perforation rate, and equivalent length on the unit’s structural sound-absorption performance was studied. By employing the particle swarm optimization algorithm, we optimized the parameters of an eight-unit coupled structure (EUCS) using the proposed model. The optimization results reveal the nonlinear robust sound-absorption characteristics of the structure, which means the EUCS can maintain a stable and good sound-absorption performance when the incident sound pressure level and frequency are within 125–155 dB and 400–3000 Hz, respectively. Experimental assessments of the EUCS sound-absorption performance within the 300–1900 Hz range confirmed the accuracy of the proposed model and the efficacy of the optimized sound-absorption capabilities of the structure. Consequently, the proposed model and sound-absorption structure demonstrated potential applications in the acoustic lining design of aircraft engines.

New Acoustic Design for the Piscina Mirabilis Located nearby the Port of Misenum

Many heritage buildings from ancient Rome are being refurbished based on their original plan’s structure. One of them is the piscina mirabilis located nearby in Naples, which was a cistern used by the Romans to collect drinkable water for the navy waiting in the port of Misenum. The piscina mirabilis has similar architectural characteristics to a “cathedral”; however, its current precarious architectural state is the result of high levels of humidity that have caused the proliferation of mold on its vertical and horizontal surfaces over the centuries. Acoustic measurements were conducted inside the piscina mirabilis, highlighting an existing condition of the room being very reverberant, not suitable for occasional speech and conversations. The design proposed by the authors involves some mitigation solutions for the acoustics, mainly focused on controlling the low–medium frequencies and the realization of a restoration project consisting of a raised timber-floored walkway that runs along the perimeter walls, with the addition of water covering the existing floor as a natural element dominating the room volume, which represents the primary function of the building in antiquity. A waterfall was designed to be on the northern side wall. Acoustic studies were an important part of the refurbishment strategy, and a mitigation solution was devised to control medium–low frequencies by using inflated balloons of different sizes that were suspended from the ceiling vaults instead of widely used acoustic panels. The proposed strategy lowered the reverberation time by 3–4 s to accommodate a minimal level of conversational understanding. Such a solution is appropriate for this heritage building as well as other future conservation projects.

An efficient acoustic energy harvester by using deep learning-based traffic prediction

With rapid urbanisation, traffic noise pollution has become a growing community concern. However, traffic noise can be valuable due to its ubiquity and cleanliness, which can be exploited for acoustic energy harvesting systems. This paper aims to develop an efficient acoustic energy harvester to improve energy utilisation efficiency and reduce noise levels by using deep-learning methods. We propose a temporal graph attention convolutional network (TGACN) to predict noise frequency, providing guidance for the acoustic energy harvester design. Power efficiency can be maximised by adjusting the harvester's neck size to the frequency predicted by the TGACN model. The relationship between neck size and the optimum frequency range is obtained through simulations and experiments. We analysed the performance differences among the various cavities in multiple-cavity acoustic energy harvesters and discussed the circuit connection methods between each cavity to identify the optimal configurations. Additionally, we evaluated the superiority of TGACN over the state-of-the-art methods in terms of prediction accuracy by conducting extensive experiments with two real-world datasets.

An Analysis of the Displacements in 3D-Printed PLA Acoustic Guitars.

This study focuses on the analysis of the displacements generated in 3D-printed acoustic guitar tops. Specifically, the influence of 3D printing direction parameters on the vibrational behavior of a guitar top designed for polylactic acid (PLA) by analyzing five points of the top surface at a reduced scale. For this purpose, finite element tests and laboratory experiments have been carried out to support the study. After analyzing the results, it can be affirmed that the vibrational response in reduced-scale top plates can be modified and controlled by varying the printing direction angle in additive manufacturing, providing relevant information about the displacement in the vibrational response of PLA acoustic guitars. Furthermore, this work shows that the behavior of a specific acoustic guitar design can be characterized according to a specific need.

Acoustic design considerations for mental and behavioral healthcare facilities

The acoustic environment in healthcare settings can impact patient comfort and clinical outcomes. Design of mental and behavioral healthcare facilities have the unique challenge of balancing acoustic needs with the considerations of patient safety, maintenance requirements, and cost-effective design. The acoustic quality of these patient care spaces is often overlooked or considered impractical to achieve due to other design constraints. This evaluation reviews the applicable acoustic guidelines and unique design considerations related to mental and behavioral healthcare facilities, current design practices, and developer feedback for recently constructed facilities.

Broadband Aircraft Noise Attenuation Across Low and High Frequencies Using Structured Materials

Controlling broadband noise throughout the spectrum, from low to high frequencies, is a significant challenge for the aerospace, transportation, and construction industries. Although recent research has focused on low-frequency noise control solutions using acoustic metamaterial designs, the narrow-band resonances of these materials remain a limitation. This paper presents a structured material system which addresses this limitation by proposing a parallel assembly of structured materials, enabling broadening of the resonance frequency band from low to high frequencies. The study involves an arrangement of structured metamaterials and Helmholtz Resonators embedded in a layer of glass wool. By meticulously grouping individual resonant frequencies, the proposed assembly effectively attenuates noise over the frequency range of interest. The present research contributes to the development of lasting solutions for aircraft noise across a broad frequency spectrum, showing promising potential for significant noise reduction within practical constraints.

Airborne acoustic assessment of impact-resistant fitness flooring systems

Fitness facilities in residential and mixed-used commercial buildings introduce important acoustic design challenges that must be considered in a building. Cardio activities such as running on treadmills, group classes for high intensity training, and weight training areas introduce high levels of unwanted noise and vibration into a building structure. Isolated floor constructions are generally coordinated and implemented during design but are not practical when buildings are completed and occupied. Impact-resistant fitness flooring systems are typically explored and installed as an alternate approach to reduce the transmission of impact noise and vibration. Non-standardized field airborne noise measurements of weight drops were conducted on an existing gym and on four possible impact-resistant fitness flooring upgrades to assess the reduction of impact noise levels in the offices located below the gym. The measurements were also compared to the HVAC background noise levels to observe the increase above background conditions and provide a subjective evaluation. The results of the measurements show that impact-resistant fitness flooring systems provide a noticeable reduction of impact noise, compared to standard fitness flooring systems. The results also show that impact-resistant fitness flooring systems that include specialty engineered shock pads as a base layer provide a significant reduction of impact noise levels.

Advanced acoustic design: 3D printed thermoplastic folded core sandwich structures with porous materials and microperforations for enhanced sound absorption

This study introduces a novel sound-absorbing sandwich structure with a folded core, created through 3D printing technology, to address the challenge of weak sound absorption in the low-frequency range in sound absorption materials (SAMs). The structure comprises chopped carbon fiber–dispersed thermoplastic polyamide (CF-PA), continuous carbon fiber (CCF) filaments, and polyurethane (PU) foam coated with graphene oxide (GO). Simulation studies revealed that optimized structural parameters and microperforation diameters resulted in enhanced sound absorption coefficient (SAC) of 99 % or more at 1250 Hz, within the low-frequency range (160–1600 Hz). The GO-coated PU foam SAMs demonstrated excellent sound absorption performance measured in the high-frequency range (1600–6000 Hz), achieving 99 % SAC at 2400 Hz. Furthermore, the manufactured folded core structure exhibited outstanding sound absorption performance, achieving SAC of 99 % at 732 Hz measured in the low-frequency (160–1600 Hz) band and 99 % at 600 Hz, showcasing broad absorption capabilities measured in the high-frequency band (160–6000 Hz). Additionally, a flatwise compression test on the structure filled with GO-coated PU foam demonstrated a 32 % improvement in compressive load, indicating the structure’s versatility for various applications.