Sound Transmission Measurements Research Articles

Is pickleball a good neighbor?

Upscale multi-family residences need the latest amenities to attract tenants. A recent project featured a party room, exercise facility, and pickleball court on the top floor of a low-rise, adaptive reuse of an office building to residential renovation. Pickleball courts located directly above residential units allowed for measurements of sound transmission during pickleball play and comparison to traditional airborne and impact isolation metrics.

Evaluating Laboratory Measurements for Sound Insulation of Cross-Laminated Timber (CLT) Floors: Configurations in Lightweight Buildings

Cross-laminated timber (CLT) floors with supplementary layers or floating floors comprise a common solution in new multistory timber structures. However, bare CLT components provide poor sound insulation, especially in low frequencies during structure-borne sound propagation. Thus, floor configurations in wooden buildings deploy more layers for improved acoustic behavior. Twelve contemporary CLT floors were analyzed after laboratory measurements of airborne sound reduction and impact sound transmission utilizing the following indicators: Rw, Rw, 100, Rw, 50, Ln,w, Ln,w,100, and Ln,w,50 (per ISO 10140, ISO 717). An increase in sound insulation was achieved thanks to added total mass and thickness, testing layers of the following: elastic mat for vibration isolation, wool insulation, gypsum boards, plywood, concrete screed, and wooden parquet floor. The results indicate that multilayered CLT floors can provide improvements of up to 22 dB for airborne sound and 32 dB for impact sound indicators compared with the bare CLT slab. Floating floor configurations with dry floor solutions (concrete screed) and wooden parquet floors stand out as the optimal cases. The parquet floor provides a 1–2 dB improvement only for impact sound indicators in floating floor setups (or higher in three cases).

Horizontal impact sound transmission measurements

Impact sound transmission is typically considered for the floor/ceiling assembly that separates vertically stacked spaces. This is the context that ASTM E492 laboratory testing and ASTM E1007 field testing are performed. However, impact sounds often have the potential for causing significant flanking transmission through structural connections of the floor system to surrounding spaces. A common concern for possible impact sound transmission can occur with hard flooring finishes that are not isolated from the floor structure to adjacent spaces. For this condition, while it is possible to achieve adequate impact isolation vertically by using isolated ceiling assemblies, the lack of isolation for the flooring may allow significant horizontal impact sound transmission, which is not affected by the ceiling assembly. This study presents findings and comparisons from measurements of impact sound transmission testing between horizontally adjacent spaces on a concrete floor slab and a wood-framed floor assembly with different flooring underlayment conditions.

On the 50th anniversary of ASTM E33, a history of ASTM International standards on building and environmental acoustics

This year marks the 50th anniversary of ASTM International Committee E33 on Building and Environmental Acoustics which combined all ASTM activity in these areas into one committee, though work on ASTM standards for measurement of sound absorption and transmission had started prior to 1950. This presentation will discuss the history of the committee and ASTM International standards in acoustics including the leadership that has made it possible.

Investigations about periodic design for broadband increased sound transmission loss of sandwich panels using 3D-printed models

Abstract Two types of sandwich panels are designed by using the periodic structure theory. A double-wall panel with mechanical links and a sandwich panel with rectangular core are studied. An oriented optimization of the elastic bending waves’ propagation versus the acoustic wavenumbers is achieved by using shifted core walls and by keeping the mass and stiffness of the system constant. Standard and optimized configurations are 3D-printed and sound transmission measurements are carried out by using a facility with an uncoupled reverberant-anechoic configuration. The experimental evidences of enlarged bending band-gaps and deformation mechanisms are proved using a reverse approach based on the acoustic radiation of the panels.

Experimental extraction of loudspeaker parameters from sound transmission measurements in a plane wave tube for moving-coil drivers and passive radiators

Moving-coil loudspeaker parameters are typically derived from electrical impedance measurements. Leishman and Anderson previously provided the theoretical foundations for extracting these parameters from sound transmission measurements conducted in a plane wave tube. This presentation will discuss experimental results of using this idea to extract the parameters of moving-coil drivers and those of passive radiators, the latter of which cannot be derived from electrical impedance measurements. The two-load method is used to account for the non-anechoic behavior of the tube to better enable accurate extraction of the sound transmission. Mechanical parameters are extracted from an open-circuit sound transmission measurement, and the electrical parameters are extracted by placing a wire across the loudspeaker’s terminals to provide a closed-circuit sound transmission measurement. Parameters extracted from measurements of electrical impedance, sound transmission, and destructive analysis of diaphragm assemblies will be compared.

Sound transmission analysis of various lightweight wall panels

Demands of lightweight wall panels and acoustical privacy in recent years have accelerated the incorporation of wall panels in the modern building element constructions. Lightweight wall panels are based on multi-layered structures which are a combination of gypsum board, glass wool/mineral wool, resilient steel channels and staggered wood studs used for inter-dwelling walls in modern buildings. The objective of this paper is to investigate the implementation of different types of combination to improve the sound insulation of sandwich constructions from above materials. The Sound Transmission Class (STC) characteristics of panel constructions with various combinations have been investigated. The measurements have been performed in the sound transmission suite of the CSIR-National Physical Laboratory, India according to ISO 10140 and ASTM 90. This paper presents the STC value of 20 samples tested in systematic evaluation for sound transmission through different sandwich structures with a frequency range of 50–6300 Hz with STC varying 46–59. As low frequency sound is the common cause for noise, the sound transmission measurements have been done on frequencies as low as 50 Hz. This work will help the noise control engineers, builders, designers, acoustic consultants, and residents/consumers to select construction suitable for wall panels to use in buildings.Demands of lightweight wall panels and acoustical privacy in recent years have accelerated the incorporation of wall panels in the modern building element constructions. Lightweight wall panels are based on multi-layered structures which are a combination of gypsum board, glass wool/mineral wool, resilient steel channels and staggered wood studs used for inter-dwelling walls in modern buildings. The objective of this paper is to investigate the implementation of different types of combination to improve the sound insulation of sandwich constructions from above materials. The Sound Transmission Class (STC) characteristics of panel constructions with various combinations have been investigated. The measurements have been performed in the sound transmission suite of the CSIR-National Physical Laboratory, India according to ISO 10140 and ASTM 90. This paper presents the STC value of 20 samples tested in systematic evaluation for sound transmission through different sandwich structures with a frequency range o...

Acoustics of seagrass photosynthesis

The paper reviews experiments in the Mediterranean that have investigated the use of low frequency sound transmission measurements (0.2–20 kHz) to study metabolism of seagrasses in situ in a noninvasive way and to better evaluate primary production at the scale of a meadow, for Posidonia oceanica and Cymodocea nodosa species. As sound interacts with the canopy and rhizosphere, the cumulative effect of multiple scattering from the aerenchymatic tissues of leaf blade, rhizome, and root changes the character of the environment impulse response. Diel variations of received energy and statistical features are due to oxygen movement which modifies the plant scattering function. During periods of high net photosynthesis, pressurization of the lacunal gas modifies the tissue mechanical properties. High internal oxygen partial pressures cause the release of oxygen into the diffusive boundary layer which can result in bubble formation on the tissue surface when local oxygen concentration exceeds solubility. In situ experimental results will be discussed in the light of laboratory acoustic and microscopic investigations of the tissues. [Work supported by ONR, ONR Global.]

Chinchilla middle ear transmission matrix model and middle-ear flexibility.

The function of the middle ear (ME) in transforming ME acoustic inputs and outputs (sound pressures and volume velocities) can be described with an acoustic two-port transmission matrix. This description is independent of the load on the ME (cochlea or ear canal) and holds in either direction: forward (from ear canal to cochlea) or reverse (from cochlea to ear canal). A transmission matrix describing ME function in chinchilla, an animal commonly used in auditory research, is presented, computed from measurements of forward ME function: input admittance YTM, ME pressure gain GMEP, ME velocity transfer function HV, and cochlear input admittance YC, in the same set of ears [Ravicz and Rosowski (2012b). J. Acoust. Soc. Am. 132, 2437-2454; (2013a). J. Acoust. Soc. Am. 133, 2208-2223; (2013b). J. Acoust. Soc. Am. 134, 2852-2865]. Unlike previous estimates, these computations require no assumptions about the state of the inner ear, effectiveness of ME manipulations, or measurements of sound transmission in the reverse direction. These element values are generally consistent with physical constraints and the anatomical ME "transformer ratio." Differences from a previous estimate in chinchilla [Songer and Rosowski (2007). J. Acoust. Soc. Am. 122, 932-942] may be due to a difference in ME flexibility between the two subject groups.

Modified acoustic transmission tube apparatus incorporating an active downstream termination.

Current techniques for measuring normal incidence sound transmission loss with a modified impedance tube, or transmission tube, require setting up two different absorbing termination loads at the end of the downstream tube [ASTM E2611-09, Standard Test Method for Measurement of Normal Incidence Sound Transmission of Acoustical Materials Based on the Transfer Matrix Method (American Society for Testing and Materials, West Conshohocken, 2009)]. The process of physically handling the two required passive absorbing loads is a possible source of measurement errors, which are mainly due to changes in sample test position, or in test setup re-assembly, between measurements. In this paper, a modified transmission tube apparatus is proposed for non-intrusively changing the downstream acoustic load by means of a combined passive-active termination. It provides a controlled variable sound absorption which simplifies the setup of standard two-load techniques, without the need of physically handling the apparatus during the tests. This virtually eliminates the risk of errors associated with the physical manipulation of the two passive terminations. Transmission loss measurements in some representative test conditions are reported, showing improvements over current implementations, in reducing by approximately 50% the measurement variations associated with the setup of the two required absorbing terminations. Measurement results agree within 0.4 dB (maximum difference in high resolution broadband), and 0.04 dB (mean difference in 1/3-octave bands), with those obtained using standard passive two-load methods.

Comparison of laboratory building acoustics standards from ASTM International, Japanese Industrial Standards Committee, and the International Organization for Standardization

Testing standards are fundamental to the practice of building acoustics. To that end, ASTM International, the Japanese Industrial Standards (JIS) Committee, and the International Organization for Standardization (ISO) all have standards that cover the laboratory measurement of airborne and impact sound transmission. These standards include ASTM E90 and E492, JIS A 1416, and A 1418 and ISO 10140. This paper will review the theory behind each methods and the derivation of the equations used. It will also discuss each of these standards in detail, including the relative strengths and weaknesses of each as well as the interoperability the resulting data. Previous research comparing the standards will also be reviewed. Finally, a brief overview of the repeatability and reproducibility of all building acoustics standards will be discussed.

Measuring sound detection spaces for acoustic animal sampling and monitoring

Sound recordings obtained from passive acoustic monitoring systems are increasingly used to sample animal biodiversity. However, sound recorders sample variable detection spaces, so that data may not be comparable between sampling sites and recording setups.Focusing on terrestrial systems, we measured understory vegetation, tree structure, sound transmission, ambient sound pressure level, and derived sound detection spaces of 38 plots in lowland rainforest, jungle rubber, and oil palm and rubber plantations, using different combinations of sound frequency (0.05 to 40kHz) and source height (0 to 5m).We show that simple vegetation structure measures poorly predict sound transmission, so that direct sound transmission measurements are indispensable. We depict highly variable sound detection spaces in different land-use types. Finally we estimated species richness of exemplary animal groups and found considerable differences between land-use types on the basis of variable detection space areas alone.Sound detection spaces respond non-linearly to sound frequency and source height, and they need to be quantified in acoustic surveys to avoid substantial bias in biodiversity estimates between sampling sites. Detection spaces also determine species detection probabilities and allow comparing data between recording setups. We provide guidelines and computer scripts for measuring sound transmission and ambient sound level using consumer audio equipment, and for computing detection spaces. Appreciating the effective sampling area of acoustic recorders closes a gap between acoustic and traditional animal survey methods. Species richness estimates can now be reported for measured sampling areas, and animal population variables such as abundance, density, and activity can be compared at equal areas.

Sound transmission measurements through porous screens

The two microphone transfer function technique is used to measure sound transmission properties of porous screens or membranes in a plane wave tube. This presentation will compare sound transmission of porous screens from several manufacturers. Measurements are made with two different plane wave tubes, one of diameter 10.2 cm to measure frequencies between 100 Hz and 2 kHz, and the other of diameter 1.3 cm to measure frequencies between 2 kHz and 16 kHz. Special considerations are made to account for the intrinsic losses in the smaller diameter tube.

The Sound Insulation of Double Facades with Openings for Natural Ventilation

Natural ventilation represents a potentially sustainable scheme for the provision of good indoor air quality and free cooling in buildings. Noise pollution is an impediment in this case, as buildings under noise exposure cannot effectively deploy the natural (window) ventilation option. The present contribution focuses on a double-leaf facade solution, which offers sufficient sound insulation while facilitating natural ventilation. The impact of various variables of such a system (e.g., the size of the opening, location of the openings, the relative displacement of the openings in the two layers, the cavity sound absorption) were examined via parametric laboratory sound transmission measurements using an experimental modular double-leaf wall. An empirically-based equation and a simple analytical one were developed for the prediction of the sound insulation of double-leaf facades with openings for natural ventilation. The results of these computational estimations are compared with the measurements results to discuss the potential and limitations of their predictive performance.

Estimating the Sound Insulation of Double Facades with Openings for Natural Ventilation

Natural ventilation represents a potentially sustainable scheme for the provision of good indoor air quality and free cooling in buildings. However, its application is frequently hindered due to outdoor climatic conditions, air pollution, or noise pollution. The later impediment represents one of the main motivations behind the research presented in this paper, as buildings under noise exposure cannot effectively deploy the natural (window) ventilation option. To address this problem, the potential of building envelope solutions that could offer sufficient sound insulation while facilitating natural ventilation is of critical importance. Specifically, the present contribution focuses on the sound insulation properties of double facades with openings for natural ventilation. Thereby, a generic double-leaf façade was conceived and installed between two adjacent reverberant chambers in the acoustic laboratory of the Department of Building Physics and Building Ecology at the Vienna University of Technology. This experimental modular double-leaf wall allows for various configurations of open elements. Multiple opening combinations were studied, such that the impact of various system parameters (e.g., the size of the opening, location of the openings, the relative displacement of the openings in the two layers) could be assessed both empirically and computationally. Furthermore, various levels of sound absorption in the double wall cavity (realized with absorber panels) were considered and tested. The resulting comprehensive set of parametric configurations was subject of systematic sound transmission measurements. Using the results of the measurements, multivariable analysis and curve-fitting techniques were deployed toward developing empirically-based equations for the prediction of the sound insulation of double-leaf facades with openings for natural ventilation. Furthermore, a simple analytical model was proposed that could be also applied toward predicting the sound transmission of such constructions. The results of empirically-based and analytical models are compared with the measurements results to discuss the potential and limitations of their predictive performance.

Underwater sound transmission through arrays of disk cavities in a soft elastic medium.

Scattering from a cavity in a soft elastic medium, such as silicone rubber, resembles scattering from an underwater bubble in that low-frequency monopole resonance is obtainable in both cases. Arrays of cavities can therefore be used to reduce underwater sound transmission using thin layers and low void fractions. This article examines the role of cavity shape by microfabricating arrays of disk-shaped air cavities into single and multiple layers of polydimethylsiloxane. Comparison is made with the case of equivalent volume cylinders which approximate spheres. Measurements of ultrasonic underwater sound transmission are compared with finite element modeling predictions. The disks provide a deeper transmission minimum at a lower frequency owing to the drum-type breathing resonance. The resonance of a single disk cavity in an unbounded medium is also calculated and compared with a derived estimate of the natural frequency of the drum mode. Variation of transmission is determined as a function of disk tilt angle, lattice constant, and layer thickness. A modeled transmission loss of 18 dB can be obtained at a wavelength about 20 times the three-layer thickness, and thinner results (wavelength/thickness ∼ 240) are possible for the same loss with a single layer depending on allowable hydrostatic pressure.

Extraction of plate bending stiffness from coincidence angles of sound transmission measurements

The bending stiffness in a homogeneous, isotropic, thin plate is experimentally derived from measurements of coincidence angles extracted from supercritical sound transmission versus frequency measurements. A computer controlled turn table rotates a plate sample and a receiver array, placed in the near field of the plate. The array is used to track the transmitted sound through the plate, generated by a far-field stationary source, using beam forming. The array technique enables measurement of plates measuring only one wavelength in width. Two examples are used for proof of concept, including an aluminum plate in air and an alumina plate under water.

An objective measure for the sensitivity of room impulse response and its link to a diffuse sound field.

This study is relevant to acoustic measurements in reverberation rooms such as measurements of sound transmission, sound absorption, and sound power levels of noise sources. The study presents a quantitative measure for the diffuseness in a room, which is first introduced theoretically and subsequently examined experimentally. The sensitivity of a room due to changes in the initial conditions is quantified by measuring a pair of impulse responses in a room differing only in the sound source position. Such changes are linked to mixing and the diffuse sound field. The measure is based on the maximum of the absolute value of the cross-correlation between the time windowed sections of the two impulse responses. By integrating this quantity normalized by the energy of the impulse response of the room, a single number rating is obtained. Results based on three sets of experiments indicate that the diffusers and absorbers in the room influence the proposed sensitivity measures systematically.

Detection of abnormalities in dyspneic patients using a new lung imaging modality

Background Although chest radiography is a useful examination tool, it has limitations. Because not all chest conditions can be detected on a radiograph, radiography cannot necessarily rule out all irregularities in the chest. Therefore, further imaging studies may be required to clarify the results of a chest radiograph, or to identify abnormalities that are not readily visible. The aim of this study was to compare traditional chest radiography with acoustic-based imaging (vibration response imaging) for the detection of lung abnormalities in patients with acute dyspnea. Methods The current investigation was a pilot study. Respiratory sounds throughout the respiratory cycle were captured using an acoustic-based imaging technique. Consecutive patients who presented to the emergency department with acute dyspnea and a normal chest radiograph on admission were enrolled and underwent imaging at the time of presentation. Dynamic and static images of vibration (breath sounds) and a dynamic image score were generated, and assessments were made using an evaluation form. Results In healthy volunteer controls (n=61), the mean dynamic image score was 6.3±1.9. In dyspneic patients with normal chest radiographs (n=51) and abnormal chest radiographs (n=48), the dynamic image scores were 4.7±2.7 and 5.1±2.5, respectively (P <0.05). The final assessment of the vibration images indicated abnormal findings in 15%, 86% and 90% of the participants in the above groups, respectively (P <0.05). Conclusions In patients with acute dyspnea who present with normal chest radiographs, respiratory sound analyses often showed abnormal values. Hence, the ability of acoustic-based recordings to offer objective and noninvasive measurements of abnormal sound transmission may be useful in the clinical setting for patients presenting with acute dyspnea.

Evaluation of moving-coil loudspeaker and passive radiator parameters using normal-incidence sound transmission measurements: Theoretical developments

The parameters of moving-coil loudspeaker drivers are typically determined using direct electrical excitation and measurement. However, as electro-mechano-acoustical devices, their parameters should also follow from suitable mechanical or acoustical evaluations. This paper presents the theory of an acoustical method of excitation and measurement using normal-incidence sound transmission through a baffled driver as a plane-wave tube partition. Analogous circuits enable key parameters to be extracted from measurement results in terms of open and closed-circuit driver conditions. Associated tools are presented that facilitate adjacent field decompositions and derivations of sound transmission coefficients (in terms of driver parameters) directly from the circuits. The paper also clarifies the impact of nonanechoic receiving tube terminations and the specific benefits of downstream field decompositions.