Sound Level Research Articles

Mapping human voice in urban spaces

Human voice plays a pivotal role as a sound source in urban environments. Despite the plethora of natural sound sources present in urban spaces, human voice often stands out as one of the sound source, exerting a significant influence on the perception and affection of these spaces. However, compared to other aspects of urban soundscapes, such as traffic noise (air, road, rail), human voice cartography and modelling remains relatively underexplored, with limited historical development and scholarly attention. This research gap led to the deployment of an experimental protocol in Nantes, France, to produce a comprehensive voice sound map and compare it to perceptual data. This protocol involved the collection of sound level measurements during two distinct measurement campaigns using the NoiseCapture smartphone application, coupled with surveys capturing perceptual information such as the circumplex circle of affect, perceived presence of sound sources, emergence of sound sources, and variability of the sound environment. Additionally, sound environment simulations were conducted using NoiseModelling. The present paper shows the method used to evaluate the audibility of human speech in urban spaces. During the presentation, comparisons with perceptual measurements will be presented.

Perception of audified acoustic emissions from compression of microscopic samples

Recording of acoustic emissions (elastic waves emitted by dislocation motion) during compression of microscopic samples is a novel emerging tool for the investigation of mechanical properties of materials. Yet the resulting signals can be so noisy and complex that they don't easily allow for identifying the deformation mode or the material involved. This study aims at testing if the human auditory system can pick patterns in the audified recordings (i.e. transposed from the ultrasonic to the audible range) that match the physical characteristics of the samples. In a Free Sorting Task, participants sorted sounds into groups according to perceived similarity. The sounds originated in recordings varying according to material, deformation mode, and size of the sample. During clustering and multidimensional analysis, sounds were found to be first grouped according to spectral features: Zinc and Magnesium recordings respectively produced high-pitched and low-pitched sounds. Sounds were further discriminated according to perceived sound level (soft vs. loud for slipping vs. twinning) and number of perceived sound events (no clearly associated physical parameter). Correlations were found between subjective groupings and audio descriptors, so that audio-inspired mechanical investigations can now be envisioned.

Ten years of experience with road noise auralisations

For more than a decade, The Danish Road Directorate has used auralisations to communicate the future road noise impact to the public. Auralisations are add-ons to the mandatory noise maps and assessments of noise exposed dwellings and people. Moreover, auralisations are very useful for public presentations like EIA etc. Road noise auralisations and presentations have been made to give the road's neighbours an impression and understanding of the impact, the road will have on the environment. Additionally, auralisations have been shown to be a very powerful tool in terms of explaining general acoustic terms and sound propagation e.g. the influence of wind direction and speed and the efficiency of future noise barriers of various heights. Presentation formats range from webpages to auditory presentations with calibrated headphones and overlaying introducing speak giving exact sound levels for the audience. Even videos and recorded soundscapes from specific locations have been used to create auralisations that are more trustworthy and recognizable for the audience. This presentation gives an overview of different formats of presentation and summarizes our experiences so far with different auralisations suiting the various cases of road projects. The use of simple auralisasions in Dynamic Noise Monitoring Maps will also be touched.

Noise annoyance and application of the Harmonica index at short time intervals

The Harmonica index (HRM) is aimed to quantify the perceived noisiness of environmental sounds on an hourly basis by a score on a linear scale from quiet to very noisy. The index is computed as the sum of the background noise (BGN) and the sound events (EVT) emerging from BGN and has been developed to facilitate communication with the public and to help local authorities in the decision-making process. In this paper, the HRM index has been applied to short time intervals, providing an increase in the time resolution of sound level acquisition from 1 s to 0.1 s. Six sound recordings were considered, taken in different urban contexts (i.e., parks, road traffic noise, construction sites), each lasting two minutes and divided into four sequential soundtracks of 30 s each. The tracks were played back randomly in laboratory listening tests to collect ratings of perceived annoyance given by participants after each soundtrack and, at the end of the four soundtrack sequences, the annoyance rating of the whole sound. The results show that the short-time application of the index is sensitive to the qualitative characteristics of the background and events, and needs improving before being used.

Noise hindering sound complexity in urban environments: Towards a novel evaluation criterion for urban sustainability

Urban environments are complex adaptive systems, wherein changes in one area can lead to unforeseen consequences in others. Environmental noise emerges as a multifaced issue influencing various receivers across different spatial and temporal scales. The perception of noise as a high-intensity or unwanted sound has defined the concept of quietness accordingly overlooking sustainability co-benefits. This study proposes an alternative evaluation criterion for urban planning and design, focusing on the sound complexity of public spaces that are vulnerable to environmental noise fluctuations. To determine the sensitivity of sound complexity to environmental noise, sound level measurements and sound recordings were conducted along the waterfront of a Mediterranean metropolis during the pandemic lockdowns (April 2021). Additionally, the bird dawn chorus phenomenon was studied. The analysis of collected data revealed an inverse relationship between complexity and noise, highlighting an additional impact on the urban sound environment. The promotion of sound complexity as a strategy for livable and sustainable cities can guide urban planners and designers in developing quiet and ecologically resilient urban environments.

Beyond loudness: development of a holistic solar-powered urban soundscape sensor

Low-cost sensor networks have increasingly been used to monitor noise pollution as an alternative to certified sound level meters. Existing sensor networks monitor loudness and, in some cases, classify sound sources. Most sensors do not capture metrics that are more representative of the human perception of sound, require a permanent power supply, or are relatively expensive. We develop an energy-efficient soundscape sensor with the goal of recording metrics complementary to loudness. We have implemented metrics from psychoacoustics and metrics inspired by biodiversity research, such as sharpness, intermittency, and acoustic entropy. Furthermore, the sensor predicts the source of sound events. For privacy-preservation, all audio is processed directly on the sensor. The sensor is based on a low-power microcontroller (ESP32-S3), available for a fraction of the cost of a Raspberry Pi, which is often used for sound source prediction. Finally, the sensor is solar-powered and therefore easy to install for research purposes at places without direct access to the power grid. A temporary deployment of several sensors in Amsterdam, the Netherlands, is planned

Fitness club adjacent to a quiet corporate office - Prototypes

There is a demand for fitness clubs in hotels, residential, and corporate buildings - sometimes adjacent to sensitive spaces. Activities involving weight drops and spinning bikes, among others, cause dynamic forces in the structure that propagate through the building's structure and radiate airborne sound. There is an effort by acousticians worldwide to establish a standardized method for measuring and rating the noise radiated by gyms into adjacent areas. This article describes the construction of a gym over a corporate office, occupying an area of 2100 m2 each. The gym's floor structure is a concrete and steel deck, and the office below has low sound levels. The goal of making gym activity inaudible in the office is undoable in practice. We tested several prototypes to arrive at a double insulation system with a floating slab with natural rubber mounts. A system of dynamic dampers was installed to reduce the movement of the floating slab with the dynamic excitation above it. The results of the prototype were auspicious. This paper presents the measurements of the natural frequency of the structure and the floating slab, the transmissibility of the system, and the differences in vibratory velocity from the floating floor to the structure.

Towards situation dependent radiation efficiency

Designing buildings to protect inhabitants against ground-borne noise from railway lines or other outdoor ground vibration sources has become a subject of importance. Prediction methods to tackle such a problem are under discussion within a European task group (CEN/TC126/WG2/TG1). From velocity response of floors and walls, the structure-borne sound level has to be evaluated; the linking quantity is the radiation efficiency. In the frequency range of interest, i.e. covering the one-third octave bands from 16 to 250 Hz, rooms modes exist for standard size living spaces in building. A parametric investigation is carried out to evaluate the effect of the room modes on the radiation efficiency. In a first step, a modal approach is used to estimate the radiation efficiency for different room sizes, heavy floor and light wall types. Randomly positioned forces are considered as excitation on these structural elements. From these results, the situation dependent radiation efficiencies are investigated and discussed.

Acoustic characterization of the Municipal Museum Abade Pedrosa

The 2016 interventions concerning the rehabilitation of the Municipal Museum Abade Pedrosa in Santo Tirso, Portugal were analyzed to verify in what way acoustics interferes in the museum enjoyment. In situ measurements were done in every exhibition room: Reverberation Time, RASTI and the Equivalent Sound Level (LAeq). RT[500, 1k, 2k Hz] values were between 2.5 and 3.9 s. The RASTI mean values varied between 0.44 and 0.55 s. LAeq values of background noise reached a top value of 43 dB(A) in the 1000 Hz frequency band and a global value of 57 dB(A) in every room. A multicriteria analysis was carried out to globally characterize the museum in a simple and perceptive way, with an algorithm that ranks all the different rooms, in which they were generally classified as "bad". A comparison of these values was done with similar studies in other museums: Soares dos Reis (Porto), Serralves (Porto) and other international museums, being possible to verify that the Municipal Museum Abade Pedrosa has worse acoustic values compared to those other museums. It was also suggested possible improvements that could contribute for the acoustic correction of the space, with a predictable cost of about 27000 €.

Consideration and case study using a time-difference-of-arrival directional device for occupational noise measurement

To protect worker's hearing in noisy workplaces, noise levels are measured periodically, and noise sources are located based on the results of recordings or video cameras. If the noise level is above a certain level, noise abatement measures are taken, or workers are suggested to wear hearing protection. Measuring the noise level can be done simply by placing a sound level meter on the floor, but finding the noise abatement is a time-consuming task. It is necessary to listen to the recordings one by one or review the video to find the noise abatement. We believe that a simple method of estimating noise abatement is very useful, since some noisy workplaces do not allow recordings or video cameras for privacy and confidentiality reasons. In this paper, noise source identification using a time-difference-of-arrival directional device in an indoor environment is examined. The results are analyzed in the context of room properties such as reverberation time, dimensions, and device localization. The paper also reports on practical use-cases in actual sites.

Experimental study on heavy-weight floor impact sound control of vibration-proofed tatami mats constructed widely on a concrete slab and dry floating floors

This study investigates the structural properties of a 55-mm thick tatami mat floor, a flooring prevalent in Japan. Building on previous research that introduced a tatami mat floor designed for vibration isolation, this work extends the investigation to heavy-weight floor impact sound mitigation on tatami mats measuring 900 × 1800 mm. The current study expands the tatami mat size to 2700 × 2700 mm and evaluates the sound insulation performance of vibration-isolated tatami mats placed on a concrete slab and dry floating floors. The experimental findings are summarized as follows: (1) The deployment of vibration-proofed tatami mats atop dry floating floors yielded notable improvements under tire-induced vibrations, achieving reductions of 4-6 dB in the 63-Hz band, 3-7 dB in the 125 Hz band, 4-6 dB in the 250 Hz band, and 6-9 dB in the 500 Hz band. (2) Similarly, with rubber ball-induced vibrations, installing vibration-proofed tatami mats on dry floating floors resulted in sound level reductions of 2-3 dB in the 63 Hz band, 4-5 dB in the 125 Hz band, 8 dB in the 250 Hz band, and 8-11 dB in the 500 Hz band.

An innovative approach for enclosure design of power generators to meet noise regulation targets

The use of diesel-powered engine generators as a power source is very common for various industrial and residential applications. There are strict regulatory requirements and legislations to limit the noise levels from these generators below statutory limits. The purpose of the paper is to present an approach using statistical energy analysis (SEA) augmented by experimental inputs for the prediction of noise levels for the generators and propose strategies for optimized enclosure design that effectively mitigate noise to achieve regulatory requirements. The study begins by developing an SEA model that represents the acoustic behavior of the generator and enclosure. The airborne sources such as engine, alternator, radiator fan and exhaust are modelled explicitly using experimental noise source characterization. Based on the established SEA model and excitation sources, noise levels are predicted through the calculation of energy flow between subsystems. The predicted sound levels for an existing Diesel Generator with enclosure were validated with its test data to ensure correctness of SEA model. Parametric studies were carried out using simulations on key variables, including critical noise paths, panel thickness, and noise control treatments. These investigations helped identify optimal process parameters that reduce noise levels emitted by genset in adherence to noise regulations.

Noise within hospital wards: a survey method

Noise pollution is one of the most disturbing environmental factors. It directly affects people's lives, especially vulnerable people such as children, old-age, and hospital patients. Hospitals are complex buildings with manifold spaces and facilities where different users live with different sensitivity to noise. Several studies highlight the discomfort that patients, staff, and visitors experience in hospitals due to inadequate noise levels. All this leads to stress, sleep disorders, interference in communication, aggression, and annoyance. Noise exposure in hospitals is due to several sound sources. Each varies throughout the day, and their detection could be challenging. The present study proposes a clustering technique to analyze long-term sound level meter monitoring in an Italian hospital (Pisa, Tuscany). Equivalent short-term levels obtained with an interval time of 0.1 s are used as the database to exploit the occurrences curves of different chunks of the monitoring. Then, through a validated method, the spectra of different kinds of sound sources are reconstructed via the Gaussian Mixture Model. Results are compared with near-field measurements of single sources.

Are single number ratings for sound insulation requirements still up-to-date?

In general, soundproofing requirements are given in form of a single number rating. Individual values are therefore singular, i.e. precise, so that no uncertainties are taken into account when checking the quality by measurement or calculation. A better description of the quality of sound insulation would be the formation of classes. In Europe requirements are mainly expressed as a weighted apparent sound reduction index R'w, or by specifying a certain weighted standard sound level difference DnT,w. Both quantities describe a quality that is not necessarily equivalent. The numerical comparison of the requirements is therefore not or only approximately possible. In light of this consideration requirements should be given therefore by classes. In this paper, the difference between a single number rating and a class rating is discussed.

How to deal with unsuspected source of annoyance in electric vehicle cabin using the "sonic augmented" concept?

The disappearance of the main source of noise with electric vehicles resulted in a breakthrough in car cabin sound experience. Despite significantly lowering the sound level pressure, one cannot claim perfect quietness is achieved. Indeed, as the auditory masking produced by the internal combustion engine is not effective anymore, unsuspected sounds such as electric whistling, whining or switching are now part of this sound environment and may be identified as unpleasant sounds. However, drivers' expectations are to have audible feedback indicative of vehicle operation that matches their expectations. Therefore, the presence of unwanted and unpleasant sounds, on the one hand, and the absence of desired and informative sounds, on the other hand, is an opportunity for sound design to create a new sound environment inside car cabins. The present work proposes a "sonic augmented" concept based on the idea of adding designed sounds, called "masks", participating both in the overall soundscape augmentation and in the attenuation of unpleasant sounds, called "defects". Sound design strategies with different parametrizations will be presented, as well as the results of two perceptive experiments whit the aims at evaluating the impact on perceptive attenuation of "defects" and the overall sound quality.

Towards a simplified model for partially open windows - connecting acoustic and thermal comfort

Traditionally, the internal environmental quality (IEQ) aspects of acoustic and thermal comfort have been considered and designed separately. However, where occupants rely on opening or closing windows to achieve these dimensions, they are not independent in use. To consider both simultaneously, it is crucial to have a simple model of a partially open window that can predict both acoustic and thermal conditions internally. CIBSE TM59 defines the assessment method for adaptive thermal comfort. In the thermal model the ventilation performance of open windows can be described with an "Equivalent Area" (EA). We propose to use the EA to calculate the facade sound insulation based on a simple assessment according to Annex D of ISO 12354-3, i.e. as a facade element with an area of EA and zero sound insulation. This study presents field measurements of sound insulation according to ISO 16283-3 with road traffic sound sources, to evaluate the acoustic uncertainty of using the EA to calculate internal sound levels. Results show encouraging correlation between measurements of element-normalized level difference, Dn,e,w + Ctr and calculations based on the EA. This model is considered adequate for acoustic design purposes, and represents a significant simplification compared with previous proposals.

A comprehensive study for a classification scheme for dwellings in Brazil

ABNT NBR 15575 was published in 2013 and establishes acoustic insulation criteria for residential buildings in Brazil. This standard presents three levels of performance - minimum (mandatory), intermediate, and superior - through an informative annex that classifies the acoustic performance for each requirement. Even after ten years of publication, the application of the standard is still not fully consolidated, although its application is mandatory under Brazilian law. This article proposes a classification of the entire acoustic system of dwellings, intending to enable the general public to understand acoustic performance quickly and intuitively, thus encouraging its application. The proposed classification scheme is based on ISO/TS 19488:2021, which presents harmonized criteria for different acoustic requirements. A large database of field measurements of building systems, typical of Brazil and obtained in different regions, was analyzed to verify the distribution of samples using this new scheme. An A/B/C/D scale is proposed, and results are presented for airborne sound insulation/impact between dwellings, airborne sound insulation for facades, and criteria for equipment sound levels in commercial buildings.

The innovated national noise monitoring network in The Netherlands

Over ten years ago, the National Institute for Public Health and the Environment started monitoring noise emissions from major roads and railways in The Netherlands. Today, this monitoring program is still going strong. The measured data is used to validate the yearly reported noise production levels calculated by the Dutch road and railway authorities, to monitor trends in noise production, and to check the validity of the Dutch noise calculation method. Measurements in the entire network are performed at an altitude of four meters close to fifty meters from the major road or railway in free field as these are the requirements for the reported calculated levels. The network therefore, has to operate stand-alone, resulting in challenges in terms of power supply, datastorage and communication. Ten years ago, we started with a battery-powered network of simple and cost-effective dataloggers. Recently, we made innovations by transitioning to a solar-powered network of modern sound level meters with remote data communication. In this presentation I will give a brief history of this monitoring network, how it developed, and show you the possibilities of the present-day innovated network.

Heavy-weight impact sound insulation characteristics related with vibrational properties of Korean domestic CLT slabs with different species and joint types

Korea has the world's most strict inter-floor noise regulations. In order to build an apartment house with more than 30 units, it must meet the minimum requirement of impact sound level, single number quantities of 49 dB. These regulations make it hard to expand residential tall wood building in Korea. For making quality satisfied CLT floors, as the preliminary investigations, the effects of wood species and CLT panel joints on the vibration and sound insulation performance of CLT were analyzed. The natural frequency range of the CLT slabs is from 20 Hz to 22 Hz. There were no significant differences depending on wood species and CLT panel joint type. As the stiffness of the slabs increased, the floor impact sound insulation performance also improved. The deflection model for CLT slabs was developed and validated with the actual deflection derived by acceleration spectrum. The measured value was 62 ~ 87% of the predicted value.

Introducing uncertainties in acoustic engineering studies

PIBE (Prévoir l'Impact du Bruit des Éoliennes - Predicting the impact of wind-turbine noise) is a research project funded by ANR (French National Research Agency) which main objectives are to better understand the sound level created by wind-turbines and assess noise-reduction solutions. One topic of this project focuses on the propagation of uncertainties. Code_TYMPAN(tm) is an open-source software for calculating industrial noise in the environment. Its open architecture, implemented by a Python API, allows advanced users to build and solve models programmatically. This open architecture made possible the implementation of a parametrical computational tool. This tool generates input data, launches the calculations with Code_TYMPAN(tm), generates and post-processes output data. Thus, sensitivity analysis and propagation of uncertainties were performed on an industrial test case. This development demonstrates the feasibility of introducing uncertainties in acoustic engineering studies.