2aNS – How virtual reality technologies can enable better soundscape design – Chung

2aNS – How virtual reality technologies can enable better soundscape design – Chung

How virtual reality technologies can enable better soundscape design.

W.M. To – wmto@ipm.edu.mo
Macao Polytechnic Institute, Macao SAR, China.
A. Chung – ac@smartcitymakter.com
Smart City Maker, Denmark.
B. Schulte-Fortkamp – b.schulte-fortkamp@tu-berlin.de
Technische Universität Berlin, Berlin, Germany.

Popular version of paper 2aNS, “How virtual reality technologies can enable better soundscape design”
Presented Tuesday morning, November 29, 2016
172nd ASA Meeting, Honolulu

The quality of life including good sound quality has been sought by community members as part of the smart city initiative. While many governments have placed special attention to waste management, air and water pollution, acoustic environment in cities has been directed toward the control of noise, in particular, transportation noise. Governments that care about the tranquility in cities rely primarily on setting the so-called acceptable noise levels i.e. just quantities for compliance and improvement [1]. Sound quality is most often ignored. Recently, the International Organization for Standardization (ISO) released the standard on soundscape [2]. However, sound quality is a subjective matter and depends heavily on the perception of humans in different contexts [3]. For example, China’s public parks are well known to be rather noisy in the morning due to the activities of boisterous amateur musicians and dancers – many of them are retirees and housewives – or “Da Ma” [4]. These activities would cause numerous complaints if they would happen in other parts of the world, but in China it is part of everyday life.

According to the ISO soundscape guideline, people can use sound walks, questionnaire surveys, and even lab tests to determine sound quality during a soundscape design process [3]. With the advance of virtual reality technologies, we believe that the current technology enables us to create an application that immerses designers and stakeholders in the community to perceive and compare changes in sound quality and to provide feedback on different soundscape designs. An app has been developed specifically for this purpose. Figure 1 shows a simulated environment in which a student or visitor arrives the school’s campus, walks through the lawn, passes a multifunctional court, and get into an open area with table tennis tables. She or he can experience different ambient sounds and can click an object to increase or decrease the volume of sound from that object. After hearing sounds at different locations from different sources, the person can evaluate the level of acoustic comfort at each location and express their feelings toward overall soundscape.  She or he can rate the sonic environment based on its degree of perceived loudness and its level of pleasantness using a 5-point scale from 1 = ‘heard nothing/not at all pleasant’ to 5 = ‘very loud/pleasant’. Besides, she or he shall describe the acoustic environment and soundscape using free words because of the multi-dimensional nature of sonic environment.

Figure 1. A simulated soundwalk in a school campus.

  1. To, W. M., Mak, C. M., and Chung, W. L.. Are the noise levels acceptable in a built environment like Hong Kong? Noise and Health, 2015. 17(79): 429-439.
  2. ISO. ISO 12913-1:2014 Acoustics – Soundscape – Part 1: Definition and Conceptual Framework, Geneva: International Organization for Standardization, 2014.
  3. Kang, J. and Schulte-Fortkamp, B. (Eds.). Soundscape and the Built Environment, CRC Press, 2016.
  4. Buckley, C. and Wu, A. In China, the ‘Noisiest Park in the World’ Tries to Tone Down Rowdy Retirees, NYTimes.com, from http://www.nytimes.com/2016/07/04/world/asia/china-chengdu-park-noise.html , 2016.

 

2aID11 – A transducer not to be ignored: The siren – J. D. Maynard

The siren is a source of sound (or sound transducer) which captures our attention because we know it may emanate from a police vehicle, fire engine, tornado warning tower or other danger warning system. However, there is another reason to heed the siren: it can be a “death ray”! Most of us know of the death ray from science fiction stories which describe a device which can annihilate whole armies silently from a distance. Around 1950 there were newspaper stories which heralded the advent of an actual death ray, with headlines and text such as: “‘Death Ray’ May Be Red [Soviet] Weapon. In the great super arms duel between east and west, has Russia successfully added the “death ray” to its growing arsenal?” (Franklin Johnson, OP, Washington, February 17, 1953) and “US sound ray kills mice in minute. The United States Army has announced the development of a supersonic death ray that kills mice in one minute. In spite of precautions the ray has inflicted burns, dizzyness and loss of balance on laboratory workers.” (American journal, New York, 1947). It may be assumed, and in some cases known, that the death ray referred to in these articles was a high intensity siren which was “silent” because it operated at a frequency above the threshold of human hearing (humans cannot hear frequencies above about 20,000 cycles per second). It was “high intensity” because it operated at a power level which was 10,000 times louder than the level of sound where the sense of “loudness” disappears and pain sets in; at the much louder level, pain becomes death, at least for mice.

A likely cause for the news articles was research with a siren undertaken by acousticians C. H. Allen and Isadore Rudnick, working under H. K. Schilling, Director of the Pennsylvania State College Acoustics Laboratory in 1946. Anyone who knew Izzy Rudnick would hypothesize that his response to the news articles would have been “Rumors of my death ray have been greatly exaggerated”. Indeed, a mouse had to be within about four inches (about 10 centimeters) of the siren in order to be killed, and its death was deemed to be a result of an increase in the temperature of the mouse due to absorption of the sound. In the same manner, the siren was used to heat a cup of coffee, ignite a ball of cotton and pop popcorn. The figure below shows the “trumpet horn” shaped opening of a siren, above which a glass tube is suspended; the lower part of the glass tube contains some popcorn kernels, and the upper part shows some popcorn popping upward.

At close range, a high intensity siren could cause human inner ear problems and deafness, and could set your hair on fire, but it could never be a real death ray. For the most part, the siren has received serious study by acousticians so as to make it a more efficient and longer range danger warning device.

Figure. A high intensity acoustic siren being used to pop popcorn.

 

J. D. Maynard
Department of Physics
The Pennsylvania State University
University Park, PA 16802

Popular version of paper 2aID11
Presented Tuesday morning, October 28, 2014
168th ASA Meeting, Indianapolis

3aPA8 – Using arrays of air-filled resonators to reduce underwater man-made noise – Kevin M. Lee

3aPA8 – Using arrays of air-filled resonators to reduce underwater man-made noise – Kevin M. Lee

Many marine and aquatic human activities generate underwater noise and can have potentially adverse effects on the underwater acoustical environment. For instance, loud sounds can affect the migratory or other behavioral patterns of marine mammals [1] and fish [2]. Additionally, if the noise is loud enough, it could potentially have physically damaging effects on these animals as well.

Examples of human activities that that can generate such noise are offshore wind farm installation and operation; bridge and dock construction near rivers, lakes, or ports; offshore seismic surveying for oil and gas exploration, as well as oil and gas production; and noise in busy commercial shipping lanes near environmentally sensitive areas, among others. All of these activities can generate noise over a broad range of frequencies, but the loudest components of the noise are typically at low frequencies, between 10 Hz and about 1000 Hz, and these frequencies overlap with the hearing ranges of many aquatic life forms. We seek to reduce the level of sound radiated by these noise sources to minimize their impact on the underwater environment where needed.

A traditional noise control approach is to place some type of barrier around the noise source. To be effective at low frequencies, the barrier would have to be significantly larger than the noise source itself and more dense than the water, making it impractical in most cases. In underwater noise abatement, curtains of small freely rising bubbles are often used in an attempt to reduce the noise; however, these bubbles are often ineffective at the low frequencies at which the loudest components of the noise occur. We developed a new type of underwater air-filled acoustic resonator that is very effective at attenuating underwater noise at low frequencies. The resonators consist of underwater inverted air-filled cavities with combinations of rigid and elastic wall members. They are intended to be fastened to a framework to form a stationary array surrounding an underwater noise source, such as the ones previously mentioned, or to protect a receiving area from outside noise.

The key idea behind our approach is that our air-filled resonator in water behaves like a mass on a spring, and hence it vibrates in response to an excitation. A good example of this occurring in the real world is when you blow over the top of an empty bottle and it makes a tone. The specific tone it makes is related to three things: the volume of the bottle, the length of its neck, and the size of the opening. In this case, a passing acoustic wave excites the resonator into a volumetric oscillation. The air inside the resonator acts as a spring and the water the air displaces when it is resonating acts as a mass. Like a mass on a spring, a resonator in water has a resonance frequency of oscillation, which is inversely proportional to its size and proportional to its depth in the water. At its resonance frequency, energy is removed from the passing sound wave and converted into heat through compression of the air inside the resonator, causing attenuation of the acoustic wave. A portion of the acoustic energy incident upon an array of resonators is also reflected back toward the sound source, which reduces the level of the acoustic wave that continues past the resonator array. The resonators are designed to reduce noise at a predetermined range of frequencies that is coincident with the loudest noise generated by any specific noise source.

resonator_array
Underwater photograph of a panel array of air-filled resonators attached to a framework. The individual resonators are about 8 cm across, 15 cm tall, and open on the bottom. The entire framework is about 250 cm wide and about 800 cm tall.

We investigated the acoustic properties of the resonators in a set of laboratory and field experiments. Lab measurements were made to determine the properties of individual resonators, such as their resonance frequencies and their effectiveness in damping out sound. These lab measurements were used to iterate the design of the resonators so they would have optimal acoustic performance at the desired noise frequencies. Initially, we targeted a resonance frequency of 100 Hz—the loudest components of the noise from activities like marine pile driving for offshore wind farm construction are between 100 Hz and 300 Hz. We then constructed a large number of resonators so we could make arrays like the panel shown in the photograph. Three or four such panels could be used to surround a noise source like an offshore wind turbine foundation or to protect an ecologically sensitive area.

The noise reduction efficacy of various resonator arrays were tested in a number of locations, including a large water tank at the University of Texas at Austin and an open water test facility also operated by the University of Texas in Lake Travis, a fresh water lake near Austin, TX. Results from the Lake Travis tests are shown in the graph of sound reduction versus frequency. We used two types of resonator—fully enclosed ones called encapsulated bubbles and open-ended ones (like the ones shown in the photograph). The number or total volume of resonators used in the array was also varied. Here, we express the resonator air volume as a percentage relative to the total volume of the array framework. Notice, our percentages are very small so we don’t need to use much air. For a fixed percentage of volume, the open-ended resonators provide up to 20 dB more noise reduction than the fully encapsulated resonators. The reader should note that noise reduction of 10 dB means the noise levels were reduced by a factor of three. A 30 dB reduction is equivalent to the noise be quieted by a factor of about 32. Because of the improved noise reduction performance of the open-ended resonators, we are currently testing this type of resonator at offshore wind farm installations in the North Sea, where government regulations require some type of noise abatement to be used to protect the underwater acoustic environment.

sound_reduction
Sound level reduction results from an open water experiment in a fresh water lake. Various types of air-filled resonators were tested including fully encapsulated resonator and open-ended resonators like the ones shown in the photograph. Because a much total volume (expressed as a percentage here) is needed, the open-ended resonators are much more efficient at reducing underwater noise.

References:

[1] W. John Richardson, Charles R. Greene, Jr., Charles I. Malme, and Denis H. Thomson, Marine Mammals and Noise (Academic Press, San Diego, 1998).

[2] Arthur Popper and Anthony Hawkins (eds.), The Effects of Noise on Aquatic Life, Advances in Experimental Medicine and Biology, vol. 730, (Springer, 2012).

 

Kevin M. Lee – klee@arlut.utexas.edu
Andrew R. McNeese – mcneese@arlut.utexas.edu
Applied Research Laboratories
The University of Texas at Austin

Preston S. Wilson – wilsonps@austin.utexas.edu
Mechanical Engineering Department and Applied Research Laboratories
The University of Texas at Austin

Mark S. Wochner – mark@adbmtech.com
AdBm Technologies

Popular version of paper 3aPA8
Presented Wednesday Morning, October 29, 2014
168th Meeting of the Acoustical Society of America, Indianapolis, Indiana

 

5aNS6 – The Perceived Annoyance of Urban Soundscapes – Adam Craig

5aNS6 – The Perceived Annoyance of Urban Soundscapes – Adam Craig

The term ‘soundscape’ is widely used to describe the sonic landscape and can be considered the auditory equivalent of a visual landscape. Current soundscape research looks into the view of sound assessment in terms of perception and has been the subject of large scale projects such as the Positive Soundscapes Project (Davies et al. 2009) i.e. the emotional attributes associated with particular sounds. This research addresses the limitations of current noise assessment methods by taking into account the relationship between the acoustic environment and the emotional responses and behavioural characteristics of people living within it. Related research suggests that a variety of objective and subjective factors influence the effects of exposure to noise, including age, locale, cross-cultural differences (Guyot at el. 2005) and the time of year (Yang and Kang, 2005). A key aspect of this research area is the subjective effect of the soundscape on the listener. This paradigm emphasises the subjective perception of sound in an environment – and whether it is perceived as being positive or negative. This approach dovetails with advancing sound and music classification research which aims to categorise sounds in terms of their emotional impact on the listener.

Annoyance is one of the main factors which contribute to a negative view of environmental noise, and can lead to stress-related health conditions. Subjective perception of environmental sounds is dependent upon a variety of factors related to the sound, the geographical location and the listener. Noise maps used to communicate information to the public about environmental noise in a given geographic location are based on simple noise level measurements, and do not include any information regarding how perceptually annoying or otherwise the noise might be.

craig_figure1

Figure 1 Selected locations for recording – image courtesy of Scottish Noise Mapping

This study involved subjective assessment by a large panel of listeners (N=167) of a corpus of sixty pre-recorded urban soundscapes collected from a variety of locations around Glasgow City Centre (see figure 1). Binaural recordings were taken at three points during each 24 hour period in order to capture urban noise during day, evening and night. Perceived annoyance was measured using Likert and numerical scales and each soundscape measured in terms of arousal and positive/negative valence (see figure 2).

craig_figure2

Figure 2 Arousal/Valance Circumplex Model Presented in Listening Tests

Coding of each of the soundscapes would be essential process in order to test the effects of the location on the variables provided by the online survey namely annoyance score (verbal), annoyance score (numeric), quadrant score, arousal score, and valence score. The coding was based on the environment i.e. urban (U), semi-open (S), or open (O); the density of traffic i.e. high (H), mid (M), low (L); and the distance form the main noise source (road traffic) using two criteria >10m (10+) and <10m (10-). The coding resulted in eight different location types; UH10-, UH10+, UM10+, UL10-, SM10+, SL10-, SL10+, and OL10+.

To capture quantitative information about the actual audio recordings themselves, the MIRToolkit for MATLAB was used to extract acoustical features from the dataset. Several functions were identified that could be meaningful for measuring the soundscapes in terms of loudness, spectral shape, but also rhythm, which could be thought of in not so musical terms but as the rate and distribution of events within a soundscape.

As expected, correlations between extracted features and locations suggest where there are many transient events, higher energy levels, and where the type of events include harsh and dissonant sounds i.e. heavy traffic, resulted in higher annoyance scores and higher arousal scores but perceived more negatively than quiet areas. In those locations where there are fewer transient events, lower energy levels, and there are less harsh and possibly more positive sounds i.e. birdsong, resulted in lower annoyance scores and lower arousal scores as well as being perceived more positively than busy urban areas. The results shed light on the subjective annoyance of environmental sound in a range of locations and provide the reader with an insight as to what psychoacoustic features may contribute to these views of urban soundscapes.

References

Davies, W., Adams, M., Bruce, N., Cain, R., Jennings, P., Carlyle, A., … Plack, C. (2009, October 26). A positive soundscape evaluation system. Retrieved from http://usir.salford.ac.uk/2468/1/Davies_et_al_soundscape_evaluation_euronoise_2009.pdf

Guyot, F., Nathanail, C., Montignies, F., & Masson, B. (2005). Urban sound environment quality through a physical and perceptive classification of sound sources : a cross-cultural study Methodology.

Scottish Noise Mapping (2014). Scottish Noise Mapping: Map Search [Online] http://gisapps.aecomgis.com/scottishnoisemapping_p2/default.aspx#/Main. [Accessed 20th June 2014]

Yang, W., & Kang, J. (2005). Soundscape and Sound Preferences in Urban Squares: A Case Study in Sheffield. Journal of Urban Design, 10(1), 61–80. doi:10.1080/13574800500062395

 

Adam Craig – Adam.Craig@gcu.ac.uk

Don Knox – D.Knox@gcu.ac.uk
David Moore – J.D.Moore@gcu.ac.uk

 

Glasgow Caledonian University
School of Engineering and Built Environment
70 Cowcaddens Road
Glasgow
United Kingdom
G4 0BA

 

Popular version of paper 5aNS6

Presented Friday morning, October 31st 2014

168th ASA Meeting, Indianapolis

 

 

1aAB4 – What does a Greater Prairie-Chicken sound like? It’s not your typical cock-a-doodle-doo! – Cara Whalen

1aAB4 – What does a Greater Prairie-Chicken sound like? It’s not your typical cock-a-doodle-doo! – Cara Whalen

It is 5 o’clock in the morning and only a hint of sunlight is visible on the horizon. Besides the sound of a light breeze swirling through the grass, all is quiet on the Nebraska prairie. Everything seems to be asleep. Then, suddenly, “whhooo-doo-doooohh” breaks the silence. The prairie-chickens have arrived.

The Greater Prairie-Chicken is a medium-sized grouse that lives on the prairies of central North America (Figure 1a) (Schroeder and Robb 1993). Prairie-chickens are well-known for their breeding activities in which the males congregate in groups each spring and perform elaborate courtship displays to attract females (Figure 1b). The areas where the males gather, called “leks,” are distributed across the landscape. Female prairie-chickens visit leks every morning to observe and compare males until a suitable one is chosen. After mating, females leave the leks to nest and raise their broods on their own, while the males remain on the leks and continue to perform courtship displays. Click the link to watch a video clip of prairie chickens lekking.

whalen_figure_1a whalen_figure_1b

Figure 1a: A male Greater Prairie-Chicken. Figure 1b: A male prairie-chicken performs a courtship display for a female.

These complex courtship behaviors do not occur in silence. Vocalization plays an important role in the mate choice behavior of prairie-chickens. As part of a larger study addressing the effects of electricity producing wind turbine farms on prairie-chicken ecology, we wanted to learn more about the acoustic properties of prairie-chicken calls. We did this by recording the sound of prairie-chicken vocalizations at leks in the Nebraska Sandhills. We visited the leks in the very early morning and set up audio recorders, which were placed close enough to prairie-chickens on their leks to obtain high quality recordings (Figure 2a). Sitting in a blind at the edges of leks (Figure 2b), we observed prairie-chickens while they were lekking and collected the audio recordings.

whalen_figure_2awhalen_figure_2b

Figure 2a: We used audio recorders to record male prairie-chicken vocalizations at the leks. Figure 2b: We observed lekking prairie-chickens and recorded vocalizations by sitting in a blind at the edge of a lek.

Male Greater Prairie-Chickens use four prominent vocalizations while on the leks: the “boom,” “cackle,” “whine” and “whoop.” The four vocalizations are distinct and serve different purposes.

The boom is used as part of the courtship display, so one function is to attract mates. Booms travel a long distance across the prairie, so another purpose of the call is to advertise lek location to other prairie-chickens (Sparling 1981, 1983). Click to listen to a boom sound clip

or to watch a boom video clip we recorded at the leks.

The “cackles” are short calls typically given in rapid succession. Prairie-chickens use the cackle as an aggressive or territorial call (Sparling 1981, 1983) or as a warning to alert other prairie-chickens of potential danger, such as an approaching prairie falcon, coyote or other predator. Click to listen to a cackle sound clip.

The “whine” is slightly longer in duration than the cackle; whines and cackles are often used together. The purpose of the whine is similar to that of the cackle. It serves as an aggressive and territorial call, although it is thought that whines are somewhat less aggressive than cackles (Sparling 1981, 1983). Click to listen to a whine sound clip

or to watch a video clip of cackles and whines (the cackles are the shorter notes and the whines are the longer notes).

The “whoop” is used for mate attraction. Males typically use the whoop when females are present on the lek (Sparling 1981, 1983). Click to listen to a whoop sound clip

or to watch a whoop video clip.

We measured acoustic characteristics of the vocalizations captured on the recordings so we could evaluate their features in detail. We are using this information about the vocalizations in a study of the effects of wind turbine sound on Greater Prairie-Chickens (Figure 3). We hope to determine whether the vocalizations produced by prairie-chickens near a wind farm are different in any way from those produced by prairie-chickens farther away. For example, do the prairie chickens near wind turbines call at a higher pitch in response to wind turbine sound? Also, do the prairie chickens near wind turbines vocalize louder? Ultimately we would like to know if components of the prairie-chickens’ vocalizations are masked by the sounds of the wind turbines.

whalen_figure_3

Figure 3: We are conducting a study of the effects of wind turbine noise on Greater Prairie-Chickens.

 

The effect of anthropogenic noise is an issue not limited to Greater Prairie-Chickens and wind turbines. As humans create increasingly noisy landscapes through residential and industrial development, vehicle traffic, air traffic and urban sprawl, the threats posed to birds and other wildlife are likely to be significant. It is important to be aware of the potential effects of anthropogenic sound and find ways to mitigate those effects as landscapes become noisier.

 

References:

Schroeder, M. A., and L. A. Robb. 1993. Greater Prairie-Chicken (Tympanuchus cupido). In The Birds of North America, no. 36 (A. Poole, P. Stettenheim, and F. Gill, Eds.). Academy of Natural Sciences, Philadelphia, and American Ornithologists’ Union, Washington, D.C.

Sparling, D. W. 1981. Communication in prairie grouse. I. Information content and intraspecific functions of principal vocalizations. Behavioral and Neural Biology 32:463-486.

Sparling, D. W. 1983. Quantitative analysis of prairie grouse vocalizations. Condor 85:30-42.

 

Cara Whalen – cara.whalen@huskers.unl.edu

Mary Bomberger Brown – mbrown9@unl.edu
Larkin Powell – lpowell3@unl.edu
Jennifer Smith – jsmith60@unl.edu
University of Nebraska – Lincoln

School of Natural Resources
3310 Holdrege Street
Lincoln, NE 68583

 

Edward J. Walsh – Edward.Walsh@boystown.org
JoAnn McGee – JoAnn.McGee@boystown.org
Boys Town National Research Hospital
555 N. 30th Street
Omaha, NE 68131

 

Popular version of paper 1aAB4

Presented Monday morning, October 27th, 2014

168th ASA Meeting, Indianapolis

 

Acoustic absorption of green roof samples commercially available in southern Brazil – Stephan Paul

Acoustic absorption of green roof samples commercially available in southern Brazil – Stephan Paul

Investigations into the benefits of green roofs have shown that such roofs provide many environmental benefits, such as thermal conditioning, air cleaning and rain water absorption. Analysing the way green roofs are usually constructed suggests that they may have also two interesting acoustical properties: sound insulation and sound absorption. The first property would provide protection of the house’s interior from environmental noise produced outside the house. Sound absorption, on the other hand, would reduce the environmental noise in the environment itself, by dissipating sound energy that is being irradiated on to the roof from environmental noise sources. Thus, sound absorption can help to reduce environmental noise in urban settings. Despite of being an interesting characteristic, information regarding acoustic properties of green roofs and their effects on the noise environment is still sparse. This work looked into the sound absorption of two types of green roofs commercially available in Brazil: the alveolar and the hexa system.

alveolar system

Fig 1: illustration of the alveolar system (left) and hexa system (right)

Sound absorption can be quantified by means of a sound absorption coefficient α, which ranges between 0 and 1 and is usually a function of frequency. Zero means that all incident energy is being reflected back into the environment and α = 1 means that all energy is being dissipated in the layers of the material, here the green roof. To find out how much sound energy the alveolar and the hexa system absorb standardized measurements were made in a reverberant chamber according to ISO-354 for different variations of both systems. The alveolar system used a thin layer of 2.5 cm of soil like substrate with and without grass and a 4 cm layer of substrate only. The hexa system was measured with layers of 4 and 6 cm of substrate without vegetation and 6 cm of substrate with a layer of vegetation of sedum. For all systems, high absorption coefficients (α > 0.7) were found for medium and high frequencies. This was expected due to the highly porous structure of the substrate. Nevertheless the alveolar system with grass, the alveolar system with 4 cm of substrate, the hexa with 6 cm of substrate and the hexa with sedum already provide high absorption for frequencies as low as 250 or 400 Hz. Thus, these green roofs systems are particularly interesting in urban settings, as traffic noise is usually low frequency noise and is hardly absorbed by smooth surfaces such as pavements or façades.

absorbtion coefficient

Fig 2: absorption coefficient of the alveolar samples (left) and hexa samples (rigth).

In the next step of this research is intended to make computational simulations of the noise reduction provided by the hexa and alveolar system in different noisy situations such as near airports or intense urban traffic.

 

Stephan Paul – stephan.paul@eac.ufsm.br

Undergrad
Program Acoustical Engineering
Fed. University of Santa Maria
Santa Maria, RS, Brazil

 

Ricardo Brum – ricardo.brum@eac.ufsm.br
Undergrad
Program Acoustical Engineering
Fed. University of Santa Maria
Santa Maria, RS, Brazil

 

Andrey Ricardo da Silva – andrey.rs@ufsc.br
Fed. University of Santa Catarina
Florianópolis, SC, Brazil
Tenile Rieger Piovesan – arqui.tp@gmail.com
Graduate program in Civil Engineering
Fed. University of Santa Maria
Santa Maria, RS, Brazil