2pNSa3 – Tuning the cognitive environment: Sound masking with ‘natural’ sounds in open-plan offices. – Alana G. DeLoach, Jeff P. Carter, and Jonas Braasch

WASHINGTON, D.C., May 19, 2015 — Playing natural sounds such as flowing water in offices could boosts worker moods and improve cognitive abilities in addition to providing speech privacy, according to a new study from researchers at Rensselaer Polytechnic Institute. They will present the results of their experiment at the 169th Meeting of the Acoustical Society of America in Pittsburgh.

An increasing number of modern open-plan offices employ sound masking systems that raise the background sound of a room so that speech is rendered unintelligible beyond a certain distance and distractions are less annoying.

“If you’re close to someone, you can understand them. But once you move farther away, their speech is obscured by the masking signal,” said Jonas Braasch, an acoustician and musicologist at the Rensselaer Polytechnic Institute in New York.

Sound masking systems are custom designed for each office space by consultants and are typically installed as speaker arrays discretely tucked away in the ceiling. For the past 40 years, the standard masking signal employed is random, steady-state electronic noise — also known as “white noise.”

Braasch and his team had previously tested whether masking signals inspired by natural sounds might work just as well, or better, than the conventional signal. The idea was inspired by previous work by Braasch and his graduate student Mikhail Volf, which showed that people’s ability to regain focus improved when they were exposed to natural sounds versus silence or machine-based sounds.

Recently, Braasch and his graduate student Alana DeLoach built upon those results in a new experiment. They exposed [HOW MANY??] human participants to three different sound stimuli while performing a task that required them to pay close attention: typical office noises with the conventional random electronic signal; an office soundscape with a “natural” masker; and an office soundscape with no masker. The test subjects only encountered one of the three stimuli per visit.

The natural sound used in the experiment was designed to mimic the sound of flowing water in a mountain stream. “The mountain stream sound possessed enough randomness that it did not become a distraction,” DeLoach said. “This is a key attribute of a successful masking signal.”

They found that workers who listened to natural sounds were more productive than the workers exposed to the other sounds and reported being in better moods.

Braasch said using natural sounds as a masking signal could have benefits beyond the office environment. “You could use it to improve the moods of hospital patients who are stuck in their rooms for days or weeks on end,” Braasch said.

For those who might be wary of employers using sounds to influence their moods, Braasch argued that using natural masking sounds is no different from a company that wants to construct a new building near the coast so that its workers can be exposed to the soothing influence of ocean surf.

“Everyone would say that’s a great employer,” Braasch said. “We’re just using sonic means to achieve that same effect.”

4pAAa13 – Impact of Room Acoustics on Emotional Response – Martin Lawless, Michelle C. Vigeant


Music has the potential to evoke powerful emotions, both positive and negative. When listening to an enjoyable piece or song, an individual can experience intense, pleasurable “chills” that signify a surge of dopamine and activations in certain regions in the brain, such as the ventral striatum1 (see Fig. 1). Conversely, regions of the brain associated with negative emotions, for instance the parahippocampal gyrus, can activate during the presentation of music without harmony or a distinct rhythmic pattern2. Prior research has shown that the nucleus accumbens (NAcc) in the ventral striatum specifically activates during reward processing3, even if the stimulus does not present a tangible benefit, such as that from food, sex, or drugs4-6.


Figure 1: A cross-section of the human brain detailing (left) the ventral striatum, which houses the nucleus accumbens (NAcc), and (right) the parahippocampal gyrus.

Even subtle changes in acoustic (sound) stimuli can affect experiences positively or negatively. In terms of concert hall design, the acoustical characteristics of a room, such as reverberance, the lingering of sound in the space, contribute significantly to an individual’s perception of music, and in turn influences room acoustics preference7-8. As with the case for music, different regions of the brain should activate depending on how pleasing the stimulus is to the listener. For instance, a reverberant stimulus may evoke a positive emotional response in listeners that appreciate reverberant rooms (e.g. a concert hall), while negative emotional regions may be activated for those that prefer drier rooms (e.g. a conference room). The identification of which regions in the brain are activated due to changes in reverberance will provide insight for future research to investigate other acoustic attributes that contribute to preference, such as the sense of envelopment.



The acoustic stimuli presented to the participants ranged in levels of perceived reverberance from anechoic to very reverberant conditions, e.g. a large cathedral. Example stimuli, which are similar to those used in the study, can be heard using the links below. As you listen to the excerpts, pay attention to how the characteristics of the sound changes even though the classical piece remains the same.

Example Reverberant Stimuli:


The set of stimuli with varying levels of reverberation were created by convolving an anechoic recording of a classical excerpt with a synthesized impulse response (IR) that represented the IR of a concert hall. The synthesized IR was double-sloped (see Fig. 2a) such that early part of the response was consistent between the different conditions, but the late reverberation differed. As shown in Fig. 2b the late parts of the IR vary greatly, while the first 100 milliseconds overlap. The reverberation times (RT) of the stimuli varied from 0 to 5.33 seconds


(a)                                                (b)

Figure 2: Impulse responses for the four synthesized conditions: (a) the total impulse response, (b) Time scale from 0 to 1 seconds to highlight the early part of the IR.

Functional magnetic resonance imaging (fMRI) was used to locate the regions of the brain that were activated by the stimuli. In order to find these regions, the images obtained due to the musical stimuli are each compared with the activations resulting due to control stimuli, which for this study were noise stimuli. Examples of control stimuli that are matched to the musical ones provided earlier can be heard using the links below. The noise stimuli were matched to have the same rhythm and frequency content for each reverberant condition.

Example Noise Stimuli:

Short                Medium                 Long

Experimental Design

A total of 10 stimuli were used in the experiment: five acoustic stimuli and five corresponding noise stimuli, and each stimulus was presented eight times. Each stimulus presentation lasted for 16 seconds. After each presentation, the participant was given 10 seconds to rate the stimulus in terms of preference on a five-point scale, where -2 was equal to “Strongly Dislike,” 0 was “Neither Like Nor Dislike,” and +2 was “Strongly Like.”


The following data represent the results of one participant averaged over the total number of repeated stimuli presentations. The average preference ratings for the five musical stimuli are shown in Fig. 3. While the majority of the ratings were not statistically different, the general trend is that the preference ratings were higher for the stimuli with the 1-2 second RTs and lowest for the excessively long RT of 5.33 seconds. These results are consistent with a pilot study that was run with seven subjects, and in particular, the stimulus with the 1.44 second RT was found to have the highest preference rating.


Figure 3: Average preference ratings for the five acoustic stimuli.

The fMRI results were found to be in agreement for the highest rated stimulus with an RT of 1.44 seconds. Brain activations were found in regions shown to be associated with positive emotions and reward processing: the right ventral striatum (p<0.001) (Fig. 4a) and the left and right amygdala (p<0.001) (Fig. 4b). No significant activation were found in regions shown to be associated with negative emotions for this stimulus, which supports the original hypothesis. In contrast, a preliminary analysis of a second participant’s results possibly indicates that activations occurred in areas linked to negative emotions for the lowest-rated stimulus, which is the one with the longest reverberation time of 5.33 seconds.


Figure 4: Acoustic Stimulus > Noise Stimulus (p<0.001) for RT = 1.44 s showing activation in the (a) right ventral striatum, and (b) the left and right amygdala.


A first-level analysis of one participant exhibited promising results that support the hypothesis, which is that a stimulus with a high preference rating will lead to activation of regions of the brain associated with reward (in this case, the ventral striatum and the amygdala). Further study of additional participants will aid in the identification of the neural mechanism engaged in the emotional response to stimuli of varying reverberance.


1. Blood, AJ and Zatorre, RJ Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion. PNAS. 2001, Vol. 98, 20, pp. 11818-11823.

2. Blood, AJ, et al. Emotional responses to pleasant and unpleasant music correlate with activity in paralimbic brain regions. Nature Neuroscience. 1999, Vol. 2, 4, pp. 382-387.

3. Schott, BH, et al. Mesolimbic functional magnetic resonance imaging activations during reward anticipation correlate with reward-related ventral striatal dopamine release. Journal of Neuroscience. 2008, Vol. 28, 52, pp. 14311-14319.

4. Menon, V and Levitin, DJ. The rewareds of music listening: Response and physiological connectivity of the mesolimbic system. NeuroImage. 2005, Vol. 28, pp. 175-184.

5. Salimpoor, VN., et al. Anatomically distinct dopamine release during anticipation and experience of peak emotion to music. Nature Neuroscience. 2011, Vol. 14, 2, pp. 257-U355.

6. Salimpoor, VN., et al. Interactions between the nucleus accumbens and auditory cortices predict music reward value. Science. 2013, Vol. 340, pp. 216-219.

7. Beranek, L. Concert hall acoustics. J. Acoust. Soc. Am. 1992, Vol. 92, 1, pp. 1-39.

8. Schroeder, MR, Gottlob, D and Siebrasse, KF. Comparative sutdy of European concert halls: correlation of subjective preference with geometric and acoustic parameters. J. Acoust. Soc. Am. 1974, Vol. 56, 4, pp. 1195-1201.


Impact of Room Acoustics on Emotional Response

Martin Lawless – msl224@psu.edu

Michele Vigeant, Ph.D. – mcv3@psu.edu

Graduate Program in Acoustics

Pennsylvania State University

Popular version of paper 4pAAa13

Presented Thursday afternoon, October 30, 2014

168th ASA Meeting, Indianapolis

1pAA1 – Audible Simulation in the Canadian Parliament – Ronald Eligator

1pAA1 – Audible Simulation in the Canadian Parliament – Ronald Eligator

If the MP’s speeches don’t put you to sleep, at least you should be able to understand what they are saying.

Using state-of-the-art audible simulations, a design team of acousticians, architects and sound system designers is working to ensure that speech within the House of Commons chamber of the Parliament of Canada now in design will be intelligible in either French or English.

The new chamber for the House of Commons is being built in a glass-topped atrium in the courtyard of the West Block building on Parliament Hill in Ottawa. The chamber will be the temporary home of the House of Commons, while their traditional location in the Center Block building is being renovated and restored.

The skylit atrium in the West Block will be about six times the volume of the existing room, resulting in significant challenges for ensuring speech will be intelligibility.


Figure 1 - House_of_Commons

Figure 1: Existing Chamber of the House of Commons, Parliament of Canada

The existing House chamber is 21 meters (70 feet) long, 16 meters (53 feet) wide, and has seats for the current 308 Members of Parliament (to increase to 338 in 2015) and 580 people in the upper gallery that runs around the second level of the room. Most surfaces are wood, although the floor is carpeted, and there is an adjustable curtain at the rear of the MP seating area on both sides of the room. The ceiling is a painted stretched linen canvas over the ceiling 14.7 meters (48.5 feet) above the commons floor, resulting in a room volume of approximately 5000 cubic meters.

The new House chamber is being infilled into an existing courtyard that is 44 meters (145 feet) long, 39 meters (129 feet) wide, and 18 meters (59 feet) high. The meeting space itself will retain the same basic footprint as the existing room, including the upper gallery seating, but will be open to the sound reflective glass roof and stone and glass side walls of the courtyard. In the absence of any acoustic treatments, the high level of reverberant sound would make it very difficult to understand speech in the room.



Figure 2 - 2010 PERSPECTIVE-1

Figure 2: Early Design Rendering of Chamber in West Block

In order to help the Public Works and Government Services Canada (PWGSC) and the House of Commons understand the acoustic differences between the existing house chamber and the one under design, and to assure them that excellent speech intelligibility will be achieved in the new chamber, Acoustic Distinctions, the New York-based acoustic consultant, created a computer model of both the new and existing house chambers, and performed acoustic tests in the existing chamber. AD also made comparisons of the two room using sophisticated data analysis and tables of data an produced graphs maps of speech intelligibility in each space.

An early design iteration, for example, included significant areas of sound absorptive materials at the sides of the ceiling areas, as well as sound absorptive materials integrated into the branches of the tree-like structure which supports the roof:




Figure 3

Figure 3: Computer Model of Room Finishes
The dark areas of the image show the location of sound absorptive materials, including triangularly-shaped wedges integrated into the structure which supports the roof.

Using a standardized measure of intelligibility, AD estimated a speech quality of 65% using the Speech Transmission Index (STI), a standardized measure of speech intelligibility, where a minimum of 75% was needed to ensure excellent intelligibility.

The computer analysis done by Acoustic Distinctions also produced colorful images relating to the degree of speech intelligibility that was to be expected:


Figure 4

Figure 4: Speech Transmission Index, single person speaking, no reinforcement
Talker at lower left; Listener at lower right
Dark blue to black color indicates fair to good intelligibility

While these numerical and graphical tools were useful in understanding acoustic conditions of the new room, in order to make it easier for the client and design team to appreciate the acoustic recommendations made by the consultant, Acoustic Distinctions also produced computer simulations of speech within the new room, enabling the team to hear the way the new room will sound when complete.

This approach, known as audible simulation or auralization, has been used to analyze a variety of room design options, and as the design progresses, new analysis and simulations are produced.

This first audible simulation is made using the room model shown above. The talker is an MP standing near the center of the bright yellow area in the STI map above. The listener is an MP seated in the opposite corner of the room, where the dark blue to black color confirms the STI value of just less than 0.70, corresponding to “good” intelligibility.
Audio file 1: Speech without Sound System. STI 0.68


To increase the intelligibility to values above the 0.75 minimum design goal, we add the sound system, being designed by Engineering Harmonics, to our model. With the sound system operating, STI value are increased for the above talker/speaker pair to 0.85. Speech will sound like this:
Audio file 2: Speech with Sound System. STI 0.85


While these examples clearly show the benefit of a speech reinforcement system in the Chamber, the design and client team were not satisifed with the extent of sound absorptive materials in the ceiling of the Chamber that were required to achieve the results of excellent intelligibility. An additional goal was expressed to reduce the total amount of sound absorptive materials in the room, to make the structure and skylight more visible and prominent.

Acoustic Distinctions therefore made changes to the model, strategically removing sound absorptive materials from specific ceiling locations, and reconfiguring the absorptive materials within the upper reaches of the structure supporting the roof. Computer models were again developed, and the resulting images showed that with careful design, excellent intelligibility would be achieved with reduced absorption.

Figure 5 - E_07_SOUND_SYSTEM_ON_40_STI_NoiseFigure 5: Speech Transmission Index, single person speaking, with sound reinforcement
Talker at upper left; Listener at lower right
Bright pink to red color indicates excellent intelligibility

Not surprisingly, communicating this to the design team and House of Commons in a way that provided a high level of confidence in the results was required. We again used audible simulations to demonstrate the results:
Audio file 3: Speech with Sound System, reduced absorption. STI 0.82


The rendering below shows the space configuration associated with the latest results:


Figure 6 - House of Commons Glass Dome rendering

Figure 6: Rendering, House of Commons, West Block, Parliament Hill
Proposed Design Configuration, showing sound absorptive panels
integrated into laylight and structure supporting roof





Audible Simulation in the Canadian Parliament
The impact of auralization on design decisions for the House of Commons

Ronald Eligator – religator@ad-ny.com

Acoustic Distinctions, Inc.
145 Huguenot Street
New Rochelle, NY 10801

Popular version of paper 1pAA1
Presented Monday morning, October 27, 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

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


Ricardo Brum – ricardo.brum@eac.ufsm.br
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