2aNSa – Soundscapes and human restoration in green urban areas – Irene van Kamp, Elise van Kempen,  Hanneke Kruize, Wim Swart

2aNSa – Soundscapes and human restoration in green urban areas – Irene van Kamp, Elise van Kempen, Hanneke Kruize, Wim Swart

Soundscapes and human restoration in green urban areas
Irene van Kamp, (irene.van.kamp@rivm.nl)
Elise van Kempen,
Hanneke Kruize,
Wim Swart
National Institute for Public Health and the Environment
Pobox 1 Postvak 10
Phone +31629555704

Popular version of paper in session 2aNSa, “Soundscapes and human restoration in green urban areas”
Presented Tuesday morning, May 19, 2015, 9:35 AM, Commonwealth 1
169th ASA Meeting, Pittsburgh

Worldwide there is a revival of interest in the positive effect of landscapes, green and blue space, open countryside on human well-being, quality of life, and health especially for urban dwellers. However, most studies do not account for the influence of the acoustic environment in these spaces both in a negative and positive way. One of the few studies in the field, which was done by Kang and Zhang (2010) identified relaxation, communication, dynamics and spatiality as the key factors in the evaluation of urban soundscapes. Remarkable is their finding that the general public and urban designers clearly value public space very different. The latter had a much stronger preference for natural sounds and green spaces than the lay-observers. Do we as professionals tend to exaggerate the value of green and what characteristics of urban green space are key to health, wellbeing and restoration? And what role does the acoustic quality and accompanying social quality play in this? In his famous studies on livable streets Donald Appleyard concluded that in heavy traffic streets the number of contacts with friends, acquaintances and the amount of social interaction in general was much lower. Also people in busy streets had a tendency to describe their environment as being much smaller than their counterparts in quiet streets did. In other words, the acoustic quality affects not only our wellbeing and behavior but also our sense of territory, social cohesion and social interactions. And this concerns all of us: citing Appleyard “nearly everyone in the world lives in a street”.

There is evidence that green or natural areas/wilderness/ or urban environments with natural elements as well as areas with a high sound quality can intrinsically provide restoration through spending time there. Also merely the knowledge that such quiet and green places are available seems to work as a buffer effect between stress and health (Van Kamp, Klaeboe, Brown, and Lercher, 2015 : in Jian Kang and Brigitte Schulte-Fortkamp (Eds) in press).

Recently a European study was performed into the health effect of access and use of green area in four European cities of varying size in Spain, the UK, Netherlands and Lithuania)

At the four study centers people were selected from neighborhoods with varying levels of socioeconomic status and green and blue space. By means of a structured interview information was gathered about availability, use and importance of green space in the immediate environment as well as the sound quality of favorite green areas used for physical activity, social encounters and relaxation. Data are also available about perceived mental/physical health and medication use. This allowed for analyzing the association between indicators of green, restoration and health, while accounting for perceived soundscapes in more detail. In general there are four mechanisms assumed that lead from green and tranquil space to health: via physical activity, via social interactions and relaxation and finally via reduced levels of traffic related air and noise pollution. This paper will explore the role of sound in the process which leads from access and use of green space to restoration and health. So far this aspect has been understudied. There is some indication that certain areas contribute to restoration more than others. Most studies address the restorative effects of natural recreational areas outside the urban environment. The question is whether natural areas within, and in the vicinity of, urban areas contribute to psycho-physiological and mental restoration after stress as well. Does restoration require the absence of urban noise?



Example of an acoustic environment – a New York City Park – with potential restorative outcomes (Photo: A.L. Brown)

Tags: health, soundscapes, people, environment, green, urban

3aSPb5 – Improving Headphone Spatialization: Fixing a problem you’ve learned to accept

3aSPb5 – Improving Headphone Spatialization: Fixing a problem you’ve learned to accept

Improving Headphone Spatialization: Fixing a problem you’ve learned to accept

Muhammad Haris Usmani – usmani@cmu.edu
Ramón Cepeda Jr. – rcepeda@andrew.cmu.edu
Thomas M. Sullivan – tms@ece.cmu.edu
Bhiksha Raj – bhiksha@cs.cmu.edu
Carnegie Mellon University
5000 Forbes Avenue
Pittsburgh, PA 15213

Popular version of paper 3aSPb5, “Improving headphone spatialization for stereo music”
Presented Wednesday morning, May 20, 2015, 10:15 AM, Brigade room
169th ASA Meeting, Pittsburgh

The days of grabbing a drink, brushing dust from your favorite record and playing it in the listening room of the house are long gone. Today, with the portability technology has enabled, almost everybody listens to music on their headphones. However, most commercially produced stereo music is mixed and mastered for playback on loudspeakers– this presents a problem for the growing number of headphone listeners. When a legacy stereo mix is played on headphones, all instruments or voices in that piece get placed in between the listener’s ears, inside of their head. This not only is unnatural and fatiguing for the listener, but is detrimental toward the original placement of the instruments in that musical piece. It disturbs the spatialization of the music and makes the sound image appear as three isolated lobes inside of the listener’s head [1], see Figure 1.


Hard-panned instruments separate into the left and right lobes, while instruments placed at center stage are heard in the center of the head. However, as hearing is a dynamic process that adapts and settles with the perceived sound, we have accepted headphones to sound this way [2].
In order to improve the spatialization of headphones, the listener’s ears must be deceived into thinking that they are listening to the music inside of a listening room. When playing music in a room, the sound travels through the air, reverberates inside the room, and interacts with the listener’s head and torso before reaching the ears [3]. These interactions add the necessary psychoacoustic cues for perception of an externalized stereo soundstage presented in front of the listener. If this listening room is a typical music studio, the soundstage perceived is close to what the artist intended. Our work tries to place the headphone listener into the sound engineer’s seat inside a music studio to improve the spatialization of music. For the sake of compatibility across different headphones, we try to make minimal changes to the mastering equalization curve of the music.
Since there is a compromise between sound quality and the spatialization that can be presented, we developed three different systems that present different levels of such compromise. We label these as Type-I, Type-II, and Type-0. Type-I focuses on improving spatialization but at the cost of losing some sound quality, Type-II improves spatialization while taking into account that the sound quality is not degraded too much, and Type-0 focuses on refining conventional listening by making the sound image more homogeneous. Since the sound quality is key in music, we will skip over Type-I and focus on the other two systems.
Type-II, consists of a head related transfer function (HRTF) model [4], room reverberation (synthesized reverb [5]), and a spectral correction block. HRTFs embody all the complex spatialization cues that exist due to the relative positions of the listener and the source [6]. In our case, a general HRTF model is used which is configured to place the listener at the “sweet spot” in the studio (right and left speakers placed at an angle of 30° from the listener’s head). The spectral correction attempts to keep the original mastering equalization curve as intact as possible.
Type-0, is made up of a side-content crossfeed block and a spectral correction block. Some headphone amps allow crossfeed between the left and right channels to model the fact that when listening to music through loudspeakers, each ear can hear the music from each speaker with a delay attached to the sound originating from the speaker that is furthest away. A shortcoming of conventional crossfeed is that the delay we can apply is limited (to avoid comb filtering) [7]. Side-content crossfeed resolves this by only crossfeeding unique content between the two channels, allowing us to use larger delays. In this system, the side-content is extracted by using a stereo-to-3 upmixer, which is implemented as a novel extension to Nikunen et al.’s upmixer [8].
These systems were put to the test by conducting a subjective evaluation with 28 participants, all between 18 to 29 years of age. The participants were introduced to the metrics that were being measured in the beginning of the evaluation. Since the first part of the evaluation included specific spatial metrics which are a bit complicated to grasp for untrained listeners, we used a collection of descriptions, diagrams, and/or music excerpts that represented each metric to provide in-evaluation training for the listeners. The results of the first part of the evaluation suggest that this method worked well.
We were able to conclude from the results that Type-II externalized the sounds while performing at a level analogous to the original source in the other metrics and Type-0 was able to improve sound quality and comfort by compromising stereo width when compared to the original source, which is what we expected. Also, there was strong content-dependence observed in the results suggesting that a different setting of improving spatialization must be used with music that’s been produced differently. Overall, two of the three proposed systems in this work are preferred in equal or greater amounts to the legacy stereo mix.

Tags: music, acoustics, design, technology


[1] G-Sonique, “Monitor MSX5 – Headphone monitoring system,” G-Sonique, 2011. [Online]. Available: http://www.g-sonique.com/msx5headphonemonitoring.html.
[2] S. Mushendwa, “Enhancing Headphone Music Sound Quality,” Aalborg University – Institute of Media Technology and Engineering Science, 2009.
[3] C. J. C. H. K. K. Y. J. L. Yong Guk Kim, “An Integrated Approach of 3D Sound Rendering,” Springer-Verlag Berlin Heidelberg, vol. II, no. PCM 2010, p. 682–693, 2010.
[4] D. Rocchesso, “3D with Headphones,” in DAFX: Digital Audio Effects, Chichester, John Wiley & Sons, 2002, pp. 154-157.
[5] P. E. Roos, “Samplicity’s Bricasti M7 Impulse Response Library v1.1,” Samplicity, [Online]. Available: http://www.samplicity.com/bricasti-m7-impulse-responses/.
[6] R. O. Duda, “3-D Audio for HCI,” Department of Electrical Engineering, San Jose State University, 2000. [Online]. Available: http://interface.cipic.ucdavis.edu/sound/tutorial/. [Accessed 15 4 2015].
[7] J. Meier, “A DIY Headphone Amplifier With Natural Crossfeed,” 2000. [Online]. Available: http://headwize.com/?page_id=654.
[8] J. Nikunen, T. Virtanen and M. Vilermo, “Multichannel Audio Upmixing by Time-Frequency Filtering Using Non-Negative Tensor Factorization,” Journal of the AES, vol. 60, no. 10, pp. 794-806, October 2012.

1pSC2 – Deciding to go (or not to go) to the party may depend as much on your memory as on your hearing – Kathy Pichora-Fuller , Sherri Smith

Deciding to go (or not to go) to the party may depend as much on your memory as on your hearing

Kathy Pichora-Fuller – k.pichora.fuller@utoronto.ca
Department of Psychology, University of Toronto,
3359 Mississauga Road,
Mississauga, Ontario, CANADA L5L 1C6

Sherri Smith – Sherri.Smith@va.gov
Audiologic Rehabilitation Laboratory, Veterans Affairs Medical Center,
Mountain Home, Tennessee, UNITED STATES 37684

Popular version of paper 1pSC (“Effects of age, hearing loss and linguistic complexity on listening effort as measured by working memory span”)

Presented Monday afternoon, May 18, 2015 (Session: Listening Effort II)
169th ASA Meeting, Pittsburgh

Understanding conversation in noisy everyday situations can be a challenge for listeners, especially individuals who are older and/or hard-of-hearing. Listening in some everyday situations (e.g., at dinner parties) can be so challenging that people might even decide that they would rather stay home than go out. Eventually, avoiding these situations can damage relationships with family and friends and reduce enjoyment of and participation in activities. What are the reasons for these difficulties and why are some people affected more than other people?
How easy or challenging it is to listen may vary from person to person because some people have better hearing abilities and/or cognitive abilities compared to other people. The hearing abilities of some people may be affected by the degree or type of their hearing loss. The cognitive abilities of some people, for example how well they can attend to and remember what they have heard, can also affect how easy it is for them to follow conversation in challenging listening situations. In addition to hearing abilities, cognitive abilities seem to be particularly relevant because in many everyday listening situations people need to listen to more than one person talking at the same time and/or they may need to listen while doing something else such as driving a car or crossing a busy street. The auditory demands that a listener faces in a situation increase as background noise becomes louder or as more interfering sounds combine with each other. The cognitive demands in a situation increase when listeners need to keep track of more people talking or to divide their attention as they try to do more tasks at the same time. Both auditory and cognitive demands could result in the situation becoming very challenging and these demands may even totally overload a listener.
One way to measure information overload is to see how much a person remembers after they have completed a set of tasks. For several decades, cognitive psychologists have been interested in ‘working memory’, or a person’s limited capacity to process information while doing tasks and to remember information after the tasks have been completed. Like a bank account, the more cognitive capacity is spent on processing information while doing tasks, the less cognitive capacity will remain available for remembering and using the information later. Importantly, some people have bigger working memories than other people and people who have a bigger working memory are usually better at understanding written and spoken language. Indeed, many researchers have measured working memory span for reading (i.e., a task involving the processing and recall of visual information) to minimize ‘contamination’ from the effects of hearing loss that might be a problem if they measured working memory span for listening. However, variations in difficulty due to hearing loss may be critically important in assessing how the demands of listening affect different individuals when they are trying to understand speech in noise. Some researchers have studied the effects of the acoustical properties of speech and interfering noises on listening, but less is known about how variations in the type of language materials (words, sentences, stories) might alter listening demands for people who have hearing loss. Therefore, to learn more about why some people cope better when listening to conversation in noise, we need to discover how both their auditory and their cognitive abilities come into play during everyday listening for a range of spoken materials.
We predicted that speech understanding would be more highly associated with working memory span for listening than with listening span for reading, especially when more realistic language materials are used to measure speech understanding. To test these predictions, we conducted listening and reading tests of working memory and we also measured memory abilities using five other measures (three auditory memory tests and two visual memory tests). Speech understanding was measured with six tests (two tests with words, one in quiet and one in noise; three tests with sentences, one in quiet and two in noise; one test with stories in quiet). The tests of speech understanding using words and sentences were selected from typical clinical tests and involved simple immediate repetition of the words or sentences that were heard. The test using stories has been used in laboratory research and involved comprehension questions after the end of the story. Three groups with 24 people in each group were tested: one group of younger adults (mean age = 23.5 years) with normal hearing and two groups of older adults with hearing loss (one group with mean age = 66.3 years and the other group with mean age 74.3 years).
There was a wide range in performance on the listening test of working memory, but performance on the reading test of working memory was more limited and poorer. Overall, there was a significant correlation between the results on the reading and listening working memory measures. However, when correlations were conducted for each of the three groups separately, the correlation reached significance only for the oldest listeners with hearing loss; this group had lower mean scores on both tests. Surprisingly, for all three groups, there were no significant correlations among the working memory and speech understanding measures. To further investigate this surprising result, a factor analysis was conducted. The results of the factor analysis suggest that there was one factor including age, hearing test results and performance on speech understanding measures when the speech-understanding task was simply to repeat words or sentences – these seem to reflect auditory abilities. In addition, separate factors were found for performance on the speech understanding measures involving the comprehension of discourse or the use of semantic context in sentences – these seem to reflect linguistic abilities. Importantly, the majority of the memory measures were distinct from both kinds of speech understanding measures, and also a more basic and less cognitively demanding memory measure involving only the repetition of sets of numbers. Taken together, these findings suggest that working memory measures reflect differences between people in cognitive abilities that are distinct from those tapped by the sorts of simple measures of hearing and speech understanding that have been used in the clinic. Above and beyond current clinical tests, by testing working memory, especially listening working memory, useful information could be gained about why some people cope better than others in everyday challenging listening situations.

Presentation #1pSC2 “Effect of age, hearing loss, and linguistic complexity on listening effort as mentioned by working memory span” by Margaret K. Pichora-Fuller and Sherri L. Smith will be take place on Monday, May 18, 2015, at 1:55 PM in Kings 4 at the Wyndham Grand Pittsburgh Downtown Hotel. The abstract can be found by searching for the presentation number here:

tags: age, hearing, memory, linguistics, speech

4pAB3 – Can a spider “sing”? If so, who might be listening? – Alexander L. Sweger, George W. Uetz

4pAB3 – Can a spider “sing”? If so, who might be listening? – Alexander L. Sweger, George W. Uetz

Can a spider “sing”? If so, who might be listening?

Alexander L. Sweger – swegeral@mail.uc.edu
George W. Uetz – uetzgw@ucmail.uc.edu
University of Cincinnati
Department of Biological Sciences
2600 Clifton Ave, Cincinnati OH 45221

Popular version of paper 4pAB3, “the potential for acoustic communication in the ‘purring’ wolf spider’
Presented Thursday afternoon, May 21, 2015, 2:40 PM, Rivers room
169th ASA Meeting, Pittsburgh

While we are familiar with a wide variety of animals that use sound to communicate- birds, frogs, crickets, etc.- there are thousands of animal species that use vibration as their primary means of communication. Since sound and vibration are physically very similar, the two are inextricable connected, but biologically they are still somewhat separate modes of communication. Within the field of bioacoustics, we are beginning to fully realize how prevalent vibration is as a mode of animal communication, and how interconnected vibration and sound are for many species.

Wolf spiders are one group that heavily utilizes vibration as a means of communication, and they have very sensitive structures for “listening” to vibrations. However, despite the numerous vibrations that are involved in spider communication, they are not known for creating audible sounds. While a lot of species that use vibration will simultaneously use airborne sound, spiders do not possess structures for hearing sound, and it is generally assumed that they do not use acoustic communication in conjunction with vibration.
The “purring” wolf spider (Gladicosa gulosa) may be a unique exception to this assumption. Males create vibrations when they communicate with potential mates in a manner very similar to other wolf spider species, but unlike other wolf spider species, they also create airborne sounds during this communication. Both the vibrations and the sounds produced by this species are of higher amplitude than other wolf spider species, both larger and smaller, meaning this phenomenon is independent of species size. While other acoustically communicating species like crickets and katydids have evolved structures for producing sound, these spiders are vibrating structures in their environment (dead leaves) to create sound. Since we know spiders do not possess typical “ears” for hearing these sounds, we are interested in finding out if females or other males are able to use these sounds in communication. If they do, then this species could be used as an unusual model for the evolution of acoustic communication.


Figure 1: An image of a male “purring” wolf spider, Gladicosa gulosa, and the spectrogram of his accompanied vibration. Listen to a recording of the vibration here,

and the accompanying sound here.

Our work has shown that the leaves themselves are vital to the use of acoustic communication in this species. Males can only produce the sounds when they are on a surface that vibrates (like a leaf) and females will only respond to the sounds when they are on a similar surface. When we remove the vibration and only provide the acoustic signal, females still show a significant response and males do not, suggesting that the sounds produced by males may play a part in communicating specifically with females.

So, the next question is- how are females responding to the airborne sound without ears? Despite the relatively low volume of the sounds produced, they can still create a vibration in a very thin surface like a leaf. This creates a complex method of communication- a male makes a vibration in a leaf that creates a sound, which then travels to another leaf and creates a new vibration, which a female can then hear. While relatively “primitive” compared to the highly-evolved acoustic communication in birds, frogs, insects, and other species, this unique usage of the environment may create opportunities for studying the evolution of sound as a mode of animal communication.

Tags: animals, vibrations, acoustics, communication, spiders

Monitoring deep ocean temperatures using low-frequency ambient noise – Katherine Woolfe, Karim G. Sabra

Monitoring deep ocean temperatures using low-frequency ambient noise – Katherine Woolfe, Karim G. Sabra

Monitoring deep ocean temperatures using low-frequency ambient noise.

Katherine Woolfe, Karim G. Sabra
School of Mechanical Engineering, Georgia Institute of Technology
Atlanta, GA 30332-0405

In order to precisely quantify the ocean’s heat capacity and influence on climate change,it is important to accurately monitor ocean temperature variations, especially in the deep ocean (i.e. at depths ~1000m) which cannot be easily surveyed by satellite measurements. To date, deep ocean temperatures are most commonly measured using autonomous sensing floats (e.g. Argo floats).However, this approach is limited because, due to costs and logistics, the existing global network of floats cannot sample the entire ocean at the lower depths. On the other hand, acoustic thermometry (using the travel time of underwater sound to infer the temperature of the water the sound travels through) has already been demonstrated as one of the most precise methods for measuring ocean temperature and heat capacity over large distances (Munk et al., 1995; Dushaw et al., 2009; The ATOC Consortium, 1998). However, current implementations of acoustic thermometry require the use of active, man-made sound sources. Aside from the logistical issues of deploying such sources, there is also the ongoing issue of negative effects on marine animals such as whales.
An emerging alternative to measurements with active acoustic sources is the use of ambient noise correlation processing, which uses the background noise in an environment to extract useful information about that environment. For instance, ambient noise correlation processing has successfully been used to monitor seismically-active earth systems such as fault zones (Brenguier et al., 2008) and volcanic areas (Brenguier et al., 2014). In the context of ocean acoustics (Roux et al., 2004; Godin et al., 2010; Fried et al., 2013), previous studies have demonstrated that the noise correlation method requires excessively long averaging times to reliably extract most of the acoustic travel-paths that were used by previous active acoustic thermometry studies (Munk et al., 1995). Consequently, since this averaging time is typically too long compared to the timescale of ocean fluctuations (i.e., tides, surface waves, etc.), this would prevent the application of passive acoustic thermometry using most of these travel paths (Roux et al., 2004; Godin et al., 2010; Fried et al., 2013). However, for deep ocean propagation, there is an unusually stable acoustic travel path, where sound propagates nearly horizontally along the Sound Fixing and Ranging (SOFAR) channel. The SOFAR channel is centered on the minimum value of the sound speed over the ocean depth (located at ~1000 m depth near the equator) and thus acts as a natural pathway for sound to travel very large distances with little attenuation (Ewing and Worzel, 1948).
In this research, we have demonstrated the feasibility of a passive acoustic thermometry method use in the deep oceans, using only recordings of low-frequency (f~10 Hz) ambient noise propagating along the SOFAR channel. This study used continuous recordings of ocean noise from two existing hydroacoustic stations of the International Monitoring System, operated by the Comprehensive Nuclear-Test-Ban Treaty Organization, located respectively next to Ascension and Wake Islands (see Fig. 1(a)). Each hydroacoustic station is composed of two triangular-shaped horizontal hydrophone arrays (Fig. 1(b)), separated by L~130 km, which are referred to hereafter as the north and south triads. The sides of each triad are ~2 km long and the three hydrophones are located within the SOFAR channel at depth ~1000 m. From year to year, the acoustic waves that propagate between hydrophone pairs along the SOFAR channel build up from distant noise sources whose paths intersect the hydrophone pairs. In the low-frequency band used here (1-40 Hz) -with most of the energy of the arrivals being centered around 10 Hz- these arrivals are known to mainly originate from ice-breaking noise in the Polar regions (Chapp et al., 2005; Matsumoto et al., 2014; Gavrilov and Li, 2009; Prior et al., 2011). The angular beams shown in Fig. 1a illustrate a simple estimate of the geographical area from which ice-generated ambient noise is likely to emanate for each site (Woolfe et al., 2015).


FIG. 1. (a) Locations of the two hydroacoustic stations (red dots) near Ascension and Wake Islands. (b) Zoomed-in schematic of the hydrophone array configurations for the Ascension and Wake Island sites. Each hydroacoustic station consists of a northern and southern triangle array of three hydrophones (or triad), with each triangle side having a length ~ 2 km. The distance L between triad centers is equal to 126 km and 132 km for the Ascension Island and Wake Island hydroacoustic stations, respectively.

Acoustic thermometry estimates ocean temperature fluctuations averaged over the entire acoustic travel path (in this case, the entire depth and length of the SOFAR channel between north and south hydrophone triads) by leveraging the nearly linear dependence between sound speed in water and temperature (Munk et al., 1995). Here the SOFAR channel extends approximately from 390 m to 1350 m deep at the Ascension Island site and 460 m to 1600 m deep at the Wake Island site, as determined from the local sound speed profiles and the center frequency (~10 Hz) of the SOFAR arrivals. We use passive acoustic thermometry is used to monitor the small variations in the travel time of the SOFAR arrivals over several years (8 years at Ascension Island, and 5 years at Wake Island). To do so, coherent arrivals are extracted by averaging cross-correlations of ambient noise recordings over 1 week at the Wake and Ascension Island sites. The small fluctuations in acoustic travel time are converted to deep ocean temperature fluctuations by leveraging the linear relationship between change in sound speed and change in temperature in the water (Woolfe et al., 2015). These calculated temperature fluctuations are shown in Fig. 2, and are consistent with Argo float measurements. At the Wake Island site, where data are measured only over 5 years, the Argo and thermometry data are found to be 54% correlated. Both data indicate a very small upward (i.e. warming) trend. The Argo data shows a trend of 0.003 °C /year ± 0.001 °C/ year, for 95% confidence interval, and the thermometry data shows a trend of 0.007 °C /year ± 0.002 °C/ year, for 95% confidence interval (Fig. 2(a)). On the other hand, for the Ascension site, the SOFAR channel temperature variations measured over a longer duration of eight years from passive thermometry and Argo data are found to be significantly correlated, with a 0.8 correlation coefficient. Furthermore, Fig. 2(b) indicates a warming of the SOFAR channel in the Ascension area, as inferred from the similar upward trend of both passive thermometry (0.013 °C /year ± 0.001 °C/ year, for 95% confidence interval) and Argo (0.013 °C/ year ± 0.004 °C/ year, for 95% confidence interval) temperature variation estimates Hence, our approach provides a simple and totally passive means for measuring deep ocean temperature variations, which could ultimately significantly improve our understanding of the role of oceans in climate change.

FIG. 2. (a) Comparison of the deep ocean temperature variations at the Wake Island site estimated from passive thermometry (blue line) with Argo float measurements (grey dots), along with corresponding error bars (Woolfe et al., 2015). (b) Same as (a), but for the Ascension Island site. Each ΔT data series is normalized so that a linear fit on the data would have a y-intercept at zero.

The ATOC Consortium, (1998). “Ocean Climate Change: Comparison of Acoustic Tomography, Satellite Altimetry, and Modeling”, Science. 281, 1327-1332.
Brenguier, F., Campillo, M., Takeda, T., Aoki, Y., Shapiro, N.M., Briand, X., Emoto, K., and Miyake, H. (2014). “Mapping Pressurized Volcanic Fluids from Induced Crustal Seismic Velocity Drops”, Science. 345, 80-82.
Brenguier, F., Campillo, M., Hadziioannou, C., Shapiro, N.M., Nadeau, R.M., and Larose, E. (2008). “Postseismic Relazation Along the San Andreas Fault at Parkfield from Continuous Seismological Observations.” Science. 321, 1478-1481.
Chapp, E., Bohnenstiehl, D., and Tolstoy, M. (2005). “Sound-channel observations of ice-generated tremor in the Indian Ocean”, Geochem. Geophys. Geosyst., 6, Q06003.
Dushaw, D., Worcester, P., Munk, W., Spindel, R., Mercer, J., Howe, B., Metzger, K., Birdsall, T., Andrew, R., Dzieciuch, M., Cornuelle, B., Menemenlis, D., (2009). “A decade of acoustic thermometry in the North Pacific Ocean”, J. Geophys., 114, C07021.
Ewing, M., and Worzel, J.L., (1948). “Long-Range Sound Transmission”, GSA Memoirs. 27, 1-32.
Fried, S., Walker, S.C. , Hodgkiss, W.S. , and Kuperman, W.A. (2013). “Measuring the effect of ambient noise directionality and split-beam processing on the convergence of the cross-correlation function”, J. Acoust. Soc. Am., 134, 1824-1832.
Gavrilov, A., and Li, B. (2009). “Correlation between ocean noise and changes in the environmental conditions in Antarctica” Proceedings of the 3rd International Conference and Exhibition on Underwater Acoustic Measurements: Technologies and Results. Napflion, Greece, 1199.
Godin, O., Zabotin, N., and Goncharov, V. (2010). “Ocean tomography with acoustic daylight,” Geophys. Res. Lett. 37, L13605.
Matsumoto, H., Bohnenstiehl, D., Tournadre, J., Dziak, R., Haxel, J., Lau, T.K., Fowler, M., and Salo, S. (2014). “Antarctic icebergs: A significant natural ocean sound source in the Southern Hemisphere”, Geochem. Geophys., 15, 3448-3458.
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Prior, M., Brown, D., and Haralabus, G., (2011), “Data features from long-term monitoring of ocean noise”, paper presented at Proceedings of the 4th International Conference and Exhibition on Underwater Acoustic Measurements, p. L.26.1, Kos, Greece.
Roux, P., Kuperman, W., and the NPAL Group, (2004). “Extracting coherent wave fronts from acoustic ambient noise in the ocean,” J. Acoust. Soc. Am, 116, 1995-2003.
Woolfe, K.F., Lani, S., Sabra, K.G., and Kuperman, W.S. (2015). “Monitoring deep ocean temperatures using acoustic ambient noise”, Geophys. Res. Lett., DOI: 10.1002/2015GL063438.

The Origins of Building Acoustics for Theatre and Music Performances – John Mourjopoulos

The Origins of Building Acoustics for Theatre and Music Performances – John Mourjopoulos

The Origins of Building Acoustics for Theatre and Music Performances

John Mourjopoulos – mourjop@upatras.gr
University of Patras
Audio & Acoustic Technology Group,
Electrical and Computer Engineering Dept.,
26500 Patras, Greece

Historical perspective
The ancient open amphitheatres and the roofed odeia of the Greek-Roman era present the earliest testament of public buildings designed for effective communication of theatrical and music performances over large audiences, often up to 15000 spectators [1-4]. Although mostly located around the Mediterranean, such antique theatres were built in every major city of the ancient world in Europe, Middle East, North Africa and beyond. Nearly 1000 such buildings have been identified, their evolution starting possibly from the Minoan and archaic times, around 12th century BC. However, the known amphitheatric form appears during the age that saw the flourishing of philosophy, mathematics and geometry, after the 6th century BC. These theatres were the birthplace of the classic ancient tragedy and comedy plays fostering theatrical and music activities for at least 700 years, until their demise during the early Christian era. After a gap of 1000 years, public theatres, opera houses and concert halls, often modelled on these antique buildings, re-emerged in Europe during the Renaissance era.
During the antiquity, open theatres were mainly used for staging drama theatrical performances so that their acoustics were tuned for speech intelligibility allowing very large audiences to hear clearly the actors and the singing chorus. During this era, smaller sized roofed versions of these theatres, the “odeia” (plural for “odeon”), were also constructed [4, 5], often at close vicinity to open theatres (Figure 1). The odeia had different acoustics qualities with strong reverberation and thus were not appropriate for speech and theatrical performances but instead were good for performing music functioning somehow similarly to modern-day concert halls.

Figure 1: representation of buildings around ancient Athens Acropolis during the Roman era. Besides the ancient open amphitheatre of Dionysus, the roofed odeion of Pericles is shown, along with the later period odeion of Herodes (adopted from www.ancientathens3d.com [6]).

Open amphitheatre acoustics for theatrical plays
The open antique theatre signifies the initial meeting point between architecture, acoustics and the theatrical act. This simple structure consists of the large truncated-cone shaped stepped audience area, (the amphitheatrical “koilon” in Greek or “cavea” in Latin), the flat stage area for the chorus (the “orchestra”) and the stage building (the “skene”) with the raised stage (“proskenion”) for the actors (Figure 2).

Figure 2: structure of the Hellenistic period open theatre.

The acoustic quality of these ancient theatres amazes visitors and experts alike. Recently, the widespread use of acoustic simulation software and of sophisticated computer models has allowed a better understanding of the unique open amphitheatre acoustics, even when the theatres are known solely from archaeological records [1,3,7,9,11]. Modern portable equipment has allowed state-of-the-art measurements to be carried out in some well-preserved ancient theatres [8,10,13]. As a test case, the classical / Hellenistic theatre of Epidaurus in southern Greece is often studied which is famous for its near-perfect speech intelligibility [12,13]. Recent measurements with audience present (Figure 3) confirm that intelligibility is retained besides the increased audience sound absorption [13].

Figure 3: Acoustic measurements at the Epidaurus theatre during recent drama play ( form Psarras et al.[13]).

It is now clear that the “good acoustics” of these amphitheatres and especially of Epidaurus, is due to a number of parameters: sufficient amplification of stage sound, uniform spatial acoustic coverage, low reverberation, enhancement of voice timbre, all contributing to perfect intelligibility even at seats 60 meters away, provided that environmental noise is low. These acoustically important functions are largely a result of the unique amphitheatrical shape: for any sound produced in the stage or the orchestra, the geometric shape and hard materials of the theatre’s surfaces generate sufficient reflected and scattered sound energy which comes first from the stage building (when this exists), then the orchestra floor and finally from the surfaces at the top and back of seat rows adjacent each listener position and which is uniformly spread to the audience area [11,13] (see Figure 4 and Figure 5).

Figure 4: Acoustic wave propagation 2D model for the Epidaurus theatre. The blue curves show the direct and reflected waves at successive time instances indicated by the red dotted lines. Along with the forward propagating wavefronts, backscattered and reflected waves from the seating rows are produced (from Lokki et al. [11]).

This reflected sound energy reinforces the sound produced in the stage and its main bulk arrives at the listener’s ears very shortly, typically within 40 milliseconds after the direct signal (see Figure 5). Within such short intervals, as far as the listeners’ brain is concerned, this is sound also coming from the direction of the source in the stage, due to a well-known perceptual property of human hearing, often referred to as “precedence or Haas effect” [11,13].

Figure 5: Acoustic response measurement for the Epidaurus theatre, assuming that the source emits a short pulse and the microphone is at a seat at 15 meters. Given that today the stage building does not exist, the first reflection arrives very shortly from the orchestra ground. Seven successive and periodic reflections can be seen from the top and the risers of adjacent seat rows. Their energy is reduced within approx. 40 milliseconds after the arrival of the direct sound (from Vassilantonopoulos et al. [12]).

The dimensions for seating width and riser height, as well as the koilon slope, can ensure minimal sound occlusion by lower tiers and audience and result to the fine tuning of in-phase combinations of the strong direct and reflected sounds [9,11]. As a result, frequencies useful for speech communication are amplified adding a characteristic coloration of voice sound and further assisting clear speech perception [11]. These specific amphitheatre design details have been found to affect the qualitative and quantitative aspects of amphitheatre acoustics and in this respect, each ancient theatre has unique acoustic character. Given that the amphitheatric seating concept evolved from earlier archaic rectangular or trapezoidal shaped seating arrangements with inferior acoustics (see Figure 6), such evolution hints at possible conscious acoustic design principles employed by the ancient architects. During the Roman period, stage building grew in size and the orchestra was truncated, showing adaptation to artistic, political and social trends with acoustic properties correlated to intended new uses favouring more the visual performance elements [4,15]. Unfortunately, only few fragments of such ancient acoustic design principles have been found and only via the writings of the Roman architect Marcus Vitruvius Pollio (70-15 BC), [14].

Figure 6: Evolution of the shape of open theatres. Roman period theatres had semi-circular orchestra and taller and more elaborate stage building.The red lines indicate the koilon / orchestra design principle as described by the ancient architect Vitruvius.

The acoustics of odeia for music performances
Although the form of ancient odeia broadly followed the amphitheatric seating and stage / orchestra design, they were covered by roofs usually made from timber. This covered amphitheatric form was also initially adopted by the early Renaissance theatres, nearly 1000 years after the demise of antique odeia [16] (Figure 7).

Figure 7: Different shapes of roofed odeia of antiquity and the Renaissance period (representations from www.ancientathens3d.com [6]).

Supporting a large roof structure without any inner pillars over the wide diameter dictated by the amphitheatric shape, presents even today a structural engineering feat and it is no wonder that odeia roofs are not preserved. Without their roofs, these odeia appear today to be similar to the open amphitheatres. However, computer simulations indicate that in period, unlike the open theatres, they had strong acoustic reverberation and their acoustics helped the loudness and timbre of musical instruments at the expense of speech intelligibility, so that these spaces were not appropriate and were not used for theatrical plays [4,5]. For the case of the Herodes odeion in Athens (Figure 8), computer simulations show that the semi-roofed version had up to 25% worst speech intelligibility compared to the current open state, but the strong acoustic reverberation which was similar to a modern concert hall of compatible inner volume of 10000 m3, made it suitable as a music performance space [5].

Figure 8: The Herodes odeion at its current state and via computer model of the current open and its antique semi-roofed version. (from Vassilantonopoulos et al. [5]). Very recent archaeological evidence indicates that the roof covered fully the building, as is also shown in Figure 10.

Thousand years ago, these antique theatres established acoustic functionality principles that even today prevail for the proper presentation of theatre and music performances to public audiences and thus signal the origins of the art and science in building acoustics.

A virtual acoustic tour of simulated amphitheatres and odeia is available at:
Please use headphones for more realistic 3D sound effect.

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