2pNS3 – Love thy (Gym) Neighbour – A Case Study on Noise Mitigation for Specialty Fitness Centres

Brigette Martin – martin@bkl.ca
BKL Consultants Ltd.
#308-1200 Lynn Valley Road
North Vancouver, BC V7J 2A2

Paul Marks – marks@bkl.ca
BKL Consultants Ltd.
#308-1200 Lynn Valley Road
North Vancouver, BC V7J 2A2

Popular version of paper “Specialty fitness centres – a case study”
Presented November 5, 2018
176th ASA Meeting, Victoria, BC, Canada

Please keep in mind that the research described in this Lay Language Paper may not have yet been peer reviewed.

The sudden rise of group fitness rooms, CrossFit, and spin cycling studios in the community over the last decade is undeniable.  These specialty fitness centres can be located in mixed-use buildings (adjacent to either residential areas or retail stores), emitting a level of noise that can be obtrusive to their neighbours. Many specialty fitness centres have been proactive in ensuring they meet the appropriate noise standards by seeking support from acousticians. This exploratory paper considers the noise levels for various popular specialty fitness centres and outlines noise mitigation options for each one.

Multi-purpose group fitness rooms are versatile in the activities they host, including weight classes that use regular high-impact activities to improve anaerobic fitness. Often, these sounds are accompanied by music blasting through loudspeakers suspended from the ceiling. In one circumstance, a building landlord engaged our team to conduct sound level measurements at their group fitness room to determine noise transmission to adjacent residential apartments. After simulating impact activities (e.g. people jumping, the dropping of 20-lb kettle bells and sandbags) on seven different potential floor build-ups and quantifying sound levels played in group fitness rooms, we were able to determine noise mitigation options that achieved the landlord’s level of acceptability. This included the implementation of isolated flooring and maintaining music levels within an acceptable threshold.

Combining aspects of running, weightlifting and gymnastics, CrossFit spaces are unquestionably noisy. In order to lessen the audibility of noise to adjoining office spaces, our team was asked by a CrossFit space’s landlord to undertake measurements and a noise assessment. Together, we worked on a noise management plan for the CrossFit gym, employing a number of measures to control noise impacts including the use of additional cushioned matting, dedicated lifting platforms, and an outline of noise control measures. Mitigation included a combination of installing acoustical treatments and management procedures limiting the types of activities in the gym.

With amplified music and enthusiastic instructors constantly cheering on rows of avid cyclists, spin classes have sound levels that are comparable to nightclubs. These can be adjacent to general offices, retail spaces or even residential apartments. Solutions for these types of spaces have including limiting the noise level or “bassbeat” in the studio, providing masking noise in the adjacent space, or increasing the sound isolation of the demising wall or shared floor/ceiling assemblies.

In an effort to address numerous noise complaints, we left an unattended sound analyzer to capture noise levels in an adjacent retail space during spin classes and times without classes. We determined that it is ultimately the bass noise level content that is the most audible part to the retail unit occupants during spin classes and recommended that spin studio additionally control bass sounds to ameliorate the intrusive effects.

While a “one-size-fits-all” solution does not necessarily exist for all specialty fitness centres, it is clear that by being proactive, fitness centres can better control noise emitted to adjacencies by including measures to mitigate the effects within their original studio designs.

2aAA8 – Nature as Muse: The characteristics of caves can help us add an individual touch to our music

Yuri Lysoivanov – yuri.lysoivanov@columbiacollege.edu
Flashpoint Chicago, A Campus of Columbia College Hollywood
28 N. Clark St. #500
Chicago, IL 60602

Popular version of paper 2aAA8
Presented Tuesday morning, November 6, 2018
176th ASA Meeting, Victoria, Canada

The use of artificial reverberation in recorded music has been available since the late 1940s and is commonly credited to the ingenuity of Bill Putnam Sr. [1]. Following decades of technological achievement audio engineers are able to access an ever-growing variety of echo chambers, metal plates, springs, and digital emulations of an abundance of environments. A popular method in use today is the convolution reverb, a digital technique that uses controlled recordings of real spaces (called Impulse Responses or IRs) and applies them to every sample of a source sound, achieving an incredibly realistic simulation of that sound in the space.

Curiously, given their unique acoustic qualities, impulse responses of caves are generally underrepresented in the audio engineer’s toolkit. A browse through the responses in Altiverb, a popular high-end convolution reverb (figure 1), shows a small selection of caves relegated to the post-production (i.e. film sound) category ready to use for enterprising sound designers. This selection is far smaller than the availability of concert halls, churches, tombs, rooms and other acoustically critical spaces.

Figure 1: A search for “cave” in Altiverb reveals Howe’s Cavern in NY and two locations in Malta, in addition to several man-made structures.

One potential reason for the lack of availability of cave impulse responses could be the logistical difficulty in getting recording and measuring equipment into the caves. Another reason may be simply a lack of consumer interest, with so many fantastic impulse responses of man-made structures readily available.

For this paper, we sought to explore nature as architect and to demonstrate how incorporating the characteristics of these distinct structures can make a meaningful contribution to the audio engineer’s creative palate. With the aid of scientists from the National Parks Service, we chose a few locations for analysis within Mammoth Cave – the longest cave system in the world.

After capturing impulse responses, we analyzed the spaces to develop a set of useful applications for audio professionals. The Methodist Church was found to have a warm and pleasant sounding reverb to the ear (Figure 2), with a decay characteristic similar to a small concert hall. Lake Lethe, is an isolated, lengthy subterranean waterway, presents a smooth long decay (Figure 3) and is ideal for a multitude of echo applications. The Wooden Bowl Room (Figures 4 and 5) and Cleveland Avenue (Figures 6 and 7), were selected by our host scientist for having beautiful low, sustained resonances (which we found to be 106.2 Hz and 118.6 Hz, respectively) – suitable for applying depth and tension to a variety of sounds.

Figure 2: Reverb Time (T20) measurement for the Methodist Church.

 Figure 3: Reverb Time (T30) measurement for Lake Lethe
nature caveFigure 4: Interior of the Wooden Bowl Room Figure 5: 1000ms waterfall analysis of Wooden Bowl Room showing a sustained resonance at 106.2 Hz

These locations, carved over millions of years, provide opportunities for engineers to sculpt sounds that add an idiosyncratic character beyond the common reverbs available on the market. We hope that our work lays a foundation for further analysis of the characteristics of cave interiors and to a more individualized approach in using cave ambiences in music and sound design.

nature - caveFigure 6: Cleveland Avenue Figure 7: 1000ms waterfall analysis of Cleveland Avenue showing a sustained resonance at 118.6 Hz

[1] Weir, William. (2012, June 21). How Humans Conquered Echo. The Atlantic. Retrieved from https://www.theatlantic.com/

5pSP6 – Assessing the Accuracy of Head Related Transfer Functions in a Virtual Reality Environment

Joseph Esce – esce@hartford.edu
Eoin A King – eoking@hartford.edu
Acoustics Program and Lab
Department of Mechanical Engineering
University of Hartford
200 Bloomfield Avenue
West Hartford
CT 06119
U.S.A

Popular version of paper 5pSP6: “Assessing the Accuracy of Head Related Transfer Functions in a Virtual Reality Environment”, presented Friday afternoon, November 9, 2018, 2:30 – 2:45pm, RATTENBURY A/B, ASA 176th Meeting/2018 Acoustics Week in Canada, Victoria, Canada.

Virtual RealityIntroduction
While visual graphics in Virtual Reality (VR) systems are very well developed, the manner in which acoustic environments and sounds may be recreated in a VR system is not. Currently, the standard procedure to represent sound in a virtual environment is to use a generic head related transfer function (HRTF), i.e. a user selects a generic HRTF from a library, with limited personal information. It is essentially a ‘best-guess’ representation of an individual’s perception of a sound source. This limits the accuracy of the representation of the acoustic environment, as every person has a HRTF that is unique to themselves.

What is a HRTF?
If you close your eyes and someone jangles keys behind your head, you will be able to identify the general location of the keys just from the sound you hear. A HRTF is a mathematical function that captures these transformations, and can be used to recreate the sound of those keys in a pair of headphones – so that it appears that the sound recording of the keys has a direction associated with it. However, everyone has vastly different ear and head shapes, therefore HRTFs are unique to each person. The objective of our work was to determine how the accuracy of sound localization in a VR world varies for different users, and how we can improve it.

Test procedure
In our tests, volunteers entered a VR world, which was essentially an empty room, and an invisible sound source made a short bursts of noise at various positions in the room. Volunteers were asked to point to the location of the sound source, and results were captured using the VR’s motion tracking system. Results were captured to the nearest millimeter. We tested three cases: 1) where volunteers were not allowed to move their head to assist in the localization, 2) where some slight head movements were allowed to assist in sound localization, and 3) where volunteers could turn around freely and ‘search’ (with their ears) for the sound source. The head movement was tracked by using the VR system to track the volunteer’s eye movement, and if the volunteer moved, the sound source was switched off.

Results
We observed that the accuracy with which volunteers were able to localize the sound source varied significantly from person to person. There was significant error when volunteers’ head movements were restricted, but the accuracy significantly improved when people were able to move around and listen to the sound source. This suggests that the initial impression of a sounds location in a VR world is refined when the user can move their head to refine their search.

Future Work
We are currently analyzing our results in more detail to account for the different characteristics of each user (e.g. head size, size and shape of ear, etc). Further, we are aiming to develop the experimental methodology to use machine learning algorithms enabling each user to create a pseudo-personalized HRTF, which would improve the immersive experience for all VR users.

1pAB – Could lobsters use sounds to communicate between each other?

Youenn Jézéquel1, Julien Bonnel2, Jennifer Coston-Guarini1, Jean Marc Guarini1, Laurent Chauvaud1

1Laboratoire des Sciences de l’Environnement Marin, UBO, CNRS, IRD, Ifremer, LIA BeBEST, UMR 6539, rue Dumont D’Urville, 29280 Plouzané, France
2Woods Hole Oceanographic Institution, Woods Hole, MA 02543 USA

Session 1 pAB, Fish and Marine Invertebrate Bioacoustics II
Buzzing sounds as a mean of intra species-specific communication during agonistic encounters in male European lobsters (Homarus gammarus)?

An important application of marine ecological knowledge today is designing new indicators of marine ecosystems’ health. Passive acoustics, which simply consists on listening to sounds, is promising because it is non invasive and non destructive. However to develop passive acoustics as a tool for monitoring, we need to identify sound-emitting species with high potential for this type of application. Then, the sounds need to be analysed and and understood within their ecological context. In the coastal waters of Brittany (France), crustaceans would seem to be good study model, because they emit a wide range of sounds and also have a high commercial and cultural importance.

Figure 1: The European lobster (Homarus gammarus). Photographer: E. Amice (CNRS)

My PhD research, is focussed on the European lobster (Homarus gammarus, Figure 1). In our first study, we have shown that when stressed, the European lobster produces a species-specific sound that we call a “buzz” (Jézéquel et al. 2018, insert link for sound file). These sounds are characteristic low frequency and continuous sounds. We have shown that they are similar to those produced by the American lobster, but we .

While no studies have described the behaviours of the European lobster with ethograms (sequences of observed behaviours during behavioural experiments), there is a large literature on behaviours of American lobsters. Researchers have found that male American lobsters use agonistic encounters through aggressive behaviours to establish dominance between individuals (Figure 2A).

lobsters2A lobsters2B

Figure 2: Agonsitic encounters between male American lobsters (A) (Atema and Voigt 1995) and male European lobsters (B) (Photographer: Y. Jézéquel, Université de Bretagne Occidentale)

This allows them to gain access more easily to shelters and suitable mates during reproduction periods. These researchers have also shown that visual and chemical signals are used, but no studies have reported the use of sounds during these events to communicate. In our study, we have done agonistic encounters with male European lobsters to understand if they use sounds as a mean of intra species-specific communication  (Figure2B).

Our results show that male European lobsters use a highly complex panel of behaviours, from physical display to aggressive claw contact, in order to establish dominance. Once the dominant and submissive individuals are determined, they each adopt different behaviours:  the “winners” (dominants) continue physical and aggressive displays toward the submissive individuals that attempt to escape from their opponent’s presence.

During these experiments, we did not record buzzing sounds, probably because of the poor propagation of low frequencies (like those of the buzzing sounds) in the experimental tanks.  We concluded that this could explain the non detection of these sounds by the hydrophones installed for the experiments (Jézéquel et al. 2018).

The mechanism of sound production in both American and European lobsters is known: they contract rapidly internal muscles located at the base of their antennas to vibrate their carapace which produces the buzzing sound. We completed a new series of agonistic encounters with male European lobsters, but this time adding high frequency sampling accelerometers on their carapace. The accelerometery data clearly showed that European lobsters vibrated their carapace during agonistic encounters (with up to 90 vibration episodes per 15 minutes of experiment per individual), but their associated buzzing sounds were not recorded with hydrophones. Carapace vibrations were emitted by both dominant and submissive individuals, even if submissive individuals produced significantly more vibration episodes than dominant ones. These vibrations were associated to particular behaviours such as physical display and fleeing.

We have shown for the first time that male European lobsters exhibit complex, rapid patterns of movements during agonistic encounters that include carapace vibration episodes. However  during these events, the reactions of the receivers toward these signals remain unclear. We remain uncertain if the lobsters “sense” the carapace vibrations or their associated buzzing sounds in the experimental tanks.

Even if it is too soon yet to talk about a new type of communication in crustaceans, we have shown that buzzing sounds might have a role in the intra species-specific interactions displayed during agonistic encounters between male European lobsters. Field  experiments with better sound propagation conditions are in progress to determine if these sounds are indeed used as a mean of communication (Figure 3).

Figure 3:Bioacoustic experiments conducted in cages in coastal waters with European lobsters. Photographer: E. Amice (CNRS)

5pAOb1 – Acoustic mapping of ocean currents using moving vehicles

Chen-Fen Huang – chenfen@ntu.edu.tw
KuangYu Chen – seven5172002@gmail.com
IO.NTU – Acoustic Oceanography Lab

Sheng-Wei Huang – swhuang1983@ntu.edu.tw
JenHwa Guo – jguo@ntu.edu.tw
ESOE.NTU – Underwater Vehicles Lab
Taipei, 10617, Taiwan, R.O.C.

Popular version of paper 5pAOb1, “Acoustic mapping of ocean currents using moving vehicles”
Presented Friday afternoon, November 9, 2018, 1:00 PM – 1:20 PM, Balcony L
176th ASA Meeting, Victoria, BC Canada

ocean currentsWith the increased availability of highly maneuverable unmanned vehicles, abundant ocean environmental data can be collected.  Among the various ways of collecting the ocean temperature and current data, ocean acoustic tomography (OAT) is probably the most efficient method to obtain a comprehensive view of those properties in the interior ocean.

OAT uses differential travel times (DTTs) to estimate the currents.  Imagine two transceivers are separated by a distance R in a moving medium with sound speed of c.  The sound transmitted from the transceiver upstream will travel faster than the sound from the transceiver downstream.  By measuring the sound traveling in both directions, we can obtain the DTTs and from the DTTs we can determine the path-averaged current between the transceivers.

What happens if the vehicles carrying the transceivers are moving?  First, the DTTs are affected. The magnitude of the DTTs is reduced by the average speed of the vehicles [1].  Second, the acoustic signals are Doppler distorted due to the relative motion between the moving vehicles.

To determine the Doppler shift, we correlated the transmitted signals of different hypothetical Doppler shifts (replicas) with the received signals.  The hypothetical Doppler shift yielding the maximum correlation is used to compensate the acoustic measurements and determine the acoustic arrival patterns.

The Doppler shift measures the relative speed between two vehicles; however, relative speed isn’t sufficient to determine the ocean current speed – absolute speed (projected onto the path connecting the two vehicles) is required.  If only one of the vehicles is moving, then the Doppler shift indicates the projected speed of the moving vehicle.  If both of the vehicles are moving, we determine their average speeds by measuring the ground speed of at least one of the mobile vehicles.

We determined the DTTs using the correlation-based method.  The time series of the acoustic arrivals received at each pair of transceivers (reciprocal arrival patterns) are correlated to obtain the cross-correlated function (CCF).  We selected the lag time corresponding to the maximum peak in the CCF as an average estimate of the DTT.

We conducted a moving-vehicles experiment using two moving vehicles (auv and ship) and one moored station (buoy) in WangHiXiang Bay nearby Keelung City, Taiwan.  The AUV sailed near the shore while the ship surveyed in counterclockwise direction along a square trajectory. We installed the tomographic transceivers on the moving vehicles and the moored station. A DVL was on the ship for the validation of our current estimate.  Taken together, the moving vehicles and the moored station construct a triangular formation which can be used to map the ocean currents.

We used the distributed sensing method [2] to obtain the current field.  The estimated current velocities near the ship show consistency with the point measurements from the DVL.  We reconstructed the current distribution in the Bay using the acoustic data (the path-averaged currents) collected over the last 20 minutes.  A small-scale eddy was revealed.

ocean currents

Figure 1. Illustration of the acoustic mapping of ocean currents. Estimation of the current velocities near the ship for a) eastward direction and b) northward direction. The red circle and line indicate the DVL measurement while the black color indicates the DTT estimate. c) Spatial distribution of the estimated current field (yellow arrows) using the acoustic transmission paths indicated by the white lines.

[1] W. Munk, P. F. Worcester, and C. Wunsch, Ocean Acoustic Tomography, Cambridge University Press, 1995.

[2] C.-F. Huang, T. C. Yang, J.-Y. Liu, and J. Schindall, “Acoustic mapping of ocean currents using networked distributed sensors,” J. Acoust. Soc. Am., vol. 134, pp. 2090–2105, 2013.