Showing papers in "Canadian Acoustics in 2014"

Putative contact calls made by humpback whales (Megaptera novaeangliae) in southeastern Alaska

Abstract: Describing the acoustic properties and usage patterns of whale vocalizations is essential for documenting their functions and biological importance. Here the authors describe the acoustic characteristics and patterns of occurrence of the most common vocalization of the humpback whale ( Megaptera novaeangliae ) on its southeastern Alaska summer feeding grounds; a simple frequency-modulated call referred to as the “whup”. The authors examined 59 randomly selected days of continuous data recorded from an anchored hydrophone in Glacier Bay National Park from May through September 2007-2010. Using an automated detector 1,336 whups were identified, and their physical characteristics measured. Two distinct components of each whup were measured: a low-frequency growl with a fundamental tone, and a broadband upsweep. The growl component averaged 0.47 sec duration, within a 56-187 Hz frequency range, and had a peak frequency of 94 Hz. The upsweep component averaged 0.19 sec duration over a broadband frequency range of 52-743 Hz, with a peak frequency of 93 Hz. Of the 1,336 whups identified, 61% were in multiple-call groupings. Whups were significantly more likely to occur at night than during the day (t= -2.647, df=22, p=0.0147). Due to its patterns of usage and acoustic similarity to other mysticete contact calls, the authors speculate that inter-group communication is the main function of this call.

Effect of Cylinder Location inside a Rectangular Duct on the Excitation Mechanism of Acoustic Resonance

Abstract: The flow-sound interaction mechanism of a single cylinder in cross-flow is investigated experimentally. The cylinder is located at different vertical locations inside a rectangular duct in order to investigate the effect of the cylinder location on the excitation mechanism of acoustic resonance. During the tests, the acoustic cross-modes of the duct housing the cylinder are self-excited. It is found that the cylinder location affects the process of the flow-excited acoustic resonance and the levels of the generated acoustic pressure. The resonance of a specific acoustic cross-mode is excited when the cylinder is located at the acoustic pressure node, or the acoustic particle velocity anti-node, of that acoustic cross-mode. However, when the cylinder is shifted away from the pressure node of a certain acoustic cross-mode, a combination of cross-modes is excited and their intensity seems to be proportional to the ratio of the acoustic particle velocities of these modes at the cylinder’s location. Moreover, as the cylinder moves closer to the top wall of the rectangular duct, the Strouhal number value decreases due to the interference between the wake of the cylinder and the duct wall. Therefore, the onset of acoustic resonance for this case occurs at a higher value of reduced flow velocity.

Effects of construction noise on the cook inlet beluga whale (delphinapterus leucas) vocal behavior

Abstract: Cook Inlet beluga whales (Delphinapterus leucas) are listed as endangered under the US Endangered Species Act. Potential threats to this population include anthropogenic noise and coastal zone development. The Port of Anchorage Marine Terminal Redevelopment (MTR) Project, taking place in the Knik Arm of Cook Inlet, Alaska, involves multiple construction activities including dredging, gravel fill and pile driving. The impacts of construction noise on beluga vocalizations were investigated in this study. Passive sonobuoys were deployed in a four mooring array during 20 d in August and September 2009 near the MTR Project. Data were recorded in real-time at a shore-based observation station. No beluga whistles or noisy vocalizations were recorded during this period; however, beluga echolocation clicks were frequently detected. An energy summation method was used to automatically detect echolocation clicks. Times with and without construction noise (i.e., dredging and pile driving) were determined from long-term spectral averages. The detected hourly click rate was higher during times without (429 detected clicks/h) than with (291 detected clicks/h) construction activity; however, the difference was not statistically significant (t (24) = -0.56, P = 0.58). Lower frequency beluga whale vocalizations (e.g., whistles) were potentially masked, there may be have been an overall reduction in beluga vocalizations, or it is possible belugas were avoiding the area during construction activity.

Stop consonant production by French-English bilingual children in Southern Alberta

Abstract: Justin Turner 1 , Nicole Netelenbos 1 , Nicole Rosen 2 , Fangfang Li 1 1. Department of Psychology, University of Lethbridge, Lethbridge, Alberta 2. Department of Linguistics, University of Manitoba, Winnipeg, Manitoba ABSTRACT In this study, we report the speech production pattern of French-English bilingual children located in English-dominant Southern Alberta, all of whom currently attend a Francophone school. Specifically, ten fifth graders were engaged in a speech repetition task, producing a series of words beginning with one of the six stop consonants (/p/, /b/, /t/, /d/, /k/, and /g/) in both English and French. Voice onset time (VOT) was employed as the acoustic measure to gauge both L1 and L2 proficiency and the interaction between L1 and L2. The results revealed native-like competence in Francophone schoolchildren's English production for both voiced and voiceless stops. With respect to their French, these children also exhibit native-like VOT values for their voiceless stops, but intermediate negative values for their voiced stops, suggesting an influence of the English-dominant social context.

Did you say "bionic" ear ?

Abstract: Over the past decades, Hearing Protection Devices have existed simply as passive acoustical barriers intended to prevent sound from reaching the ear canal. Over the last decade though, with the increasing miniaturization of electronic components and consolidation of consumer electronic goods, new electronic Hearing Protection Devices have been brought on the marketplace to protect from noise induced hearing loss in more sophisticated ways. Likewise, Hearing Aids have benefited from this sophistication and entirely new communication devices have been developed, such as the wireless cellphone earpiece. The convergence of hearing protection devices, hearing aids and communication earpieces appears to be the next step and is sometimes referred to as a "bionic" ear. This presentation will detail a possible roadmap leading to the development of this bionic technology. It will also present several other intra-aural applications ranging from in-ear energy harvesting, to hearing-health monitoring and brain-wave recording, all of which could truly make your next earpiece a "bionic" ear.

Theoretical analysis of lined -duct sound attenuation

Abstract: This paper investigates theoretically how duct geometry and liner thickness affect the attenuation of fundamental-mode sound propagation in a lined duct. The study was done to satisfy the need for a greater understanding of interior natural- ventilation openings and of silencers implemented to improve the acoustical performance (‘ventilators’), and to provide engineers and architects with optimal-design guidelines. It assumed ventilators of the simplest form – straight, acoustically- lined ducts of rectangular cross-section. An analytical solution is presented for the attenuation of the fundamental mode in such a duct. Duct-liner thickness does not affect high-frequency performance; however, it limits low-frequency performance. A 25-mm liner is likely not thick enough to be effective, but a 100-mm liner may be excessive. Increasing the duct height reduces the attenuation at all frequencies; in order to provide effective attenuation through the 4000-Hz band, the height should not exceed 100 mm. If the cross-sectional aspect ratio of a duct is greater than 10, or the duct is only lined on two opposing surfaces, the attenuation of its fundamental mode is in effect identical to that of a 2D lined duct. Provided that the duct liner and height are such that the silencer is effective at absorbing sound at a given frequency, reducing the aspect ratio towards unity will result in large attenuation gains.

Measuring rhythm in dialects of New Brunswick French: is there a role for intensity?

Abstract: In recent years, research has shown that dialect differences can be characterized, at least partially, with rhythm metrics based on durations of vocalic and consonantal intervals. In the present study, we analyze the potential contribution of another prosodic feature, intensity, in describing cross-dialect differences. Our study looks at sentences read by 140 speakers of three regional varieties of French spoken in New Brunswick (Canada). Durations and intensities were measured for all vocalic and consonantal segments; intensity-based rhythm metrics were calculated with formulas similar to those generally used for duration-based metrics. Results from discriminant analyses show that, while duration-based metrics have a modest degree of success in classifying the three dialects, a better classification is obtained with the intensity-based metrics. Furthermore, the combination of both types of metrics provides the best discrimination. This result supports a multidimensional view whereby different prosodic features contribute to a model of speech rhythm.

Prediction and Measurement of Flow-Induced Wall-Pressure Fluctuations at Low Mach Numbers

Abstract: Flow-induced wall-pressure fluctuations, on a single panel, in a wind tunnel environment are measured and analyzed for Mach numbers between 0.06 and 0.12. The effects of two, flush-mounted microphone cap configurations on measured wall pressure spectra are investigated. A selection of semi-empirical single-point frequency spectrum models, are reviewed and compared to experimental wall-pressure spectra. The measured wall-pressure spectra are compared in dimensional and non-dimensional forms to investigate dependencies on Mach number and turbulent boundary layer scaling variables. The spectra captured with the pinhole microphone configuration are in better agreement with expected behaviour presented in the literature, compared to the grid cap configuration, but show a greater Mach number dependency when scaled with mixed inner and outer boundary layer variables. The models by Laganelli and Efimtsov are most suitable for predicting wall-pressure amplitudes over the low- and mid-frequency regimes whereas, the more recent models by Smol’yakov and Goody are most appropriate for predicting the decay rate in the overlap regime. The absence of a sizeable overlap region, caused by an under-developed logarithmic region in the boundary layer, is believed to be responsible for the disparities between measured and predicted spectra, and the Mach number dependence shown by the normalized spectra.

A New Approach to Building Acoustics Regulation in Canada

Abstract: A new approach to the control of sound transmission is among the proposed changes in the 2015 edition of the National Building Code of Canada. The design objective is changing from a minimum direct STC for the wall or floor/ceiling assembly separating adjacent units to a requirement for the Apparent Sound Transmission Class (ASTC) that includes direct and flanking transmission. The approach to design is based on combining the ASTM data from conventional laboratory measurement of direct transmission through wall or floor/ceiling assemblies with measurements of flanking transmission conforming to ISO 10848 and calculation procedures based on ISO 15712-1. This paper focuses on explaining the technical intent and form of the proposed new Code requirements.

Acoustic Evaluation of a Baroque Church- Through Measurements, Simulation, and Statistical Analysis

Abstract: This paper describes the acoustic evaluation of historical baroque church in Brazil - Igreja Nossa Senhora do Rosario de Sao Benedito (Church of Our Lady of the Rosary of St. Benedict), built in the 18 th century. The evaluation was performed in three stages: 1) in situ measurements of reverberation time (RT), early decay time (EDT), definition (D 50 ) and clarity (C 80 ); 2) reproduction of field conditions in a computational simulation using ODEON room acoustics prediction software, and 3) statistical analysis of the data. The integrated impulse response method was used here, as recommended by the ISO/3382-1:2009 standard. Results were subjected to an analysis of variance (ANOVA) to test the accuracy of the model. The model can be considered accurate, especially as far as reverberation times are concerned.

Recording Techniques and their Effect on Sound Quality at Off-Center Listening Positions in 5.0 Surround Environments

Abstract: Assessments of listener preferences for different multichannel recording techniques typically focus on the sweet spot, the spatial area where the listener maintains optimal perception of the reproduced sound field. The purpose of this study is to explore how multichannel recording techniques affect the sound quality at off-center (non-sweet spot) listening positions in medium-sized rooms. Listening impressions of two musical excerpts created by three different multichannel recording techniques for multiple off-center positions are compared with the impression at the sweet spot in two different listening room environments. The choice of a recording technique significantly affects the sound quality at off-center positions relative to the sweet spot, and this finding depends on the type of listening environment. In the studio grade listening room environment featuring a standard loudspeaker configuration, the two tested spaced microphone techniques were rated better at off-center positions compared to the coincident Ambisonics technique. For the less controlled room environment, the interaction between recording technique and musical excerpt played a significant role in listener preference.

The effect of high frequency vortex generator on the acoustic resonance excitation in shallow rectangular cavities

Abstract: The flow-excited acoustic resonance in shallow rectangular cavities can be a source of severe noise and/or excessive vibration. This phenomenon is excited when one of the acoustic modes in the accommodating enclosure is coupled with the flow instabilities resulting from the shear layer formation at the cavity mouth. In this study the effect of placing a high frequency vortex generator (control cylinder) in vicinity of the upstream edge of the cavity on the acoustic resonance excitation is experimentally and numerically investigated. The effectiveness of the passive method is studied by investigating different cylinder diameters and locations on both horizontal and vertical directions. The study included two cavities with different aspect ratios ( L/D =1.0 and L/D =1.67, L : cavity length, D : cavity depth) to address the effectiveness of the method with respect to the cavity depth. The method is investigated in flow with Mach number up to 0.45 and found to be effective in suppressing the acoustic resonance excitation. All the different configurations investigated are compared to the base case which is the bare cavity with no cylinder attached. It is observed that using the optimum cylinder location and diameter can be very effective and able to keep the acoustic pressure below 140 Pa, compared to the base case with values exceeding 2000 Pa. To further understand the interaction between the cylinder vortex shedding and the shear layer at the cavity mouth and the influence on the shear layer thickness, a 2D numerical simulation using a detached eddy simulation models has been carried out and compared to the experimental results.

Noise Output of Road Racing Motorcycles From Measured Leq Data

Abstract: This paper reports the results of an experimental study of the noise output from road racing motorcycles competing in the Canadian Superbike race series. L eq data from single-point measurements are presented for five events, which are then analyzed to determine an energy-average noise output per competitor at each event. The analysis, which considers track geometry and total time spent on track by all competitors, seems to indicate a moderately rising trend in the noise output per participant over time that is attributed to the changing composition of the field. The single-number noise descriptor obtained is suggested as a useful tool for predicting noise levels at future events at this or other venues.

Supporting Better Noise Control in Canadian Buildings

Abstract: A simplistic requirement for minimum STC of the wall or floor/ceiling assembly separating adjacent units in multi-family residential buildings has been used in North American building codes for over 50 years. Effective noise control requires replacing the traditional design objective with a requirement including the effect of flanking transmission, such as the Apparent Sound Transmission Class (ASTC). Such a transition requires a supporting set of technical standards for measuring direct and flanking sound transmission for typical assemblies and junctions, plus a credible procedure for calculating system performance from these inputs. Implementing a new approach in practice also needs technical support including calculation tools suitable for both the design and regulatory communities, and data on performance of typical generic constructions. This paper discusses key projects at the National Research Council of Canada both to establish the technical infrastructure supporting such a change in Canada’s building codes and to provide the tools needed by designers seeking to provide enhanced noise control.

Comfort from Hearing Protectors

Abstract: Comfort in an important property of hearing protectors, perhaps as important as the sound attenuation. If a protector is deemed to be uncomfortable, it will not be worn or it is modified in some manner by the user, often to the detriment of the attenuation. Although doubtless important, this characteristic is not studied as often as it should. A search conducted on the database Web of Science, shows that between the years 1970 and 2014, 208 papers were published dealing with attenuation in hearing protectors, while there were only 22 papers related to comfort. One reason for the scarcity of research on comfort could be the lack of a consistent definition, due to its inherently subjective nature. Another is the dependency of comfort on factors other than the protector itself, such as temperature and humidity of the workplace and the need for intelligibility. Finally, there are the anatomical differences among wearers that cause differences of comfort. This paper analyzes comfort studies done in the last 25 years, with the intent of developing a procedure to rank hearing protectors on the basis of comfort under specified conditions. An additional aim is to assess the tradeoff between comfort and attenuation across different types of protectors, since some situations may allow for a lower attenuation in favor of a increased comfort. In addition, we intend to develop a mathematical model for predicting comfort for different types of protectors.

A new research environment for speech testing using hearing-device processing algorithms

Abstract: A common complaint among subjects with hearing loss is the difficulty of understanding speech in the presence of background noise. Speech testing is an integral part of a clinical assessment of hearing loss, complementing the pure tone audiogram and providing useful information regarding speech tolerance and recognition ability as well as helpful cues for hearing-aid fitting. Among other indicators, speech tests are used to determine the speech reception threshold (SRT) defined as the lowest level at which speech can be correctly identified at least 50 percent of the time. The use of such tests is very popular in research as it allows an experimental manipulation of listening conditions in order to study their effects on speech perception with respect to a baseline condition. In this work, we present a new software-based speech testing environment developed in MATLAB in order to facilitate research in speech perception. It includes a graphical user interface which, in addition to the controls required to run the speech test, provides parameters to specify a subject’s hearing profile and a range of listening and processing conditions. It makes use of head-related transfer functions (HRTFs) to simulate different spatial configurations for binaural listening, and a hearing-device simulator to perform a variety of signal-processing conditions commonly found in hearing devices. The system’s design and feature set will be described along with some experimental results collected using the speech material from the Hearing in Noise Test (HINT).

Control of Acoustic Resonance in Shallow Rectangular Cavities Using Surface Mounted Blocks

Abstract: Flow over rectangular cavities is a potential source of acute noise that poses environmental concerns and structural threats to surrounding components in many engineering applications. In this paper, a passive method for controlling the acoustic resonance resulting from subsonic flows with Mach numbers up to 0.45 over shallow rectangular cavities is investigated. Both experimental and numerical investigations are performed to investigate the effectiveness of attaching blocks of square cross-section in suppressing the flow-excited acoustic resonance in shallow rectangular cavities. Six different square blocks with width to height ratios of w/h = 1, 2, 3, 4, 5, and 6.66 are investigated. The blocks are attached at different locations upstream of the cavity leading edge with d/h = 0, 3, and 6, where d is the upstream distance from the cavity leading edge and h is the block height. The results show that significant attenuation of the generated acoustic pressure with up to 30 dB is achieved using blocks of w/h between 2 and 4. Moreover, it is observed that the most effective attenuation of the acoustic resonance is achieved when the blocks are located at a distance of 3 h upstream of the cavity leading edge. Blocks with moderate widths are more effective than blocks that fills the whole width of the wind tunnel. Furthermore, the numerical simulations show that the shape of the blocks initiate vortices of different length and time scales than that of the shear layer over the cavity mouth. The interaction between these vortices and the vortices shed at the cavity leading edge weaken the separated shear layer over the cavity mouth, which, in turn, attenuates the generated acoustic resonance.

Prediction and Measurement of Turbulent Boundary Layer Wall-Pressure Fluctuations on the Surface of a Single Panel at Low Mach Numbers

Abstract: Wall-pressure fluctuations induced by a turbulent boundary layer, acquired in a wind tunnel environment, are analyzed for flow speeds between 0.05 and 0.12 Mach. Three microphone configurations are considered: flush mounted with a standard grid cap, flush mounted with a pinhole cap, and a recessed approach beneath a Kevlar sheet. A selection of existing single-point frequency spectrum models, for turbulent boundary layer wall-pressure fluctuations, are reviewed and compared to measurements from the Carleton University wind tunnel facility to determine the most appropriate model for subsonic flows. The measured and predicted frequency spectra are compared in dimensional and non-dimensional forms to investigate dependencies on Mach number and turbulent boundary layer thickness.

Experimental study on custom earplug retention in real-world situations

Abstract: Custom molded hearing protectors are often assumed to maintain their attenuation performance over longer period than disposable earplugs. This experimental study presents the findings on custom earplug retention in real-world situations.

Communication headsets in the workplace: Accessibility to noise exposure measurement in Canada

Abstract: Communication headsets and other wearable listening devices contribute to the noise exposure of a range of workers in their workplace. Users of these devices in occupational settings are subjected to both the audio signal from the headset and the surrounding external noise simultaneously. Two methods are currently described in ISO 11904 for direct measurement of sound exposure from communication headsets: the Microphone in the Real-Ear and the Acoustic Manikin. In addition, other standards propose the use of artificial-ear procedures or an indirect calculation method (AS/NZS 1269.1, CSA Z107.56) as alternative methods. However, there is currently little information related to the use of all these methods by researchers, audiologists, occupational hygienists, and other relevant professionals in occupational health and safety. A questionnaire was distributed to stakeholders in occupational health and safety and hearing loss prevention in Canada to document their awareness of the problem, their knowledge of the different measurement tools, and their access to this equipment. Results illustrate that knowledge of specialized measurement techniques and access to the necessary equipment varies significantly depending on the type of training of the different professionals.

Aging voices and speech intelligibility: Implications for communication by older talkers

Abstract: There are various changes in the voice production system during the course of normal aging. While some older adults have voices that are indistinguishable from those of younger adults, other older adults have perceptibly poorer voices that are characterized by irregularities in fundamental frequency and intensity. Previous studies have demonstrated that listeners perform worse on speech-in-noise tests when speech stimuli are distorted by temporal jittering. In this study, we tested whether natural jitter in the voices of older talkers affected the intelligibility of their speech when it was presented in noise. We selected three older female talkers from a larger pool of older female adults based on several voice acoustic measures, including jitter and harmonics-to-noise ratio; one talker had a relatively poor voice, one talker had an average voice and one talker had a good voice. These talkers recorded stimuli from the NU Auditory Test No. 6, which were then presented to young adult listeners in +1 dB SNR multi-talker babble noise. Surprising, the results showed that the talker with the average voice was the least intelligible of the three older talkers, while the talker with the poorest voice was as intelligible as the talker with the best voice. This pattern of results was reproduced after equating target word intensities across all talkers. Preliminary acoustic analyses showed that the three talkers produced vowels of similar duration and intensity but that the talker with the poorest voice had the slowest speech rate and the longest consonant durations. These findings suggest that older adults with poorer voices may alter their speech behaviour to maintain communication effectiveness despite natural declines in voice quality.

Age-Friendly Communities Principles and Initiatives

Abstract: In Canada, as in many countries around the world, the proportion of older adults is increasing. In addition, more people of all ages are living in cities. The Age-Friendly Cities concept was spearheaded by the World Health Organization (WHO) in response to these two major world-wide trends of global aging and urbanization. The underlying premise of age-friendly cities is that they foster the health, security, and social participation of older adults, or what the WHO refers to as 'active aging.' In 2007, the WHO launched the "Global Age-Friendly Cities: A guide" which identified core age-friendly city features. As a follow-up, Canada launched the "Age-Friendly Rural and Remote Communities: A guide" which provided a framework for understanding some of the issues faced bv the smaller communities characteristic of Canada and other parts of the world. Along with several other provinces within Canada, Manitoba has embraced the concept of creating age-friendly communities and is recognized as a global leader in the initiative. This presentation will provide a background on the Age-Friendly Cities initiative and on creating age-friendly environments. Particular attention will be paid to the process of creating age-friendly communities in Manitoba and possible ways that the physical and social environment can intersect with issues of hearing, communication, and social participation of older adults.

Pressure Drop Evaluation of Silencers

Abstract: Porous materials are usually applied in HVAC system ducts as passive silencers. The introduction of silencer materials such as baffles in the duct stream produces pressure drop to the fan system. The pressure drop measured in pascals becomes significant in elbow silencers where 90 degree turns are the norm. The pressure drop of elbow silencer systems were evaluated using a CFD method as well as simple ASHRAE procedures. The comparison of the two methods is presented in this paper.

Transient radiation by a system of two cylindrical shells

Abstract: We consider the acoustic field radiated by a system of two submerged co-axial cylindrical shells with fluid filling the inter-shell space. We propose a semi-analytical solution to the problem, and then use it to simulate the interaction of the system with an external acoustic pulse. We demonstrate that the acoustic field radiated by the two-shell system is to a large degree dominated by the multiple reflections of the waves propagating in the inter-shell volume off the surfaces of the shells, and that the effect of the inner shell is strongly manifested in the structure of the acoustic pattern observed in the outer fluid domain

Perception of intervocalic consonant clusters by Japanese listeners

Abstract: Normal 0 false false false false EN-CA X-NONE X-NONE This study reexamines perceptual epenthesis by Japanese listeners. It has been argued that since Japanese phonology prohibits consonant clusters Japanese listeners tend to perceive an illusionary vowel /u/ between consonants in a cluster so that their percepts conform to their native phonology. As a consequence, they do not perceive difference between strings like /VCCV/ and /VCuCV/. However, consonant clusters actually occur in natural speech in Japanese as a result of vowel deletion. Additionally, it has been shown that Japanese listeners are sensitive to acoustic difference between consonant clusters with a deleted vowel and their counterparts with an undeleted vowel. These observations raise a question about the above generalization. This study hypothesizes that the perceptibility of consonant clusters for Japanese listeners is determined not only by their phonological knowledge, but also by their phonetic knowledge about how likely certain types of consonant clusters occur in natural speech as a result of vowel deletion. In order to test the hypothesis, 19 Japanese listeners were tested on discrimination between consonant clusters and their counterparts with an intervening vowel /u/. Consonant clusters were classified into 4 ranked (lowest to highest) types according to the probability of their occurrence as a result of vowel deletion: voiced stop - voiced stop (DD), voiceless stop - voiced stop (TD), voiceless stop - voiceless stop (TT), voiceless fricative - voiceless stop (ST). The result showed that performance varied depending on cluster types. However, the variation did not follow the order of probability; performance was slightly better with TD and TT types than DD and ST types. The result also showed an effect of stimuli presentation order with TT type (Figure1). These findings are discussed in the light of phonological bias and general auditory speech processing. Figur 1 Normal 0 false false false EN-CA X-NONE X-NONE Normal 0 false false false EN-CA X-NONE X-NONE Normal 0 false false false EN-CA X-NONE X-NONE

Geometry Effects on the Noise Reduction of Helmholtz Resonators

Abstract: The effect of geometry shape of the Helmholtz resonator on its resonant frequency and noise attenuation capability is discussed in this paper. The theory of resonant frequency depending on the shape of the vessel of the resonator is verified analytical and numerically using COMSOL for one and two degrees of freedom resonators. The simulation was validated experimentally and has shown very good agreements. Various shapes of the resonators were compared in arrays. A better understanding of the shape effect is shown through simulations.

Crickets: Temperature Dependent Background Sound

Abstract: Background sound in urban areas is generally characterized by human activity such as road traffic while the sounds of nature characterize more rural areas. Where the sounds of nature dominate, environmental factors such as temperature influence patterns of background sound. A trend of temperature dependence for background sound levels is shown during late summer night-time hours. Variation of the trend is evaluated over several years and at multiple sites. Audio confirmed that the background sound is dominated by crickets.

Beyond hearing aids; Technologies to improve hearing accessibility for older adults with hearing loss.

Abstract: Hearing accessibility on the telephone, to the TV, in noisy and/or reverberant spaces are some of the challenging situations that face older adults with hearing loss as they attempt to remain connected to the world around them. Hearing aids alone cannot always provide the signal to noise ratio (SNR) required by older adults for sucessful access to auditory signals and messages. This presentation will focus on newer technologies that have the potential to enhance accessibility for older adults who require higher SNRs than can be achieve by personal amplification. Solutions for the telephone, cellphone, TV, restaurants, churches and other listening challanges will be highlighted.

Comparison of Airborne and Impact Sound Insulation Improvement due to Adding Toppings on Homogeneous Floors

Abstract: In order to reduce the overlap of measured floor data, the relative direct impact and airborne sound insulation improvement of toppings on homogeneous floors (concrete and cross-laminated timber (CLT)) of different mass and stiffness will be compared. During the last years, NRC has collected data on both concrete and CLT floors that may be transferable to one another similarly to the ASTM 2179 standard (Effectiveness of Coverings on Concrete Floors). Findings and limitations of this comparison method will be discussed.

Modeling acoustic response of structurally complex shell systems

Abstract: We introduce a hybrid analytical-numerical approach to modeling the acoustic field radiated by a submerged structure of a cylindrical outer shape but without any limitations on the geometrical and/or physical complexity of the internal composition. The approach relies on the FEM methodology in modeling the structural dynamics but utilizes the analytical response-functions-based ideology for the fluid domain, providing the advantage of being able to handle complex geometries that are outside of the capabilities of the traditional analytical or semi-analytical approaches, but at the same time possessing the computational efficiency that is higher than common FEM fluid-structure interaction codes. The capabilities of the approach are demonstrated on a typical configuration of industrial interest