Showing papers in "Canadian Acoustics in 2006"

Infrasound from wind turbines - fact, fiction or deception

Abstract: Infrasound is discussed in terms of what it actually is, how the media has dealt with it and what those with limited knowledge say about it. The perception of infrasound occcurs at levels higher than the levels produced by wind turbines and there is now agreement amongst acousticians that infrasound from wind turbines is not a problem. Statements on infrasound from objectors are considered and it is shown how these may have caused avoidable distress to residents near wind turbines and also diverted attention from the main noise source, which is the repeating sound of the blades interacting with the tower. This is the noise which requires attention, both to reduce it and to develop optimum assessment methods

A survey of the use of portable audio devices by university students

Abstract: A survey was made for the use of portable audio devices by university students to determine the relationship between the sustained use of portable audio devices and hearing health in university students. Another goal of the project was to increase awareness about noise-induced hearing loss by providing an information session to those who completed the survey. A 124-item online survey was designed to probe items that would provide information on users of portable audio devices in the students. Items were designed to investigate a number of topics including demographic characteristics, transportation usage patterns, work environments, hearing history etc. It was found that majority of university students own a portable audio device. This may mean that noise induced hearing loss may be a larger concern, if the use of portable audio devices is excessive and if it is combined with exposure to other noise source.

In-cabin noise levels during commercial aircraft flights

Abstract: Air transport is one of the most commonly used mode of transportation and hence passenger comfort is highly desirable. Aircraft interior noise is important, especially in long-term flights, concerning the health, comfort, and psychological wellness of both passengers and flight crew. Noise levels, which changes according to different motions of aircraft, can be defined as the noise during takeoff and landing and during level flight (cruise). There are also non-aircraft-originating noise sources in the cabin. These can be classified into those caused by passenger activities such as conversations and luggage-related rearrangements as well as those caused by flight-crew such as flight attendant-related speaking activities, announcements from pilot and flight attendants, mechanical noises during food/beverage services and flight security demonstrations, and other announcement signals. In this study, in-cabin noise levels were measured during all flight activities in a commercial jet passenger plane. These noise levels consist of both continuous and discontinuous types. As a general tendency, continuous noise levels were seen to be 60-65 dB(A) prior to takeoff, and 80-85 dB(A) and 75-80 dB(A) during flight and landing, respectively. Discontinuous in-cabin noise levels were observed to reach levels as high as 81-88 dB(A) range. This study shows that it can be possible to control and reduce in-cabin noise levels, especially due to human activities and a few recommendations are suggested.

The role of formant amplitude in the perception of /i/ and /u/ in normal hearing listeners

Abstract: The effect of formant amplitude in the perception of vowels for speakers of English in normal hearing, was investigated. Two sets of stimuli including full-spectrum stimuli and incomplete-spectrum stimuli consisted of harmonics at the center of the first five formants were used to determine the perception of /i/ and /u/ in normal hearing. Participants were subjected a forced-choice vowel identification task with two sets of stimuli varied in amplitude of F 2 and F 3 in a fully-crossed 7×7 design and identified each stimulus 8 times. It was observed that there were a greater number of /i/ responses in the full-spectrum condition due to reduced spectral contrast while there were more /u/ responses in the incomplete-spectrum condition due to the ability of listeners to perceive F 2 at very low amplitudes. Result shows that formant amplitude influence vowel perception in synthetic monophthongs.

Perceived holistic health effects of three levels of music participation

Abstract: A study was conducted, utilizing measurements of salivary immunoglobulin A (sIgA) and cortisol to investigate the effects of active and passive participation in music. Researchers found a significant increase in sIgA between pre and post group singing, following two practices and a performance. It was also found that cortisol significantly decreased after practices, but significantly increased following the performance. A significant increase in sIgA between pre and post group singing was found without any increase for pre and post listening, while conduct research with members of a professional choir. A significant decrease in cortisol was also found between pre and post listening without any increase between pre and post singing. The members of three choirs were asked to participate in a survey, investigating effects of experiences of music. The items related to the 3 levels of participation were mixed with other items of choir practices.

Conversational speech intensity under different noise conditions in hypophonia and parkinson's disease

Abstract: The three types of background noise on conversational speech intensity in individuals with hyperphonia and Parkinson's Diseases (PD), are discussed Researces on PD subjects show that a Lombard relationship exists along with the control subject that may be related to a number of factors such as the severity of hypophonia, the type of background noise, the noise levels, the speech tasks, and the method of stimulus presentation The subjects with PD are stabilized on their anti-Parisian medication and are tested at about one hour after their regular medication Two separate two-factors repeated measures ANOVAs are used to examine the effects of each noise type on speech intensity For each noise type, the group x noise level interaction is insignificant that reveals very few significant differences The positive relationship between speech intensity and background noise is approximately parallel to that of controls

A remotely-piloted acoustic array for studying sperm whale vocal behaviour

Abstract: The vocal behavior of sperm whales was investigated using a remotely-piloted acoustic array. Acoustic array consisting of remotely-piloted vessels (RPVs) and hydrophones was deployed from a stationary 12-m sailboat and positioned as to form a favorable array geometry around a group of sperm whales. Two metal pipes were suspended from a wood plank with a distance of 1.5 m between them and hung over the sides of dinghy. The dinghy was rowed through the array and a hammer was used to strike the pipes to generate impulsive sound sources of different frequencies. Using time-of-arrival-differences (TOADs) between hydrophones, the position of GPS receivers, and the speed of sound in water, the location of a detected sound was calculated. It was observed that the hydrophone of RPV offered accurate estimate of the sound source's location. Result shows that the acoustic array offer an accuracy of 0.5 m within the array for differentiating the coda vocalizations exchanged between sperm whales.

Wind turbine noise - An overview

Abstract: This paper presents a general overview of wind turbine noise including sources, measurements standards, psychoacoustics, infrasound, propagation and regulatory perspectives. The authors presented similar material at the National Wind Coordinating Committee's special meeting on "Technical Considerations in Siting Wind Developments" [1] held in Washington D.C. In addition, many relevant papers can be found in the proceedings of the First International Conference on Wind Turbine Noise 2005 [2], some of which are summarized here.

Experimental validation of the objective measurement of individual custom earplug field performance

Abstract: A method was developed to meet the need to improve earplug field performance prediction accuracy by changing from average group performance prediction to individual performance prediction. The individual earplug field performance was objectively measured, using the Field-MIRE method. The individual attenuation was predicted from the field measurement of the Noise Reduction through the earplug. The individual attenuation was first obtained as a set of values for each octave band center frequency and these values were combined in a single number, the Predicted Personal Attenuation Rating (P-PAR). The observation confirmed that the low-frequency octave-band attenuation could be a good predictor of the overall attenuation as most earplugs attenuate significantly in high frequency. The observation also suggested that the high-frequency attenuation prediction adds much information and appeared to disturb the prediction capabilities of the measurement system.

The role of music, sound effects & speech on absorption in a film: The congruence-associationist model of media cognition

Abstract: The contribution of soundtracks that represents only one domain, speech, sound effects, and music to absorption or engagement of an audience in a story is discussed. Congruence-Association Model (C-A M) assumes that the audience's goal is to create a meaningful story from the material of the film that include scenes, text, music, effects, and speech. At lower level of analysis, the information in the distinct channels is analyzed for meaning and structures, where some information leaks upward to long-term memory which then provides inference about the narrative. The principle of association aggregates meaning for the five channels, and the principle of Congruence accounts for impact of shared structural features across channels. Judgement of realism and quality provide measures of control to assure that absorption judgments are based on a sense of general professionalism of the production.

Mandarin listeners' perception of english vowels: Problems and strategies

Abstract: Previous research suggests L2 vowel perception problems are often due to the assimilation of L2 sounds to L1 categories. However, there is also evidence for a universal strategy which states listeners will rely on duration cues whenever spectral cues are not sufficient for discriminating L2 vowel contrasts. This study examines Mandarin listeners' perceptual problems with English vowels. In a perception test, a group of adult Mandarin-English bilinguals residing in Canada identified synthesized English /i/-/I/, /u/-/℧/, and /ae/-/E/ continua that manipulated vowel spectral and duration cues. Compared with a native English group who responded exclusively to the spectral cues, the majority of native Mandarin listeners failed to show native-like perceptual patterns for the three vowel contrasts. However, they responded heavily and consistently to duration cues for the /i/-/I/ but not for the /u/- /℧/ and /ae/-/E/ contrasts. Both group and individual data suggest that native Mandarin listeners used different strategies in perceptual identification of L2 vowel contrasts. Most Mandarin listeners did not appear to have clear category distinctions for /u/-/℧/ and /ae/-/E/ pairs and some established incorrect perceptual representation of the /i/-/I/ contrast. The findings did not fully support the universal strategy of using duration cues when non-native vowel contrasts are difficult to perceive.

Effect of cardioid and limaçon directional sensors on towed array reverberation response

Abstract: The effect of cardioid and limacon directional sensors on towed horizontal line array reverberation response,was investigated. As the use of towed horizontal line arrays give axial symmetry of beam patterns that led to left-right ambiguity, application of elements with directional responses where the omni-directional elements are augmented with crossed dipole pairs allowing formation of cardioid or limacon beam patterns to improve the echo-to-reverberation ration was examined. It was observed that production of towed array beam patterns with cardioid or limacon directional sensors in place of omni-directional elements reduces the reverberation by 6 dB and suppress the ambiguous beam near broadside. The limacon sensors reduce the ambiguous beam, and echo-to-reverberation ratio, much more effectively than the cardioid sensors and it is very useful for target detection.

A cross-language vowel normalisation procedure

Abstract: A variation of log-mean normalization that can be applied in cross-language and cross-dialect experiments, is presented. Vowel normalization procedures seek to remove inter-speaker variance due to factors such as vocal tract size, which human listeners discount while identifying vowels. It is expected that the mean vocal-tract length are approximately equal over large and sufficiently balanced samples of speakers. The cross-language normalization procedure is tested using acoustic data from productions of L1-Spanish non-low front vowels and L1 English non-low front vowels. Three models are trained and tested using non-normalized log-Hertz values, language-normalized values, and cross-language normalized values respectively. The models trained on normalized L1-English vowels had a slightly higher correct-classification rate on the training data than the model trained on non-normalized data. The vowel normalization increased the correlation between monolingual English listeners.

Automated detection of white whale (delphinapterus leucas) vocalizations in St. Lawrence estuary and occurrence pattern

Abstract: A detailed behavioral and habit study on the vocalization of the white whale population, is presented. White whales are known for their high degree of acoustic activities and their vocalization are variable in time and frequency. An automated method using a sequence of signal processing algorithms is developed to detect sound of white whale. A threshold is applied to transform the spectrogram into a binary image on which residual noise is cleaned using two specific image filters. The frequency band of the vocalizations is relatively stable over the seven days of sampling, while the vocalization rate is variable from day to day. This method can detect all the diverse white whale calls and pulsed tones emerging in the signal after noise filtration. The vocalization rate intensity of the false detections is very low compared to that of the detected calls. The prime frequency band used by white whales in recorded data is slightly lower than the estimated frequency rate.

Voice-printing the Hermit Thrush (Catharus guttatus)

Abstract: A database of voice-prints for individual Hermit Thrush birds was developed and used to acoustically identify them from one breeding season to the other. A method was used to obtain audio recordings from birds in the most non-intrusive way possible. Birds that were located near roads or park trails were recorded and no birds were branded, marked, stalked, or flushed out of hiding. All the audio recordings were made using Sony digital video camera recorders and the sampling rate was 48 kHz with 16 bit quantization. The camera was pointed in the direction of the sound source when the bird was not visible. Audio files in 'wav' format were extracted from Digital 8 and Mini DV video cassettes were used by the DCR-TRV525 and DCR-VX2100 cameras. Spectral analysis was carried out using the Raven 1.2.1 interactive sound analysis software. It was found that a Hermit Thrush song began with an introductory note, followed by a series of flute-like body notes.

Sound pressure and particle velocity measurements from marine pile driving with bubble curtain mitigation

Abstract: Measurement of underwater acoustic pressure and acoustic particle velocity was performed near marine pile driving work with bubble curtain mitigation to determine the effectiveness of the bubble curtain at reducing acoustic particle velocity levels and sound pressure levels. Euler's linearized momentum equation can be used to show that the acoustic particle velocity is related to the time integral of the acoustic pressure gradient. Acoustic particle velocity from pile driving was measured by the pressure gradient method using a custom built, multi-component hydroacoustic sensor designed by JASCO. The pressure gradient sensor was composed of a pyramidal frame supporting four Reson TC4043 hydrophones and a JASCO AIM attitude/depth sensor. Pressure signals from the four hydrophones were sampled at 25 kHz per channel, with 16-bit resolution, using a laptop PC based digital acquisition system. Bubble curtain proved effective in mitigating both sound pressure and particle velocity levels generated by the pile driving.

Wake acoustic measurements around a maneuvering ship

Abstract: The underwater acoustic measurement around a maneuvering ship using Broad-band Underwater Recording Buoys (BURBs), was investigated. The BURB system composed of a set of four identical self-contained buoys with hyrodophones and GPS receivers was used for recording both underwater radiated noise and man-made acoustic transmissions. For pulse propagation tests, a Medium-frequency MultiMode Pipe Projector (MF-MMPP) was used to transmit 2 - 18 kHz × 10-ms duration LFM pulses. The transmitter was deployed at 5m depth from a small boat to freely drift on the opposite side of the ship wake from the BURBs and acoustic measurement was started 2 minutes before and 10 minutes after the ship passage. It was observed that wake effects affected shallow receivers more in comparison of deeper hydrophones. Resut shows that acoustic dropouts due to the masking effects of ship radiated noise and extinction effects from wake micro-bubbles are more pronounced in shallow acoustic paths.

Ontario ministry of the environment noise guidelines on wind power projects

Abstract: In response to the anticipated introduction of large scale wind power projects for electricity generation in Ontario, the Ministry of the Environment (MOE) prepared specific guidelines for assisting proponents of such project to address the current environmental regulatory requirements. This article is a brief overview of the MOE review and approval process concerning environmental noise impacts of wind energy projects.

Wind turbine noise primer

Abstract: A wind turbine is a modern machine that generates electricity from wind. Wind turbines generate four types of noise: tonal, broadband, low frequency, and impulsive. Another way to look at wind turbine noise is to consider its sources. There are two fundamental categories, mechanical and aerodynamic. Mechanical noise is transmitted along the structure of the turbine and is radiated from its surfaces. Aerodynamic noise is produced by the flow of air over the blades. In the United States, wind farm siting often requires compliance with state and/or local noise regulations. Common practice is to determine minimum setback distances from residences to comply with the most stringent noise limit. Geographic Information Systems (GIS) is a valuable tool in this type of analysis, particularly when current aerial photographs are available in GIS-ready format. Although recent technology advances has decreased overall noise levels, tonal noise still remains a concern during the planning process. Detailed meteorological data is available for most portions of the United States, however it is not commonly used to evaluate wind turbine noise. The authors of this paper are studying the creation of a GIS-based model that utilizes detailed met data in the propagation of wind turbine noise.

Wavelet-based solution of integral equations for acoustic scattering

Abstract: In this work, the multi-resolution wavelet analysis is used to solve Helmholtz integral equation for acoustic scattering The integral equation is solved using moment method with wavelet basis The unknown field is expressed as a two fold summation of shifted and dilated forms of a properly chosen mother wavelet The wavelet expansion covers the scatterer surface for distributing the wavelet localized functions A simpler formulation of a square wavelet operator is proposed and tested in this investigation to obtain the moment matrix The proposed operator saves some traditional stages of wavelet transform and accordingly a part of the computations required The square matrix inversion can be implemented easily on different media The resulting matrix can be made sparse by applying an appropriate threshold The solution of such sparse matrix saves a large portion of the computational load The accuracy of the proposed solution is compared to the exact solution of the problem Computational savings are illustrated for acoustic scattering on a sphere for different wave numbers and wavelet bases order

An acoustical study of IPOD use by university students in quiet and noisy situations

Abstract: An acoustical study was conducted for IPod use by university students in quite and noisy situations to determine what actual decibel levels young people choose while listening to their devices, how much they change the volume settings and whether typical use of these portable audio devices may pose an actual risk to hearing health Two samples of music were used, one from the Hip Hop segment had more low-frequency content and another from the Electronica segment which had more high-frequency content All testing was conducted in an IAC double-walled sound-attenuating booth The delivery of sound was controlled using a TDT System III Music was presented to all listeners from the same black 30 GB iPod Video, with standard earbuds The maximum output level that any individual listened to was 105 dBA which could pose a risk if listening time were not limited Health education should target individuals who are at risk so that they learn how to use their portable audio devices more safely

Relating use of portable audio devices to audiometric thresholds in university students

Abstract: The use of portable audio devices and their relation to audiometric thresholds in university students are investigated. The hearing health of young adults is a concern because of the introduction of portable audio devices with mass storage that enables a listener to hear a larger selection of music. Each individual completed a hearing test lasting less than 30 minutes. The ear to which the stimulus was presented was that which the participant believed to be of lesser ability or if both ears were believed to be equally good then the left ear was tested. Research should focus on isolating the direct effect of portable audio devices on hearing from the effects of environmental noise exposure in a large sample and also to relate audiometric measures to long-term patterns and conditions of usage of these devices.

Can silence affect perception? Duration and frequency of occurrence in perceived pitch structure

Abstract: The duration and frequency of occurrence of tones and the silence between the tones are manipulated to understand their effect on the perceived organization or pitch structure of tone sequences. Duration and frequency of occurrence are both elemental in music and act upon a single mechanism that in turn increments a magnitude accumulator. Within a sequence of tones the longer tones are judged to be more salient than the shorter but more frequent tones. Sequences were generated from six-tone tonesets, each of which contained tones of two major triads from maximally distant keys. Three sequence conditions that were created from the tonesets include the tones of one major triad that were longer than the other tones, modification of the first sequence, and modification of the original sequence. The finding suggests that the duration of an event has perceptual priority over the frequency of occurrence of the event.

An acoustical study of IPOD output: Effects of headsets and control settings

Abstract: An acoustical study was conducted to investigate the level of sound output of Apple iPod using different kinds of headsets and how output depends on factors such as equalizer and volume control settings. Three factors that differentiate one set of headphones from another are sensitivity, impedance, and frequency response. The acoustical output measurements were compared for samples of two genres of music played at four volume settings and different equalizer settings for three different headsets. Two 30 second sound clips were used for the tests, one from the Hip hop genre and the other from Electronica. Hip Hop songs are known for their strong precussion, thus most of their energy is concentrated in the low-frequency range between 1 and 4 KHz whereas Electronica song features synthetically produced sounds spanning a frequency range from 1 to 12 KHz. The largest and smallest differences at each volume level were used to determine which equalizer settings made the most differences. These physical measurements can be used to estimate the risk to human hearing.

A critical analysis of loudness calculation methods

Abstract: The physical meaning and methods of determining loudness were reviewed Loudness is a psychoacoustic metric which closely corresponds to the perceived intensity of a sound stimulus. It can be determined by graphical procedures, numerical methods, or by commercial software. These methods typically require the consideration of the 1/3 octave band spectrum of the sound of interest. The sounds considered in this paper are a 1 kHz tone and pink noise. The loudness of these sounds was calculated in eight ways using different combinations of input data and calculation methods. All the methods considered are based on Zwicker loudness. It was determined that, of the combinations considered, only the commercial software dBSonic and the loudness calculation procedure detailed in DIN 45631 using 1/3 octave band levels filtered using ANSI S1.11-1986 gave the correct values of loudness for a 1 kHz tone. Comparing the results between the sources also demonstrated the difference between sound pressure level and loudness. It was apparent that the calculation and filtering methods must be considered together, as a given calculation will produce different results for different 1/3 octave band input. In the literature reviewed, no reference provided a guide to the selection of the type of filtering that should be used in conjunction with the loudness computation method.

Development of regulatory requirements for wind turbines in Alberta

Abstract: The process of developing regulations of any type is extremely challenging in that they must be relatively simple, easy to understand, technically correct, defensible in their need and approach, and enforceable. The Energy and Utility Board (EUB) recognized that the use of wind turbines for electrical generation in Alberta was growing at an alarming rate and that noise was going to be a significant issue for individuals and communities situated near wind farms. This paper examines the considerations that were taken by the EUB to understand the issues around noise and what ultimately influenced the regulatory requirements that will be incorporated in the new edition of the province's Noise Control Directive.

Graphics processing unit cooling solutions: Acoustic characteristics

Abstract: The change in acoustic characteristics in personal computers to console gaming and home entertainment systems with the change in the Graphics Processing Unit (GPU), is presented. The tests are carried out using identical configurations of the software and system hardware. The prime components of the hardware used in the project are central processing unit, motherboard, hard disc drive, memory, power supply, optical drive, and additional cooling system. The results from the measurements taken for each GPU tested are analyzed and compared. The test results are obtained using a photo tachometer and reflective tape adhered to one particular fan blade. The test shows that loudness is a psychoacoustic metric developed by Zwicker and Fastal that aims to quantify how loud a sound is perceived as compared to a standard sound. The acoustic experiment reveals that the inherent noise generation mechanism increases with the increase of the complexity of the cooling solution.

Acoustic and geophysical measurement of infrasound from wind farm turbines

Abstract: An experiment was conducted to measure and characterize infrasound (and higher frequency acoustic energy) from turbines at a wind farm in Southern Alberta. Simultaneous telemetry and point measurements were acquired from three sensor types: low frequency geophones, acoustic microphones, and a precision sound analyzer. Measurements were recorded for three wind states: low, medium, and high. Down wind telemetry measurements were recorded for thirty (30) continuous 50m offsets, up to a distance of 1450 m from the wind farm. Point measurements, coincident with the telemetry measurements, were acquired with a low frequency precision sound analyzer for two offsets: 50m and 1000m from the turbines. The same measurements were recorded with the turbines on, and with the turbines off. The low frequency results of the experiment are presented in this paper.

Developing a guide for Flanking sound transmission in wood framed construction

Abstract: A subset for airborne sources and horizontal transmission, applied to wood-framed constructions, with the wall and floor assemblies, is presented. The estimates of the apparent sound isolation are obtained by summing the energy transmitted directly through the separating wall or floor assembly with the flanking paths involving wall. Most of the sound is transmitted via the floors and other paths such as ceiling or the abutting side walls. The gypsum board ceiling is generally mounted on resilient channels, which reduces flanking transmission through the path significant to them. Flanking through an abutting side wall transmits less sound, which could also limit overall performance provided the separating wall and the floor are improved. This experimental characterization of the direct and flanking sound transmission paths in wood-framed construction can lead to a manageable set of path transmission terms.

The effect of sentence repetition on speech intelligibility in noise

Abstract: The effect of sentence repetition on speech intelligibility in noise was investigated. The benefits of repetition on word intelligibility under continuous and fluctuation noise conditions and the effects of noise conditions on the parameters of the performance-intelligibility (PI) function for sentence spoken once or twice, was examined. Eighteen French-speaking subjects aged between 20 and 30 years with normal hearing were presented lists of 20 sentences from the Canadian French HINT test under three different noise such as continuous speech spectrum noise, and modulated speech-spectrum noise. The subjects were asked twice to repeat heard word under different noise conditions and a score was marked for each response. It was observed that repetition improves the SRT from 2.0 to 5.4 dB and increases the slope of PI function. Result shows that the speech intelligibility is highly pronounced in modulated noise and least in continuous noise.