Popular version of paper 4aEA10, “Preliminary evaluation of the sound absorption coefficient of a thin coconut fiber panel for automotive applications”
Presented Thursday morning, November 5, 2015, 11:15 AM, Orlando Room
170th ASA Meeting, Jacksonville, Fl
Absorbents materials are fibrous or porous and must have the property of being good acoustic dissipaters. Sound propagation causes multiples reflections and friction of the air present in the absorbent medium converting sound energy to thermal energy. The acoustic surface treatment with absorbent material are widely used to reduce the reverberation in enclosed spaces or to increase the sound transmission loss of acoustics panels. In addition, these materials can be applied into acoustics filters with the purpose to increase their efficiencies. The sound absorption depends on the excitation frequency of the sound and it is more effective at high frequencies. Natural fibers such as coconut coir fiber have a great potential to be used like sound absorbent material. As natural fibers are agriculture waste, manufacturing this fiber is a natural product, therefore an economic and interesting option. This work compares the sound absorption coefficient between a thin coconut fiber panel and a composite panel made by fiberglass and expanded polyurethane foam, no-woven woven, and polyester woven, which are used in the automotive industry as a roof trim. The evaluation of sound absorption coefficient was carried out with the impedance tube technique.
In 1980, Chung and Blaser evaluated the normal incidence sound absorption coefficient through transfer function method. The standard ASTM E1050-10 and ISO 10534-2 was based in Chung and Blaser’s method, Figure 1. In summary, this method uses an impedance tube with the sound source placed to one end and at another, the absorbent material backed in a rigid wall. The decomposition of the stationary sound wave pattern into forward and backward traveling components is achieved by measuring sound pressures. This evaluating is carried out simultaneously at two spaced locations in the tube’s sidewall where two microphones are located, Figure 1.
Figure 1. Impedance Tube.
The wave decomposition allows to the determination of the complex reflection coefficient R(f) from which the complex acoustic impedance and the normal incidence sound absorption coefficient (a) of an absorbent material can be determined. Furthermore, the two coefficients R(f) and a are calculated by Transfer Function H12 between the two microphones through:
where s is the distance between the microphones, x1 is the distance between the farthest microphone and the sample, i is the imaginary unity and k0 is the wave number of the air.
If R(f) is known, the coefficient a is easily obtained by expression:
In this work, eight samples of coconut fiber and eight samples of composite panel made by fiberglass and expanded polyurethane foam, no-woven woven, and polyester woven used in the automotive industry, Figure 2 and 3. The material properties are shown in Table 1.
Figure 2. Samples.
Figure 3. Composite panel structure.
Table 1. Material Properties.
The random noise signal with frequency band between 200 Hz and 5000 Hz was utilized to evaluate a. The Figure 4 shows the mean normal incidence absorption coefficient obtained from the measurements.
Figure 4. Comparison of normal absorption coefficient (a)
The results shows that the composite panel have a better sound absorption coefficient than coconut fiber panel. To improve the coconut fiber panel acoustical efficiency it is needed to add some filling material with the same effect of the polyurethane foam of the composite panel.
Chung, J. Y. and Blaser D. A. (1980) “ Transfer function method of measuring in-duct acoustic properties – I Theory,” J. Acoust. Soc. Am. 68, 907-913.
Chung, J. Y. and Blaser D. A. (1980) “ Transfer function method of measuring in-duct acoustic properties – II Experiment,” J. Acoust. Soc. Am. 68, 913-921.
ASTM E1050:2012. “Standard test method for impedance and absorption of acoustical materials using a tube, two microphones and a digital frequency analysis system,” American Society for Testing and Materials, Philadelphia, PA, 2012.
ISO 10534-2:1998. “Determination of sound absorption coefficient and impedance in impedance tubes – Part 2: Transfer-function method”, International Organization for Standardization, Geneva, 1998.
Pierre-Yves Le Bas, email@example.com, Brian E. Anderson1,2, Marcel Remillieux1, Lukasz Pieczonka3, TJ Ulrich1
1Geophysics group EES-17, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
2Department of Physics and Astronomy, Brigham Young University, N377 Eyring Science Center, Provo, UT 84601, USA
3AGH University of Science and Technology, Krakow, Poland
Popular version of paper 3aSA7, “Elasticity Nonlinear Diagnostic method for crack detection and depth estimation”
Presented Wednesday morning, November 4, 2015, 10:20 AM, Daytona room
170th ASA Meeting, Jacksonville
One common problem in industry is to detect and characterize defects, especially at an early stage. Indeed, small cracks are difficult to detect with current techniques and, as a result, it is customary to replace parts after an estimated lifetime instead of keeping them in service until they are effectively approaching failure. Being able to detect early stage damage before it becomes structurally dangerous is a challenging problem of great economic importance. This is where nonlinear acoustics can help. Nonlinear acoustics is extremely sensitive to tiny cracks and thus early damage. The principle of nonlinear acoustics is easily understood if you consider a bell. If the bell is intact, it will ring with an agreeable tone determine by the geometry of the bell. If the bell is cracked, one will hear a dissonant sound, which is due to nonlinear phenomena. Thus, if an object is struck it is possible to determine, by listening to the tone(s) produced, whether or not it is damaged. Here the same principle is used but in a more quantitative way and, usually, at ultrasonic frequencies. Ideally, one would also like to know where the damage is and what its orientation is. Indeed, a crack growing thru an object could be more important to detect as it could lead to the object splitting in half, but in other circumstances, chipping might be more important, so knowing the orientation of a crack is critical in the health assessment of a part.
To localize and characterize a defect, time reversal is a useful technique. Time reversal is a technique that can be used to localize vibration in a known direction, i.e., a sample can be made to vibrate perpendicularly to the surface of the object or parallel to it, which are referred to as out-of-plane and in-plane motions, respectively. The movie below shows how time reversal is used to focus energy: a source broadcasts a wave from the back of a plate and signals are recorded on the edges using other transducers. The signals from this initial phase are then flipped in time and broadcast from all the edge receivers. Time reversal then dictates that these waves focus at the initial source location.
Time reversal can also be more that the simple example in the video. Making use of the reciprocity principle, i.e., that a signal traveling from A to B is identical to the same signal traveling from B to A, the source in the back of the plate can be replaced by a receiver and the initial broadcast can be done from the side, meaning TR can focus energy anywhere a signal can be recorded; and with a laser as receiver, this means anywhere on the surface of an object.
In addition, the dominant vibration direction, e.g., in-plane or out-of plane, of the focus can be specified by recording specific directions of motion of the initial signals. If during the first step of the time reversal process, the receiver is set to record in-plane vibration, the focus will be primarily in that in-plane direction; similarly if the receiver records the out-of-plane vibration in the first step of the process, the focus will be essentially in the out-of-plane direction. This is important as the nonlinear response of a crack depends on the orientation of the vibration that makes it vibrate. To fully characterize a sample in terms of crack presence and orientation TR is used to focus energy at defined locations and at each point the nonlinear response is quantified. This can be done for any orientation of the focused wave. To cover all possibilities, three scans are usually done in three orthogonal directions.
Figure 2 shows three scans on x, y and z directions of the same sample composed of a glass plate glued on an aluminum plate. The sample has 2 defects, one delamination due to a lack of glue between the 2 plates (in the (x,y) plane) at the top of the scan area and one crack perpendicular to the surface in the glass plate in the (x,z) plane in the middle of the scan area.
Figure 2. Nonlinear component of the time reversal focus at each point of a scan grid with wave focused in the x, y and z direction (from left to right)
As can be seen on those scans, the delamination in the (x,y) plane is visible only when the wave is focused in the Z direction while the crack in the (x,z) plane is visible only in the Y scan. This means that cracks have a strong nonlinear behavior when excited in a direction perpendicular to their main orientation. So by scanning with three different orientations of the focused vibration one should be able to recreate the orientation of a crack.
Another feature of the time reversal focus is that its spatial extent is about a wavelength of the focus wave. Which means the higher the frequency, the smaller the spot size, i.e., the area of the focused energy. One can then think that the higher the frequency the better the resolution and thus higher frequency is always best. However, the extent of the focus is also the depth that this technique can probe; so lower frequency means a deeper investigation and thus a more complete characterization of the sample. Therefore there is a tradeoff between depth of investigation and resolution. However, by doing several scans at different frequencies, one can extract additional information about a crack. For example, Figure 3 shows 2 scans done on a metallic sample with the only difference being the frequency of the focused wave.
Figure 3. From left to right: Nonlinear component of the time reversal focus at each point of a scan grid at 200kHz and 100kHz and photography of the sample from its side.
At 200kHz, it looks like there is only a thin crack while at 100kHz the extent of this crack is larger toward the bottom of the scan and more than double so there is more than just a resolution issue. At 200kHz the depth of investigation is about 5mm; at 100kHz it is about 10mm. Looking on the side of the sample in the right panel of figure 3, the crack is seen to be perpendicular to the surface for about 6mm and then dip severely. At 200kHz, the scan is only sensitive to the part perpendicular to the surface while at 100kHz, the scan will also show the dipping part. So doing several scans at different frequencies can give some information on the depth profile of the crack.
In conclusion, using time reversal to focus energy in several directions and at different frequencies and studying the nonlinear component of this focus can lead to a characterization of a crack, its orientation and depth profile, something that is currently only available using techniques, like X-ray CT, which are not as easily deployable as ultrasonic ones.
Brian Connolly – firstname.lastname@example.org Music Department
Popular version of paper 5aMU1, “The inner ear as a musical instrument”
Presented Friday morning, November 6, 2015, 8:30 AM, Grand Ballroom 2
170th ASA meeting Jacksonville
(please use headphones for listening to all audio samples)
Did you know that your ears could sing? You may be surprised to hear that they, in fact, have the capacity to make particularly good performers and recent psychoacoustics research has revealed the true potential of the ears within musical creativity. ‘Psychoacoustics’ is loosely defined as the study of the perception of sound.
Figure 1: The Ear
A good performer can carry out required tasks reliably and without errors. In many respects the very straight-forward nature of the ear’s responses to certain sounds results in the ear proving to be a very reliable performer as its behaviour can be predicted and so it is easily controlled. In the context of the listening system, the inner ear has the ability to behave as a highly effective instrument which can create its own sounds that many experimental musicians have been using to turn the listeners’ ears into participating performers in the realization of their music.
One of the most exciting avenues of musical creativity is the psychoacoustic phenomenon known as otoacoustic emissions. These are tones which are created within the inner ear when it is exposed to certain sounds. One such example of these emissions is ‘difference tones.’ When two clear frequencies enter the ear at, say 1,000Hz and 1,200Hz the listener will hear these two tones, as expected, but the inner ear will also create its own third frequency at 200Hz because this is the mathematical difference between the two original tones. The ear literally sends a 200Hz tone back out in reverse through the ear and this sound can be detected by an in-ear microphone, a process which doctors carrying out hearing tests on babies use as an integral part of their examinations. This means that composers can create certain tones within their work and predict that the listeners’ ears will also add their extra dimension to the music upon hearing it. Within certain loudness and frequency ranges, the listeners will also be able to feel their ears buzzing in response to these stimulus tones! This makes for a very exciting and new layer to contemporary music making and listening.
First listen to this tone. This is very close to the sound your ear will sing back during the second example.
Insert – 200.mp3
Here is the second sample containing just two tones at 1,000Hz and 1,200Hz. See if you can also hear the very low and buzzing difference tone which is not being sent into your ear, it is being created in your ear and sent back out towards your headphones!
Insert – 1000and1200.mp3
If you could hear the 200Hz difference tone in the previous example, have a listen to this much more complex demonstration which will make your ears sing a well known melody. It is important to try to not listen to the louder impulsive sounds and see if you can hear your ears humming along to perform the tune of Twinkle, Twinkle, Little Star at a much lower volume!
(NB: The difference tones will start after about 4 seconds of impulses)
Insert – Twinkle.mp3
Auditory beating is another phenomenon which has caught the interest of many contemporary composers. In the below example you will hear the following: 400Hz in your left ear and 405Hz in your right ear.
First play the below sample by placing the headphones into your ears just one at a time. Not together. You will hear two clear tones when you listen to them separately.
Insert – 400and405beating.mp3
Now try and see what happens when you place them into your ears simultaneously. You will be unable to hear these two tones together. Instead, you will hear a fused tone which beats five times per second. This is because each of your ears are sending electrical signals to the brain telling it what frequency it is responding to but these two frequencies are too close together and so a perceptual confusion occurs resulting in a combined frequency being perceived which beats at a rate which is the same as the mathematical difference between the two tones.
Auditory beating becomes particularly interesting in pieces of music written for surround sound environments when the proximity of the listener to the various speakers plays a key factor and so simply turning one’s head in these scenarios can often entirely change the colour of the sound as different layers of beating will alter the overall timbre of the sound.
So how can all of these be meaningful to composers and listeners alike? The examples shown here are intended to be basic and provide proofs of concept more so than anything else. In the much more complex world of music composition the scope for the employment of such material is seemingly endless. Considering the ear as a musical instrument gives the listener the opportunity to engage with sound and music in a more intimate way than ever before.
Popular version of paper 2aAA9, “Challenges facing fitness center designers in multifamily buildings”
Presented Tuesday morning, November 3, 2015, 11:00 AM, Grand Ballroom 3
Session 2aAA, Acoustics of Multifamily Dwellings
170th ASA Meeting, Jacksonville
Transit centered living relies on amenities close to home; mixing multifamily residential units with professional, retail and commercial units on the same site. Use the nearby trains to get to work and out, but rely on the immediate neighborhood, even the lobby for errands and everyday needs. Transit centered living is appealing as it eliminates the need for sitting in traffic, seems good for the environment and adds a sense of security, aerobic health and time-saving convenience. Include an on-site fitness center and residents don’t even have to wear street clothes to get to their gym!
Developers know that a state-of-the-art fitness center is icing on their multifamily residence cake as far as attracting buyers. Gone is the little interior room with a couple treadmills and a stationary bike. Today’s designs include panoramic views, and enough ellipticals, free weights, weight & strength machines, and shower rooms to fill 2500-4000 square feet, not to mention the large classes offered with high energy music and an enthusiastic leader with a microphone. The increased focus on maintaining aerobic health, strength and mobility is fantastic, but the noise and vibration it generates? Not so great. Sometimes cooperative scheduling keeps the peace, but often residents will want to have access to their fitness center at all hours, so wise project leaders involve a noise control engineer early in the design process to develop a fitness center next to which everyone will want to live.
Remember the string and two empty cans? Stretch the string taut and conversations can travel the length of the string, but pinch the string and the system fails. As noise travels through all kinds of structures and through the air as well, it is the design goal of the noise and vibration experts to prevent that transmission. Airborne noise control can be effective using a combination of layered gypsum board, fiberglass batt insulation, concrete and resilient framing members that absorb the sound rather than transmit it through a wall or a floor/ceiling system. Controlling the structure borne noise and vibration can involve much thicker rubber mats, isolated concrete slabs and a design that incorporates the structural engineer’s input on stiffening the base building structure. And it’s not simply noise that the design is intended to restrict, it is silent, but annoying vibrations as well.
Reducing the floor shaking impact of dropping barbells on the ground is the opposite of hearing a pin drop. Heavy, steel plates loaded on a barbell, lifted 6-8 feet off the ground and then dropped. Repeatedly. Nobody wants to live under that, so designers think location, location, location. But big windows are pointless in the basement, so something has to go under the fitness center. Garage space, storage units or mechanical rooms won’t mind the calisthenics above them. And sometimes the overall design of the building structure, whether it be high-rise with underground parking, Texas wrap building
(u-shaped building with elevated parking garage on interior.), or a podium style building can offer an ideal location for this healthy necessity.
It’s not an acoustical trade secret that the best method of noise control is at the source so consider what makes the noise. Manufacturers have met the demand for replacing the old standard graduated barbell steel plates for free weight combinations with a rubber/urethane coated steel weight. These weights make much less noise when impacting each other, but are still capable of generating excessive structure-borne noise levels. This is a great example of controlling both air borne (plates clanking together) and structure borne (barbells impacting the floor) transmission paths. Speakers and sound systems and the wall/floor/ceiling systems can work together to offer clarity and quality to listeners and limitations for what the neighbors will hear, but it takes expertise and attention.
Disregarding the recommendations of noise and vibration professionals can result in an annoying, on-site gym that brings stressful tension and ongoing conflict, nothing that promotes healthy well-being.
Foresight in design and attention to acoustical specs on building materials, under the direction of a noise and vibration engineer, assures a fitness center that is a pleasant, effective space for fitness and social opportunities, an asset to the transit centered neighborhood. Do everyone a favor and pay attention to good design and product specification early on; that’s sound advice.
Popular version of poster presentation 2pSCb11, “Effect of menstrual phase on dichotic listening”
Presented Tuesday afternoon, November 3, 2015, 3:30 PM, Grand Ballroom 8
How speech is processed by the brain has long been of interest to researchers and clinicians. One method to evaluate how the two sides of the brain work when hearing speech is called a dichotic listening task. In a dichotic listening task two words are presented simultaneously to a participant’s left and right ears via headphones. One word is presented to the left ear and a different one to the right ear. These words are spoken at the same pitch and loudness levels. The listener then indicates what word was heard. If the listener regularly reports hearing the words presented to one ear, then there is an ear advantage. Since most language processing occurs in the left hemisphere of the brain, most listeners attend more closely to the right ear. The regular selection of the word presented to the right ear is termed a right ear advantage (REA).
Previous researchers reported different responses from males and females to dichotic presentation of words. Those investigators found that males more consistently heard the word presented to the right ear and demonstrated a stronger REA. The female listeners in those studies exhibited more variability as to the ear of the word that was heard. Further research seemed to indicate that women exhibit different lateralization of speech processing at different phases of their menstrual cycle. In addition, data from recent studies indicate that the degree to which women can focus on the input to one ear or the other varies with their menstrual cycle.
However, the previous studies used a small number of participants. The purpose of the present study was to complete a dichotic listening study with a larger sample of female participants. In addition, the previous studies focused on women who did not take oral contraceptives as they were assumed to have smaller shifts in the lateralization of speech processing. Although this hypothesis is reasonable, it needs to be tested. For this study, it was hypothesized that the women would exhibit a greater REA during the days that they menstruate than during other days of their menstrual cycle. This hypothesis was based on the previous research reports. In addition, it was hypothesized that the women taking oral contraceptives will exhibit smaller fluctuations in the lateralization of their speech processing.
Participants in the study were 64 females, 19-25 years of age. Among the women 41 were taking oral contraceptives (OC) and 23 were not. The participants listened to the sound files during nine sessions that occurred once per week. All of the women were in good general health and had no speech, language, or hearing deficits.
The dichotic listening task was executed using the Alvin software package for speech perception research. The sound file consisted of consonant-vowel syllables comprised of the six plosive consonants /b/, /d/, /g/, /p/, /t/, and /k/ paired with the vowel “ah”. The listeners heard the syllables over stereo headphones. Each listener set the loudness of the syllables to a comfortable level.
At the beginning of the listening session, each participant wrote down the date of the initiation of her most recent menstrual period on a participant sheet identified by her participant number. Then, they heard the recorded syllables and indicated the consonant heard by striking that key on the computer keyboard. Each listening session consisted of three presentations of the syllables. There were different randomizations of the syllables for each presentation. In the first presentation, the stimuli will be presented in a non-forced condition. In this condition the listener indicted the plosive that she heard most clearly. After the first presentation, the experimental files were presented in a manner referred to as a forced left or right condition. In these two conditions the participant was directed to focus on the signal in the left or right ear. The sequence of focus on signal to the left ear or to the right ear was counterbalanced over the sessions.
The statistical analyses of the listeners’ responses revealed that no significant differences occurred between the women using oral contraceptives and those who did not. In addition, correlations between the day of the women’s menstrual cycle and their responses were consistently low. However, some patterns did emerge for the women’s responses across the experimental sessions as opposed to the days of their menstrual cycle. The participants in both groups exhibited a higher REA and lower percentage of errors for the final sessions in comparison to earlier sessions.
The results from the current subjects differ from those previously reported. Possibly the larger sample size of the current study, the additional month of data collection, or the data recording method affected the results. The larger sample size might have better represented how most women respond to dichotic listening tasks. The additional month of data collection may have allowed the women to learn how to respond to the task and then respond in a more consistent manner. The short data collection period may have confused the learning to respond to a novel task with a hormonally dependent response. Finally, previous studies had the experimenter record the subjects’ responses. That method of data recording may have added bias to the data collection. Further studies with large data sets and multiple months of data collection are needed to determine any sex and oral contraceptive use effects on REA.
Using Acoustic Levitation to Understand, Diagnose, and Treat Cancer and Other Diseases
Brian D. Patchett – email@example.com
Natalie C. Sullivan – firstname.lastname@example.org
Timothy E. Doyle – Timothy.Doyle@uvu.edu
Department of Physics
Utah Valley University
800 West University Parkway, MS 179
Orem, Utah 84058
Popular version of paper 3pBA5, “Acoustic Levitation Device for Probing Biological Cells With High-Frequency Ultrasound”
Presented Wednesday afternoon, November 4, 2015
170th ASA Meeting, Jacksonville
Imagine a new medical advancement that would allow scientists to measure the physical characteristics of diseased cells involved in cancer, Alzheimer’s, and autoimmune diseases. Through the use of high-frequency ultrasonic waves, such an advancement will allow scientists to test the normal healthy range of virtually any cell type for density and stiffness, providing new capabilities for analyzing healthy cell development as well as insight into the changes that occur as diseases develop and the cells’ characteristics begin to change.
Prior research methods of probing cells with ultrasound have relied upon growing the cells on the bottom of a Petri dish, which distorts not only the cells’ shape and structure, butlso interfere with the ultrasonic signals. A new method was therefore needed to probe the cells without disturbing their natural form, and to “clean up” the signals received by the ultrasound device. Research presented at the 2015 ASA meeting in Jacksonville Florida will show that the use of acoustic levitation is effective in providing the ideal conditions for probing the cells.
Acoustic levitation is a phenomenon whereby pressure differences of stationary sound waves can be used to suspend small objects in gases or fluids such as air or water. We are currently exploring a new frontier in acoustic levitation of cellular structures in a fluid medium by perfecting a method by which we can manipulate the shape and frequency of sound waves inside of special containers. By manipulating these sound waves in just the right fashion it is possible to isolate a layer of cells in a fluid such as water, which can then be probed with an ultrasound device. The cells are then in a more natural form and environment, and the interference from the floor of the Petri dish is no longer a hindrance.
This method has proven effective in the laboratory with buoyancy neutral beads that are roughly the same size and shape as human blood cells, and a study is currently underway to test the effectiveness of this method with biological samples. If effective, this will give researchers new experimental methods by which to study cellular processes, thus leading to a better understanding of the development of certain diseases in the human body.