SciCombinator

Discover the most talked about and latest scientific content & concepts.

Journal: The Journal of the Acoustical Society of America

35

Cracking sounds emitted by coffee beans during the roasting process were recorded and analyzed to investigate the potential of using the sounds as the basis for an automated roast monitoring technique. Three parameters were found that could be exploited. Near the end of the roasting process, sounds known as “first crack” exhibit a higher acoustic amplitude than sounds emitted later, known as “second crack.” First crack emits more low frequency energy than second crack. Finally, the rate of cracks appearing in the second crack chorus is higher than the rate in the first crack chorus.

Concepts: Coffee, Acoustics, Frequency, Sound, Crack cocaine, Psychoacoustics, Crack, Coffee roasting

28

The ICA Early Career Award is presented at the Triennial Congress to an individual who is relatively early in his/her professional career (about 10-15 years of active career), who has contributed substantially, through published papers, to the advancement of theoretical or applied acoustics or both and who has been active in the affairs of Acoustics through his/her National Society, other National Society(ies), Regional or International organizations. The Award consists of an Award Certificate, a Medal, and an Honorarium.

Concepts: Science, Organization, Award, Certificate, Medal, Award items

28

Acousticians and other practitioners alike often describe acoustic conditions in performance spaces with standard objective parameters. Apart from a few exceptions, the parameters are calculated by integrating the sound energy of the impulse responses over time; this makes them inadequate for researching the acoustics in detail, especially in the early part of the room impulse response. This paper proposes a method based on time-frequency and spatiotemporal presentations to overcome the lack of detail in the standard analysis. In brief, the proposed methods visualize the cumulative development of the sound field as a function of frequency or direction by forward-integrating the energy in the impulse response in short time frames. Analysis on the measurements from six concert halls concentrates particularly on interpreting the results in light of the seat dip effect. Earlier research has concluded that the seat dip effect is reduced by reflection from low overhead surfaces. In contrast, the current results indicate that the seat dip attenuation in the frequency response is corrected the best when the hall provides most lateral reflections. These findings suggest that the proposed analysis is suitable for explaining concert hall acoustics in detail.

Concepts: Light, Acoustics, Sound, Subroutine, LTI system theory, Frequency response, Maximum length sequence, Impulse response

28

Propagation patterns of animal acoustic signals provide insights into the evolution of signal design to convey signaler’s information to potential recipients. However, propagation properties of vertebrate calls have been rarely studied using natural calls from individuals; instead playback calls broadcast through loudspeakers have been used extensively, a procedure that may involve acoustical and physical features differing from natural sounds. Measurements of the transmission characteristics of natural advertisement calls, which are simple tonal sounds, of the Iberian midwife toad, Alytes cisternasii, were carried out, and the results were compared with previously published results broadcasting recorded calls of the same species. Measurements of sound pressure level (SPL) of calls from individual male A. cisternasii revealed that the call amplitude decreases at distances of 1-8 m from the source at rates averaging 1-5 dB above spherical transmission loss in an omni-directional pattern. A comparison between SPLs of natural calls in the current study and of playback calls from a previous study showed that patterns of propagation did not differ in average values, but variance was significantly higher for natural calls. Results suggest that using broadcast signals for transmission experiments may result in a simplification of the conditions in which actual animals communicate in nature.

Concepts: Acoustics, Average, Sound, Sound pressure, Microphone, Level, Broadcasting, Bioacoustics

27

Head related transfer functions (HRTFs) are a key component when creating auralizations used in subjective concert hall studies. An average HRTF, rather than an individualized HRTF, is often used when creating auralizations, which can lead to front-back ambiguity and reduced out-of-head sound localization. The goal of this study was to determine how the choice of HRTF can impact subjective impression of various concert hall acoustic qualities from auralizations. Using 10 HRTFs from the CIPIC database, the best and worst case HRTFs were determined for each test subject, based on out-of-head localization. For the main test, auralizations were created using these two HRTFs, along with an average HRTF. The subjects' task was to evaluate the auralizations based upon concert hall acoustics characteristics, such as reverberance and listener envelopment. Before participating in the main part of the study, the subjects were required to complete a series of training sessions. Test subjects were limited to trained musicians and those who met a 15 dB hearing level requirement. The resulting data were analyzed to determine the significance of the differences between the three cases. The results from the listening tests and the statistical analysis will be presented. [Work supported by NSF Grant 1302741.].

Concepts: Statistics, Statistical significance, Acoustics, Control theory, Ear, Sound, Pinna, Head-related transfer function

27

For decades, “quiet” and “zero” emission vehicles have been considered the challenge for researchers and for the industry. Today, despite the great results obtained in the fields of air and noise pollution, the electric vehicles (EV) and hybrid vehicles (HV) have raised an important question regarding the pedestrian safety. At the speed permitted in urban areas (<50 km/h), these vehicles are considerably quieter than the traditional ones powered by gasoline or diesel. Nevertheless the amount of auditory cues associated to the approaching of these vehicles can be reduced, and this can determine an increase of the risk of accidents for the pedestrians. Even though the recent studies on this problem are focused, mainly, on the minimum sound levels and on the spectral content of the approaching vehicles, further aspects of the semantic content's change of the event should be considered. In this paper, a preliminary investigation on the relationship, and possible incoherence, among the approaching speed of the vehicles, the auditory cues, and the semantic content was performed, and results are presented. For the investigation, an immersive virtual reality environment was used.

Concepts: Pollution, Sound, Noise, Automobile, The Pedestrian, Internal combustion engine, Electric vehicle, Hybrid vehicle

27

In stratified lakes internal waves has great ecological significance since they affect mixing, resuspension, material transport, chemical regime and ecosystem productivity. Reconstruction of spatio-temporal heterogeneity of the basin scale internal waves and their accurate parameterization are important tasks. The effect of internal Kelvin waves (IKWs) on spatiotemporal variability of the mid-frequency (1 kHz) sound field in a deep lake using geoacoustic modeling is studied. It is demonstrated that IKWs cause significant fluctuations of the sound field, such as horizontal shift of interference structure. This shift can be easily measured in situ and used for practical reconstruction of IKW parameters. Overall, it is suggested implementing the low-cost geoacoustic methodology for accurate parameterization of the basin scale internal waves and studying their dynamics.

Concepts: Diffraction, Lake, Physical oceanography, Frequency, Wavelength, In situ, Waves, The Basin, Victoria

27

Attack transients of harmonium-type reeds from American reed organs have been studied in a laboratory setting with the reeds mounted on a wind chamber. Several methods were used to initiate the attack transients of the reeds, and the resulting displacement and velocity waveforms were recorded using a laser vibrometer system and electronic proximity sensors. The most realistic procedure had a pallet valve mechanism simulating the initiation of an attack transient that depressing an organ key would provide. Growth rates in vibrational amplitude were then measured over a range of blowing pressures. Although the fundamental transverse mode is dominant in free reed oscillation, the possibility of higher transverse modes and torsional modes being present in transient oscillation was also explored. The reeds studied are designed with a spoon-shaped curvature and a slight twist at the free end of the reed tongue, intended to provide a more prompt response, especially for larger, lower-pitched reeds for which a slow attack can be a problem. The effectiveness of this design has been explored by comparing these reeds with equivalent reeds without this feature. [Work supported by National Science Foundation REU Grant PHY-1004860.].

Concepts: Laser, Initiation, Clarinet, Saxophone, Accordion, Free reed aerophone, Reed organ, Bassoon

27

The resonator guitar was invented in the 1920s, with one or more metal cone resonators set into the body. These additions were originally meant to amplify the sound of the acoustic guitar for performance in a band. The distinct timbre of the resonator ensured that the design survived even after electrification, especially in blues and bluegrass genres. A study of the sound radiated from different models of resonator guitars, as well as a similar standard acoustic guitar, compares spectral features to understand the unique sound of the resonator guitar.

Concepts: Slide guitar, Electric guitar, Guitar, Blues, Resonator guitar, Acoustic bass guitar, Bluegrass music, Steel guitar

27

A presentation of acoustical terminology and concepts that relate directly to the design and construction of an architectural space, non-technical explanations, descriptions, and examples. Architectural acoustics can be defined as the study and application of acoustic principles as they are applied to the inside of a building or structure. Usually, these are buildings that will be used for a live performance or the presentation of other useful information. This paper is written with the architect in mind; to help define and explain some of the most basic concepts relating to architectural acoustics. In today’s pro/commercial audio marketplace, architectural acoustics must play a significant role in the design process for any programmed meeting or entertainment space. This work puts essential terms and concepts into the hands of the architect, owner, or anyone else who would like to have a better understanding of this topic. Contents: What is Sound? Sound Propagation Three Acoustical Tools Where Does All the Unused Sound Go After it’s Been Heard? Audio Volume Changes-What Do the Numbers Mean? The Inverse Square Law Room Geometry-The Good, Bad, and Ugly Reverberation and Echo Speech Intelligibility Noise Internal vs External Noise Room Modes Variable Acoustics Psychoacoustics Conclusion.

Concepts: Acoustics, Sound, Sound pressure, Construction, Psychoacoustics, Architectural engineering, Architect, Inverse-square law