• Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Journal of the Acoustical Society of America

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

Aug 2008

Volume 124, Issue 2, pp. 689-EL61

Return to All Sections
back to top
RSS Feeds
FREE

Harbor porpoise clicks do not have conditionally minimum time bandwidth product

Kristian Beedholm

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL15-EL20 (2008); (6 pages) | Cited 1 time

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The hypothesis that odontocete clicks have minimal time frequency product given their delay and center frequency values is tested by using an in-phase averaged porpoise click compared with a pure tone weighted with the same envelope. These signals have the same delay and the same center frequency values but the time bandwidth product of the artificial click is only 0.76 that of the original. Therefore signals with the same parameters exist that have a lower time bandwidth product. The observation that porpoise clicks are in fact minimum phase is confirmed for porpoise clicks and this property is argued to be incompatible with optimal reception, if auditory filters are also minimum phase.
Show PACS
43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
43.80.Lb Sound reception by animals: anatomy, physiology, auditory capacities, processing
FREE

Effects of modulation wave shape on modulation frequency discrimination with electrical hearing

David M. Landsberger

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL21-EL27 (2008); (7 pages) | Cited 1 time

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Amplitude modulations of pulsitile stimulation can be used to convey pitch information to cochlear implant users. One variable in designing cochlear implant speech processors is the choice of modulation waveform used to convey pitch information. Modulation frequency discrimination thresholds were measured for 100 Hz modulations with four waveforms (sine, sawtooth, a sharpened sawtooth, and square). Just-noticeable differences (JNDs) were similar for all but the square waveform, which often produced larger JNDs. The results suggest that a sine, sawtooth, and sharpened sawtooth waveforms are likely to provide similar pitch discrimination within a speech processing strategy.
Show PACS
43.66.Ts Auditory prostheses, hearing aids
43.66.Fe Discrimination: intensity and frequency
43.66.Hg Pitch
43.66.Nm Phase effects
FREE

Quantifying the through-thickness asymmetry of sound absorbing porous materials

Y. Salissou and R. Panneton

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL28-EL33 (2008); (6 pages) | Cited 1 time

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A method to quantify the through-thickness asymmetry of a sound absorbing porous material is proposed and discussed. Its calculation only requires impedance tube measurements of the acoustical surface impedance performed on both sides of the tested material. The method may be used for quality control or to assess the level of asymmetry of the material in terms of its acoustic properties. As a first validation, a two-layered porous system seen as an equivalent asymmetrical single porous layer with a sudden change in its physical properties is studied. From this study, a criterion of asymmetry is suggested and experimentally tested.
Show PACS
43.20.Jr Velocity and attenuation of elastic and poroelastic waves
43.20.Hq Velocity and attenuation of acoustic waves
43.55.Ev Sound absorption properties of materials: theory and measurement of sound absorption coefficients; acoustic impedance and admittance
43.58.Bh Acoustic impedance measurement
FREE

Low-frequency Fourier analysis of speech rhythm

Sam Tilsen and Keith Johnson

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL34-EL39 (2008); (6 pages)

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

multimedia

Show Abstract
A method for studying speech rhythm is presented, using Fourier analysis of the amplitude envelope of bandpass-filtered speech. Rather than quantifying rhythm with time-domain measurements of interval durations, a frequency-domain representation is used—the rhythm spectrum. This paper describes the method in detail, and discusses approaches to characterizing rhythm with low-frequency spectral information.
Show PACS
43.70.Jt Instrumentation and methodology for speech production research
43.70.Kv Cross-linguistic speech production and acoustics
43.70.Fq Acoustical correlates of phonetic segments and suprasegmental properties: stress, timing, and intonation
FREE

Laboratory studies of near-grazing impulsive sound propagating over rough water

Qin Qin, Sergei Lukaschuk, and Keith Attenborough

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL40-EL44 (2008); (5 pages)

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Acoustic impulses due to an electrical spark source (main acoustic energy near 15 kHz) have been measured after propagating near to the water surface in a shallow container resting on a vibrating platform. Control of the platform vibration enabled control of water wave amplitudes. Analysis of the results reveals systematic variations in the received acoustic waveforms as the mean trough-to-crest water wave amplitude is increased up to 7 mm. The amplitudes of the peaks corresponding to specular reflections are reduced and the variability in the tails of the waveforms is increased.
Show PACS
43.50.Vt Topographical and meteorological factors in noise propagation
43.28.En Interaction of sound with ground surfaces, ground cover and topography, acoustic impedance of outdoor surfaces
43.28.Lv Statistical characteristics of sound fields and propagation parameters
43.28.Mw Shock and blast waves, sonic boom
FREE

Particle filtering for dispersion curve tracking in ocean acoustics

Ivan Zorych and Zoi-Heleni Michalopoulou

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL45-EL50 (2008); (6 pages) | Cited 3 times

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A particle filtering method is developed for dispersion curve extraction from spectrograms of broadband acoustic signals propagating in underwater media. The goal is to obtain accurate representation of modal dispersion which can be employed for source localization and geoacoustic inversion. Results are presented from the application of the method to synthetic data, demonstrating the potential of the approach for accurate estimation of waveguide dispersion characteristics. The method outperforms simple time-frequency analysis providing estimates that are very close to numerically calculated dispersion curves. The method also provides uncertainty information on modal arrival time estimates, typically unavailable when traditional methods are used.
Show PACS
43.60.Hj Time-frequency signal processing, wavelets
43.60.Jn Source localization and parameter estimation
43.30.Pc Ocean parameter estimation by acoustical methods; remote sensing; imaging, inversion, acoustic tomography
FREE

Adaptive echolocation sounds of insectivorous bats, Pipistrellus abramus, during foraging flights in the field

Shizuko Hiryu, Tomotaka Hagino, Emyo Fujioka, Hiroshi Riquimaroux, and Yoshiaki Watanabe

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL51-EL56 (2008); (6 pages) | Cited 2 times

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Echolocation pulses emitted by wild Pipistrellus abramus were investigated while foraging for insects in the field. Similar to other European pipistrelles, the frequency structure during foraging varied. During the search phase, the bats emitted long shallow frequency-modulated pulses 9–11 ms in duration, whereas the maximum pulse duration of the bats approaching a large target wall in the laboratory was 3 ms. No significant difference was observed between decreases in the interpulse interval during these two approach flights. It is concluded that the bats use a long quasi-constant frequency pulse to find a weak echo from a small prey target.
Show PACS
43.80.Ka Sound production by animals: mechanisms, characteristics, populations, biosonar
FREE

Dispersion relation for air via Kramers-Kronig analysis

Fernando J. Álvarez and Roman Kuc

J. Acoust. Soc. Am. Volume 124, Issue 2, pp. EL57-EL61 (2008); (5 pages) | Cited 2 times

Online Publication Date: 18 Jul 2008

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A general expression for the dispersion of acoustic waves in air is obtained by combining the attenuation coefficient given by the ISO:9613-1 standard and the twice-subtracted Kramers-Kronig relation. Good agreement is found with published data of sound velocity at different frequencies and relative humidities. The resulting expression is used to investigate changes in local dispersion with temperature and humidity.
Show PACS
43.28.Bj Mechanisms affecting sound propagation in air, sound speed in the air
43.20.Hq Velocity and attenuation of acoustic waves
Return to All Sections
Close

Home Publications Meetings Contact ASA Site Map Back to Top

Copyright © Acoustical Society of America

close