Volume 124, Issue 2, August 2008
- jasa express letters
- acoustical news—usa
- acoustical news—international
- reviews of acoustical patents
- letters to the editor
- aeroacoustics, atmospheric sound 
- underwater sound 
- ultrasonics, quantum acoustics, and physical effects of sound 
- structural acoustics and vibration 
- noise: its effects and control 
- architectural acoustics 
- acoustic signal processing 
- physiological acoustics 
- psychological acoustics 
- speech production 
- speech perception 
- speech processing and communication systems 
- music and musical instruments 
- bioacoustics 
Index of content:
- JASA EXPRESS LETTERS
124(2008); http://dx.doi.org/10.1121/1.2947623View Description Hide Description
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.
124(2008); http://dx.doi.org/10.1121/1.2947624View Description Hide Description
Amplitude modulations of pulsitile stimulation can be used to convey pitchinformation to cochlear implant users. One variable in designing cochlear implantspeech processors is the choice of modulation waveform used to convey pitchinformation. Modulation frequency discrimination thresholds were measured for 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 pitchdiscrimination within a speech processing strategy.
124(2008); http://dx.doi.org/10.1121/1.2947625View Description Hide Description
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.
124(2008); http://dx.doi.org/10.1121/1.2947626View Description Hide Description
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.
124(2008); http://dx.doi.org/10.1121/1.2947627View Description Hide Description
Acoustic impulses due to an electrical spark source (main acoustic energy near ) 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 . The amplitudes of the peaks corresponding to specular reflections are reduced and the variability in the tails of the waveforms is increased.
124(2008); http://dx.doi.org/10.1121/1.2947628View Description Hide Description
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 waveguidedispersion 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.
Adaptive echolocation sounds of insectivorous bats, Pipistrellus abramus, during foraging flights in the field124(2008); http://dx.doi.org/10.1121/1.2947629View Description Hide Description
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 in duration, whereas the maximum pulse duration of the bats approaching a large target wall in the laboratory was . 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.
124(2008); http://dx.doi.org/10.1121/1.2947631View Description Hide Description
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 soundvelocity at different frequencies and relative humidities. The resulting expression is used to investigate changes in local dispersion with temperature and humidity.
- REVIEWS OF ACOUSTICAL PATENTS
124(2008); http://dx.doi.org/10.1121/1.2940798View Description Hide Description
The purpose of these acoustical patent reviews is to provide enough information for a Journal reader to decide whether to seek more information from the patent itself. Any opinions expressed here are those of the reviewers as individuals and are not legal opinions. Printed copies of United States Patents may be ordered at $3.00 each from the Commissioner of Patents and Trademarks, Washington, DC 20231. Patents are available via the Internet at http://www.uspto.gov.
- LETTERS TO THE EDITOR
124(2008); http://dx.doi.org/10.1121/1.2940578View Description Hide Description
Native and nonnative listeners categorized final /v/ versus /f/ in English nonwords. Fricatives followed phonetically long (originally /v/-preceding) or short (originally /f/-preceding) vowels.Vowel duration was constant for each participant and sometimes mismatched other voicing cues. Previous results showed that English but not Dutch listeners (whose L1 has no final voicing contrast) nevertheless used the misleading vowel duration for /v/-/f/ categorization. New analyses showed that Dutch listeners did use vowel duration initially, but quickly reduced its use, whereas the English listeners used it consistently throughout the experiment. Thus, nonnative listeners adapted to the stimuli more flexibly than native listeners did.
124(2008); http://dx.doi.org/10.1121/1.2945152View Description Hide Description
Phocoenids are generally considered to be nonwhistling species that produce only high-frequency pulsed sounds. Here our results show that neonatal finless porpoises (Neophocaena phocaenoides) frequently produce clear low-frequency pulsed signals, without distinct high-frequency energy, just after birth and can produce both low- and high-frequency pulsed signals simultaneously until about postnatal. The results indicate that low-frequency signals of neonatal finless porpoises are not an early form of high-frequency signals and suggest that low- and high-frequency signals may be produced by different sound production mechanisms.
124(2008); http://dx.doi.org/10.1121/1.2946714View Description Hide Description
Based on a standard Hamiltonian of acoustic ray, it is shown that a ray motion in a finite region can be treated as a particle motion inside a potential well. The boundary reflections of ray can be described by introducing a so-called confining potential to confine a ray motion in a closed domain. It is shown that the square well potential model for the ray motion can reproduce the reverberation time in a two-dimensional room with irregular walls which is consistent with the Norris–Eyring law. It is also shown that the sound reverberation relates the ray chaos of the billiards in polygons with smooth convex walls.
- AEROACOUSTICS, ATMOSPHERIC SOUND 
124(2008); http://dx.doi.org/10.1121/1.2940580View Description Hide Description
The classic Herschel–Quincke tube is a parallel connection of two ducts yielding multiple noise attenuation maxima via destructive interference. This problem has been discussed to different degrees by a number of authors over the years. This study returns to the basics of the system for the purpose of furthering the understanding of the conditions necessary for noise attenuation and especially their sensitivity to mean flow. First, the transmission loss for an -duct system with mean flow and arbitrary conditions of state in the different ducts is derived. Next, the two types of conditions yielding the attenuation maxima are studied. In addition to a discussion of the underlying physics, generic expressions for frequencies at which maximum attenuation occur are presented. Experiments without mean flow generally show good agreement with theory based on straight duct elements. However, more detailed models may be required for accurate simulations in the presence of mean flow. A simple model compensating for the losses associated with bends is shown to improve the results significantly for the geometry studied.
124(2008); http://dx.doi.org/10.1121/1.2945151View Description Hide Description
Recently, the study of acoustics in urban terrain has been concerned with the propagation of sound through street canyons typical of residential areas in large cities, while sparsely built suburban and rural areas have received little attention. An isolated building’s effect on propagating sound is a fundamental case of suburban acoustics and urban acoustics in general. Its study is a necessity in order to determine the processes that might be required to model the sound field in the building’s vicinity, e.g., diffraction and wind effects. The work herein presents the results of an experimental effort to characterize the interaction between propagating sound and a single story, gabled-roof building typical of some North American suburban and rural areas. Recorded data are found to reasonably compare to a common diffraction model in some instances.
124(2008); http://dx.doi.org/10.1121/1.2945162View Description Hide Description
The coherence function of sound waves propagating through an intermittently turbulent atmosphere is calculated theoretically.Intermittency mechanisms due to both the turbulent energy cascade (intrinsic intermittency) and spatially uneven production (global intermittency) are modeled using ensembles of quasiwavelets (QWs), which are analogous to turbulenteddies. The intrinsic intermittency is associated with decreasing spatial density (packing fraction) of the QWs with decreasing size. Global intermittency is introduced by allowing the local strength of the turbulence, as manifested by the amplitudes of the QWs, to vary in space according to superimposed Markov processes. The resulting turbulence spectrum is then used to evaluate the coherence function of a plane sound wave undergoing line-of-sight propagation. Predictions are made by a general simulation method and by an analytical derivation valid in the limit of Gaussian fluctuations in signal phase. It is shown that the average coherence function increases as a result of both intrinsic and global intermittency. When global intermittency is very strong, signal phase fluctuations become highly non-Gaussian and the average coherence is dominated by episodes with weak turbulence.
Sound transmission at ground level in a short-grass prairie habitat and its implications for long-range communication in the swift fox Vulpes velox124(2008); http://dx.doi.org/10.1121/1.2946704View Description Hide Description
The acoustic environment of swift foxes Vulpes velox vocalizing close to the ground and the effect of propagation on individual identity information in vocalizations were quantified in a transmission experiment in prairie habitat. Sounds were propagated ( above the ground) at distances up to . Effects of transmission were measured on three sound types: synthesized sweeps with bandwidths spanning in the range of ; single elements of swift fox barking sequences (frequency range of ) and complete barking sequences. Synthesized sweeps spanning 0.3–1.6 and propagated the furthest and the latter sweeps exhibited the best transmission properties for long-range propagation. Swift fox barking sequence elements are centered toward the lower end of this frequency range. Nevertheless, measurable individual spectral characteristics of the barking sequence seem to persist to at least . Individual temporal features were very consistent to at least . The communication range of the barking sequences is likely to be farther than and it should be considered a long-ranging vocalization. However, relative to the large home ranges of swift foxes (up to in the experimental area) the barking sequence probably functions at intermediate distances.
- UNDERWATER SOUND 
124(2008); http://dx.doi.org/10.1121/1.2939128View Description Hide Description
This work examines underwater source spectra of a small (, length), single-screw oceanographic vessel, focusing on directionality and effects of maneuvers. The measurements utilized a set of four, self-contained buoys with GPS positioning, each recording two calibrated hydrophones with effective acoustic bandwidth from . In straight, constant-speed runs at speeds up to , the ship source spectra showed spectral levels in reasonable agreement with reference spectra. The broadband source level was observed to increase as approximately speed to the fourth power over the range of , partially biased at low speeds by nonpropulsion machinery signals. Source directionality patterns were extracted from variations in source spectra while the ship transited past the buoy field. The observed spectral source levels exhibited a broadside maximum, with bow and stern aspect reduced by approximately , respectively, independent of frequency. An empirical model is proposed assuming that spectral source levels exhibit simultaneous variations in aspect angle, speed, and turn rate. After correction for source directionality and speed during turning maneuvers, an excess of up to in one-third octave source levels was observed.