JASA express letters最新文献

Echolocating big brown bats (Eptesicus fuscus) broadcast downward frequency-modulated sweeps covering the ultrasonic range from 100-23 kHz in two harmonics. They perceive target range from the time delay between each broadcast and its returning echo. Previous experiments indicated that the bat's discrimination acuity for broadcast-echo delay declines when the lowest frequencies (23-35 kHz) in the first harmonic of an echo are removed. This experiment examined whether echo detection is similarly impaired. Results show that detection thresholds for echoes missing these lowest frequencies are raised. Increased thresholds for echoes differing in spectra facilitates the bat's ability to discriminate against clutter.

Previous experimental studies suggested that restraining the vocal fold vertical motion may reduce the coupling strength between the voice source and vocal tract. In this study, the effects of vocal fold vertical motion on source-filter interaction were systematically examined in a two-dimensional two-mass model coupled to a compressible flow simulation. The results showed that when allowed to move vertically, the vocal folds exhibited subharmonic vibration due to entrainment to the first vocal tract acoustic resonance. Restraining the vertical motion suppressed this entrainment. This indicates that the vertical mobility of the vocal folds may play a role in regulating source-filter interaction.

Broadband active noise control systems incorporating fixed controllers exhibit limited ability to reduce sinusoids. This study presents a semi-adaptive feedforward hybrid active noise control (HANC) system to address this issue. The proposed system pairs fixed high-order optimal controllers for broadband noise with adaptive low-order FXLMS-based controllers for narrowband noise. Notably, parallel broadband and narrowband controllers work independently. The proposed semi-adaptive feedforward HANC system demonstrates low computational complexity which makes it suitable for multichannel systems. Simulations and experiments validate the effectiveness of the proposed system in controlling mixed noise.

Musical instrument playability can be analyzed by visualizing a subspace defined by musicians' control parameters. This is common for bowed-string instruments in the form of Schelleng diagrams. Such diagrams can be populated either through experimental measurements or physical modeling. It was recently suggested to use similar diagrams for analyzing wind instrument playability. This study explores this direction using a physical model, previously validated against experimental measurements. It is shown that reed beating needs to be taken into account before playability analysis. This could help arrive at specific reed and mouthpiece designs according to the musicians' desires.

A key step in applying the auxiliary superfield method to complex systems is the representation of the Green's function of the system as derivatives of a generating functional. This representation is known to be valid for Hermitian systems, but this precludes the application of the method to systems with fluid loading or damping. Here, it is demonstrated that the known representation continues to be valid for fluid-loaded and damped systems. Thus, the auxiliary superfield method may be applied to such systems.

Mechanical properties of Arctic sea ice can be inferred by observations of in-ice propagation of compressional, shear, and flexural waves. During the 1980s, impulsive signals were generated by a lead ball or sledgehammer dropped onto the sea ice, and the inference required observation of wave speeds. During ICEX20 and ARCEX23, passive cryophone observations were made of naturally occurring compressional wave resonances. Average first-year ice thicknesses during ICEX20 and ARCEX23 were inferred to be 1.3 and 1.6 m, respectively; these are consistent with independent observations and indicate the potential for remote, autonomous monitoring of sea ice thickness.

Listeners performed two different tasks in which they remembered short sequences comprising either complex tones (generally heard as one melody) or everyday sounds (generally heard as separate objects). In one, listeners judged whether a probe item had been present in the preceding sequence. In the other, they judged whether a second sequence of the same items was identical in order to the preceding sequence. Performance on the first task was higher for everyday sounds; performance on the second was higher for complex tones. Perceptual organization strongly shapes listeners' memory for sounds, with implications for real-world communication.

Synthetic aperture sonar (SAS) is an acoustic method for detecting objects in an environment. Conventional SAS image reconstruction techniques invert a forward model based on geometric scattering and straight-line propagation. Acoustic features that do not fit this model, such as multiple scattering and late-time returns, appear out of focus. This paper describes an image reconstruction technique that selectively applies range-general and range-specific methods to improve the focus of late-time returns while maintaining image quality away from the focal plane. The technique is demonstrated on experimental data and compared with a range-specific algorithm.

Acoustic propagation in the Beaufort Sea is particularly sensitive to upper-ocean sound-speed structure due to the presence of a subsurface duct known as the Beaufort duct. Comparisons of acoustic predictions based on existing Arctic models with predictions based on in situ data collected by Seaglider vehicles in the summer of 2017 show differences in the strength, depth, and number of ducts, highlighting the importance of in situ data. These differences have a significant effect on the later, more intense portion of the acoustic time front referred to as reverse geometric dispersion, where lower-order modes arrive prior to the final cutoff.

This study investigates heritage bilingual speakers' perception of naturalistic code-switched sentences (i.e., use of both languages in one sentence). Studies of single word perception suggest that code-switching is more difficult to perceive than single language speech. However, such difficulties may not extend to more naturalistic sentences, where predictability and other cues may serve to ameliorate such difficulties. Fifty-four Mexican-American Spanish heritage bilinguals transcribed sentences in noise in English, Spanish, and code-switched blocks. Participants were better at perceiving speech in single language blocks than code-switched blocks. The results indicate that increased language co-activation when perceiving code-switching results in significant processing costs.