Combined variable rotor speed and active blade twist helicopter technologies have the potential to reduce environmental acoustic impact of modern rotorcraft. This paper explores aeroacoustics, ground noise combined rotors, optimized for simultaneous mitigation source NOx emissions. An integrated approach is employed including free-wake aeroelastic modeling time-domain aeroacoustic formulations ...

Underwater communication networks are currently being developed for use in underwater control systems, underwater telemetry systems, and underwater image transmission systems. The transmission bandwidth and transmission rates of an underwater communication system are low, and its transmission delay is high. In this paper, we propose a direct mapping orthogonal variable spreading factor (OVSF)-b...

When we want to develop a recognition system for a new environment, we have to decide which is the best option in what respect to the acoustic modeling: developing acoustic models from scratch using the data available for the new environment or to do cross-task adaptation starting from reliable HMM models. In this paper, we show the performance of several alternatives, comparing cross-task MAP ...

Benthic assemblages of variable density cover three progressively deeper ridges that parallel the Broward County, Florida, coast. An acoustic bottom classification survey using QTCView5 with a 50 kHz transducer showed different acoustic classes on the shallow reef-ridge and the two deeper reef-lines, which both showed the same acoustic signature. Ground-truthing showed that the differences in a...

We are interested in the experimental characterization of the Hofstadter butterfly by means of acoustical waves. The transmission of an acoustic pulse through an array of 60 variable and resonant scatterers periodically distribued along a waveguide is studied. An arbitrary scattering arrangement is realized by using the variable length of each resonator cavity. For a periodic modulation, the st...

In most of studies on nasal vowel production, the nasal tract area at the uvula is used. The ratio between the nasal and the oral tract areas is also proposed. The aim of this paper is to determine which velar variable is more relevant of acoustic changes in nasal vowel transfer functions. It can be considered that each value of a velar variable corresponds to a probability distribution in the ...