Low Frequencies

Este artigo apresenta os conceitos básicos da terapia  vibro-acústica, especificamente,  aquela abordada pelo pesquisador e terapeuta norueguês Olav Skille.  Além dos componentes que formam o arcabouço da vibro-acústica de Skille serão apresentados procedimentos para a construção de  um  “setting” para experiências  de musicoterapia vibro-acústica, bem como a sintetização, por meio digital, das freqüências senoidais usadas em sessões terapêuticas de vibroacústica.

All life on earth has developed within these earthly ‘Schumann Resonances’ as well as the ‘Inner and Outer’ Van Allen donut shaped energy toroid complex energy fields. When one calculates additional frequency relationships of the Van Allen’s such as the radius wavelengths from the Earth center or its surface it may be easily seen that again the other higher brain-wave frequency spectrums appear in number as fundamental natural frequencies.
It may now be becoming clear that our brain/body structure is intimately coupled to the ‘natural music’ near-fields of the planet rhythms. To summarize the above information, each and every day our individual consciousness cycles through the resonances with these fundamental aspects of the earth’s structure as we shift our daily activities from physical, to rest and sleep.

Method and apparatus are provided for a non-invasive bubble measuring instrument operable for detecting. distinguishing, and counting gaseous embolisms such as bubbles over a selectable range of bubble sizes of interest. A selected measurement volume in which bubbles may be detected is insonified by two distinct frequencies from a pump transducer and an image transducer, respectively. The image transducer frequency is much higher than the pump transducer frequency. The relatively low-frequency pump signal is used to excite bubbles to resonate at a frequency related to their diameter. The image transducer is operated in a pulse-echo mode at a controllable repetition rate that transmits bursts of high-frequency ultrasonic signal to the measurement volume in which bubbles may be detected and then receive, the echo. From the echo or received signal, a beat signal related to the repetition rate may be extracted and used to indicate the presence or absence of a resonant bubble. In a prefe...

The dielectric properties and AC conductivity of Au/polyvinyl alcohol (Co, Ni-doped)/n-Si Schottky diodes (SDs) were investigated in the frequency range 1 kHz–1 MHz and in the temperature range 80–400 K. The frequency and temperature dependence of dielectric constant (ϵ′), dielectric loss (ϵ″), loss tangent (tan δ), AC electrical conductivity (σ ac ) and the real and imaginary parts of the electric modulus (M′ and M″) were found to be a strong function of frequency and temperature. The values of ϵ′, ϵ″ and tan δ decrease with increasing frequency, while they increase with increasing temperature, especially above 275 K. The values of σ ac increase with both increasing frequency and temperature. Such temperature-related behavior of σ ac can be attributed to the high mobility of free charges at high temperature. Electric modulus formalism was also analyzed to obtain experimental dielectric data. The values of M′ and M″ increase with increasing frequency, while they decrease with increasing temperature. The interfacial polarization, which more easily occurs at low frequencies and high temperatures, consequently contributes to the improvement of the dielectric properties of SDs.

The condition number of the matrix of electro-acoustic head-related transfer functions (HRTF) in a two-channel sound reproduction system has been used as a measure of robustness of the Atal-Schroeder (1962) crosstalk canceler. A comparative study has been made using results produced by computer simulations and HRTFs measured in an anechoic chamber by means of a dummy head. It has been found that acoustic scattering by the head has a very important and beneficial influence on robustness, specially for large loudspeaker separations. For narrow loudspeaker separations of less than about 40 degrees it is found that crosstalk cancellation exhibits a large variation of alternating very low and very high robustness. Also, simulations and measurements have been made of the natural channel separation under the same conditions. Scattering by the head is seen to provide a good level of natural channel separation at high frequencies and large loudspeaker angles. At low frequencies or small loudspeaker angles natural channel separation is poor

ABSTRACT The uncertainty of field measurements of a façade was evaluated by a Round Robin Test (RRT) conducted in a full-scale experimental building at the Construction Technologies Institute of the National Research Council of Italy (ITC-CNR). Each of the 9 teams involved in the RRT replicated the tests 5 times, for a total of 45 measurements, while reverberation time was repeated 110 times. Both for façade sound insulation and reverberation time the main variations in the one-third octave bands were found in the low frequencies range. The study was also focused on the evaluation of single number quantities (SNQs) and their uncertainties. Single number quantities were evaluated in both narrow (from 100 to 3150 Hz) and extended (from 50 to 5000 Hz) range. Concerning the SNQs and their uncertainties, no significant differences were observed whether the low frequencies were included or not, unlike the case of airborne sound insulation (investigated in the first part of this study). The uncertainty results were compared with the relevant standards and with literature results. Based on these comparisons, it was highlighted that the standard deviation of reproducibility of façade elements is not adequately reflected in the ISO 12999-1 and further research is needed to specify the in situ standard deviation of reproducibility for façade elements.

: Low (10 - 100 Hz) and very low (1 - 10 Hz) frequency acoustic propagation loss is predicted for a site on the Bermuda Rise near 30 deg N 69 deg W. An extensive survey of the open literature is reported, and a geo- acoustic model of the acoustic environment at the site is developed. The results of a brief numerical investigation of the effect of shear waves and detailed sub-bottom layering on the acoustic propagation-loss predictions are discussed. The acoustic propagation-loss model used is SAFARI, which accounts for shear waves in the sediment but assumes a range-invariant environment. The propagation-loss predictions for 5, 10, 20, and 50 Hz are then presented. Also presented are predictions of the reflection loss in the form of grey-scale plots as a function of frequency and grazing angle. No comparison with experimental data is attempted.