Octave Frequency Research Articles

Coupler-joint on coaxial transmission lines

Constructions and results оf the experimental research of directional couplers based on semi-rigid coaxial series-produced transmission lines in 2….18 GHz frequency range are described. Couplers provide coupling from 3 to 20 dB with directivity up to 28 dB in one octave frequency range and accommodated for simultaneous decision of the tasks of energy branching and connecting of separate microwave units in apparatus.Reference 2, figures 6.

Reproduction of sound source directionality in reduced scale model

The study of acoustic phenomena through reduced scale models is a useful tool for predicting the acoustic performance of closed and outdoor environments. When using reduced scale models, begins a process of constructive adequacy details of the study environment and sound source characteristics, reproducing its level and directionality. It is presented in this paper, a study on the reproduction of sound source directionality with application in outdoor reduced scale model. The sound source is an electric power converting substation. The directionality of this source was calculated using sound pressure levels measured, in 1/3 octave frequency bands between 50 Hz and 12.5 kHz, in 24 points positioned on a circle located around of the sound source. The sound was recorded in a point outside the circle for later playback. For playback of the sound signal, the noise was emitted in each monitoring direction, considering in each one the directionality through the signal equalization. The reduced scale used in the model was 1:5 and, based on this, it was transposed the frequencies of the signal. It was concluded that the sound source used in the reduced scale can be an efficient tool for reproduction of the directionality characteristics of the source.

Proposal of cheap microperforated panel absorbers manufactured by infiltration

Microperforated panels (MPPs) are tunable systems providing sound absorption in a couple of octaves frequency band. Their absorption curve can be reliably predicted by using well established models, such as the Maa and fluid equivalent models, which depend on the perforation diameter, the perforation ratio, and the panel and air gap thicknesses. However, while MPP absorbers can be soundly designed by these models, their widespread use in noise control applications is dissuaded due to their high manufacturing cost. MPPs usable in the frequency range of noise control applications require thousands of sub-millimetric holes which are usually done by a laser technology, this in turn resulting in a rather expensive absorption system. Here we propose a fabrication technique which significantly lowers the manufacturing cost of MPP absorbers. This technique consists of mixing common salt grains of controlled size with a commercial epoxy resin. The mixture is introduced into a mould. When the epoxy cures, the sample is released and introduced into a water tank to dissolve the salt grains appearing holes with the shape of the grains. The parameters of the resulting MPP are controlled by the size and percentage of salt grains in the initial mixture. Preliminary experimental results demonstrate the viability of this cheap technique to manufacture MPP absorbers.

Spectral features for the classification of partial discharge signals from selected insulation defect models

Time-domain features of partial discharge (PD) signals are often used to classify PD patterns. This paper proposes spectral features that are extracted using a filter bank, consisting of band-pass filters. By applying the fast Fourier transform to the PD signal, the resulting frequency bins are grouped into L octave frequency sub-bands. Two new features called the octave frequency moment coefficients (OFMC) and octave frequency Cepstral coefficients (OFCC) are defined in this paper. In addition, time-frequency domain coefficients (TFDC) obtained via wavelet analysis are also analysed. A PD signal can now be represented as an L -dimensional feature vector of OFMC, OFCC or TFDC. These features are compared with discrete wavelet transform-based higher-order statistical features (HOSF) using three different classifiers: probabilistic neural network, support vector machine and the recently emerged sparse representation classifier. Results show that the proposed spectral features are robust and provide a better classification accuracy of PD signals, compared with HOSF.

Effect of age on inter and intra-subject variability in acceptable noise level (ANL) in listeners with normal hearing

Article history: Received September 28, 2012 Received in revised format 19 November 2012 Accepted 20 November 2012 Available online November 27 2012 Several industrial engineering and psychological studies have shown that noise affects the important aspects of communication for both adults and children. For speech understanding by hearing aids users and language development in children, an accurate hearing is very important. A metric has been developed for measuring an individual's acceptance of noise while listening to speech in quiet. This metric is known as Acceptable Noise Levels (ANLs). Studies have shown large inter-subject variability in acceptance of background noise. An argument has been made that an acceptance of background noise is a “means” that will help to solve the puzzle and monumental problem of hearing aid rejection. Meanwhile, within subject age dependency has not been investigated. This study is conducted to determine if ANL inter and intra-subject variability under music signal depends on age. Twenty subjects participated in the study (average age = 29; SD = 3.7; range 23-35 years). All participants had hearing level not worse than 25dB HL at octave frequencies from 250Hz to 4000Hz. Listeners’ task was to adjust the level of music played in quiet to their most comfortable listening level and then to adjust the level of background noise to the maximum level that they still consider acceptable while listening to music. Further, music is not a speech signal that many researchers have used to determine the significance of age on ANL inter-subject variability. Results of this study supported the findings of others on age dependency, which shows that ANL inter and intrasubject variability is independent of age.

Correction: Long-Term Tinnitus Suppression with Linear Octave Frequency Transposition Hearing Aids

The published Funding and Competing interests statements were incorrect. The correct statements are: Funding: No current external funding was received for this study. Competing interests: One or more of the authors are employed by Laboratoire Chelles surdite. This does not alter our adherence to all the PLOS ONE policies on sharing data and materials.

Self-phase modulation of a single-cycle THz pulse

We demonstrate self-phase modulation (SPM) of a single-cycle THz pulse in a semiconductor, using bulk n-GaAs as a model system. The SPM arises from the heating of free electrons in the electric field of the THz pulse. Electron heating leads to an ultrafast reduction of the plasma frequency, which results in a strong modification of the THz-range dielectric function of the material. THz SPM is observed directly in the time domain as a characteristic reshaping of single-cycle THz pulse. In the frequency domain, it corresponds to a strong frequency-dependent refractive index nonlinearity of n-GaAs, which is found to be both positive and negative within the broad spectrum of the THz pulse. The spectral position of zero nonlinearity is defined by the electron momentum relaxation rate. Nonlinear spectral broadening and compression of the single-cycle THz pulse was also observed. Self-phase modulation (SPM), a fundamental nonlinear-optical effect, leads to intensity- dependent temporal and spectral reshaping of optical signals as they propagate through a nonlinear medium. Here we demonstrate the SPM in a new mode - at THz frequencies, using a doped semiconductor, n-GaAs, as an efficient nonlinear medium. However, any other semiconductor with complex band structure will also show SPM along the lines described in this work. Further, we demonstrate the SPM occurring in a single-cycle regime, with the signal spectrum covering many octaves of frequencies. As will be shown below, single-cycle THz pulses can be used as accessible model tools for direct observation of general nonlinear optical effects occurring in the single-cycle regime, and the findings obtained in the THz range can be generalized to other spectral ranges. The THz-range optical nonlinearity of a semiconductor, such as n-GaAs used in this work, arises from the nonlinear response of the free-carrier plasma to the THz ponderomotive excitation. Semiconductors with free carriers are good absorbers of THz radiation, and their THz-range complex-valued dielectric function ߝ is well described by the basic Drude plasma model (1,2) ߝ ሺ ሻ ൌሺ ൅ ߙ/2ሻ

Measurement of Output Power Density from Mobile Phone as a Function of Input Sound Frequency

Measurements of power density emitted by a mobile phone were carried out as a function of the sound frequency transmitted by a sound generator, ranging from 250 to 14000 Hz.Output power density was monitored by means of the selective radiation meter Narda SRM 3000 in spectrum analysis mode, and the octave frequency analysis of each tone used for the experimental design was acquired by the sound level meter Larson Davis LxT Wind. Vodafone providers were used for mobile phone calls with respect to various local base station in Southern-Italy.A relationship between the mobile phone microwaves power density and the sound frequencies transmitted by the sound generator was observed. In particular, microwaves power density level decreases significantly at sound frequency values larger than 4500 Hz. This result can be explained assuming that discontinuous transmission mode of global system for mobile communications is powered not only in silence-mode, but also at frequencies larger than 4500 Hz.

Long-Term Tinnitus Suppression with Linear Octave Frequency Transposition Hearing Aids

Over the last three years of hearing aid dispensing, it was observed that among 74 subjects fitted with a linear octave frequency transposition (LOFT) hearing aid, 60 reported partial or complete tinnitus suppression during day and night, an effect still lasting after several months or years of daily use. We report in more details on 38 subjects from whom we obtained quantified measures of tinnitus suppression through visual analog scaling and several additional psychoacoustic and audiometric measures. The long-term suppression seems independent of subject age, and of duration and subjective localization of tinnitus. A small but significant correlation was found with audiogram losses but not with high frequency loss slope. Long-term tinnitus suppression was observed for different etiologies, but with a low success rate for sudden deafness. It should be noted that a majority of subjects (23) had a history of noise exposure. Tinnitus suppression started after a few days of LOFT hearing aid use and reached a maximum after a few weeks of daily use. For nine subjects different amounts of frequency shifting were tried and found more or less successful for long-term tinnitus suppression, no correlation was found with tinnitus pitch. When the use of the LOFT hearing aid was stopped tinnitus reappeared within a day, and after re-using the LOFT aid it disappeared again within a day. For about one third of the 38 subjects a classical amplification or a non linear frequency compression aid was also tried, and no such tinnitus suppression was observed. Besides improvements in audiometric sensitivity to high frequencies and in speech discrimination scores, LOFT can be considered as a remarkable opportunity to suppress tinnitus over a long time scale. From a pathophysiological viewpoint these observations seem to fit with a possible re-attribution of activity to previously deprived cerebral areas corresponding to high frequency coding.

The fusion of classifier outputs to improve partial discharge classification

The detection of partial discharge signals and classifying its patterns is an area of interest in the analysis of defects in high voltage cables. This paper investigates a filter-bank based approach to extract frequency domain based features to represent partial discharge signals. By applying the fast Fourier transform, the sampled partial discharge data are mapped into equivalent discrete frequency bins, which are then grouped into N equal sub-bands and also octave sub-bands, each providing N-dimensional features for partial discharge pattern classification. Two classifiers, namely, the support vector machine and the sparse representation classifier, are implemented and their outputs are fused, in order to improve the accuracy of classifying partial discharge. Classification accuracy is also compared with wavelet domain based octave frequency sub-band features.

Augmented Ocular Vestibular Evoked Myogenic Potentials to Air-Conducted Sound in Large Vestibular Aqueduct Syndrome

To demonstrate the value of recording air-conducted ocular Vestibular Evoked Myogenic Potentials (oVEMP) in a patient with bilaterally enlarged vestibular aqueducts. Cervical VEMP and oVEMP were recorded from a patient presenting with bilateral hearing loss and imbalance, attributable to large vestibular aqueduct syndrome. The stimuli were air-conducted tone bursts at octave frequencies from 250 to 2000 Hz. Amplitudes and thresholds were measured and compared with the normal response range of 32 healthy control subjects. oVEMP reflexes demonstrated pathologically increased amplitudes and reduced thresholds for low-frequency tone bursts. Cervical VEMP amplitudes and thresholds were within normal limits for both ears across all frequencies of stimulation. This study is the first to describe the augmentation of AC oVEMPs in an adult with large vestibular aqueduct syndrome.

Dual-Polarized Sinuous Antennas on Extended Hemispherical Silicon Lenses

This paper examines the performance of dual-linear sinuous antennas on silicon extended hemispherical silicon dielectric lenses. A theoretical impedance of 106 Ω is identified based on the analysis of an ideal self-complementary structure, and this result compares well with simulations and measurements. The radiation properties of a linearly polarized sinuous antenna are simulated using Method of Moments software coupled to a GO/PO code, and also agree well with measurements. The results indicate that the sinuous antenna is an excellent wideband planar feed for a silicon lens, with cross-polarization levels below -17 dB, and polarization variations of ±5° over two octaves in frequency. The application areas are millimeter-wave, wideband, dual-polarized radio-astronomy receivers.

Psychoacoustic study on contribution of fan noise to engine noise

There are more researches on engine fan noise control focusing on reducing fan noise level through optimizing fan structure, and a lot of research achievements have been obtained. However, researches on the effect of fan noise to engine noise quality are lacking. The influences of the effects of fan structure optimization on the engine noise quality are unclear. Thus, there will be a decline in fan noise level, but the deterioration of engine noise quality. Aiming at the above problems, in consideration of fan structure design and engine noise quality, an innovative method to analyze the contribution of fan noise to engine noise quality using psychoacoustic theory is proposed. The noises of diesel engine installing different cooling fans are measured by using the acoustic pressure method. The experiment results are regarded as analysis samples. The model of sensory pleasantness is used to analyze the sound quality of a diesel engine with different cooling fans. Results show that after installing 10-blade fan in medium diameter the sensory pleasantness at each test point is increased, and the increase is 13.53% on average, which indicate the improvement of the engine noise quality. In order to verify the psychoacoustical analysis, the subjective assessment is carried out. The test result shows the noise quality of engine installed 10-blade fan in medium diameter is most superior. 1/3 octave frequency spectrum analysis is used to study the reason of the improvement of engine noise quality. It is found that after installing proper cooling fan the sound pressure level below 400 Hz are obviously increased, the frequency assignment and spectral envelope are more reasonable and a proper cooling fan can optimize the spectrum structure of the engine noise. The psychoacoustic study is applied in the contribution of fan noise to engine noise, and the idea of engine sound quality improvement through the structure optimization is proposed.

Spatial frequency bandwidth of surround suppression tuning curves.

The contrast detection threshold of a grating located in the periphery is increased if a surrounding grating of the same frequency and orientation is present. This inhibition between center and surround has been termed surround suppression. In this work we measured the spatial frequency bandwidth of surround suppression in the periphery for different spatial frequencies (0.5, 1.1, 3, and 5 cycles/deg) of a sinusoidal grating (target) surrounded by a grating with different spatial frequencies (surround). Using a Bayesian adaptive staircase, we measured contrast detection thresholds in an 8AFC detection task in which the target (grating with a 2.3-deg Butterworth window) could appear in one of eight possible positions at 4° eccentricity. The target was surrounded by a grating (with a 18° Butterworth window) with the same or an orthogonal orientation. In each session we fixed the spatial frequency of the target and changed the spatial frequency and the orientation of the surround. When the surround was orthogonal to the target, the thresholds were similar to those obtained without surround, independent of the surrounding spatial frequency. However, when the target and surround had the same orientation and spatial frequency, the contrast threshold was increased by a factor ranging from 3 to 6 across subjects. This suppression reduced rapidly as the spatial frequency of the surround moved away from that of the target. The bandwidth of the suppressive effect depended on spatial frequency, declining from 2.9 octaves at 0.5 c/deg to 1 octave for frequencies above 3 c/deg. This is consistent with the bandwidth of individual simple cells in visual cortex and of spatial frequency channels measured psychophysically, both of which decline with increasing spatial frequency. This suggests that surround suppression may be due to relatively precise inhibition by cells with the same tuning as the target.

SYNCHROTRON SPECTRAL CURVATURE FROM 22 MHz TO 23 GHz

We combine surveys of the radio sky at frequencies 22 MHz to 1.4 GHz with data from the ARCADE-2 instrument at frequencies 3 to 10 GHz to characterize the frequency spectrum of diffuse synchrotron emission in the Galaxy. The radio spectrum steepens with frequency from 22 MHz to 10 GHz. The projected spectral index at 23 GHz derived from the low-frequency data agrees well with independent measurements using only data at frequencies 23 GHz and above. Comparing the spectral index at 23 GHz to the value from previously published analyses allows extension of the model to higher frequencies. The combined data are consistent with a power-law index beta = -2.64 +/- 0.03 at 0.31 GHz, steepening by an amount Delta beta = 0.07 every octave in frequency. Comparison of the radio data to models including the cosmic ray energy spectrum suggests that any break in the synchrotron spectrum must occur at frequencies above 23 GHz.

A GIS tool for modeling anthropogenic noise propagation in natural ecosystems

SPreAD-GIS is a tool for modeling spatial patterns of anthropogenic noise propagation in natural ecosystems. SPreAD-GIS incorporates commonly available datasets on land cover, topography, and weather conditions to calculate noise propagation patterns and excess noise above ambient conditions for one-third octave frequency bands around one or multiple sound sources. User-specified noise source characteristics, ambient sound conditions, and frequency-weighting make SPreAD-GIS flexible to incorporate field measurements and model noise propagation for any type of source, environment, or species. SPreAD-GIS is a free, open-source application written in Python and implemented as a toolbox in ArcGIS software.

Virtual models for the prediction of acoustic fields of Manuel de Falla Auditorium in Granada, Spain

This paper presents the results of the acoustic simulation of the Manuel de Falla Auditorium (MFA), Granada, Spain, carried out in CATT-Acoustic and CATT–TUCT. The 3D geometrical acoustic model created for this purpose is tuned by adjusting the absorption and scattering coefficients of the convex reflector ceiling of the auditorium through an iterative process aimed at rendering differences between simulated and measured values for reverberation time in each octave frequency band lower than 5%. The model is validated by comparing simulated and measured figures for the most significant monaural and binaural room acoustic parameters assessed at multiple locations both on the stage and within the audience areas, then by performing both spectral and spatial analyses of their behaviour, and ultimately studying dissimilarities between the two sets of data in terms of just noticeable difference (JND). The influence of the degree of detail of the geometric model on the outcome is also considered by incorporating the 44 iconic lamps specifically designed for this enclosure, into the model. Likewise, the acoustic effect of an already executed seating replacement in the performance space is analyzed in relation to the degree of occupancy of the room. The simulated results confirm the appropriateness of the choice of the new seating for the refurbishment of the concert hall.

Vestibular evoked myogenic potentials to sound and vibration: characteristics in vestibular migraine that enable separation from Menière’s disease

It can be difficult to distinguish vestibular migraine (VM) from Menière's disease (MD) in its early stages. Using vestibular-evoked myogenic potentials (VEMPs), we sought to identify test parameters that would help discriminate between these two vestibular disorders. We first recorded ocular and cervical VEMPs (oVEMP/cVEMP) to air-conducted clicks and bone-conducted vibration in 30 control participants, 30 participants with clinically definite VM and 30 participants with clinically probable VM. Results were compared with a group of 60 MD patients from a previous study. oVEMPs and cVEMPs were then recorded at octave frequencies of 250 Hz to 2000 Hz in 20 controls and 20 participants each with clinically definite VM and MD. Inter-aural amplitude asymmetry ratios and amplitude frequency ratios were compared between groups. For click, tendon-hammer-tap and minishaker-tap VEMPs, there were no significant differences in reflex amplitudes or symmetry between controls, definite VM and probable VM. Compared with MD patients, participants with VM had significantly fewer reflex abnormalities for click-cVEMP, click-oVEMPs and minitap-cVEMPs. The ratio of cVEMP amplitude generated by tone bursts at a frequency of 0.5 kHz to that generated by 1 kHz was significantly lower for MD affected ears than for VM or controls ears. cVEMP asymmetry ratios for 0.5 kHz tone bursts were significantly higher for MD than VM. The 0.5/1 kHz frequency ratio, 0.5 kHz asymmetry ratio and caloric test combined, separated MD from VM with a sensitivity of 90.0% and specificity of 70.0%.

The Haar Wavelet Transfer Function Model and Its Applications

In the paper the Haar wavelet transfer function models are suggested as a way toparsimoniously parametrise the impulse responses and construct models with parameters providingan insight into the frequency content of the relationships under scrutiny. Besides, the models enable to verify hypotheses concerning changes of the regression parameters across dyadic scales (octave frequency bands). In the paper some theoretical properties of the models are investigated and an empirical illustration is provided. In the empirical study returns on WIG are modelled with the help of returns on S&P 500. Interestingly, besides the insight into the frequency content of the relationship, the empirical wavelet transfer function models also provided good forecasts.

Functional Specialization of Mouse Higher Visual Cortical Areas

The mouse is emerging as an important model for understanding how sensory neocortex extracts cues to guide behavior, yet little is known about how these cues are processed beyond primary cortical areas. Here, we used two-photon calcium imaging in awake mice to compare visual responses in primary visual cortex (V1) and in two downstream target areas, AL and PM. Neighboring V1 neurons had diverse stimulus preferences spanning five octaves in spatial and temporal frequency. By contrast, AL and PM neurons responded best to distinct ranges of stimulus parameters. Most strikingly, AL neurons preferred fast-moving stimuli while PM neurons preferred slow-moving stimuli. By contrast, neurons in V1, AL, and PM demonstrated similar selectivity for stimulus orientation but not for stimulus direction. Based on these findings, we predict that area AL helps guide behaviors involving fast-moving stimuli (e.g., optic flow), while area PMhelps guide behaviors involving slow-moving objects.