Sound Intensity Research Articles

Acoustical analysis and optimization design of the hair dryers

Abstract The sound qualities and wind speeds of the four commercial hair dryers (Panasonic, Confu, Flyco, and Philips) were investigated through experimental methods in the present study. The sound qualities included loudness, sharpness, roughness, and fluctuation strength. The experimental results showed that the maximum sound pressure level (SPL) of all hair dryers occurred at about 200 Hz except Flyco hair dryer, which occurred at about 400 Hz. The highest loudness and highest sharpness were found when the hair dryers were set to hot mode and cold mode, respectively. No consistent relationship was found between the effect of room space and SPLs of the hair dryers. The Box–Behnken design method was used to design 13 pieces of oval and rectangular nozzles, and their sound levels and wind speeds were measured. Thereafter, these experimental results were used to derive correlation coefficients between the hair dryer nozzle area, aspect ratio, nozzle length, loudness, and wind speed using the Anova analysis method. Finally, an oval nozzle and a rectangular nozzle with an area of 0.0005 m 2 {}^{2} , an aspect ratio of 1, and nozzle lengths of 0.052 and 0.055 m, respectively, were designed and were tested. These nozzles managed to reduce the sound loudness by 15 and 9.6%, respectively, while maintaining the same level of wind speed.

Innovative Approaches and Challenges in the Demolition of Large-Span Post-Tensioned Beams: Insights from a Case Study

Large-span, post-tensioned (PT) beams play a crucial role in maximizing the benefits of post-tensioning techniques. Bonded and unbonded systems are prevalent, with the latter being more widespread in the United States. While bonded systems are advantageous for creating long spans when multiple tendons are grouped in ducts, limited studies in the literature exist on their demolition. With a case study, this paper addresses the unique challenge of demolishing large-span-bonded, post-tensioned beams that occurs due to a building’s functional change. Emphasizing insights for engineers, it explores the use of cutting and dismantling methods, thereby considering the presence of prestressed cables. The demolition process is distinctive due to the presence of numerous prestressed cables along the beams, necessitating a specialized and cautious cutting approach. This is accomplished through the use of a drilling technique that selectively distresses the tendons, ensuring they are not all affected simultaneously. An intriguing observation discussed in this paper pertains to the occurrence of horizontal cracks accompanied by loud sounds following the drilling process, thereby offering insights from the design perspective of PT systems. This paper details an innovative method for safely demolishing large-span, bonded PT beams using ground-penetrating radar and computer models to navigate structural complexities and ensure nearby structures’ safety.

Thermosonication process of sour cherries: Microbial inactivation kinetics, experimental and computational fluid dynamics simulation

In this study, the inactivation of Listeria monocytogenes PTCC 1302 and Shigella sonnei PTCC 1974 of sour cherries by thermosonication (37 kHz, 300 W; 50and 60°C; 0–12 min) was evaluated. Several statistical models including polynomial, Weibull, and biphasic linear models were implemented to obtain the variation of microorganism population through time. The coupled non-linear Westervelt and heat transfer equations were solved to determine the acoustic pressure and thermal fields using computational fluid dynamics (CFD). According to the obtained results, average inactivation improvements of 15.47 and 17.13% were obtained when the temperature level was increased for both S. sonnei and L. monocytogenes, respectively. S. sonnei was more affected by the sonication procedure at the initial stages, while similar behavior was also found for L. monocytogenes but at the final stages. The maximum and minimum pressure level was obtained at ∼380 and −230 kPa, respectively. In the beginning, the hot spot was formed near the bottom of the simulated sour cherry, where the acoustic intensity was higher. Although, with the elapse of time, the temperature field became more uniform, and the hot spot moved toward the center of the sour cherry.

Symphonies of Growth: Unveiling the Impact of Sound Waves on Plant Physiology and Productivity.

The application of sound wave technology to different plant species has revealed that variations in the Hz, sound pressure intensity, treatment duration, and type of setup of the sound source significantly impact the plant performance. A study conducted on cotton plants treated with Plant Acoustic Frequency Technology (PAFT) highlighted improvements across various growth metrics. In particular, the treated samples showed increases in the height, size of the fourth expanded leaf from the final one, count of branches carrying bolls, quantity of bolls, and weight of individual bolls. Another study showed how the impact of a 4 kHz sound stimulus positively promoted plant drought tolerance. In other cases, such as in transgenic rice plants, GUS expression was upregulated at 250 Hz but downregulated at 50 Hz. In the same way, sound frequencies have been found to enhance the osmotic potential, with the highest observed in samples treated with frequencies of 0.5 and 0.8 kHz compared to the control. Furthermore, a sound treatment with a frequency of 0.4 kHz and a sound pressure level (SPL) of 106 dB significantly increased the paddy rice germination index, as evidenced by an increase in the stem height and relative fresh weight. This paper presents a complete, rationalized and updated review of the literature on the effects of sound waves on the physiology and growth parameters of sound-treated plants.

Deep Learning-Based Design Method for Acoustic Metasurface Dual-Feature Fusion.

Existing research in metasurface design was based on trial-and-error high-intensity iterations and requires deep acoustic expertise from the researcher, which severely hampered the development of the metasurface field. Using deep learning enabled the fast and accurate design of hypersurfaces. Based on this, in this paper, an integrated learning approach was first utilized to construct a model of the forward mapping relationship between the hypersurface physical structure parameters and the acoustic field, which was intended to be used for data enhancement. Then a dual-feature fusion model (DFCNN) based on a convolutional neural network was proposed, in which the first feature was the high-dimensional nonlinear features extracted using a data-driven approach, and the second feature was the physical feature information of the acoustic field mined using the model. A convolutional neural network was used for feature fusion. A genetic algorithm was used for network parameter optimization. Finally, generalization ability verification was performed to prove the validity of the network model. The results showed that 90% of the integrated learning models had an error of less than 3 dB between the real and predicted sound field data, and 93% of the DFCNN models could achieve an error of less than 5 dB in the local sound field intensity.

Modeling hyperthermia-based prostate cancer treatment in the presence of core-shell nanoparticles and large blood vessels under different ultrasound sonication patterns

The use of nanoparticles, as enhancing agents to transform ultrasound energy into heat for tumor destruction, is a promising approach to improve the efficacy of thermal-based cancer therapies. This study aimed to evaluate the effectiveness of core-shell type nanoparticles and the heat loss due to blood flow in large vessels under different patterns of ultrasound sonication in the hyperthermia-based treatment of the prostate cancer. For this purpose, the ultrasound attenuation coefficient in the prostate tumor embedded with nanoparticles was calculated using a scattering theory that was developed for core-shell type particles. Using the attenuation coefficient and the linear pressure wave equation, the acoustic power dissipated per unit volume of a three-dimensional (3D) model of the prostate tumor and its surrounding tissues was calculated. By simultaneous solving the bioheat, the convective energy, the continuity, the Navier-Stokes, and the thermal dose equations, the temperature and thermal dose distribution were computed in the model. The attenuation coefficient of the tumor showed a decreasing trend with increasing the thickness of the silica shell coating the magnetite or titania core. The capability of nanoparticles to enhance heat production in the medium was directly, and the blood flow heat loss was inversely, related to the degree of focus of the ultrasound beam. The thermal response of the tumor was influenced by its size and geometry, as well as the acoustic intensity. Titania nanoparticles were more efficient than the magnetite nanoparticles in ultrasound attenuation and heat production in the medium. Our findings can be useful in understanding the factors affecting the hyperthermia-based treatment of the prostate cancer using a combination of ultrasound and nanoparticles.

Neural correlates of tonal loudness, intensity discrimination, and duration discrimination.

A long-standing quest in audition concerns understanding relations between behavioral measures and neural representations of changes in sound intensity. Here, we examined relations between aspects of intensity perception and central neural responses within the inferior colliculus of unanesthetized rabbits (by averaging the population's spike count/level functions). We found parallels between the population's neural output and: (1) how loudness grows with intensity; (2) how loudness grows with duration; (3) how discrimination of intensity improves with increasing sound level; (4) findings that intensity discrimination does not depend on duration; and (5) findings that duration discrimination is a constant fraction of base duration.

Effect of an internal Kelvin wave on sound propagation in a coastal wedgea).

Spatiotemporal variability of the low-frequency sound field in a coastal wedge in the presence of an internal Kelvin wave (IKW) is studied both experimentally and theoretically. The experiments were carried out in Lake Kinneret, Israel (also known as the Sea of Galilee) in August 2021, with a wideband sound source deployed near the shore and receiving vertical line arrays located at the lake's center. Parameters of the IKW were obtained earlier from long-term thermistor string measurements combined with conductivity, temperature, and depth data. The IKW initiated range-dependent vertical displacements of the thermocline with a maximum amplitude near the shore and almost zero amplitude in the center of the lake. It corresponded to a thermocline inclination angle of ±0.08° with respect to the horizontal. Temporal variations in depth-averaged acoustic intensity, reaching almost 8 dB, and remarkable changes in the normal mode composition were registered. These effects are explained based on simulations using a parabolic equation and normal mode models. The role of mode coupling in acoustic intensity variations is assessed.

Research on the unsteady flow field and aerodynamic noise characteristics in the circular space of ultra-high-speed elevators

Due to the non-streamlined blunt body shape of the elevator car, intense aerodynamic loads and noise are generated in the annular space when the elevator operates at high speed in a narrow hoistway. This article uses large-eddy simulation and Curle acoustic theory to establish a numerical model of the wellbore flow field under different guiding shapes of the elevator car. First, the mechanism of action between the flow guide shape, vortex characteristics, and aerodynamic load was studied, and the influence of operating speed on aerodynamic load under different flow guide shapes was analyzed. Second, the distribution and spectral characteristics of noise in the annular space under different flow guide shapes were studied from the near field and far field scales. Finally, it can be concluded that increasing the guide surface can significantly reduce the pressure difference between the upper and lower parts of the car, weakening the separation of the tail airflow. The number of guide surfaces, installation position, and vertex offset significantly impact drag and lateral force, with the optimal reduction of 34.65% and 57.6%, respectively. The maximum sound source intensity of near-field noise is mainly concentrated at the arc transition in the upper part of the annular space, and the frequency is mainly concentrated in the range of 500–1000 Hz. The sound pressure level is linearly related to the logarithm of the longitudinal distance, and the noise attenuation speed becomes faster with the increase in the number of guiding surfaces.

Harbour porpoises respond to recreational boats by speeding up and moving away from the boat path.

Recreational boats are common in many coastal waters, yet their effects on cetaceans and other sensitive marine species remain poorly understood. To address this knowledge gap, we used drone video footage recorded from a recreational boat to quantify how harbour porpoises (Phocoena phocoena) responded to the boat approaching at different speeds (10 or 20 knots). Furthermore, we used a hydrophone to record boat noise levels at full bandwidth (0.1-150 kHz) and at the 1/3 octave 16 kHz frequency band for both experimental speeds. The experiments were carried out in shallow waters near Funen, Denmark (55.51° N, 10.79° E) between July and September 2022. Porpoises were more likely to move further away from the path of the boat when approached at 10 knots, but not when approached at 20 knots. In contrast, they swam faster when approached at 20 knots, but not when approached at 10 knots. The recorded received sound level did not depend on how fast the boat approached, suggesting that differences in porpoise responses were related to the speed of the approaching boat rather than to sound intensity. In addition, porpoises generally reacted within close proximity (<200 m) to the approaching boat and quickly (<50 s) resumed their natural behaviour once the boat had passed, indicating that the direct impact of small vessels on porpoise behaviour was most likely small. Nevertheless, repeated exposure to noise from small vessels may influence porpoises' activity or energy budget, and cause them to relocate from disturbed areas. The approach used in this study increases our understanding of recreational boats' impact on harbour porpoises and can be used to inform efficient mitigation measures to help focus conservation efforts.

Shallow mud detection algorithm for submarine channels based on improved YOLOv5s

Submarine mud poses a risk to channel navigation safety. Traditional detection methods lack efficiency and accuracy. As a result, this paper proposed an enhanced shallow submarine mud detection algorithm, leveraging an improved YOLOv5s model to increase accuracy and effectiveness in identifying such hazards in marine channels. Firstly, the sub-bottom profiler was employed to assess the submarine channel of Lianyungang Port to acquire the image data of the shallow mud sound print. Concurrently, the analysis incorporated the characteristics of changes in sound intensity peaks to precisely identify the shallow mud's location. Furthermore, the incorporation of C2F feature module into the backbone module enhances the gradient flow of the algorithm, augments the feature extraction information, and improves the algorithm's detection performance. Subsequently, Efficient Multi-Scale Attention (EMA) mechanism is incorporated into the neck module, aiming to optimize the algorithm's channel dimensions, minimize computational overhead, and enhance its detection efficiency. Finally, the study introduced Normalized Wasserstein Distance (NWD) loss function into bounding box regression loss function. This integration effectively addresses the issue of multi-scale defects, emphasizes the transformation of target planar position deviation, and improves the accuracy of the algorithm's detection capabilities. The results indicate that the improved YOLOv5s-EF algorithm outperforms the original YOLOv5s algorithm and other widely used detection algorithms. It achieved a validation set precision rate of 97.8%, recall rate of 97.6%, F1 value of 97.7%, mean Average Precision (mAP)@0.5 of 98.2%, mAP@0.95 of 69.6%, and Frames Per Second (FPS) of 51.8. YOLOv5s-EF algorithm proposed in this study offers a novel technical approach for detecting mud in submarine channels, which is importance for ensuring the safe operation and maintenance of dredging in such channels.

Towards an understanding of the mechanisms of therapeutic ultrasound on biomimetic models of cancer

Therapeutic ultrasound is transforming the treatment of a range of malignancies in a non-invasive and non-systemic manner. Low-intensity ultrasound (LIUS) has been proposed to selectively eradicate cancer cells but the underlying biological mechanisms remains unknown. To gain an understanding of this phenomenon, 2D breast cancer monocultures were sonicated at varying acoustic intensities (0.1–0.5 W·cm−2) and excitation times (1–10 minutes). Additionally, 2D monocultures consisting of healthy cell lines were sonicated at varying acoustic intensities (0.1–0.5 W·cm−2) to determine any distinguishing biological responses. To begin recapitulating in vivo conditions, breast cancer cells were also seeded into 3D collagen hydrogels. At a 1 MHz frequency, 20% duty cycle, 100 Hz pulse repetition frequency, a significant drop in cancer cell viability is observed at a sonication intensity of 0.5 W·cm−2 and over 10 minute excitation time. Healthy counterparts subjected to the same parameters revealed no distinguishing effects. Sonication of breast cancer cells seeded in 3D collagen hydrogels revealed no effect in cell viability compared to non-sonicated controls. The acoustic wave propagation software OptimUS was used to determine the influence culturing plates have on ultrasound propagation, revealing these materials can significantly vary the acoustic field at frequencies relevant to LIUS.

Uso de auriculares y la audición en estudiantes de medicina de una universidad pública de Lima, Perú

Introduction: Hearing loss affects millions globally, especially young people who frequently use headphones. Objectives: To establish the relationship between headphone use and hearing among medical students in Lima, Peru. Methods: An observational, analytical, and cross-sectional study was conducted at the Universidad Nacional Federico Villarreal. Participants included 98 medical students (18-32 years) who regularly used headphones. Those with previous hearing pathologies were excluded. Data collection included surveys on headphone use and audiometries performed in a silent booth. Results were analyzed using descriptive and inferential statistics, employing the Spearman's Rho correlation coefficient to assess the relationship between variables. Results: 59.2% of the students were women. 39.2% had mild hearing loss at high tones, while 36.2% had normal hearing. 71.4% reported decreased hearing capacity, and 56.1% experienced ear pain. Headphone use showed a positive and significant correlation with hearing (Rho = 0.298, p = 0.003). Exposure time was also significant (Rho = 0.260, p = 0.010), but sound intensity was not (Rho = 0.193, p = 0.057). Conclusion: There is a positive relationship between headphone use and hearing loss in medical students. It is recommended to implement awareness programs on safe headphone use and conduct regular hearing evaluations to prevent auditory deterioration.

Visual assessment of Korotkoff sounds improves the accuracy of a validated professional automated auscultatory blood pressure monitor KOROT P3 Accurate.

A novel automated auscultatory upper-arm cuff blood pressure (BP) monitor for office use (KOROT P3 Accurate, previously InBody BPBIO480KV), which displays Korotkoff sound curves for each BP reading was recently developed. This study investigated whether the review of Korotkoff sound curves by healthcare professionals further improves the accuracy of the device by identifying unreliable BP readings. Three observers assessed independently the morphology of Korotkoff sound curves of BP measurements obtained during an ISO 81060-2:2018 validation study, and classified them as of good, fair, or poor quality (low amplitude or sound intensity, aberrant morphology, background noise, signal artifact, auscultatory gap, irregular rhythm). The observers were blinded to the study BP measurements. Korotkoff sound curves of 255 BP readings obtained in 85 individuals were analyzed (mean age 57.3 ± 15.0 years, 53 men). Of the SBP readings 80.4/12.2/7.4% were classified as good/fair/poor, and DBP 76.9/12.2/10.9%. Inter-observer agreement in detecting poor-quality curves was 84.7/83.1% (systolic/diastolic). Of poor-quality curves, 10.5/60.7% (systolic/diastolic) clustered in the same individuals. The validation criterion 1 [mean test-reference BP difference ≤5 ± 8 (SD) mmHg] was satisfied for readings with good (0.1 ± 4.9/0.3 ± 3.8 mmHg, systolic/diastolic) and fair-quality curves (-0.4 ± 6.4/0.2 ± 5.0), but not for poor-quality ones (2.7 ± 8.8/3.6 ± 8.1). By excluding poor-quality readings (40 of 255), criterion 1 of the validation study was improved (0.2 ± 4.9/0.2 ± 3.9 versus 0.3 ± 5.5/0.6 ± 4.7 mmHg). The visual assessment of Korotkoff sounds generated during automated auscultatory BP measurement by the KOROT P3 Accurate professional monitor identifies unreliable readings and further improves the device accuracy.

Aeroacoustic Source Potential Based on Poisson’s Equation

Poisson’s equation is an important equation to postprocess the aerodynamic fields into linearized momentum modes and was recently found to be important for the computation of an isotropic pressure-like source for scalar aeroacoustic wave models, like the aeroacoustic wave equation based on Pierce’s operator (AWE-PO). Mathematically viable boundary conditions of the Poisson equation, which computes the AWE-PO source, are investigated. For the different source fields, the wave propagation is computed using the AWE-PO, and the details of the sound prediction results are compared to a reference direct numerical simulation of a mixing layer. The different boundary conditions of the Poisson equation were found to have a minor influence on the overall sound prediction characteristics of the AWE-PO equation. The AWE-PO is reformulated into a simplified version of the Phillips’s equation, which mitigates the intermediate step of computing an isotropic source potential. By doing so, a previously obtained interference radiation valley in the radiated acoustic intensity of the AWE-PO results is attributed to a missing shear-noise source term.

Reconfigurable piezoelectric metamaterial for selective noise directivity

This work explores strategies to change the directivity of sound radiated from an oscillating metamaterial plate. To this end, the vibro-acoustic behavior of a plate that hosts an array of piezoelectric unit cells, whose inductive shunt resonance frequencies can assume different predefined configurations in space, is numerically investigated. The effects of such configurations on (i) the structural normal velocity of the plate, (ii) the hemispherical acoustic field estimated based on Rayleigh’s integral, and (iii) the non-negative acoustic intensity are discussed. The numerical results show that simple changes in the unit cell’s tuning configuration in space can reduce, totally attenuate, or enhance the sound radiated in specific directions, findings that may pave the way to the use of reconfigurable metamaterials as effective systems for selective radiated noise directivity.

Impacts of noise pollution from high-speed rail and road on bird diversity: a case study in a protected area of Italy

The disturbance of infrastructures may affect biological communities that are exposed to them. This study assesses the impact of high-speed (highway and railway) infrastructures in a protected study site, the Natural Reserve Fontanili di Corte Valle Re (Emilia–Romagna, Italy). We compared bird diversity with sound intensity and frequency in three sampling areas, increasingly distant from the infrastructures at the border with the reserve, during the last 4 years (2019–2022), monitoring sedentary, nesting, and migratory bird species. We hypothesize a decreasing diversity closer to the source of disturbance, which is mostly attributable to noise pollution. Our findings confirmed this trend, and we show that, in particular, disturbance seems to influence species richness more than the total abundance of birds. We also discovered that highway disturbance was much higher than railway in terms of frequency and duration. In light of these results, we suggest that some species, which have a behavioral ecology strongly based on singing to communicate with each other for their reproductive and defensive strategies, may suffer more from constant acoustic disturbance. The installation of effective noise barriers to shield the sound produced by the highways should be considered a mandatory request not only in proximity to houses but also in the vicinity of protected areas.

Prevalence of Noise Induced Hearing Loss among the Textile Workers

Background: Noise remains a common environmental pollutant in industrial workplaces and has been a constant issue since the industrial revolution. Occupational hearing loss is the dominant cause of preventable sensorineural hearing loss in adults. The degree of NIHL is determined by intensity, duration of exposure, spectral characteristics of the noise, and individual susceptibility Methods: This cross-sectional study was carried out among theNassa Taipei Textile Mills Ltd. and Nassa Taipei Spinners Ltd in kachpur,Narayangonj.200 Textile workers aged from 18 to 50 years were recruited in this study. Study subjects were interviewed by trained data collector through a structured questionnaire. Environmental sound intensity level in various departments were measured using a sound level meter (Quest sound level meter, Oconomowoc WISCONSIN. Model no: 2400). Pure Tone Audiometry was done by pure tone clinical audiometer (KAMPLEX Audiometer, Model no: AC 30; Calibrated by P.C. Werth Limited in October 2004) with a frequency range of 125Hz to 8000Hzand sound intensity levels of between -10dB to 120dB was used to test each ear of the subject separately. Data was analyzed using Statistical Package for Social Sciences (SPSS) program version 26. Results: Out of 200 Textile workers whose were recruited in this study, 138(69%) were males and predominant age group was 18 to 27 years (54.5%). The prevalence of NIHL was found to be 14.5%. The most common age group was 28 to 37 years and positive association (p&lt;.05) between hearing loss and long working hours. Non-user of PPD had little bit higher among the workers who developed hearing loss. Conclusion: The prevalence of NIHL was higher in textile industry workers. This suggests the need to provide protective gear to workers in stations generating loud noise. The prevalence was higher in male, those who experienced prolong exposure and not to used PPD. Bangladesh J Otorhinolaryngology 2023; 29(2): 89-95

Structural, thermal, and physicochemical properties of ultrasound-assisted extraction of faba bean protein isolate (FPI)

This study aimed to understand the impact of ultrasonication (24 kHz) at a fixed power (100 W) and duration (5–60 min) on the physicochemical, structural, and thermal properties of faba bean protein isolates. Ultrasound-relevant parameters such as acoustic density, intensity, and yield conversion were estimated. The average protein purity (∼85% protein) and yield (up to 22 %) of the ultrasound-assisted protein isolate were higher than those of the control protein isolate. Compared to the original flour, the isolate had significantly lower levels of vicine and convicine. Electrophoresis revealed no substantial alterations in the primary structure of the native and sonicated faba bean isolates. SDS-PAGE and SE-HPLC showed that sonicated samples had profiles similar to those of the native protein isolate. FTIR spectra and X-ray diffraction (XRD) patterns were used to measure structural changes in all faba bean protein isolates (FBPI). XRD study revealed two distinct diffraction peaks at 2 θ = 10° and 2 θ = 20° for protein isolates, indicating that alteration in native conformational crystallite size was altered after the ultrasound application.

Numerical Analysis of Broadband Noise Generated by an Airfoil with Spanwise-Varying Leading Edges.

Here, the single-target parameterization of alternatives to leading-edge noise is carried out using analytical models based on the Wiener-Hopf technique. Four leading-edge serration profiles with different frequencies, amplitudes, and phases are implemented to aid the understanding of sound suppression mechanisms. The effects of the serrated shape factor, wavelength, and amplitude are analyzed at tip-to-root ratios of 0.5, 1, and 2, respectively. An effective double-wavelength sinusoidal serration design can substantially reduce the noise emissions of 5.2 dB at h¯ = 2. Additionally, compared to single-wavelength serrations, an additional 1.47 dB noise reduction effect can be obtained by double-wavelength serrations under the appropriate design parameters. The surface pressure and phase distribution of different spanwise-varying leading edges indicate that the phase interference effect affected by source-radiated noise reduction is enhanced by this serration at the hills for serrations with a small curvature, and noise emission in the low-frequency band is more effectively suppressed. The sharper the serration is, the more conducive it is to a reduction in high-frequency noise. Nevertheless, the effectiveness of serrations is usually partially limited by the non-negligible trailing-edge self-noise. The sound source intensity of the root is decreased by the ogee-shaped serrations with a large curvature transition. A secondary noise reduction mechanism with a local source cut-off effect caused by nonlinearity is demonstrated.