Noise intermittent

The extent to which a ventilation noise is perceived as disturbing depends not only on its dB(A) level, but also on the spectral distribution and the presence of tones or intermittent components in the noise. From an experiment carried out on respondents exposed to ventilation noises with different characteristics in a simulated office room, it emerged that the highest acceptable level was about 7 dB higher for ventilation noise with a superimposed tone at 30 Fiz than for other types of noise. In another experiment, it was found that the tolerance level was much higher for a tone than for a noise at 100 Hz, whereas the opposite tendency applied at 1000 Hz. ... 

The standard rates the offending noise according to its nature 5dB(A) is added where the noise has a definite continuous note and a further 5 dB(A) added for noise of an intermittent nature. The number of occasions that happen in an 8-hour period is then plotted on a graph and the correction for intermittency is derived. When these calculations have been performed, the noise level is compared to the background level. The standard states that where the noise exceeds the background by 5 dB or more, the nuisance is to be classed as marginal, and where the background is exceeded by lOdB(A) or more, complaints are to be expected. 

The final estimation of the value of ay may appear tedious and several assumptions are made in its derivation, but experimental evidence suggests that it may be used with reasonable accuracy to assess the levels of potentially damaging cavitation erosion. In small valves with nominal bores up to 65 mm cavitation inception occurs in intermittent bursts when the value oy is approximately unity. The cavitation becomes continuous and audible as Oy is reduced to about 0.6, but the risk of damage does not become significant until the value falls below 0.4. As a design criterion the condition of light, steady noise has been described by Tullis as the critical level and is sug-... 

Intermlttency Manneville [mann80] showed that for the special case of a generic intermittency threshold in which the tangent point lies at the endpoint of the interval (in the case of a one dimensional iterative map of an interval to itself), the resulting chaotic dynamics has a power spectrum S f) 1/ (/(log/) ) for low /. Miracky, et. al. were able to modify the map to obtain an exact 1// behavior [mirack87]. Because the result depends on the fine-tuning of an external parameter, however, it does not so mucdi explain the generic appearance of flicker noise phenomena as beg the obvious question, why do systems typically sit at whatever... 

Facilities should be designed to avoid disturbances such as intermittent or continuous noise from within or outside the facdity, frequent traffic in and out of animal rooms, obnoxious odors (e.g., chemical odors that are carried by ventilation systems from laboratories to animal housing areas). 

Results indicated that the intermittent-detonation device was capable of operating on at least two resonant spark-energization frequencies — approx 20 50 cps. Reaction thrust, noise output, and actual combustion frequency were noticeably greater at resonant conditions than at other operating points, . ... 

The vapor-absorpdon refrigerator is free from intermittent noises, but it requires a continuous supply of heat. Once very popular for households, refrigeration systems of this type are now most frequently found in camping facilities and some rural areas where commercial electric power may not be easily available. 

We give two examples of fractal time series. The first is fractal Gaussian intermittent noise characterized by a long-time correlated waiting-time sequence, and the second is a Levy-walk intermittent noise. These examples were developed in an environmental context to explain the observed distribution of earthquakes in California [66]. 

The Gaussian intermittent noise has an autocorrelation function given by Eq. (20) and power-law index given by 277 2. The statistics of this sequence is... 

Figure 11. DEA and SDA for (A) a fractal Gaussian intermittent noise with /(t) = exp[—t/y] with y = 25 and H—d — 0.75 the fractal Gaussian relation of equal exponents is satisfied. (B) A Levy-walk intermittent noise with /(t) oc and p = 2.5 note the bifurcation between H — 0.75 and 5 = 0.67 caused by the Levy-walk diffusion relation [66].

The Levy-walk intermittent noise is characterized by an uncorrelated waiting-time sequence and a Levy or an inverse power-law waiting-time distribution function such as given by Eq. (97) with 1 < a < 2. This interval for the scaling index insures that although the second moment diverges, the first moment is finite. The presence of a Levy-walk process in a given time series can be detected by means of the asymptotic relation Eq. (99), which we refer to as... 

This phenomenon is often observed and is caused by the intermittent addition of small sample pulses into the illuminated region of the flow cell. As the sample concentration in the pulse tends to be different from the mean concentration inside the illuminated region, optical artefacts are formed along the radiation beam, which affects the measurements in a regular fashion. This leads to sinusoidal absorbance fluctuations superimposed on the main recorded signal (Fig. 4.13). As a constant frequency is involved, the related undulation can easily and efficiently be filtered out (see e.g., Ref. [4]). The signal-to-noise ratio, however, is adversely affected. 

Fig. 1.22. Period doubling and Hopf bifurcations. Top enlarged part at low coupling strength K and noise intensity Tioc Bottom Global view of selected bifurcations. AH Andronov-Hopf bifurcation In, onset of regime with n subthreshold oscillations between two spikes h onset of non-intermittent spiking). Parameters e = 0.01, a = 1.05. [41]...

Finally, FCs produce negligible noise since they have neither moving parts nor intermittent irreversible reactions (like combustion or explosion). They can have high power-to-weight ratios (up to 0.7 kW/Kg) and power density (up to 1 kW/litre). 

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