Idle noises

Therefore, rapid sensory methods are used to substitute for conventional profiling. They are used as a first step to select a subset of products to study. In terms of sensory description, we use than to develop a first base sensory lexicon, as described in the example on idle noise in diesel engines. They are also used to compare experts and consumers perceptions. Indeed, the experts point of view is sometimes so accurate that it can be too precise, and way above the perceptions of the consumers. Rapid sensory methods are then used to calibrate the experts according to the sensations of consumers in terms of intensities and vocabulary this aspect will be illustrated by the example on Gearboxes sensations and comfort. ... 

Eleven idle noises of diesel engines were evaluated anonymously. They are coded in this paper by their short names (Table 20.3). These cars were chosen to represent different types of engine (3-, 4-, 6- and 8-cyIinder). 

Another conclusion concerns the relationships between the terms used by novices, marketing department employees and experts. A Hierarchical Ascendant Classification of the terms allows us to group terms used by each type of assessors. For instance, the term Claquance used by E2 is quite technical, but it is highly correlated with more understandable terms such as farm tractor noise or jackhammer noise. The terms Central frequencies and Middle High Frequencies are technical, but knowing that they are anti-correlated to Engine Power, used by several novices, allows us to understand how consumers can perceive this particular aspect of the idle noises. 

The IDL is dependent on various factors such as sensitivity of the detector for the analyte of interest and electronic and detector (instrumental) noise of various origins, e.g., thermal noise, shot noise, flicker (1 //) noise, environmenfal noise, efc. Several books and articles have been published on fhe different types of instrumental noise, e.g., Skoog and Leary s Principles of Instrumental Analysis . ... 

As the sensitivity increases, the IDL decreases, and as the instrumental noise decreases, so does the IDL. These aspects are key to selecting the correct instm-ment/detector system to perform the analysis. 

The IDL is an instrument parameter and is the lowest concentration of the measurand that results in an instrument response, reliably. This can be obtained from measurements of pure analyte. This is in contrast to the MDL (LoD) which is based on measurements of a blank real sample or a low-level spike that has been processed through all of the steps of the method. Clearly, it is the latter that is relevant for test samples. The IDL can also be estimated from the instrument signal-to-noise ratio it is approximately three times this ratio. In this case, the value obtained has to be converted to concentration units. 

Note that f-statistics should be followed when the sample size is small, i.e., <30. In the MDL measurements, the number of replicate analyses are well below 30, generally 7. For example, if the number of replicate analyses are 7, then the degrees of freedom, i.e., the ( -1) is 6, and, therefore, the t value for 6 should be used in the above calculation. MDL must be determined at the 99% confidence level. When analyses are performed by GC or GC/MS methods, the concentrations of the analytes to be spiked into the seven aliquots of the reagent grade water for the MDL determination should be either at the levels of their IDL (instrument detection limit) or five times the background noise levels (the noise backgrounds) at or near their respective retention times. 

Environmental laboratories routinely determine IDLs in the course of ICP-AES analysis as a measure of background and interelement interferences at the lowest measurable concentration level above the background noise. The IDL is a trace element analyte concentration that produces a signal greater than three standard deviations of the mean noise level or that can be determined by injecting a standard to produce a signal that is five times the signal to noise ratio (APHA, 1998). 

Consistent with these definitions, there are two methods for IDL determination. The first method consists of multiple analyses of a reagent blank, followed by the determination of the standard deviation of the responses at the wavelength of the target analyte. The standard deviation multiplied by a factor of three is the IDL. This calculation defines the IDL as an analyte signal that is statistically greater than the noise. 

The laboratories, however, typically rely on the second method for the IDL determination, which is detailed in the CLP SOW (EPA, 1995c). The second method consists of multiple analyses of a standard solution at a concentration that produces a signal five times over the signal-to-noise level. The standard deviation of the measurements is multiplied by a factor of three to produce the IDL. This method assumes that the level of signal-to-noise is known, and this information is usually available from the instrument manufacturer. 

The concentration of analytes that can be measured in various materials has been decreasing over the years as sensitivity and detection limits of analytical techniques have improved. The method detection limit (MDL) is the order of magnitude of the smallest quantity or concentration of substance which can be detected in principle the limit of detection (LOD), on the contrary, is a precisely calculable statistical value for a particular, defined analytical procedure. The instrument detection limit (IDL) is the smallest signal above background noise that an instrument can detect reliably. It is expressed either as an absolute limit (in units of mass, eg, ng), or as a relative limit (in terms of concentration, eg, g mL 1). 

Initially, difficulties were encountered with high-end vehicles that featured a multitude of electrical auxiliaries, particularly if only short daily distances were travelled in low ambient temperatures, e.g., in stop-start traffic. In such situations, discharged batteries were increasingly found to be the cause of inoperative vehicles. This was due to the decrease in idle speed, which was achieved via improvements in motor control electronics and yields fewer emissions and noise. Modern alternators are able to provide energy, even at such low rates of revolution, sufficient for standard demands but not for all the comfort components simultaneously. 

Limit of Detection fLODl. "The limit of detection (1X)D) is defined as the lowest concentration level that can be determined to be statistically different from a blank. The concept is reviewed in [ref. 38) together with the statistical basis for its evaluation. Additional concepts include method detection limit (MDL), which refers to the lowest concentration of analyte that a method can detect reliably in either a sample or blank, and the Instrument detection limit (IDL), which refers to the smallest signal above background noise that an Instrument can detect reliably. Sometimes, the IDL and LOD are operationally the same. In practice, an indication of whether an analyte is detected by an Instrument is sometimes based on the extent of which the analyte signal exceeds peak-to-peak noise" (16). 

Instrumental detection limit (IDL) protocols are used to determine when an analog signal is sufficiently different from the background noise to conclude that a measureable "real" signal has been observed. But IDL terminology and estimation protocols are not standard. 

Equation (2.18) represents a step up from the meager guidelines introduced earlier it incorporates the slope of the calibration as a means to address detector sensitivity. It becomes obvious that to minimize Vjdl requires that the signal at the detection limit, S idl, be maximized while the noise level remains minimized and that the steepness of the calibration curve be maximized. 

To conclude this discussion on IDLs, it is useful to compare Eqs. (2.19) and (2.29). Both equations relate Xp to a ratio of a standard deviation to the slope of the least squares regression line multiplied by a factor. In the simplified case, Eq. (2.19), the standard deviation refers to detector noise found in the baseline of a blank reference standard, whereas the standard deviation in the statistical case, Eq. (2.29), refers to the uncertainty in the least squares regression itself. This is an important conceptual difference in estimating IDLs. This difference should be understood and incorporated into all future methods. 

The first conclusion of this study is the suitability of a quick profiling method such as Flash Profiling, even for novices, to describe products recognized as requiring high expertise idle engine noises. 

Speed reducer Noise, rapid vibration, oil leaks Check oil level check oil for water or other contamination check breather pipe for clogging check shaft for misalignment. Run idle units for 10 min. 

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