Decibel scale

Logarithms are especially useful for expressing values that span a range of powers of 10. The Richter scale for earthquakes, the decibel scale for sound, and the pH scale for acids and bases all use logarithmic scales. 

Hence at a measured overpressure of P2 = 0.02 bar, on a flat decibel scale, the noise level equates to... 

In the laboratory we can measure RF power in watts, but when we set up NMR experiments we use a relative power scale that is logarithmic the decibel scale. For comparison of power levels, we compare to a standard power level P0 that corresponds to zero on the decibel scale ... 

Every time the power is increased by a factor of 2, we are adding 3 dB to the power level in decibels log(2) = 0.301, 10 log(2) = 3.01. Because the decibel scale is logarithmic, multiplying power by a factor corresponds to adding to or subtracting from the power level in decibels. 

We can also compare pulse amplitudes using the decibel scale, as we know that power is the square of pulse amplitude ... 

Bruker and Varian not only use different zero points for their decibel scales, but also use the opposite sign Varian considers decibel to be a power level as described above, but Bruker sees the decibel setting as an attenuation—higher decibel values correspond to lower power. As long as you know this, you will not have any problem, but be very careful because setting the wrong power level can fry equipment ... 

You can then use the decibel scale to estimate power settings. For example, suppose you calibrated the 90° pulse on a Bruker 500 to be 17.6 pis for XH at a power setting of 3 dB, and you want to know the power setting that will give a 30 pis 90° pulse (yB l2n = 1/(4 x 30 pis) = 8333 Hz). Just plug in the ratio of pulse widths ... 

The frequency response measured between a pair of transducers having A<, = 32 ftm and Np = 50 finger pairs is shown in Figure 3.21 (page 79). The amplitude, shown on a log (decibel) scale, shows the characteristic sin(X)/X behavior. The delay line phase shift

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Logarithmic scales are used for many purposes. The pH scale used to measure acidity and the decibel scale used to measure loudness are both logarithmic scales (that is, they are the logarithms of the acidity and loud-... 

From the standpoint of sound toxicity, the most important properties of sound are power (or loudness) and frequency (or pitch). Sound power is usually expressed in terms of a logarithmic scale known as the decibel scale and is given by... 

Decibel scale linear numbering scale used to define a logarithmic amplitude scale, thereby compressing a wide range of amplitude values to a small set of numbers. 

Relative loudness is usually measured on the assumption of proportionality to the logarithm of fee intensity (for a given frequency), i.e. proportionality to fee relative intensity on the decibel scale. A subjective judgment is made of fee relative intensity above threshold feat a note of 1000 Hz must have to match the specimen sound fee loudness of this, in phons, is then equal to feat relative intensity in decibels. 

Figure 13.3 Decibel scale and the relation between the Sound Power Level (Lb ), Sound Intensity Level (L/), and Sound Pressure Level (Lp).

The usual basis for measuring noise or sound level is the decibel scale. 

Noise is accepted as a problem in most industries and may be defined as any disagreeable or undesirable sound or sounds, generally of a random nature, which do not have clearly defined frequencies. The usual basis for measuring noise or sound level is the decibel scale. Whether noise of a particular level is harmful or not also depends upon the length of exposure to it. This is the basis of the widely accepted limit of 85dB of continuous exposure to noise for eight hours per day. 

Amplitude a peak voltage of the signal waveform is usually assigned. Amplitudes are expressed on a decibel scale instead of linear scale... 

In Fig. 2, however, a comparison has been made of the respective numerical values for physically inconunensurable quantities such as acceleration power density with velocity and displacement power density. Therefore, Eqs. 2 and 3 and the following two text lines do not imply that the decibel units on both sides of the equal sign mean the same. They only look the same because the incommensurable reference levels were omitted. For this reason, three decibel scales for acceleration power, velocity power, and displacement... 

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