To calculate and monitor the changes of some numeric value, you can use SIGVIEW’s
instruments. They calculate different values from the signals or 3D graphics and display them as
a number or in graphical form – as round-scale instrument.
Right-click menu on the instrument window includes many useful options: copying instrument
value to the clipboard, logging instrument values, editing instrument properties etc.
You can create instruments by using one of options in the Instruments and markers main menu
section. SIGVIEW supports the following instrument types:
Marker at...: You can define X value from the signal and instrument will monitor Y value (for
example you can monitor FFT value on certain frequency)
Marker with harmonics at...: Available for FFT windows only. Shows value at desired frequency
along with markers on all harmonics of that frequency.
Mean: calculates mean value of the signal
Sum: calculates sum of all signal values
Const: Creates an instrument with a constant numerical value. It can be used for expressions in
the Signal calculator
RMS (Root Mean Square): If the signal include negative values, the sum instrument will probably
not be useful. In that case you can use this instrument – the square
root of the mean of the squares of the signal values. RMS=sqrt((x1^2+x2^2+…..)/N).
RMS –normalized: The same as standard RMS function, but will normalize the signal first by
subtracting its mean value from all signal values.
Standard deviation: Calculates the standard deviation of the visible part of the signal.
Variance: Measure of the amount of variation within the signal values, equal to the square of the
Skewness: Measure of symmetry, or more precisely, the lack of symmetry of distribution. A
distribution, or data set, is symmetric if it looks the same to the left and right of the center point.
The skewness for a normal distribution is zero, and any symmetric data should have a skewness
near zero. Negative values for the skewness indicate data that are skewed left and positive
values for the skewness indicate data that are skewed right.
Kurtosis: Measure of whether the data are peaked or flat relative to a normal distribution. That
is, data sets with high kurtosis tend to have a distinct peak near the mean, decline rather rapidly,
and have heavy tails. Data sets with low kurtosis tend to have a flat top near the mean rather
than a sharp peak. A uniform distribution would be the extreme case. SIGVIEW uses "excess
kurtosis" meaning that standard normal distribution has a kurtosis of zero.
Crest factor: Calculates the crest factor of the visible part of the signal.
Integral: Calculates numerical integral over the visible signal part
Weighted mean (Mean frequency): Calculates sum of products Xi * Yi divided with sum of Yi (Xi
are values on x-axis and Yi corresponding values on y-axis from origin plot). If applied to a FFT
plot, it is equivalent to a mean frequency.
Weighted median (Median frequency): Xi are values on x-axis and Yi corresponding values on
y-axis of the origin plot. This function calculates Xi value so that sum of Xi * Yi on both sides of
the Xi is the same (or nearly the same). If applied to a FFT plot, it is equivalent to a median
Signal-To-Noise Ratio (SNR): Calculates ratio between signal power and noise power in the
overall signal. The higher the ratio, the less obtrusive the background noise is. Since SIGVIEW does not have any information about the real nature of your signal, it will not be able to deliver
accurate values in all cases. Therefore, you should use it with pure tone signals (i.e. sine) signals
to achieve best accuracy. SNR units are decibel (dB).
Overall dB (weighted): You can calculate overall sound pressure values weighted with standard
A, C or Z curves. This calculation is internally based on the 1/1 Octave plot
values. These values
are calculated in the background, weighted with the appropriate A, C or Z-weighting coefficients
and all bands are combined into one dB value.
Please note that the values calculated by using one of these functions may not match the values
calculated by a sound pressure level meter. In order to achieve that, you would have to calibrate SIGVIEW first.
Total Harmonic Distorsion (THD) and Total Harmonic Distorsion + Noise (THD+N): THD is a
measurement of the harmonic distortion present in the signal and is defined as the ratio of the
sum of the powers of all harmonic components to the power of the fundamental frequency.
Lesser THD allows the components in a loudspeaker, amplifier or microphone or other equipment
to produce a more accurate reproduction by reducing harmonics added by electronics and audio
media. You should measure it in signals containing one pure tone (sine) component. THD+N
means total harmonic distortion plus noise. This measurement is much more common and more
comparable between devices. Both instrument values are calculate in decibel (dB). To convert dB
values to percent values, you can use one of online calculators, for example here.
Maximum: calculates maximum value from the signal
Minimum: calculates minimum value from the signal
Maximum position: calculates the position of maximum from the signal (for example frequency
of the max. peak in FFT)
Maximum position (interpolated): estimates the position of the maximum value more precisely
by using interpolation. It is especially useful for determining fundamental frequency in the
spectrum with precision better then the frequency resolution of the spectrum.
Minimum position: calculates the position of minimum value from the signal
Sum 3D over frequency range: it is the only instrument applicable to 3D graphics (usually Time
FFT). It calculates the sum of all values from the 3D graphics for one segment of the Y axis
Peak count: Shows number of peaks detected by the Peak detection function
The context menu for each signal window includes “Show 5 highest peaks” option. With this
option turned on, SIGVIEW will show 5 markers on 5 highest signal values in the visible part of
To copy the values of all visible markers to the clipboard in a TAB-separated format, you can use
the context menu option "Copy markers to clipboard" on the signal containing the markers.