Display Options for the Spectrum Window

This section describes how to choose the type of curve displayed in the spectrum window and the options relating to the axes of the graph.

To Change the Display of a Spectrum

Open or calculate a spectrum.

Right-click the spectrum.
From Spectrum Type, select the required type of display for the current block.
Refer to Spectrum Calculation Details for more information about the supported spectrum types and their calculation details.

Tip: Use View > Spectrum type (all blocks) to change the display type for all the blocks in a window.

To Change the Frequency-weighting of a Spectrum

Open or calculate a spectrum.

Right-click the spectrum.
Select Processing > Weighting > SPL / A / B / C to display the spectrum with the desired frequency-weighting.

Note: The frequency weighting of a spectrum is applied using the weight (A, B or C) corresponding to the frequency of the band, calculated using the formulas from Frequency Weighting (A, B and C-weighting):

for a narrow band spectrum (such as PSD, Autospectrum, RMS), the frequency of the i^th band is the frequency of the bin:
f(i) = i x Δf
where Δf = FS / Nfft, FS is the sampling frequency, and Nfft is the FFT size.
for a band spectrum (octave, third octave), the frequency of the i^th band is the center frequency of band number i. These frequencies are defined here for Octave and Third Octave Bands.

To Display the Spectrum of a Converted Signal

Open or calculate a spectrum.

Right-click the spectrum.
From Processing, select the Conversion submenu and select the required type of conversion for the current block.

Tip: Use Tools > Processing > Conversion (every block) to apply the conversion for all the blocks in a window.

Related Information:

Signal Conversion

To Adjust the Display of the Spectrum:

Open or calculate a spectrum.

In the toolbar:

Click Frequency scale to show the frequency axis as a linear scale.
Click Frequency scale to show the frequency axis as a logarithmic scale.

Right-click the spectrum window and then:

Select Scale in dB to dispay the values on the vertical axis in logarithmic units (for example dB SPL).
Clear Scale in dB to dispay the values on the vertical axis in linear units (for example Pa).

Right-click the spectrum window and then:

Select logarithmic levels to change the points of the spectrum curves to dB values (values corresponding to the physical unit expressed in dB).
Select linear levels to change the points of the spectrum curves to linear unit values (values corresponding to the physical unit).

The display of the spectrum is adjusted accordingly.