Graph Panel

The graph panel shows plots of measured data, impulse responses, filter responses, target responses and the predicted effects of the correction filters on the measured data. The plots are split into groups of traces, selected via the tabs at the top of the graph area.
Trace Selector

Options that affect the appearance of the traces can be found in the View settings.

Each trace can be turned on or off via the selection buttons at the left of the trace name. Trace names are in the same colour as the trace itself, whilst the line style for the trace is shown between the label and the trace's value at the cursor position. Corrected response traces use dotted lines (the default) or a lighter shade of the measurement trace colour according to the option selected in the View settings.
Trace Labels

Frequency Axis Log/Linear Button

The Freq Axis button in the toolbar toggles the frequency axis between logarithmic and linear modes. This function is also available via a command in the Graph menu and the associated shortcut keys.
Log/Linear Frequency Axis Button

Horizontal Axis Zoom Buttons

The horizontal axis zoom buttons Frequency Axis Zoom Buttons zoom in or out by a factor of approximately 2 centred around the cursor position.

Graph Limits Button

The Graph Limits button Graph Limits Button allows desired top, left, bottom and right graph limits to be defined. A dialog pops up in which the values are entered, they are applied as entered or by the Apply Settings button.
Graph Extents Dialog

Vertical Axis Zoom Buttons

The vertical axis zoom buttons zoom in and out on the Y axis.
Y Axis Zoom Buttons

Save Graph as JPEG Button

Save Graph as JPEG Button This button, in the bottom left corner of the graph area, allows the current graph view to be saved as a JPEG image. A dialog pops up to set the desired width of the image (default is to be the same width as the graph).

Zoom control grid

This function is also available via a command in the Graph menu and the associated shortcut key.

Variable Zoom

The Wizard provides a variable graphical zoom capability by either pressing and holding the middle mouse button, or pressing and holding the right button then pressing and holding the left button, and dragging the pointer.

When variable zoom is active a cross is displayed, split into quadrants allowing frequency and/or spl to be zoomed in our out depending on the mouse position. The amount of zoom is governed by how far the mouse pointer is dragged from the start position.

Zoom control grid

Zoom to Area

When the Ctrl key is pressed followed by the right mouse button a zoom box can be drawn by dragging the mouse. Measurement cursors are shown on the outside of the box, to zoom to the shaded area click within it. If the shaded area is too small to zoom in to a message will indicate which dimension is too small for zooming and what the limit is to allow zoom.
Zoom to area

Undo Zoom

To undo the last Variable Zoom or Zoom to Area, press Ctrl+Z or select the Undo Zoom entry in the Graph menu. This will restore the graph axes to the settings they had when the right or middle mouse button was last pressed. This Undo feature can be used even if you have not zoomed, just press the right mouse button when the axis settings are to your preference then you can return to these settings (undoing any subsequent movements or control changes) by pressing Ctrl+Z.

Filter Adjust

The Filter Adjust group shows the measured data and corrected response for the current measurement along with the target response, the response of the equaliser filters with and without the target and the Mic/Meter and Soundcard calibration responses (if loaded).
Filter Adjust Graph Group

This graph group, in common with all groups that have a frequency axis, also shows any filters that have been defined, displaying the filter's number along the top margin of the plot at the position corresponding to its centre frequency.

Measurement

The frequency response of the measurement is labelled with the measurement name

Corrected

The Corrected response shows the predicted effect of the measurement's filters.

Target

The Target trace shows the target frequency response for the measurement, including any desired House Curve response shape. If a House Curve has been loaded the symbol will be displayed by the trace value. The response includes the Bass Management curve appropriate to the Speaker Type selected for the measurement. The overall level of the curve is controlled by the Target Level.

Filters

The Filters trace shows the combined frequency response of the filters for this measurement.

Filters+Target

The Filters+Target trace shows the frequency response of the filters overlaid on the desired Target response. Selecting the filter responses to be drawn inverted and adjusting the filters so that this curve matches the measured response will result in the corrected response matching the target.

Invert Filters

When this box is selected the responses of the filters are drawn inverted. This is useful for graphically matching the shape of a filter to the shape of the peak it is being used to correct, when the shapes match the overall response in that region will be flat.

Mic/Meter Cal

The Mic/Meter Cal trace shows the frequency response of the Mic calibration data (if a calibration file has been loaded via the Mic/Meter settings). If the Type has been set to C Weighted SPL Meter this curve will show the effect of C weighting (only outside the range of the calibration data file that has been loaded). The trace is not shown if cal data has not been loaded. The trace is drawn relative to the Target Level.

Soundcard Cal

The Soundcard Cal trace shows the measured frequency response of the soundcard relative to its level at 1kHz (if a calibration file has been loaded via the Soundcard settings). The trace is not shown if cal data has not been loaded. It is drawn relative to the Target Level.

Impulse

The Impulse graph shows the impulse response for the current measurement, the left and right windows and the effect of the windows on the data that is used to calculate the frequency response.
Impulse Graph

The Y axis used for the impulse response can be selected as % FS or dB FS (FS = Full Scale) via a control in the bottom right corner.
Impulse Response Y Axis Selector

Dashed vertical black lines show the extents of the impulse response windows, a dashed red line shows the reference position. If the window settings are changed the region outside the new area is shown shaded until the settings are applied. It is best to set the Y axis to dB to adjust the windows as it is then much easier to see where the response has decayed into the noise.
Impulse Response dB Scale

After each measurement the left window width is automatically set up. For full range measurements (and down to end frequencies of 1kHz) the width is 125ms, below that it increases to allow for pre-ringing effects of using a limited sweep range.

The impulse response is that of the whole system, including the mic/meter and the soundcard. The mic/meter and soundcard calibrations are only applied when calculating the frequency response.
Tip: To apply or remove a mic/meter or soundcard calibration for a measurement after it has been taken, simply load or clear the cal data as required and press the Apply Windows button to recalculate the frequency response.

Impulse Graph Controls

The impulse response may be plotted with or without normalisation to its peak value according to the setting of the "Plot Normalised" control. When normalised plotting is selected the peak will be at 100% or 0dBFS. This setting applies to both the Impulse graph and the All Impulses graph.
Plot Normalised Control

The response may be plotted inverted according to the setting of the "Invert Impulse" control. Note hat this has no effect when the Y axis is set to dB FS.
Invert Impulse

The "Scale Response" control re-scales the impulse response to achieve a desired maximum SPL figure in the corresponding frequency response. The target peak SPL figure (in dB) is updated to reflect the current frequency response maximum SPL whenever the "Apply Windows" button in the IR Windows control is hit.
Scale Impulse Response Controls

Distortion Components

A property of the log sweep analysis method is that the various harmonic distortion components appear as additional impulses at negative time, with decreasing spacing as the distortion order increases. For example, this plot shows spikes from distortion components up to the 8th harmonic on a laptop soundcard loopback measurement:
Impulse Response with Harmonic Peaks

Here is a similar measurement for an external USB soundcard, it is a 44.1k card rather than 48k, which limits us to the 6th harmonic in the 1s pre-impulse period - however, only the 2nd, 3rd and 5th harmonic peaks are evident, the 4th harmonic peak is barely visible above the noise floor (which is about 10dB lower than the laptop card). The extended lobes after the impulse are due to the card's much lower -3dB frequency, 1.0Hz versus 22.1Hz (note that the right side of the time axis is 2.0s in this plot compared to 0.5s in the previous plot):
Impulse Response with Harmonic Peaks

Low Frequency Decay

This group shows LF spectral decay traces over the region from 10Hz (or the frequency resolution for the selected window width if higher) to approximately 750Hz (for a 48kHz sample rate) or to the end of the measurement sweep if lower. The time separation of the slices is controlled by the setting just above the Generate LF Decay button, the width of the impulse response section that is used to generate the slice is set by the Window control. The corresponding frequency resolution is shown next to the window width.

Low Freq Spectral Decay Controls

The traces for each slice can be drawn as conventional lines or as filled areas, selected by the "Fill slices" check box. The alternative views are shown below.
Low Freq Spectral Decay, normal traces
Low Freq Spectral Decay, filled traces

These Spectral Decay plots are generated by shifting the impulse response window to the right by the slice interval to generate each succeeding slice. Note that if the slice width and interval are large, fewer than 8 slices may fit within the impulse duration, in which case some slices will not be generated. The default window type for this plot is Tukey 0.25, other types may be selected via the Low Frequency Decay entry in the Analysis settings.

Low Frequency Waterfall

This group shows a waterfall plot over the region from 10Hz (or the frequency resolution for the selected window width if higher) to approximately 750Hz (for a 48kHz sample rate) or to the end of the measurement sweep if lower. The time span for the waterfall is controlled by the setting just above the Generate LF Waterfall button, the width of the impulse response section that is used to generate the slices is set by the Window control. The corresponding frequency resolution is shown next to the window width. Best results are obtained when the window is smaller than the time span.
Low Freq Waterfall

The waterfall plot is generated in the same way as the Spectral Decay plots, shifting the impulse response window to the right by a proportion of the time range to generate each succeeding slice. The default window type for this plot is Tukey 0.25, other types may be selected via the Low Frequency Decay entry in the Analysis settings.

The slice slider selects which slice is at the front of the plot - as the slider value is reduced the plot moves forward one slice at a time. The trace value shows the SPL figure for the frontmost slice, the corresponding time for that slice is shown at the top right of the graph.

Low Freq Waterfall Controls

The labels at the sides of the plot show the time axis values
Waterfall Time Labels

The waterfall allows another measurement's plot to be overlaid on the current measurement. The overlay is generated slice-by-slice, plotting a slice of the current measurement's waterfall, then a slice of the overlay, then the next slice of the current measurement and so on. N.B. before a measurement is available to overlay it is necesary to generate the LF waterfall data for it.
Low Freq Waterfall Overlay

Transparency can be applied to the main plot, the overlay, or both. When transparency is set to 0%, as above, both plots are solid. If only one plot is selected for display it is drawn solid regardless of the transparency setting. In the image below the main plot (before acoustical treatment) is drawn at 75% transparency, allowing the overlay (after acoustical treatment) to show through. The transparency mode can be switched between main/overlay/both to ease comparison between the plots.
Low Freq Waterfall Overlay

The controls for transparency are brought up by the More Waterfall Controls link. The More Controls dialog also has x and y sliders to alter the viewing angle of the plot, the z slider alters the strength of the perspective effect.
More Waterfall Controls

All Measured

This group shows the measured responses for all measurements on the same plot. The "Separate the traces" check box offsets each trace downwards from the preceding trace to make it easier to distinguish individual features when the traces are at similar levels.

Averaging

The Averaging group allows the average of selected measurements to be generated. Any of the traces which are selected when the Average The Responses button is pressed will be included in the averaging. The frequency range of the average trace covers the region where all included traces have data, for example if one trace was measured to 200Hz, another to 500Hz and a third to 1000Hz the average would range to 200Hz (to the lowest end frequency).

New measurements (those made after the last average was generated) show new next to the trace value, whilst those included in the last average show avg.

Note that Average traces do not have any impulse response data so waterfall and spectral decay plots will not be available.

All Predicted

This group shows the predicted effects of the equaliser filters for all measurements on the same plot.

All Impulses

This group shows the impulse responses for all measurements on the same plot. If the "Plot Normalised" check box is selected all responses will be plotted normalised to their peak value, placing the peaks at 100% or 0dBFS.

All Energy-Time

The full range energy-time curves are displayed on this graph. The energy-time curve is the magnitude of the analytic function whose real part is the impulse response and whose imaginary part is the Hilbert transform of the impulse response. The energy-time curves can be smoothed by a moving-average filter of the selected duration.
Energy-time curve controls
Energy-time curve

Oscilloscope

This group shows the generated sweep test signal and the raw captured system response as acquired via the soundcard, which may be useful for troubleshooting. This is not a live display, it updates with new content after a sweep has completed. Only the signals for the last measurement are shown. The Y axis is the percentage of digital full scale. The generated sweep is shown normalised so that its peak value is 100%. If the captured trace reaches +100 or -100% it is clipping and the sweep level or AV processor volume should be reduced.
Oscilloscope Plot

A check box is provided to invert the captured trace for easier comparison with the test signal if the soundcard input is inverting.

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