David's Audio Sweep Generator - Details


Click on an area to learn more about it.


Frequency Range

The frequency range group allows you to set a start and end frequency for the sweep to predetermined values. The four settings correspond to typical uses for hi-fi testing (Wide), radio & telephony testing (Speech) and two others for the high and low ranges typically required. You can edit the actual values in the edit boxes as required.


Set Frequency

This option is only visible when the manual sweep speed is chosen. You can alter the frequency being generated by operating either trackbar. The frequency requested will be shown at the bottom of the trackbars.

The Lock L + R frequencies check box allows the left and right channels to have their frequency set independently. This box can be checked and unchecked while the manual sweep is running.


Setting the Frequency in manual mode

In manual sweep mode there are two methods to alter the frequency.


Sweep Modes

SweepGen can progress a frequency sweep in two ways, linear and log. These have different uses, with Log being nearer to how the ear perceives a gradually rising frequency.


Sweep Speed

This controls the operating mode of the sweep.


Frequencies

The start and end frequencies of a sweep may be changed by typing new values in these two edit boxes. They are disabled while a sweep is in progress.


Half-octave Markers

This option is only allowed during the slow sweep mode. It is intended to provide a simply way of estimating frequency when you don't have the display readily visible.

If the option is enabled, whenever the frequency changes octave (I used binary octaves, 256Hz, 512Hz etc.), there will be a brief silence, although the sweep frequency continues to increase. Experience has show that octave markers may not occur sufficiently frequently, so there are markers at the mid-octave frequencies as well.


Output Level

Provides two level adjustment controls, and two on-off controls. Normally, the level controls are linked and either may be used to control the output level of both channels. If the Channels, Independent option is checked, the controls will operate independently. The level is adjustable in 1dB steps from 0dB to -26dB, providing a 20:1 output voltage range adjustment. The initial level is pre-set at -12dB, i.e. the middle of the range.

Unchecking the L or R checkboxes will mute that channel. If you really want to, you can operate with both channels muted - I don't check this unusual combination!


Channels

There are three choice for the Channels box.


Start Button

Pressing the Start button will start the sweep or turn on the continuous sine wave. The green LED should light up. It is only at this point that the capability of your audio board to handle a 44.1KHz CD Quality audio stream is checked. An error message will result if the card can't handle this quality.

The Channels box and Markers check box will be disabled at this time, and re-enabled when the sweep has ended.


File Menu

From version 2.2 onwards, you can save the sweep as a standard Windows Wave file in CD quality 16-bit 44.1KHz stereo.

For repeated waveforms, such as the fast sweep and the white and pink noise waveforms, the short segment which would normally be repeated will be saved, creating a file about 225KB in size. The pure sinewave alone cannot be saved, but you can always try a sweep with the same start and end frequencies!

Long sweeps will occupy rather more disk space, about 7.8MB.


Back to SweepGen introduction
This page last revised: 1997 October 05

E-mail: David Taylor