Daqarta
Data AcQuisition And Real-Time Analysis
Scope - Spectrum - Spectrogram - Signal Generator
Software for Windows
Science with your Sound Card!
The following is from the Daqarta Help system:

Features:

Oscilloscope

Spectrum Analyzer

8-Channel
Signal Generator

(Absolutely FREE!)

Spectrogram

Pitch Tracker

Pitch-to-MIDI

DaqMusiq Generator
(Free Music... Forever!)

Engine Simulator

LCR Meter

Remote Operation

DC Measurements

True RMS Voltmeter

Sound Level Meter

Frequency Counter
    Period
    Event
    Spectral Event

    Temperature
    Pressure
    MHz Frequencies

Data Logger

Waveform Averager

Histogram

Post-Stimulus Time
Histogram (PSTH)

THD Meter

IMD Meter

Precision Phase Meter

Pulse Meter

Macro System

Multi-Trace Arrays

Trigger Controls

Auto-Calibration

Spectral Peak Track

Spectrum Limit Testing

Direct-to-Disk Recording

Accessibility

Applications:

Frequency response

Distortion measurement

Speech and music

Microphone calibration

Loudspeaker test

Auditory phenomena

Musical instrument tuning

Animal sound

Evoked potentials

Rotating machinery

Automotive

Product test

Contact us about
your application!

Sound Card Burst Overview

When you turn a pure tone on or off suddenly, the clicking sound you hear is "spectral splatter" that adds many other frequencies both higher and lower than the desired tone. In effect, you are multiplying the original wave by a rectangular wave from the on/off switch. The rectangular wave has many harmonics, and the multiplication gives sum and difference frequencies of each harmonic with the original tone frequency.

These spurious components can be greatly reduced by turning the tone on and off slowly. The burst modulator fades the tone up and down with smooth rise and fall times instead of toggling it instantly on and off, analogous to using a light dimmer instead of a toggle switch. Slower changes cause greater reductions in the splatter components farthest from the tone frequency, so you can tailor the effective width of the splatter by controlling the rise and fall times.

The burst modulator allows you to control the shape and slope of the rise and fall times, as well as the durations of the on and off intervals. You can also create "trains" of bursts, like "Beep, beep, beep, (pause), beep, beep, beep, (pause)...".

The overall burst cycle time can be up to 2^32 - 1 samples, which is over 27 hours at a 44100 Hz sample rate.

In addition, you can further modulate any of the durations to produce trains with variable timing. For example, you can cause the length of the "beep" to increase and decrease in duration on subsequent repetitions, or to move earlier or later in the overall cycle. You can have trains with a variable number of bursts between pauses, or a variable pause duration after each train. Modulation control dialogs are invoked by the small buttons that hold the timing control labels.

Besides "normal" burst operation, you can use Burst in unusual ways. See Jitter-Free Square Waves - Burst Method under Square Wave for a way to create ultra-low-frequency square and sine waves with high frequency resolution. Creating Complex Arb Waves and Creating Rectified-Wave Arbs discuss some additional alternative uses.


See also Burst Button, Basic Burst Operation, Modulating Burst Values, Burst Controls, Waveform Stream Controls, Burst Application: Auditory Evoked Responses, Burst Rise/Fall vs. Spectral Width, Fundamental Time - Frequency Domain Concepts


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