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!

Working With dB

When a voltage is reduced by half, it is -6 dB. When it's doubled, it's +6 dB. Every halving or doubling changes the result by 6 dB, so 1/4 is -12 dB, 1/8 is -18 dB, and so on.

When a voltage is changed by a factor of 10, there is a 20 dB change. So if the output is 60 dB less than the input, the voltage is 1/1000.

A 10 dB change represents a factor of 3.16 voltage change. This value has the magical property that the reciprocal has the same digits, so -10 dB is a factor of 0.316 voltage change.

A 1 dB change represents about 11% voltage change.

Putting all these little rules of thumb together, you can make approximate conversions between dB and voltage in your head. Since adding or subtracting dB is the same as multiplying or dividing by the ratios, you can break an oddball value into separate steps.

For example, if an output signal is -56 dB relative to the input, you can break it into -40, -10, and -6 dB. You know that every -20 dB is a factor of 10 (one decimal place) smaller, so -40 dB is 0.01. The -10 dB will make that 0.316 smaller, down to 0.00316. And since -6 dB is just 1/2, the overall output must be 0.00158 of the input.


See also dB, dB From Voltages, Typical dB Applications, Working With dB, RMS "Sum" of dB Values, Formulas For Working With Sound

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