User Manual

3.10 FFT Analysis Modes

Waveform Example

Octave Analysis________________________________________________

Octave analysis consists of frequency analysis of the signal passed through a

constant-width band-pass filter. The power spectrum displays the power level in

each subband after dividing the spectrum into fixed-width segments (subbands),

while octave analysis scales the spectrum logarithmically and displays each

octave (subband) as a bar graph.

The center frequency of the octave bands and filter characteristics are deter-

mined according to IEC61260 standards. With this instrument, 1/1- and 1/3-

octave analyses are calculated using power spectrum Analysis results.

1/1 Octave Analysis: 6 subbands

1/3 Octave Analysis: 16 subbands

1/1 and 1/3 Octave Analysis OCT

The sound pressure level of the spectrum of a signal such as noise is displayed through a fixed-width

one- or one-third octave band-pass filter.

Not available with external sampling enabled.

Main uses:

To analyze frequency components of noise

See About the Functions "3.10.2 Analysis Mode Functions" (⇒ p. 102), "Octave Filter Characteristics" (⇒ p. 114)

Axis Display Type Description

X axis Log Displays the center frequency of each band.

Y axis

Lin-Mag

Octave analysis values are displayed linearly.

Log-Mag (logarithm)

Octave analysis values are displayed as dB values. (0 dB reference value: 1eu)*

* eu: engineering units that are currently set are the standard (e.g., when the unit settings is volts, 0 dB = 1 V)

1/1 Octave

X axis: Log

Y axis: Lin-Mag

Filter: Normal

1/1 Octave

X axis: Log

Y axis: Log-Mag

Filter: Normal

1/3 Octave

X axis: Log

Y axis: Lin-Mag

Filter: Normal

1/3 Octave

X axis: Log

Y axis: Log-Mag

Filter: Normal