Manual

3-19
To enter the 1/3
rd
OCTAVE SPL mode (Fig 24), select 1/3
rd
OCT. -> SPL in
the measurement functions submenu.
Arrow Readout: The arrow readout displays the frequency and the level
of the 1/3
rd
octave band that it points to. The arrow automatically
points to the highest level in the 1/3
rd
octave spectrum, or, alternatively
may be controlled manually.
Arrow Mode: The arrow readout may be moved manually to a certain
specific 1/3
rd
octave band.
• Select the arrow mode field and press the enter key.
• Move the arrow to any frequency by using the left/right keys.
Run/Pause: The 1/3
rd
octave spectrum may be freezed.
• Select the run/pause field and press the enter key.
• The1/3
rd
octave spectrum is freezed.
• The arrow mode or zoom symbol may be selected for the detailed
read out of the 1/3
rd
octave spectrum.
• At selecting any other field the measurement will be continued.
• Press the enter key again to continue the measurement.
Zoom (Y-Axis): The scaling of the spectrum’s Y-axis (sensitivity) is fixed
and may be adjusted manually.
• Select the zoom (Y-axis) field and press the enter key.
• Use the up/down keys to scroll the displayed level along the Y-axis
and the left/right keys zoom out/in the Y-axis, e.g. alter the
resolution of the division.
Time Constant: The time constant corresponds to the integration time
of the 1/3
rd
octave recording. It may be set to five value: 0.2 / 0.5 / 1.0
/ 2.0 / 5.0 seconds. A lower time constant results in a quicker, more
‘nervous' display, whilst a higher time constant ‘averages’ more
samples, thus providing a more stable spectrum.
Bargraph: Below the spectrum, the actual sound pressure level is
indicated by a bargraph. Select the different indication ranges by
moving the cursor to the left or right arrow below RNGE and press
enter. The available bargraph ranges are:
• 20 - 100 dB
SPL
• 40 - 120 dB
SPL
• 60 - 140 dB
SPL
Measurement Functions
3-18
Measurement Functions
Zoom (Y-Axis): The scaling of the spectrum’s Y-axis (sensitivity) is fixed
and may be adjusted manually.
• Select the zoom (Y-axis) field and press the enter key.
• Use the up/down keys to scroll the displayed level along the Y-
axis and the left/right keys zoom out/in the Y-axis, e.g. alter the
resolution of the division.
Time Constant: The time constant corresponds to the integration time
of the 1/3
rd
octave recording. It may be set to five value: 0.2 / 0.5 / 1.0
/ 2.0 / 5.0 seconds. A lower time constant results in a quicker, more
‘nervous' display, whilst a higher time constant ‘averages’ more
samples, thus providing a more stable spectrum.
Bargraph: Below the spectrum, the fullband input RMS level (20 Hz - 20
kHz) is indicated by a bargraph without auto ranging. Select the
different indication ranges by moving the cursor to the left or right
arrow below RNGE and press enter. The available ranges are:
• -120 to -20 dBu, residual noise of ML1 < -120dBu (<1µV), enables
measurement of low signal levels
• -100 to 0 dBu
• -80 to +20 dBu, please note in this range the residual noise of
ML1 is gained by 20 dBu.
3.103.10
3.103.10
3.10
1/31/3
1/31/3
1/3
rdrd
rdrd
rd
Octave SPL Octave SPL
Octave SPL Octave SPL
Octave SPL
The 1/3
rd
OCTAVE SPL screen shows the signal frequency spectrum of
the acoustic signal, divided into 31 bands.
Fig 24 1/3
rd
Octave SPL Screen