Measurement with 1/1 and 1/3 octave filters

1. Notes

Please note the followings before you perform the frequency analysis using the 1/1 or 1/3 octave filter.

• To perform the frequency analysis using 1/1 or 1/3 octave filter, optional 1/1 octave filter (LA-0561) or 1/3 octave filter (LA-0562) is required.

• 1/1 and 1/3 octave filters have a gain of 10 dB. Therefore, the level range display is 10 dB lower than the actual range. The measurement value displayed includes the gain, so allowing direct reading.

• During calculation, 1/1 and 1/3 octave filters cannot be selected.

• When the dual calculation mode is selected, the 1/1 or 1/3 octave filter cannot be selected. Therefore, dual mode calculation using the 1/1 or 1/3 octave filter is not possible.

• When the wide range is selected, 1/1 or 1/3 cannot be selected. Select 1/1 or 1/3 octave filter after setting an appropriate range other than wide range.

• The AC/ DC signal output terminal of the Sound Level Meter outputs only the central part of the frequency band.

• The selection of 10 kHz or 12.5 kHz for the 1/3 octave filter is available with the LA-2111. However, the LA-2111 is the normal type Sound Level Meter, above setting is out of the measurement frequency range.

 

2. Measurement procedure of the instantaneous value

Follow the procedure below to measure the instantaneous value with the 1/1 or 1/3 octave filter.

 

◆Operating procedure

1. Set the measurement condition of the instantaneous value.

Frequency weighting compensation: Arbitrary (Panel switch [A/C/FLAT])
Dynamic characteristic: Arbitrary (Panel switch [F/S/IMP])
Measurement mode: Instantaneous value (Panel Switch [Tact Max])
Level range: Other than wide range (Panel switch [LEVEL ▲ ▼])

2. Select octave filter.

Press the panel switch [THRU/FILTER] to select octave filter. When an octave filter is selected, the screen is changed to small screen. When neither the 1/1 nor 1/3 octave filter is installed, message [OPTION] is displayed.

3. Press the panel switch [1/1 1/3 R.T] to select either the 1/1 or 1/3 octave filter.

 

4. Press the panel switch [FILTER FREQ] to change the central frequency.

 

5. Read displayed instantaneous value.

Generally, instantaneous value is displayed when press the panel switch [THRU/FILTER] to cancel octave filter selection.

3. Measurement method of each calculation

Follow the procedure below to measure the equivalent noise level and the time-rate noise level with the 1/1 or 1/3 octave filter.

 

◆Operation procedure

1. Set the measurement condition of the instantaneous value.

Frequency weighting compensation: Arbitrary (Panel switch [A/C/FLAT])
Dynamic characteristic: Arbitrary (Panel switch [F/S/IMP])
Measurement mode: Instantaneous value (Panel Switch [Tact Max])
Level range: Other than wide range (Panel switch [LEVEL ▲ ▼])

2. Set the measurement time.

Press the panel switch [MEAS TIME] to set the measurement time.
To set FREE for the measurement time, switch the setting time to 00:00:00. When FREE is set, measurement is continued until the panel switch [PAUSE/CONT] is pressed, and it is up to 100 hours (99:59:60). Please note that 100 hours or longer time cannot be set.

3. Set the sampling interval.

Press the panel switch [Period] of the function 2 to set the sampling interval. When set the sampling interval to 10 ms, overflow may occur when the measurement time is extended. To avoid this, set the measurement time to less than one hour. The following table shows overflow time when the measurement value changes periodically. Set the appropriate sampling interval and measurement time according to the table. However, when you do not measure the time-rate noise level, above setting is unnecessary.

 

4. Select the octave filter.

Press the panel switch [1/1 1/3 R.T] to select either the 1/1 or 1/3 octave filter.

5. Press the panel switch [FILTER FREQ] to change the central frequency.

 

6. Start the measurement

Press the panel switch [START] to start measurement. During measurement, measurement in progress mark is displayed. The measurement setting display shows the measurement elapsed time.

7. Read the measurement values in the digital display.

The measurement is terminated when the setting measurement time is elapsed. Then, the measurement in progress mark is disappeared.

4. Reading of measurement value

Follow the procedure below to switch and display the value which is measured by the 1/1 or 1/3 octave filter.

 

 

Revised:2001.10.12


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