When the analysis is started at the head or middle of the ORF file data, the data is suddenly read to the octave filter. It seems as if the impulse-like data has been inputted. Each frequency data becomes larger than the original sound pressure level at this time.

Especially when the maximum value is calculated by the average processing in the measurement of small sound, impulse-like data at the beginning is considered as the largest sound pressure level, and the original Max value cannot be obtained.

This problem never occurs in on-line analysis which the filter is regularly applied.

■Countermeasure

When you click the average start button while the off-line ON/OFF button is turned OFF , the off-line processing ON/OFF button is automatically turned ON and the analysis is started. However, the filter affects to the result in this situation.

Therefore, turn the off-line processing ON/OFF button from OFF to ON at first, then click button after a while to start the analysis. This enables the average processing without the effect of above (filtering). 0.5 seconds of delay time (Not an operating time but the data analysis position time) in the time constant of 10ms will be enough.

Click button after a second while observing the analysis position cursor in the viewer screen. Change the delay time according to the time constant.