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Difference between revisions of "NVGate Octave Analyzer"
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→Structure and Operation overview
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The sample frequency depends on the value of the High Filter Setting <br> | The sample frequency depends on the value of the High Filter Setting <br> | ||
Next, the input signals can be time weighted filters.<br> | Next, the input signals can be time weighted filters.<br> | ||
*A, B and C weight filters : These filters available in acoustic frequency range (i.e. from 20 Hz to 20 kHz) satisfy requirements from last standards IEC 651 type 0 and IEC 804 type 0. | *A, B and C weight filters : These filters available in acoustic frequency range (i.e. from 20 Hz to 20 kHz) satisfy requirements from last standards IEC 651 type 0 and IEC 804 type 0. | ||
*Any other NVGate filter need to be apply on Input Front end (real time) or Input Player (post analyisis). | *Any other NVGate filter need to be apply on Input Front end (real time) or Input Player (post analyisis). | ||
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After time domain filtering, the signals go to the digital 1/n<sup>th</sup> octave filter bank. | After time domain filtering, the signals go to the digital 1/n<sup>th</sup> octave filter bank. | ||
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The filter range uses base 10 so that we get exact frequencies at 0.1 Hz, 1.0 Hz, 10 Hz, 100 Hz, 1 kHz and 10 kHz.<br> | The filter range uses base 10 so that we get exact frequencies at 0.1 Hz, 1.0 Hz, 10 Hz, 100 Hz, 1 kHz and 10 kHz.<br> | ||
====Computation central frequency==== | |||
The following calculations are used to compute the central frequencies: | The following calculations are used to compute the central frequencies: | ||
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====Detector==== | |||
The next step is the detector process for each 1/n<sup>th</sup> filter: | The next step is the detector process for each 1/n<sup>th</sup> filter: | ||
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A hold box allows to get Maximum and Minimum spectra during one measure. | A hold box allows to get Maximum and Minimum spectra during one measure. | ||
====Stabilisation delay==== | |||
A stabilization delay is implemented in order to ignore and suppress the transient response of passband filters. It is automatically taken into account after any change of input setup. It is equal to 5 periods of the lower frequency filter for 1/3<sup>rd</sup> octave and octave filters. This delay is four times greater for 1/12<sup>th</sup> octave filters (i.e. 20 periods of the lower frequency filter) and eight times greater for 1/24<sup>th</sup> octave filters (i.e. 40 periods of the lower frequency filter).For example, if lower frequency filter is centered at 1 Hz, then the stabilization delay is equal to 5 seconds for octave and 1/3<sup>rd</sup> octave, 20 seconds for 1/12<sup>th</sup> octave and 40 seconds for 1/24<sup>th</sup> octave. During this delay the detectors are inactive. | A stabilization delay is implemented in order to ignore and suppress the transient response of passband filters. It is automatically taken into account after any change of input setup. It is equal to 5 periods of the lower frequency filter for 1/3<sup>rd</sup> octave and octave filters. This delay is four times greater for 1/12<sup>th</sup> octave filters (i.e. 20 periods of the lower frequency filter) and eight times greater for 1/24<sup>th</sup> octave filters (i.e. 40 periods of the lower frequency filter).For example, if lower frequency filter is centered at 1 Hz, then the stabilization delay is equal to 5 seconds for octave and 1/3<sup>rd</sup> octave, 20 seconds for 1/12<sup>th</sup> octave and 40 seconds for 1/24<sup>th</sup> octave. During this delay the detectors are inactive. | ||