Four parallel frequency weighting networks (A/C/Z/+) are available. Most sound level
measurements are performed using the A-network (it corresponds to normal human hearing
ability at low or moderate sound levels) while peak levels often are detected using
the C-network. The Z-network is in fact flat, in other words, no weighting.
The fourth network can be either the AU network or a selectable user specified network.
The frequency range can be divided into bands of octave or 1/3rd octave width. The
possible frequency range in the Nor150 is from 0.4 Hz to 20 kHz and thus
covers both the sound and vibration range. If Ultrasound is enabled the frequency range
changes to 0.8 Hz to 40 kHz.
The bandwidth decides the width of each filter. The bandwidth can be either 1/1 octave or 1/3 octave.
A lower limit can be set to the lowest frequency of interest. If the frequency is set lower than 6.3 Hz,
the
high-pass filter is disabled. The lowest selectable frequency is 0.4 Hz.
The upper frequency limit should be set to the highest frequency of interest. For the standard microphone,
the maximum frequency is 20 kHz. For other tranducers, the upper limit may be higher.
Preweighted Filter
The filter values can be A or C weighted before the network values are calculated. When this is enabled, the
text A/CPrw is displayed with orange colour in the different views. The old A-Preweighted is now called A-Post-weighted and it is enabled in the context menu.
These two functions cannot be enabled simultaneously.
Enable/disable the FFT (Fast Fourier Transformation) functionality. The FFT uses a Hanning time window.
The FFT is processed every ~700 ms, and is not overlapping. FFT data will be stored together with the measurement.
The instrument supports two resolutions, 8192 lines with 2.96 Hz line width and 16384 lines with 1.46 Hz line width.
If the Nor150 is equipped with the Ultrasound option you are allowed to enable Ultrasound.
With Ultrasound enabled the Nor150 will measure up to 40 kHz. The sensor connected has
to be a suitable � inch microphone. The AU network is automatically enabled when Ultrasound is switched on.
If enabled, the mesurement will calculate and display the NR/NC reating when the measurement is compleate. If measuring 1/1 octaves,
the actual rating curve will also be shown in the L/f graph together with the numerical value. In the context
menu for L/f graph you may select which of the curves to be displayed.
The NR/NC calculation is based on the Leq filter values. The Lfeq function must be enabled by the user.