Speed of Sound
The speed of sound, in air, can be specified here in units of meters per second (343 m/s, by default).
Density of Air
The density of are can be specified here in units of kilograms per cubic meter (1.21 kg/m^3, by default).
Velocity Integration Time Constant
Acoustic particle velocity is estimated by integrating the difference between the 2 microphones in the
intensity probe. The length of the integration is determined by this time constant. Larger values mean
more acoustic pressure samples contribute to the current velocity estimate.
Frequency Weighting
SignalScope provides a means of weighting the spectral content of input
signals according to standard A and C frequency weighting curves (the Z, or zero, weighting selection
does not apply any weighting to the signal).
These A and C weighting curves are intended to mimic human perception
of loudness at two different loudness levels. The desired frequency
weighting can be selected from the segmented control.
Auto Stop Options
Auto Stop
Intensity measurements can be configured to automatically stop after a predetermined amount of time. The
elapsed time after which the current measurement will stop can be set in increments of 1 second up to
two weeks in duration. When the octave level averaging time is set to ∞, the measurement will continue
to average the octave-band results as long as the tool is running, so the auto-stop duration can be used
to specify the total averaging time of the measurement.
Octave Options
Bandwidth
The Intensity tool performs either whole-octave-band or third-octave-band measurements with
center frequencies recommended by ANSI standards.
Averaging Time
The Intensity tool offers three averaging times for the sound intensity measurement: 1/8s, 1s, and ∞.
With 1/8s or 1s, the pressure, velocity, and intensity are calculated over a 1/8 or 1-second
time interval, respectively. In this case, the measurement values are updated at those same
intervals.
With ∞, the values are calculated over the entire duration of the measurement.
Min/Max Frequency Band
The range of whole or 1/3-octave frequencies to display and to include in the overall level calculations
is determined by the selections for minimum and maximum frequency band.
FFT Options
FFT Time/Frequency Resolution
SignalScope simplifies narrowband (FFT) configuration by allowing you to choose a time or frequency
resolution for narrowband spectral analysis. SignalScope then automatically calculates the FFT length
required for that frequency resolution at the audio input hardware's current sample rate. It should
be noted that in this case, frequency resolution refers to the distance between adjacent spectral
lines (or frequency bins) in the spectrum.
Min/Max Frequency
A frequency range can be specified for the narrowband spectrum display. Only values that correspond to
frequencies between min and max will be plotted. Only
those values will be included when exporting spectral data to a file. The Cursor Peak Track
function will operate within the selected frequency range.
Averaging
Successive measurements may be averaged according to the selection of this
segmented control. Available average types include: Linear
(Stable) and Exponential. Linear averaging weights
all measurements equally. Exponential averaging applies an exponential
weighting such that more recent measurements contribute to the current
average value more than older measurements. When linear averaging is selected, the
analyzer will automatically stop after the specified number of spectra have been averaged.
Averages
The number of measurements to include in the current average is specified in the Averages text
box. When linear averaging is the selected average type,
the analyzer will automatically stop after the specified number of
measurements have been included in the average. Exponential averaging
allows the analyzer to continue running even after the specified number
of measurements have been processed. The exponential average can be
thought of as including only the most recent N (time-exponential-weighted) measurements, where N is the
specified number of averages.
Data Export
Current Location
When this option is enabled, the latitude, longitude, and altitude at the time of the
measurement will be included in exported data files. Horizontal and vertical accuracy (in
meters) will also be included.