SPL over time

SPL over time calculates from a microphone signal the progression of SPL over time. The adjustable parameters are the same as for a level meter (A-weighting, integration time), however additional filtering options are available and the averaging between channels is also possible. After the calculation the y-axis display mode is automatically set to Level.

Int. length [s] sets the integration time in seconds.

Apply to all channels allows the application of the function to all channels of a file, or the activated channel only.

Average magnitude all chan. averages magnitude progressions of sound pressure after integration and A-weighting (not the Level).

A weighting applies an A-weighting filter.

Use filter 1 (2) activates additional filters. At first the category is selected as Low pass or High pass. For the filter characteristics the types Butterworth, Chebyshev PB, Chebyshev SB and Elliptic are available. While the former offer smoother filter shapes, the latter are able to provide steeper curves, with the drawback of a higher ripple. Filter order determines the gradient of the filter slope in units of 6dB/oct. Cut off [Hz] sets the cutoff frequency for the filter. Passb. rip. [dB] and Stopb.rip. [dB] define the maximum ripple in the passband and the stopband for the Chebyshev and the elliptic filters. OK starts the integration.

As an example the following plot shows motor noise recorded at 4 microphone positions.

The A-weighted SPL over time of these signals is plotted here:

SPL over time can also be used in combination with the Fract. octave Filterbank in order to evaluate SPL progressions in frequency bands.