Spectrogram 3D Limits (3DL)

The Spectrogram 3D Limits is an add-on feature for the Sound Pressure (SPL) Task of the Klippel QC Software. In addition to the standard results of the SPL Task, the 3DL performs a time-frequency analysis of the measured chirp response using an auditory filter bank which is based on human hearing. In contrast to common Short-Time Fourier Transform (STFT) this filter bank delivers a superior time resolution for identifying impulsive distortion (Rub&Buzz).

The resulting spectrograms provide diagnostics of the spectral fingerprint of any abnormal sound and distortion produced by the device under test (DUT). Testing is made easy through three-dimensional limits that are automatically calculated based on approved reference units.

For a chirp signal, both the excitation frequency (time point) as well as the dominant spectral content of any distortion are identified easily in the provided Exceedance plots that indicate where the spectrogram limits are exceeded. Diagnostics is simplified by the provided 2D projection plots based on the Exceedance.