What is the spectral resolution?

Objectives

This article explains what is the notion of spectral resolution in MANATEE software dedicated to the vibroacoustic design of electric motors.

Principle

Some MANATEE models work in time or frequency domain. When frequency domain is used, physical phenomena are only taken account with a certain frequency discretization step called frequency resolution. Due to FFT limitations, discretization cannot be improved both in time and frequency domains, an important tradeoff has to be made in time-frequency analysis and especially in spectrograms for e-NVH applications.

The frequency resolution is an output of MANATEE based on user inputs. If the frequency resolution is too high, it is possible to change it by increasing the number of revolutions which corresponds to increase the final time of the simulation.

One should only care about frequency resolution when modelling low frequency modulation effects such as eccentricities. In this case MANATEE automatically checks the frequency resolution to be sure that the NVH impact of eccentricities are correctly taken into account. In particular, some sidebands at mechanical frequency should appear in noise and vibration spectrograms.

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