or acoustic sound is defined as the frequency spectrum that is
audible to the human ear.
A frequency converter
or a drive uses frequencies in the audible spectrum to control the
As the motor converts these electrical signals to mechanical motion,
the conversion replicates the process, which occurs in loud
speakers. Fortunately, a motor acts as a very poor loud speaker, but
a substantial part of the electrical signals are still converted
into audible noise.
most sensitive area of frequencies to the human ear is typical
around 4 kHz and sound or noise in that range will often be regarded
as the most annoying.
Sound or noise is for
the most part transmitted through the air, but can under certain
circumstances also be transmitted through mechanical constructions,
such as duct fixtures, duct walls or building construction elements.