Low frequency noise, below 500 Hz, is mostly generated through structure-borne vibration emanating from the powertrain and transmitted through the various connection points to the vehicle body and into the passenger compartment. This noise contribution has been reduced dramatically over the last few years resulting in a much quieter passenger compartment. However, a consequence of this is that high frequency noise has become much more intensive because of the reduction in the masking effect of low frequency structure-borne noise. High frequency noise comes from a variety of sources, and is generally airborne rather than structure-borne. Of all the ancillary components the principal noise source at high frequency is generally the vehicle alternator. By the nature of its design and operation, the alternator will always produce high frequency noise at various frequencies related to its specific design. At low rotational speeds the noise is dominated by vibrations produced by alternating magnetic forces, an effect which increases with increasing load on the alternator. The frequency of these noises is related to the interaction between the rotor and the stator, and is typically of 30th, 36th and 42nd alternator rotational order. These vibrations also excite resonances in the alternator structure that are perceived as peaks in the overall noise at the various resonance frequencies. This paper reports about the development of a procedure to determine target levels for the tonal noise emitted by a vehicle alternator. The investigation begins with a study into the contribution of the alternator to the noise inside the vehicle. This is followed by the description of an experiment to determine subjectively threshold levels for alternator tonal noise. From the results of these tests alternator noise target levels are derived. Finally, the derived alternator target noise levels are compared with current alternator performance. A number of conclusions can be drawn from the research reported in this paper: -At high engine speeds the alternator makes a significant contribution to the high frequency noise level in the passenger compartment. At low engine speeds and low frequency the contribution of the alternator is less significant; -Alternator noise target levels have been derived based upon subjective determination of threshold levels for tonal noise; -Initial results have shown that a vehicle fitted with an alternator which meets the derived target has an acceptable interior noise level. Conversely, when the vehicle was fitted with an alternator which did not meet the derived target the interior noise level was unacceptable.


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    Titel :

    Alternator tonal noise target setting


    Weitere Titelangaben:

    Bestimmung von Zielvorgaben für die Geräuschemission von Kraftfahrzeug-Generatoren


    Beteiligte:
    Walsh, S.J. (Autor:in) / Robinson, I. (Autor:in) / Stimpson, G. (Autor:in)

    Erschienen in:

    Erscheinungsdatum :

    2003


    Format / Umfang :

    9 Seiten, 13 Bilder, 1 Tabelle, 13 Quellen



    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch




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