1 Introduction
2 Review of noise generation in electric machines and drives
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Vibrations are defined as oscillations up to \(20\text{ Hz}\), which are perceived exclusively as vibrations of the structure. (Road-excited vibrations being an example.)
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Harshness represents a transition zone, which is caused by oscillations in the range from \(20\text{ Hz}\) to \(50\text{ Hz}\). This type of oscillation is both audible and tactile. A typical example is the idle shaking of a combustion engine.
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Noise describes audible oscillations in the range from \(50\text{ Hz}\) to \(20\text{ kHz}\). In automotive acoustics, these oscillations are rather located in the area of comfort than in driving dynamics.
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low voice: \(40\text{ dB}\)(A)
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normal conversation: \(55\text{ dB}\)(A)
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heavy city traffic: \(92\text{ dB}\)(A)
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jet plane take-off: \(150\text{ dB}\)(A)
3 Overview of fan noise investigations
Fansystem | voltage in V | current in A | speed in rpm | number of blades | type |
---|---|---|---|---|---|
E | 8 – 16 | 0.135 | 5000 | 64 | radial |
F | 9 – 16 | – | 5000 | 64 | radial |
G | 9 – 16 | – | 4000 | 64 | radial |
H | 9 – 16 | – | 6000 | 64 | radial |
I | 8 – 16 | – | 5000 | 0 | radial |
J | 14 | 0.3 | 7000 | 37 | radial |
K | 14 | 0.3 | 6850 | 37 | radial |
L | 14 | 0.3 | 6650 | 37 | radial |
M | 14 | – | – | – | radial |
N | 14 | – | – | 37 | radial |
4 Preliminary investigation of aerodynamic noise
5 Air-borne sound measurements in a low reflection chamber
5.1 SPL position dependence
5.2 SPL speed dependence
5.3 Separation of in- and outflow noise
5.4 Standardized measurements
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Curve 1: passenger-operated auxiliary device which is activated when the combustion engine is on.
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Curve 2: passenger-operated auxiliary device which is activated when the combustion engine is off and those which operate automatically when the combustion engine is on.
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Curve 3: automatic auxiliary device when the combustion engine is off.