Audio signal for a synthetic noise of a motor vehicle as well as method for generating said audio signal

Abstract

A method for generating an audio signal for a synthetic noise of a motor vehicle is provided. An audio signal for the synthetic noise of a motor vehicle is also provided. In one step of the method, a signal is provided that represents a noise. Moreover, a fundamental frequency is specified that represents an operating rotational speed of the motor of the vehicle. In another step of the method, several filters are applied to the noise signal. These filters each have a mid-frequency linked to the specified fundamental frequency via an order factor. At least several of the order factors are whole numbers, so that these filters filter the harmonic components of the fundamental frequency. The order factors and the amplitude curves of the filters are selected according to the sound characteristic of the motor vehicle noise that is to be synthesized. The noise signal weighted by the filters constitutes the audio signal for the synthetic noise of the motor vehicle as a function of the operating rotational speed of the motor of the vehicle.

Claims

1. A method for generating an audio signal for a synthetic noise of a motor vehicle, comprising the following steps: providing a noise signal representing a noise; specifying a fundamental frequency representing an operating rotational speed of the motor of the vehicle; and applying multiple filters to the noise signal, the filters each having a mid-frequency linked to the fundamental frequency via an order factor, at least several of the order factors being whole numbers, and whereby the order factors and amplitude curves of the filters are selected according to a sound characteristic of the motor vehicle noise to the synthesized; the noise signal weighted by the filters constituting an audio signal for the synthetic noise of the motor vehicle as a function of an operating rotational speed of the motor of the vehicle.

2. The method as recited in claim 1 wherein at least one broadband pass filter is also applied to the noise signal, the broadband pass filter being independent of the fundamental frequency and representing a noise during the operation of the motor vehicle independent of the operating rotational speed of the motor of the vehicle.

3. The method as recited in claim 1 wherein the sound is in the form of white noise.

4. The method as recited in claim 1 wherein the fundamental frequency is specified in that a pulse sequence is provided representative of the operating rotational speed of the motor of the vehicle and having the fundamental frequency.

5. The method as recited in claim 1 wherein several of the order factors are selected from the group consisting of the whole numbers from 2 up to and including 10.

6. The method as recited in claim 1 wherein several of the order factors are whole numbers greater than or equal to 20.

7. The method as recited in claim 1 wherein the fundamental frequency is specified as a quantity varying over time, the fundamental frequency varying between a minimum value and a maximum value during the time span.

8. The method as recited in claim 7 wherein, when the filters are applied to the noise signal, the mid-frequencies of the filters change with the fundamental frequency varying over time.

9. The method as recited in claim 1 further comprising the following additional steps carried out during the operation of the motor vehicle: measuring a momentary value of the rotational speed of the motor of the vehicle is measured; selecting a time segment for the audio signal representing the synthetic noise of the motor vehicle, the time segment being one during which the fundamental frequency comes closest to the momentary value of the rotational speed of the motor of the vehicle; emitting the selected segment of the audio signal representing the synthetic noise of the motor vehicle via a loudspeaker installed in the motor vehicle; and periodically repeating the measuring, selecting and emitting steps.

10. An audio signal for a synthetic noise of a motor vehicle generated employing the method as recited in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Additional details and refinements of the invention can be gleaned from the description below of a preferred embodiment of the method according to the invention, making reference to the drawing. The following is shown:

(2) FIG. 1 a depiction of the course over time of white noise that is provided according to a preferred embodiment of the invention;

(3) FIG. 2 a spectral depiction of the noise shown in FIG. 1, before and after filtering through several filters; and

(4) FIG. 3 a depiction of the course over time of the noise shown in FIG. 2, before and after filtering through several filters.

DETAILED DESCRIPTION

(5) FIG. 1 is a depiction of the course over time of a signal 01 of white noise that is provided according to a preferred embodiment of the method according to invention. Only a short time segment of about 0.1 s is depicted. The signal 01 of the white noise has a time duration of, for instance, 60 s.

(6) FIG. 2 comprises spectral depictions of the noise shown in FIG. 1, before and after filtering through several filters. The lower segment shows the signal spectrum 01 of the white noise from 0 Hz to 2,500 Hz. According to the invention, the signal 01 of the white noise is filtered through several Kalman filters. In the embodiment shown, the noise being synthesized is that of a vehicle that has an electric motor as the drive motor. The rotational speed of the electric motor forms a fundamental frequency. The Kalman filters used have mid-frequencies that are 20, 40, 47, 80, 120 and 240 times the value of the fundamental frequency. The upper part of FIG. 2 shows a signal spectrum 02 of the filtered noise. The narrow-band Kalman filters of the 20.sup.th, 40.sup.th, 47.sup.th, 80.sup.th, 120.sup.th and 240.sup.th order yield corresponding narrow-band spectral ranges.

(7) The noise signal filtered through the Kalman filters constitutes the audio signal 02 that is to be generated. The audio signal 02 is suitable to represent the noise of a vehicle that has an electric motor as the drive motor, whereby the noise is related to the rotational speed of the electric motor.

(8) FIG. 3 comprises a depiction over time of the audio signal 02 shown in FIG. 2. Here, too, only a small time segment of about 0.06 s is depicted. The audio signal 02 has the same total duration as the signal 01 of the white noise shown in FIG. 1.

LIST OF REFERENCE NUMERALS

(9) 01 white noise signal 02 audio signal generated by filtering the noise signal