Abstract:
A method is provided for generating noise in an interior and exterior of a motor vehicle in which a control unit is provided which can be activated and which is operatively connected to a noise generator. The noise generator is connected to at least one noise emitting device ( 3 ). The noise emitting device ( 3 ) is mounted underneath a hood of the motor vehicle, and is connected to the vehicle interior via at least one hose with at least one sound transmitting element. Sound waves are extracted from the noise emitting device ( 3 ) and are transmitted into the vehicle interior.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority under 35 USC 119 to German Patent Appl. No. 10 2012 107 814.9 filed on Aug. 24, 2012, the entire disclosure of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a method and a device for generating noise in the vehicle interior and vehicle exterior of a motor vehicle. 
         [0004]    2. Description of the Related Art 
         [0005]    What is referred to as sound design for motor vehicles has, for many reasons, become a problem for the manufacturers of motor vehicles. On the one hand it is conceivable that an engine noise of a motor vehicle does not please a potential driver of the motor vehicle in terms of its form and the driver may like to change the noise that can be heard in the vehicle interior of the motor vehicle. For example, a user might like the engine sound that can be heard in the interior of the motor vehicle to be somewhat more sporty or somewhat quieter than has been provided hitherto. On the other hand, there are always wide ranging limiting values for external vehicle noise that have to be complied with. Thus, engine noise or other acoustic indications of driving states, such as speed or acceleration are manipulated in a targeted fashion in modern passenger cars. 
         [0006]    In addition, motor vehicles are being developed increasingly with electric motor drives. These electric vehicles, of course, have extremely low noise emissions. However, this low noise emission has a disadvantageous safety aspect that should not be underestimated. These vehicles often are so quiet that they are not heard by a passersby or playing children when they approach. In particular, in the case of playing children noise from approaching vehicles is stored in the subconscious as an approaching danger. If a vehicle then approaches almost without any driving noise, the child will not perceive the vehicle or will perceive it too late. This can easily lead to accidents. On the other hand, motor vehicles have an entirely specific driving noise, exhaust noise and engine noise that is responsible, in a significant way, for the feeling of wellbeing of the driver and of the vehicle occupants. The feeling of wellbeing of the driver in turn makes quite a significant contribution to the vehicle being controlled in a safe way, and therefore contributes to general road safety. Accordingly, acoustic perception is an important safety factor. 
         [0007]    The above-mentioned aspect also occurs in hybrid vehicles, and a driver perceives different noise in various driving modes that differ from the known, conventional driving noise, especially when the vehicle is driven exclusively via the electric motor. 
         [0008]    DE 100 16 104 discloses a device for emitting noise to a passenger compartment of a motor vehicle. In this context, a resonance body is fit onto a signal source that is made available. The surface of the signal source forms one of the walls of the resonance body to which a line and further means for passing a noise into the passenger compartment are connected. 
         [0009]    DE 10 2010 007 051 discloses a method and a device for generating sound in vehicles without an internal combustion engine. In this context, values for the parameters of the sound and frequency are selected as a function of the time, the position of the vehicle, the speed of the vehicle and the acceleration of the vehicle and are used to characterize the generation of sound. Differentiated irradiation toward the inside and toward the outside takes place during the generation of sound. 
         [0010]    EP 1 936 605 discloses a sound transmitting device for transmitting sound of an operational noise of a motor vehicle, namely an air filter noise, into the vehicle interior of the motor vehicle. The presented sound transmitting device comprises a transmitting line for transmitting the noise from the noise source into the vehicle interior. The transmitting line is formed at least partially by at least one component that already is present independent of the sound transmission on the motor vehicle. 
         [0011]    U.S. Pat. No. 5,635,903 describes a noise generator for electrical vehicles. The noise generator generates a noise that is emitted into the vehicle interior of the motor vehicle. Amplifiers and loudspeaker units also are provided to permit the emission. 
         [0012]    WO 03/100764 describes a device for carrying out noise control in a motor vehicle. The device has a hollow body that is divided into at least two spaces by a sound transmitting device. One space is connected via an input line to a gaseous part of an internal combustion engine of the vehicle, and the other space is coupled acoustically by an output line to an interior of the vehicle and/or to the space surrounding the vehicle. The output line also has at least one branch from which at least two branch lines run at different locations in the vehicle interior and/or the space surrounding the vehicle. 
         [0013]    An object of the invention to create a suitable acoustic profile for an electric vehicle or a hybrid vehicle that takes into account different noise sources and supplies an authentic vehicle sound that can be used independently of a driving mode. In this context, the external noise of a vehicle is also of particular importance alongside the frequently considered internal noise. The invention simply and efficiently solves the problems of external noise and internal noise as well as simply and efficiently manipulating the noise in the interior of a motor vehicle and simulating an engine noise that is not present when a hybrid vehicle is driven electrically. 
       SUMMARY OF THE INVENTION 
       [0014]    The invention relates to a method for generating noise in the interior and exterior of a motor vehicle. The method of the invention provides a control unit that can be activated and that is operatively connected to a noise generator. The noise generator is connected to at least one noise emitting device. The noise emitting device preferably is mounted underneath a hood of the motor vehicle and is connected to the interior of the motor vehicle via at least one hose line which that has at least one sound transmitting element. Thus, sound waves are extracted from the noise emitting device and are transmitted into the vehicle interior. 
         [0015]    Purely electrically driven vehicles are virtually without sound. Thus, a noise generator and a noise emitting device are provided to ensure driving safety. The noise emitting device is arranged under a hood of the motor vehicle in such a way that sound waves are emitted approximately in the direction of travel of the vehicle. As a result, a desired sound is produced outside the motor vehicle. Sound waves also are directed by the noise emitting device into the region of the interior of the vehicle via the hose. Sound waves also would be directed into the interior of the vehicle without the hose due to normal emission characteristics. However, low-frequency and medium-frequency components of the sound waves would be missing or would be highly attenuated. As a result, sound in the interior of the vehicle would appear less powerful and virtually without an emotional effect and would differ significantly from the sound outside the vehicle. The at least one hose of the invention provides a connection between the noise emitting device and the vehicle interior to extract sound waves from the noise emitting device. 
         [0016]    The at least one hose may have a branch at which the extracted sound waves are directed into two hoses that are separate from one another. 
         [0017]    In a further embodiment of the method according to the invention. One of the two hoses may be guided into a left A pillar of the vehicle, and the other hose may be guided into a right A pillar of the vehicle. The two hoses may be guided from the branch on both sides in the region of a respective wheel housing and through a respective end wall region and may be connected in a lower region of the respective A pillar. 
         [0018]    The transmission of sound waves through a hose line enables low-frequency and medium-frequency components of the sound waves to be heard in the interior of the vehicle. As result, a powerful and authentic sound is produced in the interior of the vehicle without influencing the sound outside the vehicle. 
         [0019]    The noise emitting device preferably is a loudspeaker arranged in a loudspeaker box. The loudspeaker may be inserted into an underside of the loudspeaker box so that sound waves are irradiated primarily in the direction of the engine compartment as well as in the direction of travel. 
         [0020]    The control unit preferably is activated as a function of driving state variables, for example a current velocity. The activated control unit generates a signal that is passed to the noise generator and triggers the noise generator to generate noise corresponding to the signal and to pass the noise to the noise emitting device. 
         [0021]    The noise emitting device may also include a solid-borne sound actuator for excitation over an area. 
         [0022]    The loudspeaker in the loudspeaker box emits sound into the engine compartment region. Further propagation of sound then takes place with a primary orientation in the direction of travel to achieve the desired sound with the objectives of warning pedestrians and sound design. Connecting a hose to the loudspeaker box enriches the internal noise in a targeted fashion via the loudspeaker. 
         [0023]    The noise generator retrieves noises from a noise carrier, converts the noises into noise information and directs the noises to the noise emitting device. 
         [0024]    The noise preferably is digitized noise, sounds or tones of different frequencies. The noise carrier is, for example, a nonvolatile memory element, a compact disk or a digital tape. Noises that are available for selection are stored in a retrievable fashion on the noise carrier. 
         [0025]    A first switching element may be provided and can be used to interrupt the connection between the noise generator and the noise emitting device, thereby switching of the noise irradiation by the noise emitting device. A second switching element may be provided and can be used to interrupt the at least one hose, thereby switching off the sound irradiation from the noise emitting device into the vehicle interior. Thus, noise emission generated by the noise generator can be suppressed entirely or noise emission through the hose line into the vehicle interior can be switched off. 
         [0026]    Freely selectable driving noise of a vehicle may be imitated with the noise generator and irradiated via the noise emitting device. 
         [0027]    In the case of a hybrid vehicle with an internal combustion engine, an intake section of the internal combustion engine may be connected to the interior of the motor vehicle via a branch in the at least one hose. As a result, pressure fluctuations that are excited by aspiration of the internal combustion engine in the form of sound waves are radiated into the hose in addition to the extracted sound waves. Thus, the vehicle interior receives a combination of the noise generated by the internal combustion engine and the noise generated by the noise generator. As a result, the noise generated by the internal combustion engine can be manipulated intentionally. A further switching element can be provided to interrupt the hose in the direction of the noise emitting device when driving a hybrid vehicle with the internal combustion engine so that only noises from the internal combustion engine are directed into the vehicle interior. However, the line that is branched off from the hose and that leads to the internal combustion engine or to the intake section can be switched on or off by a switching element. Thus, only noise from the noise emitting device or a combination of the two types of noise can enter the vehicle interior. 
         [0028]    The phrase formulation “operatively connected” as used herein means suitable information transmitting means are provided to transmit corresponding information between the units that are operatively connected. 
         [0029]    A further noise emitting device, such as an internal loudspeaker that can once more amplify the noise that is to be emitted can be provided in addition to the hose leading into the vehicle interior. In addition, the noise that is to be emitted into the vehicle interior again can be manipulated here. 
         [0030]    The volume of sound waves that are emitted can be varied by a regulator. 
         [0031]    The invention also relates to a device for generating noise in the interior and exterior of a motor vehicle. 
         [0032]    The device of the invention comprises a control unit that can be activated, a noise generator and at least one noise emitting device. The control unit preferably is connected operatively to the noise generator, and the noise generator in turn is connected to the at least one noise emitting device. The noise emitting device can be a loudspeaker unit that is mounted underneath a hood of a motor vehicle and is connected to the vehicle interior of the motor vehicle via at least one hose that is provided with at least one sound transmitting element. As a result, sound waves extracted from the noise emitting device can be transmitted into the vehicle interior. 
         [0033]    The device of the invention preferably is configured to carry out the method of the invention. 
         [0034]    The invention also relates to the use of the device and/or of the method of the invention in a motor vehicle having an electric drive, namely, a hybrid vehicle, a plug-in hybrid or a vehicle with purely electric drive. The use of the device of the invention is also possible in a motor vehicle with an internal combustion engine and without an electric drive to modify noises of the internal combustion engine in a targeted fashion. 
         [0035]    The noise generator may provide different types of noise for selection so that a large spectrum of sounds and noise can be covered. 
         [0036]    The device of the invention may be arranged in a hybrid vehicle and is correspondingly used there. 
         [0037]    Further details and refinements of the invention can be found in the detailed description and the appended drawings. 
         [0038]    Of course, the features that are specified above and/or explained below can be used not only in the specified combination, in other combinations or alone without departing from the scope of the invention. 
         [0039]    The invention is illustrated schematically on the basis of embodiments in the drawings and is described in detail with reference to the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]      FIG. 1  is a schematic illustration of a front view of a front region of a motor vehicle in which an embodiment of a device of the invention is installed. 
           [0041]      FIG. 2  is a schematic illustration of a plan view of a front region or engine region of a motor vehicle in which a further embodiment of the device of the invention is arranged. 
           [0042]      FIGS. 3   a  and  3   b  are schematic illustrations of side views of another embodiment of the device of the invention. 
           [0043]      FIG. 4  is a schematic illustration of a side view of a further embodiment of the device of the invention. 
           [0044]      FIG. 5  shows a schematic illustration of a side view of yet another embodiment of the device of the invention. 
           [0045]      FIG. 6  is a graphic illustration of the profile of external noise for a motor vehicle with and without a hose line to the vehicle interior, which is to be provided according to the invention. 
           [0046]      FIG. 7  is a graphic illustration of an interior noise profile with and without a hose of the invention between the noise emitting device and the vehicle interior. 
           [0047]      FIG. 8  is a graphic illustration of an interior noise profile with local differentiation, also with and without a hose to the vehicle interior. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0048]      FIG. 1  is a front view of a front region of a motor vehicle and illustrates an engine region of the motor vehicle underneath a hood which is illustrated folded open here is shown. A noise emitting device  3  is arranged above a bumper  2 . The noise emitting device  3  can be a loudspeaker system composed of a loudspeaker box and a loudspeaker in the loudspeaker box. The loudspeaker box is connected to a noise generator (not shown here). In addition, the loudspeaker box has a connection  4  via which a hose  5  is coupled to the loudspeaker box  3 . In the illustration shown here, the hose  5  has a Y-branch  6  at which the hose line  5  is divided into hose lines  5 _ 1  and  5 _ 2  that are separate from one another. Thus, sound waves that are extracted from the loudspeaker box  3  are led through the hose  5  and are directed at the branch  6  into the two hose lines  5 _ 1  and  5 _ 2 . As is shown in  FIG. 2 , the hoses  5 _ 1  and  5 _ 2  extend on the left and on the right sides of the motor vehicle from the front region into a vehicle interior. 
         [0049]      FIG. 2  is a plan view of a front region of a motor vehicle and shows a bumper  20  and a noise emitting device  21  with a hose connection  22  to which a hose  23  is connected. The hose  23  is divided at a branch  24  into two hoses  23 _ 1  and  23 _ 2 . The hose  23 _ 1  runs on the right side, when viewed from the front, in the region of a right wheel housing  25 _ 1 , is led through an end wall region  26 _ 1  and then is connected to a lower region  27 _ 1  of the right A pillar  28 _ 1 . The same profile is present on the left side for the hose line  23 _ 2 , which is guided in the region of a left wheel housing  25 _ 2 , is led through a left end wall region  26 _ 2  and is connected to a lower region  27 _ 2  of the left A pillar  28 _ 2 . 
         [0050]      FIG. 3   a  shows a noise emitting device without a connection for a hose line. The noise emitting device is a closed housing  30  in which a loudspeaker  31  is arranged. Noise emission takes place only into the exterior region  32 , as indicated by the double arrow  37 , and into the interior region  33  of the closed housing  30 , as indicated by double arrows  36 . 
         [0051]    In contrast,  FIG. 3   b  shows a noise emitting device in the form of an open housing  30 ′ in which a loudspeaker  31 ′ is arranged. The open housing  30 ′ also has a connection  35 ′ for a hose line (not shown). The connection  35 ′ makes the housing  30 ′ an open housing, unlike the closed housing  30 . Thus, noise emission no longer takes place only into the exterior region  32 ′, as indicated by the double arrow  37 ′, but also in the direction of the hose line, as indicated by the arrow  38 ′. 
         [0052]      FIG. 4  shows a further embodiment of the device according to the invention. A loudspeaker box  40  with a loudspeaker  41  inserted therein is shown as a noise emitting device. The loudspeaker box  40  has a connection  42  for a hose  43 . The hose  43  is led to the vehicle interior of a motor vehicle which is not illustrated here. The loudspeaker  41  emits sound waves that are guided both to the exterior region  44  and into the interior region of the loudspeaker box  45  and as a result also in the direction of the hose line  43 . As a result, the extracted sound waves ultimately are directed into the vehicle interior of the motor vehicle. 
         [0053]    The hose line  43  can have a switching unit that makes it possible to interrupt the connection to the vehicle interior so that sound waves optionally are not transferred into the vehicle interior by the loudspeaker box or the loudspeaker arranged therein. 
         [0054]      FIG. 5  shows a further embodiment of the invention with a loudspeaker box  50  and a loudspeaker  51  arranged therein. The loudspeaker box  50  has a connection  52  at which a hose  53  is led off in the direction of the vehicle interior of a motor vehicle (not illustrated here). The hose  53  has a branch  56  from which a branched hose  57  leads to an intake section of an internal combustion engine. This structure makes it possible that both extracted sound waves from the loudspeaker  51  and sound waves from the intake section pass via the branched line  57  into the vehicle interior of the motor vehicle. These sound waves are superimposed in the vehicle interior and a resulting sound is produced. Switching units may be provided to connect the hose line at suitable locations depending on requirements and the driving mode so that only sound waves from the intake section, only sound waves from the loudspeaker box or both pass in into the vehicle interior. 
         [0055]      FIG. 6  illustrates the volume or the level L of exterior noise in various frequency ranges that is generated by an exterior loudspeaker or a noise emitting device in the region of the hood of the motor vehicle. Frequency is plotted in Hertz (Hz) on an abscissa  60 . The volume or the level L is plotted in decibels (dB) on an ordinate  61 . Exterior noise was picked up by a microphone installed in front of a motor vehicle that has a noise emitting device in the front region, at a distance of approximately 2 m and at a height of approximately 1.5 m. A sine sweep, i.e. a periodic signal that changes frequency from a starting value to an end value in a defined time, was selected as the excitation signal. In the present case, 20 Hz was selected as the starting value and 5 kHz as the end value. The change in the frequency from the starting value to the end value took place with a time increment of Δt=30 s. The curve  62  shows the profile of the exterior noise generated by the noise emitting device on the basis of the excitation signal without the noise emitting device being connected to a hose line that leads to the vehicle interior. The noise emitting device is a loudspeaker arranged in a loudspeaker box forming a closed housing as in  FIG. 3   a.    
         [0056]    The curve  63  then shows the profile of the exterior noise plotted against the frequency for the case in which a hose line, which leads into the vehicle interior of the motor vehicle, is connected to the loudspeaker box. By connecting a hose line, the previously closed housing structure is made into an open system. In this context, possible effects such as a change in the emitted frequency spectrum can occur. However, as can be seen here, the curve  63  largely follows the curve  62 , with the result that the exterior noise does not appear to be affected adversely by the hose line and extraction of sound waves from the loudspeaker box associated therewith. 
         [0057]      FIG. 7  shows the profile of noise in the interior of a motor vehicle over a specific frequency range. The volume or the level L is specified in decibels (dB) on an ordinate  71 . The frequency is plotted in Hertz (Hz) on an abscissa  70 . A curve  72  shows the interior noise that can be perceived in the vehicle interior of a motor vehicle is plotted for the case in which, as explained in  FIG. 6 , a noise emitting device is provided in the front region of the motor vehicle to generate a suitable exterior noise. This noise emitting device is not connected to the vehicle interior of the motor vehicle via a hose. Thus, noise generated by the noise emitting device is directed partially as sound waves into the region of the vehicle interior of the motor vehicle. However, for structural reasons, characteristic low-frequency and medium-frequency components of the sound waves are missing or at least attenuated. As a result, the component that can be heard in the vehicle interior is described as less powerful and with a smaller emotional effect. 
         [0058]    The profile  73  shows interior noise for the case in which the noise emitting device, such as a loudspeaker box, is connected via a hose to the vehicle interior. It is apparent that, in the low-frequency and medium-frequency range, a clear difference in volume can be perceived between the two profiles  72  and  73 . The difference is strongest in the low-frequency range such as, for example, at a frequency of 50 Hz, as indicated by the double arrow  74 . Here, a difference of 18 dB was measured. In the region of a frequency of 100 Hz there is also a difference of 6 dB, as indicated by the double arrow  75 , and in the region of approximately 400 Hz there is a difference of approximately 4 dB, as indicated by the double arrow  76 . The higher the frequency, the lower the deviations between the profiles  72  and  73 . However, it is clearly apparent that the hose from the noise emitting device into the vehicle interior significantly improves interior noise and provides noise that can be perceived better. As a result, the hose enriches interior noise in a targeted fashion. To measure interior noise, in the present case a plastic head was provided in the vehicle interior to perform the measurements of the vehicle interior. Otherwise, the measuring conditions with respect to the excitation signal would be the same as those which used as the basis for  FIG. 6 . 
         [0059]      FIG. 8  shows, under the same test conditions as in  FIGS. 6 and 7 , the profile of an interior noise taking into account various regions of the vehicle interior, wherein here essentially the left and right regions have been considered separately from one another. The frequency in the range of 20 Hz to 5 kHz is plotted on an abscissa  80  and the volume or the level is plotted in decibels on an ordinate  81 . The curves  82 _ 1  and  82 _ 2  each represent the profile of the interior noise without a hose line between the noise emitting device in the front region of the motor vehicle and the vehicle interior. In this context, the curve  82 _ 1  describes the profile of the interior noise in the left region of the vehicle interior, and the curve  82 _ 2  describes the interior noise in the right region of the vehicle interior. In contrast, the curves  83 _ 1  and  83 _ 2  show the profile of the interior noise when a hose line is provided between the noise emitting device in the front region of the motor vehicle and the vehicle interior. It is also clear again that in the low-frequency and medium-frequency range there is a considerable difference between the respective curves  82  and  83 . The curve  83 _ 1  describes the profile of the noise in the left region, while the curve  83 _ 2  indicates the profile of the interior noise in the right region. It is apparent that in the range from 120 to 400 Hz the difference between the curves  82 _ 2  and  83 _ 2  is somewhat larger than the difference between the corresponding curves  82 _ 1  and  83 _ 1 . This means that the difference in noise in the right region between providing a hose line and without a hose line is somewhat greater than in the left region. The interior noise was also measured again here with a plastic head in the vehicle interior. 
         [0060]    From  FIGS. 6 to 8  it is clear that the hose between the noise emitting device and the vehicle interior exhibits clear effectiveness in the frequency range between 25 Hz and 550 Hz. In addition, the overall noise pattern directs air-borne sound and the introduced air-borne sound appears authentic. There is no orientation or localization in the region of the respective A pillars to which the respective hose lines are coupled due to the low frequency range, but instead there is a uniform sound pattern. In addition it is apparent (see  FIG. 6 ) that the exterior noise is not influenced by the provision of the hose line. It is also advantageous that it is not necessary to have a further control apparatus or an actuator for enrichment of the interior noise.