Patent Publication Number: US-2013251157-A1

Title: System for reproducing an audio signal

Description:
BACKGROUND OF THE INVENTION 
     1. Priority Claim 
     This application claims the benefit of priority from European Patent Application No. EP12002030.0-1247, filed Mar. 22, 2012, which is incorporated by reference. 
     2. Technical Field 
     The present invention relates to a method for retrieving and a system for reproducing an audio signal. 
     3. Related Art. 
     Convolution can be used in acoustics such as in a sound recording studio. The increasing computing power of special DSPs (DSP—Digital Signal Processor) and the home computer also permits the use of convolution in sound studios. When one excites a room with a short (broadband) pulse, one hears an echo that is characteristic for this room and that emphasizes or damps specific frequency components of the pulse as a result of the room&#39;s geometry and dimensions, the room&#39;s basic structure, the room&#39;s interior, and other specific characteristics. If the echo is now recorded, one thus obtains the impulse response of this room. The impulse response contains the complete characteristic of the (linear) room. In the technique of convolution, this impulse response is now utilized in order to combine any other desired acoustic signals with the impulse response through the mathematical process of convolution. For example, a discrete, fast convolution (FFT—Fast Fourier Transformation) for discrete (digitized) periodic signals is used to generate the acoustic characteristic of the room. As an alternative to determining impulse responses for a specific room, the impulse response can also be obtained through modeling, such as ray tracing and a source image model. 
     When a room is bounded by flat surfaces, the reflected sound components can be calculated by means of the source image method by constructing mirror-image sound sources. By means of modeling, it is possible to alter the position of the sound source and thus generate a new impulse response. By means of the impulse response, a signal for reproduction is faded out using an associated filter. The spatial impression is the auditory perception that one receives from the room itself when a sound event occurs. The spatial impression augments the acoustic information that comes directly from the sound source with important information about the environment, about the size and character of the room. The spatial impression consists of multiple components: the perception of the width and depth of the room, (room size); the perception of liveliness, which prolongs each sound event and can fuse a sound event with a following sound event; and the perception of space. Digital filters are a tool used in digital signal processing. One implementation of a filter can be achieved using convolution. This type of filter is called an FIR filter (Finite Impulse Response). Small rooms can be simulated based on an approximate image expansion, such as for rectangular non-rigid wall enclosures. 
     SUMMARY 
     An audio signal reproduction system can retrieve an audio signal. The system may include a selection mode for retrieving the audio signal. The selection mode may be started based on a first user input. In the selection mode, a first audio signal can be reproduced. In addition, in the selection mode, a second audio signal can be reproduced substantially simultaneously with the first audio signal. In the selection mode, the first audio signal and the second audio signal can be filtered. The first audio signal may be at a first location and the second audio signal may be at a second location when separated acoustically in a virtual acoustic space by the filtering. In selection mode, in order to select the first audio signal, the first location in the virtual acoustic space can be positioned acoustically closer to a listening position of the user than the second location of the second audio signal. 
     In the audio signal reproduction system, the first audio signal can be automatically selected and the selection mode can end if a timing out of a time counter is detected. In order to end the selection mode, the first audio signal can be reproduced and the second audio signal can be faded out. The selection of the audio signal can occur conveniently. A selection of the audio signal can also be made solely acoustically. For example an occupant in a vehicle need not look at a display to make a selection, and may instead use audible sound a hands free command, such as voice commands to make a selection. 
     The system for reproducing an audio signal can be connected to electroacoustic transducers, such as loudspeakers or headphones. The system for reproducing an audio signal can be configured to start a selection mode for retrieving an audio signal. The starting of the selection mode can be based on a first user input. The system may be configured to reproduce a first audio signal in the selection mode. The system may be configured to reproduce a second audio signal substantially simultaneously with the first audio signal in the selection mode. The system may be configured to filter the first audio signal and the second audio signal in the selection mode by means of a filter. The first audio signal may be at a first location and the second audio signal may be at a second location. The first location and the second location can be separated acoustically in a virtual acoustic space based on the filtering. Here the filtering can position the first audio signal at a different three dimensional location in the virtual acoustic space than the second audio signal, such as by using convolution techniques. The filter may be realized by a digital signal processor. 
     The system for reproducing an audio signal can be configured to position the first location in the virtual acoustic space acoustically closer to a listening position of a listener/user than the second location of the second audio signal in order to select the first audio signal. The system can be configured to position the first location in the selection mode. The system for reproducing an audio signal can be configured to end the selection mode, if a timing out of a time counter is detected. The system can be configured to reproduce the first audio signal and to fade out the second audio signal in order to end the selection mode. 
     In an example, in the selection mode, a second user input may be detected before the timing out of the time counter. The first audio signal may be selected and the selection mode may end, if the second user input for selecting the first audio signal is detected. Therefore the system for reproducing an audio signal may operate to end the selection mode, if the second user input for selecting the first audio signal is detected. 
     The first audio signal and the second audio signal may be digital signals, which have a number of channels, for example, two stereo channels. A reproduction mode for the reproduction of audio signals can be provided before the selection mode and after the selection mode. In the reproduction mode, in contrast to the selection mode, a single audio signal, for example, a stereo signal of a radio receiver may be reproduced at a given time. In addition, other modes, for example, for outputting navigation instructions, telephone, or other audible sound can be provided. Additionally, in other examples, at least a third audio signal and/or a fourth audio signal may be reproduced during selection mode. The user can hear the first, second, third and fourth audio signals concurrently, but acoustically separated. In some examples, two or more audio signals are reproduced during selection mode. 
     In another example, the first audio signal and the second audio signal can be reproduced substantially simultaneously, but separated in a virtual acoustic space. This example operation can also be called spatialization. In this case, there are several possibilities for separation of the first audio signal and the second audio signal. For example, the first audio signal can be reproduced exclusively by at least one first loudspeaker, whereas substantially simultaneously the second audio signal can be reproduced exclusively by at least one second loudspeaker. In this case, the distance of the arrangement of the first loudspeaker and of the second loudspeaker can provide the distance between the first location of the first audio signal and the second location of the second audio signal in the virtual acoustic space. In other examples, additional audio signals and loudspeakers may be used. 
     In another example, more than two audio signals can be output over at least two loudspeakers arranged at a distance from one another. The audio signals can be reproduced by both loudspeakers at different volume such that an audio image perceived by a listener can be closer to one loudspeaker or the other loudspeaker, such as further left or further right in the virtual acoustic space. In addition, an audio signal can be reproduced such that an audio image is perceived as being in the middle between the loudspeakers, such as when both loudspeakers are at the same volume. Separation in the virtual acoustic space of the perceived audio image to be in several intermediate positions between far left and far right is also called panning 
     In another example, the first audio signal and the second audio signal can be arranged in different spatial depths of the virtual acoustic space. For this purpose, convolution is used in that each audio signal is filtered with different filter coefficients. For example, an FIR filter (Finite Impulse Response Filter), sometimes also called a transversal filter, can be used for the convolution. The location of the audio signal can be positioned as desired in the virtual acoustic space by means of the filter parameters, where the filter parameters may be developed by the convolution. A number of first filter coefficients can be loaded in a first filter block of a filter for filtering for the first location and a number of second filter coefficients can be loaded in a second filter block of a filter for the second location. In this case, the location in the virtual acoustic space is the perceived source position at which the listener locates the corresponding audio signal acoustically. 
     To end the selection mode, if the timing out of a time counter is not detected, the user need not wait for the time counter to lapse, but can end the selection mode at any time using a second user input for selecting the first audio signal. However, the timing out of the time counter provides an automatic ending of the selection mode, so that the selection mode may be manually concluded by a user, or automatically concluded based on the time counter. For example, in certain conditions in a vehicle, such as a traffic situation, a driver has the choice of making or not making the second user input. There also could be other events, such as acoustic events, interrupting or terminating the selection mode, like receipt of a phone call or issuance of navigation instructions. 
     In an example, in the selection mode, the first location of the first audio signal in the virtual acoustic space and/or the second location of the second audio signal in the virtual acoustic space can be changed based on a third user input. The first audio signal and/or the second audio signal at a location in the virtual acoustic space can be perceived as being positioned closer to a listening position of the user or farther from the listening position of the user by using the third user input. Advantageously, audio signals, positioned acoustically closer to the listening position, can be defined for a selection. In the selection mode, preferably for selection of the first audio signal, the first location in the virtual acoustic space can have a perceived position closer to a listening position of the user than the second location of the second audio signal. 
     In the selection mode, the second and/or third user input may occur via touching of a touch screen or actuation of a button or actuation of a selector wheel or any other form of user input for adjusting a perceived position. 
     In an example, the selection mode the first audio signal and the second audio signal can be reproduced at a different volume in the virtual acoustic space. Advantageously, in the selection mode for the selection of the first audio signal a first volume of the first audio signal can be controlled to be higher than a second volume of the second audio signal in the virtual acoustic space. In this case, the first audio signal in the virtual acoustic space is perceived to be closer to a listening position of the user than the second audio signal. 
     According to an example, the first audio signal is associated with a first audio source and the second audio signal is associated with a second audio source. For example, the first audio signal originates from a first radio receiver and the second audio signal originates from a second radio receiver. With the first radio receiver a first radio station is received, whereas with the second receiver a second radio station is received. In selection mode, the user can hear both radio stations concurrently but acoustically separated. With the second input the user may decide which radio station is selected for continuous playback, and exit the selection mode. 
     According to an example, the first audio signal can be associated with a first database entry and the second audio signal can be associated with a second database entry. The first audio signal in this case is advantageously generated from a first audio file and the second audio signal in this case is advantageously generated from a second audio file. 
     In an example, a first visual information item, associated with the first audio signal, can be displayed. Moreover, a second visual information item, associated with the second audio signal, can be displayed. One of the first or second visual information item can be, for example, a text and/or a picture and/or a video. The other of the first or second visual information item can be, for example, a cover or title or a station name or the like. An acoustic arrangement of the first location of the first audio signal and the second location of the second audio signal can correspond to a visual arrangement of the first visual information item and the second visual information item on a display. The display can be any mechanism or device for providing visual images, such as, for example, a screen or a projector. 
     There can be several options for arranging the first visual information item with respect to the second visual information item. For example, if the first visual information item is arranged in a position in front of the second visual information item, such as if the first visual information item partially conceals from view the second visual information item, then the first location of the first audio signal can also be arranged in a similar corresponding perceived acoustic position in front of a perceived acoustic position of the second location of the second audio signal in the virtual acoustic space. For example, if the first visual information item is arranged to the left of the second visual information item, then the first location of the first audio signal can also be arranged to the left of the second location of the second audio signal in the virtual acoustic space. For example, if the first visual information item is arranged above the second visual information item, then the first location of the first audio signal can also be arranged above the second location of the second audio signal in the virtual acoustic space. 
     Other systems, methods, features and advantages of the invention will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
         FIG. 1  is a block diagram example of the audio signal reproduction system, loudspeakers, and a virtual acoustic space that also shows an example display for radio reception. 
         FIGS. 2   a  and  2   b  is another block diagram example of the audio signal reproduction system, loudspeakers, and a virtual acoustic space that also shows an example display of selection from a database. 
         FIGS. 3   a  and  3   b  is yet another block diagram example of the audio signal reproduction system, loudspeakers, and a virtual acoustic space that also shows an example display for selecting an individual title. 
         FIG. 4  is an operational flow diagram illustrating an example operation of the audio signal reproduction system. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , an example of an infotainment system of, for example, a motor vehicle. The infotainment system includes a system for reproducing an audio signal  100 . The system for reproducing an audio signal  100  can include any number of tuners, such as three tuners  110 ,  120 ,  130 , which output as audio sources a first digital audio signal S A , a second digital audio signal S B , and a third digital audio signal S C . The system  100  can include an arithmetic unit  140  with a controller  141  and a digital filter  142 . The term “unit” is defined to include one or more executable modules, at least some of which may be embodied in a computer readable storage medium as executable instructions. Accordingly, as described herein, units are defined to be hardware executable by the processor, such as a computer readable storage medium that may include instructions executable by the processor, a field programmable gate array (FPGA), and/or various devices, components, circuits, gates, circuit boards, and the like that are executable, directed, and/or controlled for performance by a processor. 
     The controller  141  may include a processor. The processor may be one or more general processors, digital signal processors, application specific integrated circuits, field programmable gate arrays, digital circuits, analog circuits, combinations thereof, and/or other now known or later developed devices for analyzing and processing data. 
     The arithmetic unit  140  may also include memory. The memory may include a main memory, a static memory, and/or a dynamic memory. The memory may include, but is not limited to computer readable storage media, or machine readable media, such as various types of non-transitory volatile and non-volatile storage media, including but not limited to random access memory, read-only memory, programmable read-only memory, electrically programmable read-only memory, electrically erasable read-only memory, flash memory, magnetic tape or disk, optical media and the like. In one example, the memory includes a cache or random access memory for the processor. In addition or alternatively, the memory may be separate from the processor, such as a separate cache memory of a processor, the system memory, or other memory. The memory may also include (or be) an external storage device or database for storing data. Examples include a hard drive, compact disc (“CD”), digital video disc (“DVD”), memory card, memory stick, floppy disc, universal serial bus (“USB”) memory device, or any other device operative to store data. The memory is operable to store data and instructions executable by the processor. The functions, acts or tasks illustrated in the figures or described may be performed by or in connection with the programmed processor executing the instructions stored in the memory. The functions, acts or tasks may be independent of the particular type of instructions set, storage media, processor or processing strategy and may be performed by software, hardware, integrated circuits, firm-ware, micro-code and the like, operating alone or in combination. Likewise, processing strategies may include multiprocessing, multitasking, parallel processing and the like. 
     The filter  142  is configured, for example, as a DSP (Digital Signal Processor). Further, the system  100  can include, or be coupled with a first output circuit  180 , which can be connected to a first loudspeaker  810 . Further, the system  100  can include, or be coupled with a second output circuit  190 , which can be connected to a second loudspeaker  820 . Output circuit  180 ,  190  may include, for example, a digital-to-analog converter and an amplifier for amplifying and outputting an analog signal to loudspeaker  810 ,  820 . In other examples, any number of output circuits and loudspeakers may be included. 
     If the loudspeakers are arranged at a distance to one another, a surround sound is generated by the system  100  by means of spatialization. The surround sound can be generated, for example, by outputting the third audio signal S C  exclusively by first loudspeaker  810  and the second audio signal S B  exclusively by second loudspeaker  820 . In this case, the third audio signal S C  for user X at a listening position is heard exclusively from the direction “far left,” whereas the second audio signal S B  for user X is heard exclusively from the direction “far right.” The first audio signal S A  may be output through both loudspeakers  810 ,  820  at the same volume and therefore is perceived as being heard by user X from the middle M between the two loudspeakers  810 ,  820 . The middle M in this case designates a first location P A  in a virtual acoustic space  890 , “right” designates a second location P B  in acoustic space  890 , and “left” designates a third location P C  in acoustic space  890 . In addition, the user X designates a listening position in the virtual acoustic space. In other examples, any other locations and listening positions may be used. 
     The substantially simultaneous reproduction of the first audio signal S A , the second audio signal S B , and the third audio signal S C , as shown in  FIG. 1 , are provided for a selection mode in which user X would like to retrieve one of the audio signals S A , S B , S C . The tuners  110 ,  130  and  130  providing the first audio signal S A , the second audio signal S B , and the third audio signal S C , may receive and provide respective audio content, such as audio content transmitted from different radio stations. 
     In the example of  FIG. 1 , different radio stations identified as “Jam FM,” “Big FM,” or “1LIVE,” may be providing audio content as the first audio signal S A , the second audio signal S B , and the third audio signal S C . In an example, if user X does not know the transmitted program of the radio stations “Jam FM,” “Big FM,” or “1LIVE,” then the user can navigate through the substantially simultaneous, but spatially separated hearing of several radio stations. The navigation through the receivable radio stations can occur, for example, by receipt of a user input, such as by an input by means of a selection wheel. In the selection mode, the navigation through the radio stations can occur acoustically, so that user X, while driving the vehicle through dense traffic, need not look away from the street while acoustically sampling the different radio stations, and can concentrate completely on the traffic. 
     For the system to enter the selection mode, a user input received from user X may direct the system to leave, for example, a reproduction mode in which a radio station is reproduced as a stereo signal. Receipt of the input can be the result of, for example, the actuation of a button, touching of the touch screen, performing a gesture command, or by a voice command recognized by speech recognition, e.g., “search function.” With the start of the selection mode, the stereo reproduction of the reproduction mode is deactivated. 
     In the example of  FIG. 1 , three tuners  110 ,  120 ,  130  are provided, each of which outputs one digital audio signal S A , S B , S C . This digital audio signal S A , S B , S C  can be output, for example, as a mono signal or stereo signal or multichannel signal. In the selection mode, it can be advantageous to change the first audio signal S A  and respectively the second and third audio signal S B , S C  in each case to a mono signal, for example, by filtering only one channel of the particular stereo signal through filter  142 . In a virtual acoustic space  890 , the first audio signal S A  is separated acoustically by the filtering by filter  142  so as to be acoustically perceived by a user at the listening position as being positioned at a first location P A . In addition, the second audio signal S B  can be acoustically perceived by the user as being positioned at a second location P B , and the third audio signal S C  acoustically perceived by the user as being at a third location P C . In the example of  FIG. 1  the locations are indicated as “middle”-“right”-“left,” respectively. 
     The selection mode of the system shown in  FIG. 1  can be ended by user X when the user X selects the first audio signal S A  by a further user input. The user input is, for example, detected as a signal input based on a button actuation, touching of a touch screen, gesture command, or voice command input. At the end of the selection mode, the reproduction mode (not shown) of the system can be started by reproducing the selected first audio signal S A  as a multi-channel signal and fading out the second audio signal S B  and the third audio signal S C  such that the selected first audio signal S A  is played in the loudspeakers  810  and  820 . 
     In addition to the acoustic retrieval of the audio signal S A , in the example of  FIG. 1 , an optional visualization is shown by displaying an animated radio station list on a display  900 . The display  900  may be any form of visual display device, such as a liquid crystal display (LCD), an organic light emitting diode (OLED), a flat panel display, a solid state display, a cathode ray tube (CRT), a projector, or other now known or later developed display device for outputting determined information. The display  900  may act as an interface for the user to see the functioning of the controller  141 , or specifically as an interface with the software stored in the memory. The system may also include an input device configured to allow a user to interact with any of the components of system. The input device may be a keypad, a keyboard, or a cursor control device, such as a mouse, or a joystick, touch screen display, remote control or any other device operative to interact with the system. 
     The radio station list is generated by controller  141 . In the example of  FIG. 1 , a first text string V A  “Big FM” associated with the first audio signal S A  is shown as the first visual information item V A , a second text string V B  “1LIVE” associated with the second audio signal S B  as the second visual information item V B , and a third text string V C  “Jam FM” associated with the third audio signal S C  as the third visual information item V C . 
     The visual arrangement of the first visual information item V A , the second visual information item V B , and the third visual information item V C  can correspond to an acoustic arrangement of the first location P A  of the first audio signal S A , the second location P B  of the second audio signal S B , and the third location P C  of the third audio signal S C  in the virtual acoustic space  890 . Thus, in the  FIG. 1 , the third location P C  is arranged to the left of first location P A  and the second location P B  to the right of first location P A  in the virtual acoustic space  890  and, accordingly, the third visual information item V C  is arranged to the left of the first visual information item V A  and the second visual information item V B  to the right of the first visual information item V A  on display  900 . 
     In addition, filter  142  can be configured to influence additional audio properties of the first audio signal S A , the second audio signal S B , and the third audio signal S C . For example, the frequency response of the audio signals S A , S B , S C  can be changed by the filtering. In addition, filter  142  can be configured to selectively boost or cut the frequency ranges in the first audio signal S A  and/or in the second audio signal S B  and/or in the third audio signal S C . For example, in  FIG. 1 , a frequency response of the first audio signal S A , which is available directly for selection, is not changed by the filter  141 . In contrast, a frequency bandwidth of the second audio signal S B  and of the third audio signal S C  is changed by significantly attenuating, for example, the bass and/or treble of the second audio signal S B  and of the third audio signal S C  due to a high-pass filter or bandpass filter being included in the filter  141 . 
     Another example of an infotainment system is shown schematically in  FIGS. 2   a  and  2   b . In this example, visual image rendering applications, such as Album art applications make it possible to look at visual information items or visual images, such as music covers V A , V B , V C , V D , V E , V F , V G  and to page through these visual information items to select corresponding audio content. The visual information items and/or the audio content may be stored in a location, such as a database included in, or accessible by, the infotainment system. If a user knows this database very well and can recognize and match the visual information items or images, such as covers V A , V B , V C , V D , V E , V F , V G  with associated music capable of being output by the infotainment system, this could be sufficient for a user to select and retrieve desired music from the database. If, on the other hand, a user is unable to select audio content based on corresponding visual images, for example a user who does not know the covers corresponding to music content, it could be more helpful to preview the audio content acoustically as well, and to make a selection of audio content based on the audible sounds instead of only the visual images, such as graphic information V A , V B , V C , V D , V E , V F , V G . The audio sounds may include, for example, audio titles of the audio content. In  FIG. 1 , the audio signal S A  associated with the current cover image V A  is acoustically perceived at the listening position as being played frontally before user X by a method of the virtual acoustics, and, in this case, the audio signals S B , S C  of adjacent cover images V B , V C  are acoustically perceived or heard as being spatially farther away/closer and can thereby be moved three dimensionally into the depth of the virtual acoustic space  890 . As a result, a more pleasant acoustic mixture of the audio signal S A , S B , S C  can be achieved and more than three audio signals can be played simultaneously. In addition, the system allows a user the capability to browse or page through audio content and corresponding visual information items, while at the same time having the acoustically perceived location of the audio content move three dimensionally to be closer or farther away from the listening location, as the corresponding visual information items move three dimensionally closer or farther away on the display. 
     A system for reproducing an audio signal  200  included in the infotainment system in the example of  FIG. 2   a  includes a filter  242 , which can be used in connection with four loudspeakers  810 ,  820 ,  830 ,  840  of, for example, a motor vehicle. The system  200  can include a controller, and be in communication with a memory  300  via an interface, for example, a USB interface or a SATA interface. For purposes of brevity, discussion of similar features and functionality described with regard to the system for reproducing audio signals  100  of  FIG. 1  will be minimized. Entries DE A  to DE G  of a database are stored in memory  300 . Each entry DE A , DE B , DE C , DE D , DE E , DE F , DE G  includes a file with an audio signal S A , S B , S C , S D , S E , S F , S G . In addition, a visual information item V A , V B , V C , V D , V E , V F , V G , associated with each audio signal S A , S B , S C , S D , S E , S F , S G , can be stored. In one example, the audio signal S A , S B , S C , S D , S E , S F , S G  may be audio content in the form of music, and the visual information item may be in the form of a cover image V A , V B , V C , V D , V E , V F , V G , which are all shown on display  900  in the example of  FIG. 2   a . In this case, the illustration in  FIG. 2   a  is greatly simplified since a much greater number of entries can be present in the database. For example, in the case of music audio content, a plurality of titles with one audio file each is stored for an album of a cover V A , V B , V C , V D , V E , V F , V G . 
     In the example of  FIGS. 2   a  and  2   b , a selection mode for retrieving one of the audio signals S A , S B , S C , S D , S E , S F , S G  is started based on a first user input of user X that is received as an input signal by the system for reproducing an audio signal  200 . For example, user X can operate an associated button (not shown) on display  900  configured as a touch screen. In the selection mode, audio signals S A , S B , S C , S D , S E , S F , S G , associated with the visual information items, such as cover images V A , V B , V C , V D , V E , V F , V G , can be reproduced substantially simultaneously. Moreover, the visual information items, such as cover images V A , V B , V C , V D , V E , V F , V G  can be displayed substantially simultaneously on touch screen  900 . 
     The audio signals S A , S B , S C , S D , S E , S F , S G  can be filtered in the selection mode by filter  242  in such a way that, as shown schematically in  FIG. 2   b , the audio signals S A , S B , S C , S D , S E , S F , S G  are separated acoustically to be perceived as being at different locations P A , P B , P C , P D , P E , P F , P G  in a virtual acoustic space  890 . A plan view of the virtual acoustic space  890  is shown schematically in  FIG. 2   b . Filter  242  may include a number of filter blocks. Each of the filter blocks can filter an audio signal S A , S B , S C , S D , S E , S F , S G . Alternatively, the filter  242  may be a number of different separate filters having filter blocks filtering corresponding audio signal S A , S B ,  S   C , S D , S E , S F , S G . A filter coefficient set, which is associated with a respective one of the locations P A , P B , P C , P D , P E , P F , P G  in the virtual acoustic space  890 , can be selectively loaded in each filter block in accordance with the operation of the system. For example, in the selection mode, filter coefficients may be loaded in the filter blocks to create acoustically perceived audio outputs at the different locations, whereas in a continuous playback mode or reproduction mode, filter coefficients may be loaded in the filter blocks to output audio content of a multi-channel audio signal to the loudspeakers to create, for example, a stereo or surround sound listening experience at the listening position. The output signals of the filter blocks can be added, such as by superposition, to form output signals to drive each loudspeaker  810 ,  820 ,  830 ,  840 . In other examples, each filter block may drive a separate loudspeaker. 
     The acoustically perceived location P A , P B , P C , P D , P E , P F , P G  of the respective audio signal S A , S B ,  S   C , S D , S E , S F , S G  in virtual acoustic space  890  corresponds thereby to the position of the associated visual information items, such as cover image V A , V B , V C , V D , V E , V F , V G  on touch screen  900 . The arrangement of the acoustically perceived locations P A , P B , P C , P D , P E , P F , P G  of the audio signals S A , S B , S C , S D , S E , S F , S G  in virtual space  890  and accordingly the arrangement of the visual information items, such as cover images V A , V B , V C , V D , V E , V F , V G  on touch screen  900  can be changed by means of an input by user X, for example, by moving a finger across touch screen  900 . For example, if the finger slides from right to left across touch screen  900 , the cover V G  is faded out far left, a new cover is faded in on the right (not shown), and instead of the cover V A , the cover V B  is moved to the foreground (indicated by an arrow in  FIG. 2   a ). 
     The filter coefficient sets in the filter blocks are correspondingly re-loaded such that, the audio signal S G  is faded out, a new audio signal associated with the new cover is faded in (not shown), and instead of the audio signal S A , the audio signal S B  is acoustically positioned three dimensionally in the foreground (indicated by an arrow) of the virtual acoustic space  890 . 
     In addition to the three dimensional virtual placement in the virtual acoustic space  890 , each of the audio signals S A , S B , S C , S D , S E , S F , S G  can be reproduced at a different volume in accordance with the desired acoustically perceived location. For example, in the situation of  FIG. 2   b , the first audio signal S A  at location P A  is reproduced at a higher volume than the other audio signals S B , S C , S D , S E , S F , S G . The selection mode is ended at a time when user X selects the cover image V A  on touch screen  900  or, when a time counter times out after a predetermined time of being in the selection mode, for example, a 20 second time counter times out. 
     At the end of the selection mode, the display on touch screen  900  of  FIG. 2   a  can be changed. For example, in the case of audio content that is music, and a corresponding visual information item, such as the cover image V A , the cover image V A  can be moved to another position and the titles of the album may be listed, as is shown schematically, for example, in  FIG. 3   a  for a cover  980 . In addition, in the example of  FIGS. 2   a  and  2   b , the associated audio signal S A  can be reproduced in the reproduction mode as a stereo signal or multichannel signal to drive the loudspeakers, and all other audio signals S B , S C , S D , S E , S E , S G  can be faded out. 
     A further example of an infotainment system is shown schematically in  FIGS. 3   a  and  3   b . For purposes of brevity, discussion of similar features and functionality described with regard to the system for reproducing audio signals  100  and  200  of  FIGS. 1 and 2  will be minimized. In  FIG. 3 , it is possible in the selection mode during paging through the visual information items, such as titles V A , V B , V C , V D , V E , to begin playing the audio signal S A  corresponding to the title V A  “Low tide,” currently shown in the foreground, at a normal volume. Audio signals S B , S C , S D , S E  of the other visual information items, such as titles V B , V C , V D , V E  may be mixed in to the audio output of the loudspeakers more quietly so as to be acoustically perceived to be before and behind. For example, when the titles V A , V B , V C , V D , V E  are to be paged through from left to right, the audio signal S C  of the corresponding left-sided title V C  “Afternoon” can be reproduced exclusively on left loudspeaker  810  and the audio signal S B  of the right-sided title V B  “Call your name” can be exclusively reproduced on right loudspeaker  820 . In the example of  FIGS. 3   a  and  3   b , however, the audio signals S A , S B , S C , S D , S E  are arranged in an acoustically perceived staggered alignment in the virtual acoustic space  890  and thereby correspond to the visually perceived staggered arrangement of the titles in  FIG. 3   a . It may also be possible by appropriate filtering of the frequency response to arrange the locations P A  to P E  at a different acoustically perceived height level in the acoustic space, for example, with an increasing/decreasing height level. 
     A process flow in the form of a schematic flow diagram with example operational process steps  1  to  8  of the system for reproducing audio signals is shown schematically in  FIG. 4 . Here, the flow diagram is simplified for easier comprehension. In a first process step  1 , a selection mode SM is started and in a next second step  2 , the audio signals S A , S B , S C  are filtered in such a way that the audio signals S A , S B , S C  are separated acoustically in a virtual acoustic space  890 , so that they are heard, or perceived, by the user at locations P A , P B , P C  in virtual acoustic space  890  at a distance from one another. 
     In a third step  3 , a user input “Input 1 ” is detected. The user input in this case, for example, is made by selection of the audio signal S A  for continuous play, for example, by touching the associated title V A  on a touch screen  900 . If there is a user input, the selection mode SM is ended in a sixth step  6 , then the filter coefficients for reproducing the selected audio signal S A  are changed in the filter blocks in step  7 , and the selected audio signal S A  is reproduced continuously in an eighth step  8 . 
     If, in contrast, the user input “Input 1 ” does not occur in the third step  3 , in a fourth step  4  another user input “Input 2 ” is detected. The additional user input is, for example, a moving of a visual information item, such as a cover on touch screen  900  by a sliding movement of the finger. If the further user input is detected, the filter coefficients in the filter blocks are correspondingly changed in the fifth step  5 , so that in the next step  2  the specific audio signal S A , S B , S C  is heard at moved acoustically perceived locations in virtual space  890  or faded out and/or a new audio signal is faded in. If no further user input occurs in the fourth step  4 , the filtering occurs unchanged with the previous filter coefficients. 
     The invention is not limited to the shown embodiment variants in  FIGS. 1 through 4 . For example, it is possible to use other signal sources, like CD-player or aux-in etc as audio sources for audio signals. It is also possible to use a different or settable number of audio signals in the virtual acoustic space. The selection mode can be used, for example, for mobile audio devices with headphones, for smartphones, for personal computers or for tablets. The functionality of the exemplary embodiments can be used especially advantageously for an infotainment system of a motor vehicle. 
     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents. 
     LIST OF REFERENCE CHARACTERS 
       
     
       
         
           
               
               
             
               
                   
               
             
            
               
                 100, 200 
                 circuit, infotainment system 
               
               
                 110, 120, 130 
                 audio source, receiver 
               
               
                 140 
                 arithmetic unit 
               
               
                 141 
                 controller, μC 
               
               
                 142, 242 
                 filter, DSP 
               
               
                 180, 190 
                 output circuit 
               
               
                 810, 820, 830, 840 
                 sound transducer, loudspeaker 
               
               
                 890 
                 virtual acoustic space 
               
               
                 900 
                 display, touch screen 
               
               
                 A, B, C, D, E, F, G 
                 item, assignment 
               
               
                 DE A , DE B , DE C , DE D , DE E , DE F , 
                 database entry 
               
               
                 DE G   
               
               
                 M 
                 middle 
               
               
                 P A , P B , P C , P D , P E , P F , P G   
                 location in the virtual acoustic space 
               
               
                 S A , S B , S C , S D , S E , S F , S G   
                 audio signal 
               
               
                 SM 
                 selection mode 
               
               
                 V A , V B , V C , V D , V E , V F , V G   
                 visual information, cover 
               
               
                 X 
                 user, listener