DE4125893A1 - Audio reproduction system for motor vehicle - has multiple loudspeakersoperated to compensate for insufficiencies of acoustics insidevehicle - Google Patents

Abstract

A pair of primary loudspeakers (9,10) is installed at the front of the passenger compartment and a further pair (17,19) at the rear. Secondary speakers (11,12) are positioned on either side of the front two seats (20,21). A second pair (14,15) can be located adjacent to the rear seats. A further improvement may be obtained by speakers (8,18) set in the centre positions at the front and rear. The secondary loudspeakers may be operated with phase delays to provide optimum sound reproduction. ADVANTAGE - Achieves concert hall reproduction quality.

Description

The invention relates to an arrangement for Preparation of the playback acoustics in Motor vehicle interiors.

It is known to generate spatially extended sound events in motor vehicles indoors using common arrangements by means of at least two loudspeakers Filter, phase shift and Delay circuits are attempted unnatural overall acoustics of motor vehicles to upgrade and improve interiors (see for example DE-PS 30 19 099, DE-PS 33 11 531, DE-PS 28 51 876, FR-PS 25 99 581, GB-PS 15 55 409, US-PS 48 66 776, US-PS 47 69 843).

It is primarily attempted through various Left-right signal mixing the vehicle occupants in the usual seating positions possible complete sound reinforcement situation, starting out at least two pairs of stereo speakers, one pair each in the front and one is arranged in the rear section to convey. The purpose of this is that both sound signals components of the stereo sound signal to be reproduced as unaffected by z. B. reflections and Attenuation on objects from several Directions, the listening vehicle occupant to reach.  

It is also known in addition to the stereo speaker pairs in the front and Rear end of the motor vehicle interior too

• a) midway between the pairs of stereo speakers,
• b) laterally in the doors and
• c) in the front seats to the rear aligned to arrange additional speaker systems.

The loudspeaker systems arranged according to a) are with a specially made from the stereo sound signal components

• a1) mixed or
• a2) Delayed sound signal fed.

In particular case a1) does not result in live or concert hall-typical acoustics, e.g. B. at a musical performance on a stage consequently the left and right side standing sound events later at one arrive in the audience, as central sound events.

Mixing (case a2)) seems more sensible here, but is not a mature solution, to include acoustic leaks in stereo listening events to reduce. (Under an "acoustic leak" one understands the reduction of the reproduction volume when a person is at a distance of three meters, with respect to the connection axis of a pair of speakers, removed in the middle stops and outside the main emission direction the loudspeaker is sonicated with reduced intensity, with the two speakers spaced twelve apart Radiating meters towards the person are arranged).  

Furthermore, can be used for motor vehicle interiors typical acoustic leaks that u. a. by padded seats and elongated interior dimensions are conditional, not suitable by means of Fix arrangement according to c). This occurs frequently from the natural as well as from the intake side hearing different from certain stereo sound images events that indicate an influence or "Shift" of the two-channel sound signals from the usual runtime stereophony towards intensity based on stereophony. These out of touch Hearing events can be done with the known phenomena of Stereo base width reduction from stereophonic monophonic listening events and the head-related stereophonic sound system situation as is the "in-the-head localization" represents, are compared.

The inventor of the present invention has stated asked that the described, subjectively narrowed perceived, unrealistic stereo sound images already in the vehicle interior an opening of windows and / or one Sunroof are to be improved. Doing so subjectively "free" unfolded listening events. One draws to illustrate the example improvement achieved by opening a window Listening situation the conditions with the headphones sound for comparison, this corresponds to Listening situation with the windows open the open and the one with the windows closed, the closed headphone principle. Generally corresponds however, due to the overall sound situation hearing event generated in motor vehicle interiors, considered frequency-dependent, rather that of a damping, near-field sound systems with resonance and standing waves  of headphones than the ones you see on the Loudspeaker sound reinforcement in a low reflection or resounding living space or concert hall.

Consequently, in previous sound systems windings for motor vehicle cabins exactly this o.g. acoustic framework of the interior completely ignored which specifically in the relatively small motor vehicle interior dimensions can be found, with what for Speech and music playback unusual reflections on the windows, standing waves mostly in the middle frequency or listening range, in contrast to the standing waves in the lower frequency range larger living space dimensions. Let alone that in motor vehicle interiors typical multiple from different directions reflections (Hall) reach the vehicle occupant, which for sound-technically good living room acoustics as well as concert hall atmosphere are relevant.

It is also in motor vehicle interiors a relatively high level of sound insulation a wider listening frequency range, due to seat cushions as well as measures against high motor vehicle interior noise Immission values.

Finally arise in the motor vehicle interior Sound signal compatibility problems. Common audio recording methods today are based on the specification of a diffuse field equalization of u. a. Recording microphones as well associated equalized playback systems (Headphones and speakers). While at the Stereo headphone sound with artificial head  created sound carriers in advance Compatibility considerations (including possibly Subsequent equalization) on tools a sound engineer or the manufacturer belong to home hi-fi devices incomprehensible this essential Requirements for a qualitative high quality audio signal transmission (playback) so far with the motor vehicle interior Sound is neglected, and this, though there are clear indications that Motor vehicle interiors are highly soundproofed (the "dry" reproduction acoustics produced thereby correlates with the sound propagation in anechoic rooms and / or the free field equalization and a. with stereo headphones) and insofar as the static, pseudo-local PA characteristics of headphones are very similar.

The overall problem is exacerbated by the Presence of one in its (specific) loudness relatively strongly fluctuating noise immissions enlarged in motor vehicle interiors, such as from the engine, the wheels or Tires as well as headwind run out.

The problems mentioned are in the above Prior art publications do not considered, which is why this is also no suggestion to eliminate the associated disadvantages can be seen.

There are also a variety of dissertations Publications and patent applications on the subject of "electrical simulation of acoustics of rooms using sound engineering methods "  become known which is the development a wide range of products from today available, mostly digital, So-called "effect processors" (including for Hall and echo generation) for different Areas of application. For example are often found in semi-professional consoles and synthesizers are affordable preset reverb modules (including a given echo or chorus effect- Generation) built in to compact musicians easy and quick generation of the desired Final sound product "Sound with room acoustics" to enable. Such preset reverb modules don't even take the third place Cigarette boxes. This is suitable this technique in specially programmed State (Hall programs) also for Areas of application more distant, such as subsequent reverberation of sound signals in Motor vehicle interiors.

A scientific insight into the subject areas of spatial hearing, psychoacoustics, Grant electro-acoustics and recording studio technology J. BLAUERT (Spatial Hearing - The Psychophysiks of Human Sound Localization, The MIT Press Cambridge / Massachusetts / London, England, 1983), E. ZWICKER and M. ZOLLNER (Electroacoustics, Springer-Verlag, 2nd edition, Berlin / Heidelberg / New York / London / Paris / Tokyo, 1987) and M. DICKREITER (Handbuch des Tonstudiotechnik, Volume 1, 5th edition, K.G. Saur Verlag KG Munich / New York / London / Oxford / Paris, 1987).  

The invention is based on the object Create procedures of the type in question, that's an almost natural as well as distortion poor sound signal playback situation, especially with the specification of concert hall acoustics, in Allows motor vehicle interiors.

This task is solved by the characteristic Features of claim 1.

Advantageous developments of the invention are listed in the subclaims.

It is advantageous from one psychoacoustic equalization, which, when sounding people through Loudspeakers in motor vehicle interiors, eliminates those linear distortions that lead to directional hearing event shift (@ 1) and loudness-dependent falsification (@ 2) to lead. For (@ 1) according to the invention via measurements received transducer system transmission dimensions empirically checked for comb filter structures as well as their direction-specific level drops and / or resonances as a function of level held by the frequency. For (@ 2) is under Based on a common recording-playback- Equalization, e.g. B. Diffuse field equalization (this represents a flat measure of transmission), a ear-related sound image compatibility built up, which on subjective test subjects' hearing tests based and / or the human factor includes binaural loudness perception. Deviations from a reference hearing event become frequency-dependent grasped in their intensity. these can  analog to the flat transfer dimension of Speakers or to the sound image compatible Diffuse field equalization of headphones considerably fail because in motor vehicle interiors Sound propagation conditions more common Monitoring room with a defined amount of reverb (corresponds to the test / measuring medium for Diffuse field transfer measurements) not are available.

One to counteract (@ 1) and (@ 2) Correction equalization, which is obtained from the u. a. Level data lists is determined (frequency dependent leveling with superposition), therefore causes a directional and sound-neutral reproduction.

In this context there is also a Process for the measurement of situation and sound distortion Defects in sound events in motor vehicles interiors, which predominantly on spectral changes in the broadband via electroacoustic device to be reproduced Stereo sound signals advantageous. Contribute to this

• a) Near field measurements a few centimeters apart in front of the respective speakers,
• b) Far field measurements during listening and / or residence typical locations of motor vehicle occupants and
• c) the use of broadband as well as highly dynamic working microphones (for a)) and artificial head Microphones (for b)).

It is advantageous if the spectrum-changing data of sound events the following points should be noted:

• - Realization of frequency-dependent-selective graduated bandpass measurements using an extension of the standard measuring frequency sequence a quarter third according to DIN 45 401 stepped logarithmic corner frequency scale, which limit the measuring tape passes as well as secondly, at least the frequency-dependent Resolving power of the geometric Provides ratio twelfth root of two.
• - Pink noise is used as the measurement signal.
• - The speaker systems to be examined are with the measurement signal and a sound pressure controlled from 94 dBSPL according to DIN 45 580.
• - The determination of transfer dimensions takes place in a frequency dependent Level investigation range of at least 20 Hz to 20 kHz with a level test accuracy less than 0.5 dB.
• - The determination of the transfer dimension used microphone-like device has a frequency range of 20 Hz up to 20 kHz over an accuracy of sound conversion and transmission properties of less plus / minus 0.5 dB.
• - The one for the microphone-like device used transducer capsules have a Dynamics greater than 58 dB.

It is also an advantage if

• - The near and far field measurements of the Sound events across a variety of various sound signal reproduction systems that designed for certain motor vehicle interiors  were made
• - the near and far field measurements on sound signal Playback systems across a variety of different types of motor vehicle (interior) be made
• - The data collected from the local and Far field measurements of a statistical, selective depending on frequency Subsequent level inspection and
• - split into near and far field measurements medium data lists and / or graphical Representations from the frequency-dependent selective level data collected can be calculated.

Furthermore, an upgrade is advantageous the unnatural or unusual acoustic Conditions in motor vehicle interiors intended. This can be Listening experiments achieve what room simulations for an upgrade of the sound signal reproduction Provide conditions in motor vehicle interiors. In doing so, subjective sound image parameters, like reverberation transparency, presented spatial Width / depth effect etc., especially considered.

It is also advantageous that for implementation acoustic conditions close to the concert hall in Motor vehicle interiors using listening tests determine which basic Room reflection patterns or hall simulations (suitable parameters, such as the room size, shape and design are to be found) and others generated by audio signal delays Effects such as B. the chorus effect (simulates the Beats between the played instruments  a string orchestra), for certain Language and music performances are suitable.

It is also advantageous if used analog amplifier, analog-digital (A / D-) and digital-to-analog converter (D / A converter) as well as the chain of digital signal processing regarding the quality of the electrical transmission behaving preferably at least the following Meet requirements:

• - General useful signal-to-noise ratio <96 dB; including a gain factor of 40 dB this results for the analog amplifier Useful signal-to-noise ratio of at least 136 dB;
• - dynamics greater than 60 dB,
• - linear distortions (max. deviation) less than 0.5 dB and
• - nonlinear distortions less than 0.1%,
• - Larger according to an A / D and D / A conversion 16 bit.

It is also advantageous if one dependent on the motor vehicle interior noise, loudness-dependent that can be switched on and off additively Playback sound image equalization is performed hence those frequency ranges of the broadband reproduced sound signal preferably raised by strikingly noisy Frequency sections of the motor vehicle interior Noise is masked and / or hidden. For this purpose, it is also advantageous that in addition to the variably adjustable playback level one can be switched on and off by the motor vehicle noise-dependent, self-regulating Level reproduction is made which when raising and lowering the level  loudness-dependent noise perception of the People considered. The Readjustment time (or the time constant of a dynamic amplifier) and the ratio between playback volume and noise realized variably adjustable.

The audio signal is expediently processed digitally as this z. B. for digital broadcasting is provided.

It is also advantageous that the invention according to the planned empirical investigation, Revision or selection of data, as well Evaluation of hearing events, hearing-related Parameters to which u. a. the frequency dependent Loudness sensation, the concealment effect and the directional perception count, are taken into account.

Finally, it is advantageous that, in addition to the Equalization of sound signals, a refresh or Replication of the overtone content is made, at z. B. for a subsequent transfer area increase from band limited via Radio receiver section (frequency modulation) reproduced stereo sound signals.

The advantages achievable with the aid of the invention compared to the prior art at Subject sound in motor vehicle interiors consist in particular in that

• a) minimized tone color distortions,
• b) independent of the speaker set-up Misdirection of sound events avoided,
• c) acoustic leaks without neglecting the stereo base width created on the recording side  of sound preserves, reduced,
• d) the "dry", static-like headphones perceivable sound properties of several speakers in motor vehicles interiors through variably configurable, acoustic conditions close to the concert hall replaced and
• e) therefore typical for the motor vehicle interior Attenuation, resonances, reflections and standing Waves are suppressed and consequently no longer are audible.

The invention is based on the Drawing will be explained in more detail; in this show:

Fig. 1 shows a motor vehicle interior shown schematically with the present invention arranged and driven loudspeaker systems,

Fig. 2 shows a psychoacoustic correction equalization according to the invention for certain loudspeaker systems for generating a directional and sound image-neutral reproduction of hearing events and

Fig. 3 shows a certain spatial reflection pattern with temporally and energetically different initial reflection distribution.

The outlines of a motor vehicle 6 are shown schematically in FIG. 1. The motor vehicle 6 has a motor vehicle interior 7 , which is provided with a frequently encountered, standardized positioning of primary loudspeaker systems 9 , 10 and 17 , 19 in the front and rear consoles near the window.

In addition, at least in the area of the two front seats 20 and 21, side loudspeaker systems 11 and 12 are installed laterally in the doors, by means of which, according to the invention, separately generated room reflection patterns are emitted to enhance the acoustic conditions in the interior 7 . The exact lateral arrangement of the secondary loudspeaker systems 11 , 12 , which is essential in this context in accordance with the invention, is determined from hearing comparison examinations to be carried out for this purpose, in order to determine the spatial quality of hearing events, which is based on the knowledge of the relevance of laterally incident space reflection patterns (cf. good concert hall acoustics at the Stage-occurring, reverb-free musical sound propagation towards the auditorium). The aim is to arrange the loudspeaker systems 11 and 12 in the frontal plane of vehicle occupants in the frontal plane, depending on the position of the person's head, depending on the physical size of a person. The reference value is the axis between the left and right ear canals.

The basic arrangement (solid lines) of loudspeaker systems 9 , 10 , 11 , 12 , 17 , 19 shown in FIG. 1 is in particular for two-seater motor vehicles and / or the predominant use of motor vehicles with a motor vehicle driver and passenger in the front seats 20 and 21 suitable, with an expansion of the arrangement for the case that people are also positioned on the rear seats 22 and 23 is taken into account in dashed lines. Adequate to the front seats 20 , 21 , therefore, the lateral sound reinforcement of the rear seats 22 , 23 is carried out with room reflection patterns ( 26 , 31 ) by means of a second pair of secondary loudspeaker systems 14 , 15 . There is a "reverse" stage effect typical of rear seat sound systems, since the sound component of the loudspeaker systems 17 , 19 covers that of the loudspeakers 9 , 10 when the front-rear fader position is balanced. Conversely, for front-seated listeners, the sound component of the front speakers 9 , 10 predominates.

Finding the optimal side Speaker system arrangement through a special Examination procedure will be closer below described.

First, however, the invention Elimination of acoustic leaks will be discussed in more detail.

In the interior of the motor vehicle 7 there is an unusual acoustics that differs from the concert hall atmosphere that is often sought. This is based e.g. B. on effectively sound-absorbing obstacles in the small interior 7 in terms of dimensions ( Fig. 1). In order to counter such objects which prevent natural free sound propagation in the present sound reinforcement problem, auxiliary / secondary sound sources are provided in / on the front and / or rear console in the form of loudspeaker systems 8 , 18 . The stereo base width of sound preserves created on the recording side should not be reduced during the sound reinforcement of motor vehicle occupants, which places special demands on the sound signal generation or processing electronics which control auxiliary loudspeaker systems. It turned out to be of little use to emit mono sum signals, which are mixed together from the stereo sound signal components, via the auxiliary loudspeaker systems 8 , 18 . For the desired improvement in sound reproduction in motor vehicle interiors, it was found that it is much more expedient to emit a mixed signal created specifically from these sound signal components via auxiliary loudspeaker systems 8 and 18 . The mixed signal is made of variable in the delay time and level-adjustable, left and right sound signal components in the circuit 1 , the z. B. consists of an analog adding amplifier and a digitally implemented delay element, electrically mixed together so that the chorus effect corresponding beats between the speaker systems 9 , 8 and 10 arise. The thus generated, variable, delayed by a few millisecond sound signal components are then again via a, for. B. after a sine or triangular function, voltage-controlled delay element 4 , delay time-shortened and / or lengthened continuously by the amount of a few milliseconds. The resulting auxiliary sound event 8 supports the stereo speakers emitted by the primary loudspeakers 9 , 10 (usual main emission direction of sound events to the front approx. 90 degrees), in particular for sound-technically mixed mono-centered original stereo signals such that the acoustic leak if z. B. a person at a distance of about 40 centimeters to the side of the loudspeaker 9 (outside the main emission direction from the loudspeaker 10 ) is unevenly sonicated, eliminated and the stereo base width is not reduced, but rather widened. In addition, the stereophonic performances to be heard are improved in terms of their volume, which includes the perceived number of musical instruments played. The elimination of the acoustic leak and the improvement of the volume are controlled via the mixing ratio of the sound event emitted via the loudspeakers 9 , 10 and 8 and the selected delay times or the delay time ranges (circuits 1 and 4 ).

In addition, loudspeaker systems 14 , 16 , which emit additional room reflection patterns from the motor vehicle interior ceiling, act in this context. In this way, for example, the reflections of the concert hall ceiling for the seating positions at 20 to 23 , which typically occur later and arrive later in comparison to the lateral reflections of a concert hall, are separated from the speakers 11 , 12 , 14 , 15 , for test subjects in the interior 7 by simulates sound radiation via the ceiling speakers 13 and 16 .

Below is the sound signal according to the invention supply of the speaker systems discussed in more detail will.

The sound signal of a conventional playback device (e.g. car CD player or casseiver) is via a basic supply device with left-right volume-controlled sound signal inputs 32 , 33 from control amplifiers 35 , 36 with fader function (front-rear volume control) and with left-right channel-wise separate, preferably variable, psychoacoustic frequency response equalization to produce a direction and sound pattern neutrality leads to:

• - Switchable, with regard to the delay time controllable elements with a unique sound signal delay (see multiple reflection generator 24 to 26 , for generating Hall), which are followed by power amplifiers 3 , 5 , 27 , 29 , to which the loudspeakers 9 , 10 , 17 and 19 are connected, via which the stereo sound signals are emitted at the front and rear;
• - Separately switchable, with respect to the multiple delays variably adjustable room reflection pattern / Hall simulators with z. B. integrated power amplifiers 2 , 24 , 25 , 26 , 30 , 31 to control the secondary speaker systems 11 to 16 to reproduce the room reflection pattern (secondary sound signals) laterally in the frontal plane of 20 to 23 people seated;
• - Switchable, with respect to the delay time adjustable elements with one-time audio signal delays and mixing amplifiers 1 , 34 , ie volume-adjustable left-right audio signal adders;
• - Switchable, with respect to the variable after a certain time function, variable delay time, adjustable delay elements 4 , 28 for generating the chorus effect with z. B. integrated power amplifiers with which the auxiliary speaker systems 8 , 18 are controlled.

A distinction is made between the basic concept (lateral secondary loudspeakers in the front half of motor vehicle interior 7 and the expanded concept (additional, lateral secondary loudspeaker systems also in the rear half as well as on the interior ceiling and front and possibly rear auxiliary loudspeakers). For both Variants separately are each self-regulating coupled

• a) the elements 2 , 4 , 24 , 30 with the elements 3 , 5 , 27 , 29 , that is, depending on whether, for example by means of the elements 3 and / or 27, a predetermined, individual sound signal delay for playback via the speakers 10 and / or 17 is created (e.g. a person sitting laterally in 7 to 20 , viewed in time, via the loudspeaker 10 the sound event earlier than from 9 ), the room reflection patterns to be generated of the elements 24 , 30 including room acoustics Considerations with a delay, and
• b) expanded to a), the elements 2 , 4 , 24 , 25 , 26 , 28 , 30 , 31 in their mode of operation with the elements 3 , 5 , 27 , 29 .

Accordingly, all created room simulation programs, which ensure a preferably concert hall acoustics in the motor vehicle interior 7 , depending on the original sound signal, ie e.g. voice signal, light music, classical music, as well as with reference to the seating positions of people. The acoustic conditions (resonances, damping, etc.) of the motor vehicle interior 7 must also be taken into account.

The design of the room simulation in the vehicle interior space will now be described in more detail.

Due to the high level of complexity, the functions of the individual delay elements 2 , 3 , 4 , 5 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , which are essential for the space simulation generation method according to the invention, are to be shown schematically as follows; with reference to Fig. 1 means:

• I) a switchable, single (simple) sound signal delay T, which is provided, for example, in delay element 3 , corresponds to 1 × T _FL , "FL" standing for the supply of loudspeaker 10 in the front console on the left; The same applies to FR = front-right, HL = rear-left and HR = rear-right;
• II) a switchable, variably adjustable multiple delay m × T, which is provided, for example, in the delay element 24 , corresponds to m _A × T _AL , "AL" representing the spatial reflection pattern A on the left front part of FIG. 7 with m-fold reflections at A, which are reproduced by the loudspeaker 11 ; The same applies to BR = spatial reflection pattern B for front-right, CL = spatial reflection pattern C for rear-left and DL = spatial reflection pattern D for rear-right;
• III) corresponding to II), the elements 2 , 25 generate a multiple signal delay m _E × T _OM and m _F × T _OM , where, in addition to the separately generated spatial reflection patterns E and F, the special appearance position and playback situation in the top center (ceiling of the Motor vehicle interior 7 is correspondingly taken into account with reflection patterns based on the dome or ceiling of a concert hall; the same can also be carried out in the center of the motor vehicle console, e.g. between driver 20 and passenger 21 (see floor reflections in the concert hall);
• IV) corresponding to I), the elements 4 , 28 generate a single _{signal delay} T _FM∼ and T _HM∼ (FM = front center, HM = rear center, "∼" = after a certain function variable sound signal delay), which is for example as here is temporally, continuously variable delay elements, the delay time z. B. moves up and down by a few hundred microseconds around the mean five milliseconds after a sine or triangle function; this creates the simulation of a chorus effect (beats between several tonally slightly inconsistent sound signal sources).

To simplify the technical effort, the elements 24 , 26 and 2 , 25 and 30 , 31 are preferably combined in one delay element each. Otherwise, these elements are regulated separately according to volume.

Conversely, sound signal left-right mixes with variable intensity are also provided. For example, right audio signal components that feed the circuit 30 and are emitted several times delayed via the loudspeaker system 12 are also mixed in using the separately operating multiple delay element 24 , reduced volume on the left and processed in accordance with the function of the circuit 24 , reproduced via the loudspeaker 11 . This prevents shadowing effects that often occur on stereo sound signal components.

Given that as ideal for the automotive interior Targeted concert hall acoustics are those above discussed aspects of the invention in their Simulation quality using artificial head space impulse responses checked. The basis for this are given acoustic ones Relationships between living rooms, recording studio listening rooms or for example the Wiener Musikvereinssaal, which is in the Time course of the impulse response of these rooms with the of the motor vehicle interior match as possible (Further information, see later under "Simulation" the concert hall atmosphere).

An optimization method is in accordance with the invention applied that the quality of the audio signal transmission elements, in particular by means of equalization of Speaker systems.  

Below is the psycho according to the invention acoustic equalization are discussed in more detail.

For this purpose, near (I) and far field measurements (II) are carried out on different loudspeaker systems for a specific motor vehicle interior 7 . These are for

• I. at a distance of about five centimeters in front of the individual loudspeaker systems 9 , 10 , 17 , 19 with a conventional broadband condenser microphone and
• II. Realized at the individual sitting positions at 20, 21, 22, 23 in such a way that an artificial head microphone exactly occupies the location of a middle listening test person / test person.

The speaker-specific distortions, which are analyzed with II in the motor vehicle interior 7 as a real hearing-related sum source, are recorded specifically by I. This is done with and without people in the motor vehicle interior, since the damping effect of motor vehicle occupants is determined from this.

In this case, pink noise is fed as a test signal, for example from an auto-compact disc player, into the connections 32 , 33 and amplified in a broadband stereophonic manner (amplifier 35 , 36 ) to the speaker system pairs 9 , 10 and 17 , 19 . In the circuits 35 , 36 , any bass and treble controls that may be present are brought to the center position, ie +/- 0 dB. Measurements of I. are carried out separately for each loudspeaker, with the basic control unit 35 , 36 using the panorama controller (ie left / right potentiometer) and fader (ie left / right channel simultaneously between the front and rear sections) to select the loudspeakers . The same thing happens with measurements to II. With the difference that a panorama / fader control setting suitable for the individual sitting positions is found beforehand by means of music signal sound. If this is guaranteed for the individual measurements of I. and II., The loudspeakers described are controlled with an acoustic pressure of 94 dBSPL according to DIN 45 580 and a test signal bandpass analysis of 20 Hz to 20 kHz is carried out.

Data records created during the bandpass analysis about the playback behavior of the speaker systems then become a frequency dependent, for example empirically carried out, level averaging subjected. From the near field measurements are those that occur per speaker system Frequency response non-linearities and from the Far field measurements are the same, supplemented with the further information to be found on the Directed by an artificial head depending on the direction Overall sound system situation, registered.

For a sound reinforcement situation according to FIG. 1 there is, for example, a loudspeaker system transmission dimension which, with the following changes, corresponds to the inverse frequency-dependent level curve shown in FIG. 2. The increase occurring at 60 Hz is replaced by a curve of the level graphic that drops towards low frequencies (level minimum at 20 Hz with minus 20 dB), which corresponds to the actually measured bass drop, starting at 150 Hz, towards low frequencies. Likewise, an inversion of the level values results in an increase in the level-frequency curve corresponding to the measurement at the frequencies of approx. 240 Hz (level value plus 5 dB), 2300 Hz (level value plus 4 dB) and a frequency response drop towards high frequencies ( Level minimum at 20 kHz with 13 dB) with an additional resonance at 9 kHz of plus 5 dB.

Equalization of speaker systems according to the actually measured data the frequency response As is well known, nonlinearities reflect independently from the area of application (e.g. also for headphones sound), not the subjectively perceived Hearing sensation reflected (note: the psychoacoustics describes human, deviating from the objective measure hearing-related parameters). Furthermore, it will especially in the highest or lowest frequency hearing and Automobile PA system broadcast area equalized inaudible sound event parts.

For simplification, additional loudness-related equalizations in the loudspeaker transmission dimension are preferably dispensed with, which, due to the unfamiliar described above, for example not with z. B. a living space comparable sound situation in the motor vehicle interior 7 to build a sound image compatibility with respect to common recording-playback equalization (keyword: free field, diffuse field equalization with loudness perception included in the considerations).

It is therefore extrapolated from a superposition of a loudspeaker transmission dimension explained above with an equalization graphic curve (see FIG. 2), including or exclusive loudness-related perception considerations of sound fields, not the level or total transmission dimension curve that is commonly aimed for today, but an exterior, The course of the middle and inner ear behavior of a medium-sized subject, including specific spatial influences. This is based on the knowledge that in order to obtain a sound-aesthetic and directionally neutral hearing event viewpoint reproducing device, the following can be neglected without significant, audible loss of information for the sound image processing according to the invention: below a sound signal transmission frequency of 40 Hz, spectral components of noise and instruments are usually recorded on the recording side not recorded (filtering in recording studios), because compared to other spectral components of noise in motor vehicle interiors there is a lower energy component, in the bass range the noisy vehicle noise is relatively high and the perception of bass sound by the human ear takes place only very (frequency) unselectively, which is why A flat frequency response can be dispensed with when playing deep bass. A slight level increase in the lower mid-range (200 Hz to 300 Hz) remaining after the correction equalization of speakers contributes more to a subjectively "warm" sound. The same applies to a slight increase in the present area (2 kHz to 5 kHz). In addition, this is where the direction-dependent linear distortions (level irregularities) relevant for a pre-location of hearing events lie. The same as for frequencies below 40 Hz applies above a frequency of approx. 15 kHz, which is perceived as very level-selective (there is also an upper cut-off frequency of 15 kHz for FM radio transmissions), which is why a linear transmission or Playback behavior must be guaranteed.

The above results in the psychoacoustic equalization curve shown in FIG. 2, which is generated by means of analog or digital filters which show the transmission behavior of FIG. 2. This leaves z. B. at the frequencies 20 Hz a residual attenuation of 10 dB, at 240 Hz an increase of 2 dB, at 2300 Hz an increase of 1 dB and at the highest frequency shown a residual attenuation of 3 dB. The 9 kHz dip almost completely covers the resonance of the behavior of the vehicle interior, which in such a narrow-band implementation with slightly audible distortions of sound (keyword: concealment effect) prevents an up-in-the-head localization of hearing events.

In addition, with the help of the equalization behavior shown in FIG. 2, energy savings are achieved in the modulation of power amplifier units, which contribute to avoiding overdriving of the entire audio signal reproduction system. The lowest-frequency bass pulses are damped and fed into loudspeaker systems. In addition, compared to the use of flat transmission behavior, transducers and power transistors, e.g. B. in output stages, more durable.

In FIG. 1, the psychoacoustic loudspeaker system correction equalization (see transmission curve in FIG. 2) is carried out by means of elements 35 , 36 , with which the two-channel input signal 32 , 33 filters the loudspeakers and / or further sound signal processing elements (e.g. 3 and 24 ) reached.

Regarding an adaptively designed Device for special types of motor vehicles the psychoacoustic equalization according to the invention logically not only afterwards made, but parallel to the development or manufacture of motor vehicles.

Within the framework of the preferably individual control availability of the various loudspeakers, the consideration of a hearing disturbing motor vehicle interior noise can advantageously also be included in the overall concept. For this purpose, for example, the motor vehicle operating state, such as the speed or engine speed, and the spatial conditions of the motor vehicle interior are taken into account with regard to the disturbing noise occurring there by means of modulation of the loudspeakers in the motor vehicle interior that are counteracted in a targeted manner as a function of intensity and frequency. In this case, for example, the noise in the motor vehicle interior is detected by means of a microphone and leads to a frequency-dependent, preferably (variable) evaluating, self-regulating inverse amplifier. This amplifier is here in each case a component of the elements 35 , 36 in FIG. 1. The mixing of the inverse noise component takes place there electrically or alternatively also acoustically as follows.

Using separate elements to be integrated (in addition to 35, 36 ) and loudspeakers, a separate acoustic noise subtraction (real existing noise component of a moving vehicle minus the noise component artificially emitted by inverse amplification via loudspeakers) is carried out.

The following is intended to improve the invention serving the acoustic PA situation Simulation of a concert hall atmosphere in motor vehicles the interior of the witness.

The essential point of the method according to the invention indicated at the beginning is the simulation of spatial reflection patterns on parts of the motor vehicle interior (including sound-absorbing doors in motor vehicles), which, owing to the unfavorable sound-acoustic properties there, are extremely extreme compared to those of a z. B. Concert halls with good acoustics (specially designed areas for the targeted generation of diffuse sound fields) deviate. Matching the sound signal processing elements 2 , 3 , 4 , 5 , 24 , 30 symbolically shown in FIG. 1, which are designed for an improved sound reinforcement situation for the front half of the motor vehicle interior, the time-distributed level pattern of means are correspondingly labeled in FIG. 3 Loudspeaker systems 8 to 13 reproduced sound signals. In Fig. 3 is shown in the sub-figures 3 a to 3 f (passing from top to bottom)

• a) an instantaneous sound signal component passing through the delay element 5 (or 29 ) and reproduced via the loudspeaker system 9 (or 19 ) (the level L _FR = a function of the time t),
• b) an audibly slightly audible (a few ten milliseconds) delay element 3 (or 27 ) and reproduced via the loudspeaker system 10 (or 17 ), left audio signal component (L _FL = another function of t),
• c) a delay time which is mixed together in delay element 4 (or 28 ) and changes (five millisecond base delay time changes its value in ten seconds each by +/- a few hundred microseconds up and down according to a rectangular function) and via auxiliary loudspeaker system 8 ( or 18 ) reproduced sound signal component (L _FM ∼ = a specific function of t),
• d) a sound event (L _OM = a specific function of t), mixed together via the multiple delay element 2 (or 25 ), processed into spatial reflection patterns and reproduced via the secondary loudspeaker system 13 (or 16 ), which is a, in comparison to, for example Sidewall early reflection times, larger value of the ceiling early reflection delay time includes,
• e) a spatial reflection pattern (L _BR = a function of t) formed via the multiple delay element 30 (or 31 ) with the spatial reflection pattern (L _BR = a function of t) which is formed from the audio signal component according to a) and which is transmitted via the secondary loudspeaker system 12 (or 15 ) is reproduced, and
• f) via the multiple delay element 24 (or 26 ) with the (also dependent: here delayed) spatial reflection pattern (L _AL = a function of t) formed from the sound signal component according to b), which via the secondary loudspeaker system 11 (or 14 ) is played.

According to the sub-figures 3d) to 3f), the amplitudes or intensities, which are similar to a spectral analysis and which follow one another in time, each (in terms of time and amplitude) of different first wall reflection patterns (duration approx. 120 milliseconds), represent a real concert hall that after the delays according to sub-figure 3a), a level L _BR [see sub-figure 3e)], then a few milliseconds later a level L _AL [see sub-figure 3f)] and finally a few milliseconds later a level L _OM [ see sub-figure 3d)] occurs. The reference point is the level L _FR present without a time delay [see sub-figure 3a)].

Because of the continuously condensing temporal amplitude frequency a diffuse occurs at a certain moment Reflection pattern on that in the sub-figures 3d) to 3f) is marked with hatching. The graphic chosen here (L = level = one The function of time t) is usually when examining room reverb structures using pulse-like excitation (needle pulse) is used.

The level ratios shown in the sub-figures 3c) to 3f) (e.g. from L _FM ∼ -30; in dB) are to be set according to "individual taste", particularly in practical use, when an additional sound event (L _FM ∼) eliminates an acoustic leak be. Ie also that a loudly higher secondary sound event level level, or vice versa, a smaller reverb distance than 30 dB z. B. because of high noise volume in the vehicle interior is chosen. Usual reverb distances, with respect to the wall reflection patterns of known concert halls, are, for example, below 15 dB, which are suitable, inter alia, for the reproduction of classical music performances. In the case of subjectively generally rather "dry" reproduction of pop music, other reverberation distances and predominantly shorter reverberation times are relevant, which are then largely based on the duration of the first-wall reflections.

The same applies to the time duration of room reflection pattern simulations (reverberation time), which are determined from listening tests in the motor vehicle interior with several experienced test subjects. From this a certain selection of different spatial reflection patterns is determined, which are used with advantage depending on the stereo sound material. In Fig. 3 the essential section (approx. 150 milliseconds) of such a spatial reflection pattern simulation is shown as an example (here a reverberation time of approx. 0.8 seconds is normally given).

The modulated basic delay time in sub-figure 3c), which resembles a broadcast signal carrier, is determined as a function of the respectively selected delay time [according to sub-figure 3a) and / or 3b)] of the delay elements 3 and / or 5 in FIG. 1. It can be determined by means of experiments which of the respective sound signal delays [according to sub-figures 3a) to 3c)] lead to pleasantly felt beats of the overall hearing event without noticeably influencing, ie reducing, the stereo base width of the sound signals. The factor of the individual playback channel loudness also plays an important role to be controlled here.

In conclusion, it is pointed out that, according to FIG. 1, an optimized simulation of a concert hall atmosphere in motor vehicle interior 7 can be selected via radiation of the stereophonic direct tone signal via loudspeaker systems 8 to 10 and 11 to 19 , via a specifically varied radiation of room reflection patterns.

All of the sound signals explained above processing, be it the psychoacoustic Equalization or spatial reflection pattern simulation can be miniaturized in analog and / or optimally implement digital technology.

Claims (32)

1. Arrangement to improve the speakers reproduction in motor vehicle interiors with a sound signal processing circuit for Compensation for vehicle interior specific acoustic inadequacies of the speakers reproduction. 2. Arrangement according to claim 1, d.g. that the preparation circuit for the compensation of hearing-related sound event-mislocations by a psychoacoustic Audio signal equalization is designed. 3. Arrangement according to claim 1 or 2, d.g. that the Conditioning circuits for generating includes predetermined spatial reflection patterns that consist of the sound signal or signals are obtained. 4. Arrangement according to one of claims 1 to 3, d.g., that the conditioning circuit has a plurality of Controls speakers. 5. Arrangement according to claim 4, d.g. that the speakers a mixture of the unchanged and / or the Play back the processed audio signal.   6. Arrangement according to claim 4, d.g. that certain Loudspeaker selected processed audio signal play components. 7. Arrangement according to claim 6, d.g. that in the area of front and / or rear motor vehicles arranged a pair of primary speakers are essentially unchanged, if necessary delayed and / or psychoacoustic frequency response equalizes the sound signal, especially a Radiate stereo sound signal. 8. Arrangement according to claim 7, d.g. that additionally at least one pair of secondary speakers on the left and to the right of the side of the motor vehicle driver's seat and Passenger seats in the frontal plane, essentially are arranged radiating in these, at least roughly the ears of those in these seats People. 9. Arrangement according to claim 7, characterized by a comparable delegation of primary and / or Secondary speakers for in the back seats of the Passengers located in the motor vehicle interior. 10. Arrangement according to claim 8 or 9, d.g. that over the Secondary speakers with the room reflection patterns provided sound signals are emitted.   11. Arrangement according to one of claims 7 to 10, d.g., that in addition at least one secondary speaker arranged on the ceiling of the motor vehicle interior is. 12. An arrangement according to claim 11, d.g. that the Secondary speakers essentially down radiates sound events. 13. Arrangement according to claim 11 or 12, d.g. that the Secondary speaker on the ceiling of the motor vehicle interior essentially in a vertical plane is arranged, which is the central longitudinal axis of the Motor vehicle interior penetrated. 14. Arrangement according to one of claims 11 to 13, d.g., that over the secondary speaker on the ceiling predominantly of the motor vehicle interior Space reflection patterns are emitted. 15. Arrangement according to one of claims 1 to 14, d.g. that additionally at least one auxiliary speaker in the middle in the front and / or rear console between the Primary loudspeakers of the motor vehicle interior is arranged. 16. An arrangement according to claim 15, d.g. that the Auxiliary speakers essentially the same Direction of sound emission has like that Primary speaker.   17. An arrangement according to claim 15 or 16, d.g. that over the auxiliary speaker in the delay time time-continuously varying-delayed sound signal mixture is emitted. 18. Arrangement according to claim 17, characterized by a variable sound signal mixing ratio of Components of the stereo sound signal. 19. The arrangement according to claim 18, characterized by one continuous in the delay time varied-delayed mix of a stereo sound signal component with the other component. 20. Arrangement according to one of claims 7 to 19, characterized by one of in the beep preparation circuit generated correlation over the individual loudspeaker emitted sound event shares in favor of optimal playback acoustics. 21. Arrangement according to one of the preceding claims, That is, the psychoacoustic equalization that for Directional perceptions of sound events significant linear distortions are taken into account. 22. Arrangement according to claim 21, d.g. that the considering psychoacoustic equalization of the acoustic medium motor vehicle interior is assessed depending on loudness.   23. Arrangement according to one of the preceding claims, characterized by a sound signal channel-separated Public address for motor vehicle occupants generated from the processed original sound signal Room reflection pattern and / or delayed Sound signals. 24. Arrangement according to one of the preceding claims, characterized by playback channels variably switchable sound signal delays. 25. The arrangement according to claim 24, characterized by by means of sound signal delay elements variably adjustable delay times. 26. Arrangement according to one of claims 7 to 25, d.g., that in addition to the primary speakers provided speakers are preferred on such surfaces of the motor vehicle interior which are for the elimination of acoustic leaks and / or to create positions of the concert hall acoustics Suitable for creating spatial reflection patterns. 27. Arrangement according to one of claims 1 to 26, characterized by a separate channel Generation of spatial reflection patterns, which are based on a variable mixing ratio from the underlying, stereophonic, not retrospective delayed original signal is based.   28. Arrangement according to claim 27, d.g. that the separately controlled speakers each be fed with a processed sound signal, that for every motor vehicle interior area an adequate partial surface reflection pattern generated. 29. Arrangement according to one of claims 1 to 28, d.g., that a separate, variably realized Generation of spatial surface sound reflection patterns, preferably according to one in size and Design variably simulable Concert hall. 30. Arrangement according to one of claims 1 to 29, That is, for each audio signal transmission channel in the simulation of room reflections preferably realistically typical different early reflection patterns from Walls and / or objects are taken into account. 31. Arrangement according to one of claims 1 to 30, That is, that to maintain a predetermined sound neutrality and / or transparency by im Hearing events felt in the motor vehicle interior as part of the psychoacoustic equalization measures and / or creation of room acoustics measures by means of targeted radiation Room reflection pattern a volume readjustment and / or frequency response equalization depending on in the motor vehicle interior perceptible noise immissions  is made that is essentially dependent are on the speed and / or the speed of the moving motor vehicle. 32. Arrangement according to claim 31, d.g. that the sound strength adjustment and / or frequency response equalization is on and off and / or from each other separately for the audio signal components the psychoacoustic equalization measures as well as the room acoustics creation measures is made.