EP3677053B1 - Loudspeaker system for surround sound with rejection of undesirable direct sound - Google Patents

Description

The invention relates to a loudspeaker system in which a channel or multiple channels are used that are emitted laterally and/or towards the ceiling, in order to ensure a spatial sound experience in the listening area through reflection on walls and/or ceilings. These are the so-called surround sound channels, which are generated by loudspeakers that do not radiate from the front. Undesirable output signals are also generated, so-called direct sound, which reaches the listening area directly without reflections and disturbs the spatial sound experience. To attenuate the undesired direct sound, a signal that has been appropriately adjusted by an FIR filter is sent out through at least one front speaker for each surround sound channel. The temporal generation of a surround sound signal is adjusted by at least one delay element. The direct sound and the adjusted signal now meet in a listening area, so that the direct sound is weakened.

The invention also relates to a method for attenuating direct sound.

Background and prior art

Surround sound systems can give the listener the experience that they are surrounded by sound sources on all sides and are therefore "in the middle of the action". This is particularly interesting for feature films, in which sound and visual information can be reconciled by generating sounds behind the viewer that match or anticipate the current events on the screen. Very realistic impressions can be conveyed in this way. This technique is also relevant for concert recordings. Spatial sound experiences are often described as much more "enthralling" compared to normal stereo broadcasts. In surround sound systems is exploited that a listener z. B. can determine the direction from which a sound or a noise comes by determining the runtime differences between the two ears and the evaluation of different sound levels.

A disadvantage of surround sound systems is the increased number of loudspeakers required. At least two additional speakers are typically required, placed in an area behind the listening area, to produce the additional sounds coming from further afield. The costs of such a system are often very high, and due to the large number of loudspeakers, the space requirement is higher. Such a system is simply not suitable for small rooms.

Systems are now also known which use reflections from walls to create the illusion of additional sound sources. Loudspeakers, which are conventionally placed in front of the listener, are aligned in such a way that the sound they generate is reflected on walls and/or ceilings. The reflected sound no longer shines for a listener come directly from the speaker emitting it, but from the point or area on the wall where the sound bounces off and from there reaches the listener. The loudspeakers used can be aligned in such a way that the desired sound pattern can be generated regardless of the precise arrangement of the walls and ceilings of the auditorium.

In this way, sound waves can be generated from the side or even from behind and/or above the listener, which can intensify the sound experience. Not only can sound be produced with more than two channels, but the experience of an ordinary two-channel signal or even mono-channel can also be "broadened".

However, these types of systems have a disadvantage that "real" surround sound systems do not have. Despite the use of laterally placed and oriented speakers to create the desired reflection, some portion of the sound will reach the listener via a direct path from speaker to listener. Due to the shorter path compared to reflection, this sound always reaches the listener first. Even if the sound level of this direct sound is often much lower than the desired, reflected sound, the so-called Haas effect gives the listener the impression that the sound is coming directly from the loudspeaker. The aforementioned psychoacoustic effect means that, under certain conditions, a listener perceives a sound primarily from the direction from which the signal first reaches him. This unwanted direct sound thus reduces the spatial sound experience considerably.

Direct sound can be minimized by using so-called directive loudspeakers. So-called waveguides, which are small elements for conducting sound, are placed in front of the loudspeaker, which have a positive effect on emission that is true to the direction. Larger loudspeakers can also preferably be used, since they have a higher directivity. However, larger loudspeakers are less suitable for producing high tones and reduce the compactness of the system. These systems also have the disadvantage that the sweet spot is relatively small.

So revealed US2017/0053641 a system of multiple loudspeakers for sound expansion. Loudspeakers are used that radiate to the side and/or upwards, as well as front loudspeakers. The signals sent from the side and top speakers arrive at the listener as signals reflected off walls and ceilings. The signals from the front speakers can reach the listener directly, weakening or eliminating signals from the other speakers. In particular, filters with a finite impulse response are integrated, so-called FIR filters (finite impulse response filters), in order to adapt the signal from the front loudspeakers accordingly. Several FIR filters are used for each surround sound channel.

U.S. 5,815,578 discloses a system for generating virtual surround sound. One side and one front speaker are used on each side, ie left and right. The side speaker reflects signals to broaden the sound, while the front speaker generates standard signals that go directly to the listener. In addition, the front speaker audio signals to eliminate unwanted, non-reflected signals of the generate side speakers. A digital filter is used for this, which converts a desired transfer function. A possible transfer function is described in detail. This can be calculated by dividing the transfer function of the unwanted direct sound by the transfer function of the front speaker and the required order of the filter. One filter option is described by combining a minimum phase filter with a time delay element. A use of FIR filters is not suggested.

Furthermore describes US2007/0263888 a method and system for surround sound beamforming, and US2015/0304791 shows a method and a system with virtual height filtering.

It is also known in the prior art to reduce the Haas effect by so-called beamforming. A large number of directive loudspeakers are used, the control of which is configured in such a way that the sound propagation can be controlled very precisely by adjusting the runtime between these loudspeakers. In this way, undesired direct sound can be almost completely avoided. However, the number of loudspeakers and thus the complexity of the system increases. Elaborate DSP systems (digital signal processing systems) are required. The acquisition costs of a beamforming system are often very high and the compactness is lost.

The prior art therefore lacks inexpensive, flexible, compact and simple systems for generating surround sound which do not require any directive loudspeakers, do not require additional loudspeakers behind the listener and at the same time have a wide sweet spot.

object of the invention

The object of the invention is to provide a loudspeaker system and a method for attenuating direct sound without the disadvantages of the prior art. In particular, it was an object of the invention to provide a compact, simple, flexible and inexpensive loudspeaker system for generating surround sound, which does not require additional loudspeakers behind the listening area, does not require any directive loudspeakers and does not generate any unwanted direct sound. A sweet spot should be as large as possible.

Summary of the Invention

The object is solved by the features of the independent claims. Advantageous configurations of the invention are described in the dependent claims.

• mindestens einen nicht frontal strahlenden Lautsprecher und einem dem nicht frontal strahlenden Lautsprecher zugeordneten Kanal, der ein Raumklangkanal ist,
• mindestens einen Frontlautsprecher und
• pro Raumklangkanal einen dem Frontlautsprecher vorgeschalteten Filter und
• pro Raumklangkanal mindestens ein dem nicht frontal strahlenden Lautsprecher vorgeschaltetes Verzögerungsglied

wobei der Filter ein FIR-Filter ist und das Verzögerungsglied und der FIR-Filter konfiguriert sind für eine relative Anpassung der Ausgangssignale des Frontlautsprechers und mindestens eines nicht frontal strahlenden Lautsprechers eines Raumklangkanals zu einer Abschwächung eines unerwünschten Direktschalls des nicht frontal strahlenden Lautsprechers in einem Zuhörerbereich.In a first aspect, the invention relates to a loudspeaker system for the reproduction of at least one channel, comprising

• at least one non-frontally radiating speaker and one channel assigned to the non-frontally radiating speaker, which is a surround sound channel,
• at least one front speaker and
• a filter connected in front of the front speaker for each surround sound channel and
• at least one delay element connected upstream of the non-frontally radiating loudspeaker for each surround sound channel

wherein the filter is an FIR filter and the delay element and the FIR filter are configured for a relative adjustment of the output signals of the front speaker and at least one non-front-radiating speaker of a surround sound channel to an attenuation of an undesired direct sound of the non-front-radiating speaker in a listening area.

In the case of the inventive loudspeaker system, a channel or several channels emitted laterally and/or towards the ceiling are used in order to ensure a spatial sound experience in the listening area through reflection on walls and/or ceilings. These are the so-called surround sound channels, which are generated by loudspeakers that do not radiate from the front. Undesirable output signals are also generated, so-called direct sound, which reaches the listening area directly, without reflections, and disturbs the spatial sound experience. To attenuate the undesired direct sound, a signal adapted by a finite impulse response filter (FIR filter) is sent through at least one front speaker for each surround sound channel. The temporal generation of a surround sound signal is adjusted by at least one delay element. Direct sound from the surround sound channel and the adjusted signal now meet in a listening area, so that the direct sound is weakened. Unwanted direct sound is effectively and easily attenuated by using an FIR filter per surround sound channel and at least one delay element per surround sound channel, with the inventive loudspeaker system being characterized in comparison to the systems known from the prior art in that a high-pass filter is connected upstream of the FIR filter.

A loudspeaker system has at least one channel. Then the loudspeaker system is suitable for the production of monophony (mono) and monophonic surround sound channel. At least 2 channels are preferred. The reproduction of at least 2 channels preferably means the reproduction of at least two separately encoded channels whose sound information can be independent. The playback of 2 separate channels in stereo has been around for a long time known. One audio channel contains audio information intended for the left ear of at least one listener and the other audio information intended for the right ear, with the information being assigned to a single playback. This information can be different, e.g. B. to play back the different spatial positions of members of a recorded orchestral concert or to correspond to "spatially" differently positioned sound sources of a film played on a screen.

A loudspeaker system typically consists of at least two side loudspeakers and one front loudspeaker, especially if it is a two-channel (stereo) system.

Basically, in the loudspeaker system, an electrical (audio) signal is translated into sound waves, which are referred to as the output signal(s). For this purpose, a suitable surface of the loudspeaker, the membrane, is made to vibrate accordingly, e.g. B. by electromagnets. The output signals are to be differentiated into the output signals of a front loudspeaker and those of a loudspeaker that does not radiate from the front.

In addition to a 2-channel recording and playback system (stereo), there are also multi-channel systems in which, in addition to the sound information for left and right, further spatial sound information such as e.g. B. middle channel (center) and surround channels for rear sounds (either one channel or in turn divided into left and right) and a low-frequency channel can be encoded on the sound source medium and can be reproduced by a suitable system. A surround sound channel preferably designates a channel that is not a center and/or low-frequency channel. The coding can be carried out both on a corresponding number of discrete channels of a playback medium and via a so-called matrix coding on the two standard stereo channels, so that the playback medium does not have to be particularly suitable for multi-channel playback. Multi-channel systems can thus preferably include 3 channels, 4 channels, 5 channels, 6 channels, 7 channels, 8 channels, 9 channels, 10 channels and more than 10 channels as standard. The loudspeaker system is preferably such a multi-channel system. The number of channels does not have to match the number of speakers. A person skilled in the art knows what number of channels are common in multi-channel systems. Likewise, a person skilled in the art knows that not all channels use the full available frequency bandwidth. For example, it is known to use one or more channels only for low frequencies (low-frequency channel or bass). The number of channels can also be used in the usual notation, e.g. B. 5.1, 7.1, etc., where the number before the dot designates the number of channels that have the full frequency range and the number after the dot the number of bandwidth-limited channels, preferably low-frequency channels. In this case, the number of channels of the inventive loudspeaker system can preferably include all the usual channel combinations that produce surround sound. The coding can be analog or in a digital format. In particular, it is preferred that the coding is performed in a standard format, the format being selected from the group comprising Dolby Stereo, Dolby Surround, Dolby Pro Logic, Dolby Pro Logic II, Dolby Pro Logic IIx, Dolby Pro Logic IIz, Dolby Digital, Dolby Digital Plus, Dolby Atmos, Dolby TrueHD, Dolby Virtual Speaker, DTS Coherent Acoustics, DTS-ES, DTS Neo:6, DTS Neo:X, DTS-HD Master Audio and/or DTS:X.

A channel preferably includes all of the sound information that can be assigned to at least one loudspeaker during playback. In this case, both the electrical signal and the output signal of at least one loudspeaker are included.

The loudspeaker system is preferably equipped with a suitable decoder that can read out the multi-channel information of the playback medium. The multi-channel information is adapted to the number of loudspeakers connected to the system in such a way that the multi-channel information is reproduced as sensibly as possible in terms of the best possible surround sound that can be achieved with the existing number of loudspeakers. Suitable decoders are known to those skilled in the art and are available as standard. The playback medium is preferably a medium that can be read by one of the following playback devices: a CD player, a DVD player, an MP3 playback device, a media player or network player, a tuner for radio reception, a minidisc player, a record player, a television, a computer and other devices known to those skilled in the art for reproducing audio signals. The medium itself can then have the appropriate form, e.g. B. be a compact disc (CD). The playback device is preferably connected to the loudspeaker system by cable or wirelessly and transmits the information specified by the playback medium.

The loudspeaker system is also preferably equipped with an amplifier which amplifies the information in the signal transmitted by the playback device and decoded by the decoder and passes it on to the loudspeaker(s) connected. At least one amplifier is preferably present for each channel, insofar as the number of loudspeakers allows this and the respective multi-channel signal is supported. Signal processing, in particular digital signal processing (DSP), can preferably be connected upstream of one or more amplifiers in order to influence and adjust a sound image through processing. For example, an amplifier can B be a class AB, D or E amplifier.

The loudspeaker system is preferably constructed in such a way that it has at least one input to which the playback device can be connected. The input signal can preferably be analog and/or digital. Since digital circuits are preferably integrated within the loudspeaker system, e.g. B. for implementing DSP or as a digital FIR filter, it may be preferable to use at least one suitable analog-to-digital converter (A/D converter) upstream of these circuits in order to convert at least one analog input signal into a digital signal. After such a circuit and before at least one amplifier, there is preferably at least one suitable digital-to-analog converter at a suitable point, which converts the digital signal back into an analog signal in order to feed an analog signal to the amplifier.

The speaker system has at least one non-frontally radiating speaker for each surround sound channel. The term "frontal" refers to a loudspeaker oriented directly towards the listening area, which essentially radiates the sound generated in this direction. The speaker that does not radiate frontally is preferably not a directional (or synonymously: "directive") speaker. The person skilled in the art knows that each loudspeaker has a preferred direction in which the sound is essentially emitted or in which an acoustic emission cone is oriented. A directive or directional loudspeaker preferably means a loudspeaker that has no edges, horns or sound guides or waveguides to reduce an acoustic emission cone.

Larger loudspeakers can preferably be used for the loudspeakers that do not radiate frontally, since these have a higher directivity and this can reduce direct sound, which is disadvantageous for surround sound effects. However, larger loudspeakers are less suitable for producing high tones and reduce the compactness of the system. A compromise with regard to the size is therefore preferably used for the properties desired in each case (eg size of the sweet spot, frequency level).

The "sweet spot" is preferably the area in which the sound image to be achieved by the loudspeaker system is essentially best achieved, e.g. B. the attenuation of the direct sound. This area is determined when setting up and configuring the loudspeaker system and preferably corresponds to the listening area. The audience area can be e.g. B. in the middle between two side speakers positioned on different sides, for example in front of a front-radiating speaker. In the following, lateral loudspeakers are preferably used synonymously for loudspeakers that do not radiate from the front. A typical configuration of the loudspeaker system is as follows: There are at least two side loudspeakers positioned at a certain distance from each other, one on the left and one on the right. There can preferably also be more than one lateral loudspeaker on each side. Left and right are preferably defined from the point of view of the listening area, which is preferably located in the middle in front of the loudspeakers. If you look at the imaginary connecting line, which runs through both side loudspeakers, as the boundary between the front and the back, then the front is the area in which the sound waves of the loudspeakers essentially radiate. At least one central loudspeaker, which emits sound waves essentially frontally in the direction of the listening area, is preferably positioned approximately in the middle between the left and right lateral loudspeakers. The loudspeakers on the side do not radiate frontally, but at a certain angle α in relation to the frontal direction of radiation. This angle α is essentially selected in such a way that the sound waves are reflected on the walls of the room in which the loudspeaker system is located and in this way essentially reach the listening area after a reflection. A left, lateral loudspeaker would radiate in the direction of a left wall of the room from the listening area, so that the emitted sound waves are essentially reflected on this wall and thus essentially reach a listener in the listening area. A right side speaker is similarly oriented toward a right wall of the room. A person skilled in the art knows in which way and in which direction a reflection essentially takes place in relation to the orientation of the wall and the direction of incidence of the sound. The person skilled in the art also knows that a sound wave emitted by a loudspeaker does not run in a line, but occupies a certain spatial area in front of the loudspeaker at a certain spatial angle, the so-called sound emission cone, and that this sound emission cone diverges as the distance from the loudspeaker increases. Accordingly, a sound direction and a reflection never only affects one direction and one point on the wall, but a larger area. Nevertheless, the sound propagation of a directed sound wave at a not too great distance can preferably be approximately described by a straight line, whose point of intersection and angle of intersection with the wall can then be used approximately to describe the direction of a reflection. To a listener, the reflected sound no longer appears to come directly from the emitting loudspeaker, but rather from the location or area on the wall where the sound was reflected and from where it reaches the listener. In this way, a surround sound experience can be created. Therefore, the non-front radiating speakers are associated with channels that are surround channels.

The listening area is preferably where a listener is in front of the speaker system. This can preferably be in front of the at least one front speaker. It can also be preferred that the listener (his head) and/or the listening area forms an approximately equilateral triangle with the respective outer or outermost loudspeakers. The audience area is preferably so large that at least one listener is standing or sitting or his head is surrounded by it. This particularly preferably applies to two listeners standing or sitting next to each other or their heads, more preferably 3, 4, 5, 6, 7, 8 or 9 listeners and in particular 10 listeners. However, at least 10, 15, 20, 50, 100, 300 or 1,000 or 10,000 listeners may also be preferred. It may also be preferred that the audience area is at least 0.5 m ² , at least 1 m ² , at least 2 m ² , at least 3 m ² , at least 5 m ² , at least 10 m ² , at least 20 m ² , at least 30 m ² , at least 50 m ² , at least 100 m ² , at least 200 m ² , at least 500 m ² , at least 1,000 m ² or at least 10,000 m ² . The loudspeaker system would preferably be sized and/or configured according to the size of the listening area, however the inventive principle would remain. Likewise, the loudspeaker system would continue to be described as compact in relation to a large number of known loudspeaker systems from the prior art with a comparable spatial sound functionality and a comparable listener area.

Terms such as essentially, approximately, about, approx. etc. preferably describe a tolerance range of less than ±40%, preferably less than ±20%, particularly preferably less than ±10%, even more preferably less than ±5% and in particular less than ± 1%. Similarly, preferred describes sizes that are approximately the same. Partially describes preferably at least 5%, more preferably at least 10%, and especially at least 20%, in some cases at least 40%.

A loudspeaker that does not radiate frontally can also preferably be a so-called ceiling loudspeaker directed towards the ceiling. These terms can preferably also be used synonymously. A loudspeaker that does not radiate frontally can thus comprise at least one loudspeaker on the side and/or at least one loudspeaker in the ceiling. A ceiling-directed speaker emits sound waves generally in an upward direction toward a ceiling of a room so that sound waves reflect off it and reach at least one listener in the listening area from above. In this way, additional spatial sound effects can be created. The deviation of the ceiling loudspeaker from a loudspeaker radiating from the front can preferably be described by a vertical angle β.

It can be preferred that the deflection of the loudspeakers of the loudspeaker system that do not radiate frontally, in particular the angles α and/or β, are fixed ex works during manufacture and are based on the dimensions and geometries of average rooms, e.g. B. average living room of consumers. It can also be preferred that these angles can be changed by a specialist and/or a consumer and can therefore be adapted to individually different spaces. Such an adjustment can also take place automatically.

The speaker system also includes at least one front speaker. This essentially emits the sound waves in the direction of the listening area. In this case, the at least one front speaker can preferably fulfill various functionalities of the surround sound system. He can e.g. B. map a separate channel within the surround sound system, the so-called center loudspeaker, on whose channel, for example, dialogues are often encoded in films.

It may also be preferred to provide a front speaker for at least one channel that is also emitted via a non-front radiating speaker, e.g. B. One front speaker (left and one right) for two channels of stereo sound and/or for each additional surround sound channel.

It can also be preferred that the at least one front loudspeaker forms a low-frequency channel. The person skilled in the art knows that low frequencies can only be localized to a lesser extent or not at all by a listener and that the exact emission location within a room is therefore of little relevance. Therefore, low tones can also be emitted frontally on a single channel. In this regard, the front speaker can be adapted in terms of its dimensions; in particular, it can be larger than e.g. B. smaller, more suitable for higher frequencies non-frontal speakers. In this case, the low-frequency channel can preferably not be encoded as a separate channel, but rather be generated from at least one, preferably a plurality of channels, which are filtered by a low-pass filter. It can also be preferred that a low-frequency channel is reproduced by at least one additional loudspeaker, a so-called subwoofer, the location and/or orientation of which is essentially arbitrary.

It can also be preferred that the low-frequency channel is reproduced on a number of channels and/or loudspeakers or even on all channels.

The front loudspeaker is preferably used in addition to the above-mentioned tasks or also exclusively for emitting an output signal which attenuates undesired direct sound from a loudspeaker which is not radiating from the front.

The output signal can therefore only be a signal for attenuation and/or contain the sound information of (at least one) channel. The signal for attenuation is preferably referred to as an attenuation signal, which alone or together with an audio channel forms the output signal of the front speaker.

Despite the use of oriented, non-front radiating speakers to create the desired reflection, some sound will reach the listening area via a direct route from speaker to listening area. This sound, referred to below as direct sound, always reaches the listener beforehand due to the shorter path compared to reflection. Even if the sound level of this signal is often much lower than the desired, reflected sound, the listener gets the impression that the sound is coming directly from the loudspeaker due to the so-called Haas effect. The aforementioned psychoacoustic effect means that, under certain conditions, a listener always perceives a sound primarily from the direction from which the signal first reaches him. This unwanted direct sound thus reduces the spatial sound experience considerably.

A person skilled in the art knows how a sound signal can be weakened and/or canceled by interference by a second sound signal brought into spatial overlap. In particular, this requires essentially destructive interference between these two signals. The front-radiating loudspeaker emits the second sound signal in order to weaken the undesired sound signal of the direct sound. In this case, such a signal for attenuation is sent out for each channel of a loudspeaker that does not radiate from the front. This can preferably be sent out from a single front loudspeaker or at least one front loudspeaker per channel. This attenuation signal can be sent out simultaneously with a channel from a front speaker or as the only output signal from the front speaker.

Sound signals, sound waves or also output signals emitted by a loudspeaker are preferably spatially spread sound waves with a spectral distribution, with each emitted frequency at any location at any time being able to be assigned an amplitude and a phase relative to every other emitted frequency as well as an absolute phase. A person skilled in the art knows which quantities are required to completely describe a sound wave. A sound wave is preferably a superimposition of a large number of individual vibrations.

A weakening of the direct sound should preferably be achieved in the listening area. The sweet spot is preferred where the attenuation is particularly good with a good spatial sound experience at the same time due to reflected signals. This preferably corresponds to the audience area. In this case, attenuation preferably means that the direct sound becomes measurably smaller. In this case, an attenuation preferably relates to a sound intensity. A preferred magnitude of the attenuation is dependent, for example, on the rooms in which the loudspeaker system is present and on the exact configuration of the system (eg alignment and/or type of the non-frontally radiating loudspeakers). These factors have an influence on the direct sound. Experts often assume that this direct sound should be at least 10 dB lower than the reflected sound of the surround sound channel so that the Haas effect does not occur. Therefore, an attenuation that ensures this ratio between undesired direct sound and reflected surround sound signal is preferred. Since the intensity of the direct sound is initially lower than the reflected signal due to the non-frontal radiation with proper configuration of the system and with walls not too far away from the loudspeakers (on which the sound is reflected), lower attenuations than 10 dB are preferred sufficient. An attenuation can preferably amount to at least a factor of 2 at least in at least one area of the audience area, in particular in the entire audience area. Attenuations of at least a factor of 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50, 100, 200, 300, 400, 500 or 1000 are also possible. An attenuation can also be expressed in dB, extinction ratios of at least 3 dB, at least 10 dB, at least 20 dB, at least 30 dB or at least 40 dB being preferred. The attenuation is preferably so strong that perception of the attenuated, undesired direct sound is essentially prevented by the human ear and there is essentially no clouding of the room sound by the Haas effect. In this case, it can be preferable to only attenuate certain frequency ranges of the signal. For example, low frequency ranges, for example approx. 0 Hz - 300 Hz, preferably 50 Hz - 200 Hz, particularly preferably between 100 Hz and 150 Hz can be excluded from the attenuation. A reason for this can e.g. B. lie in the difficult localization of such deep tones. Higher frequencies can also be excluded from the attenuation and/but not be generated as output signals, since they e.g. B. are essentially not perceived by the human ear and/or can only be generated with difficulty by loudspeakers of a certain minimum size. It has been shown, inter alia, in experiments that the inventive loudspeaker system can achieve sufficient attenuation in a listening area to essentially prevent the Haas effect.

At least one filter is connected in front of a front loudspeaker of the loudspeaker system. One filter is used for each surround sound channel. This is also preceded by the amplifier that precedes the loudspeaker. The filter is a finite impulse response (FIR) filter. This filter has a finite impulse response and is well known in the art. The filter is preferably a digital filter. Digital filters can be implemented in a particularly simple and cost-effective manner.

FIR filters are easy to implement, inexpensive and are particularly stable in terms of their signal response and less susceptible to oscillations compared to infinite impulse response filters (IIR filters), i.e. filters with an infinite impulse response.

A FIR filter is preferably implemented by an integrated circuit, e.g. B. a microprocessor. Other integrated circuits that can be used in digital electronics for fast data processing can also be used. For example, an FIR filter can be implemented by a DSP processor chip. An integrated circuit can also include a number of FIR filters. Digital FIR filters in particular are particularly easy to program. It was surprising that an FIR filter could be used to attenuate a direct sound of a surround sound channel, which can also be implemented using an inexpensive standard DSP chip that can be programmed easily and quickly. In this way, costs can be saved and the development times of the loudspeaker system can be kept short.

A delay element is connected in front of a loudspeaker that does not radiate frontally, with which the runtime of an electronic signal can be changed. This is preferably connected upstream of the amplifier. This delay element preferably works on a digital basis. With the delay element, a specific electronic signal, which is to become an output signal generated by the non-radiating loudspeaker, can be delayed within the time setting range of the delay element. This delay can preferably be a few nanoseconds (ns), a few microseconds (μs), a few milliseconds (ms) and/or up to 0.5 seconds (s) and can be set with a suitable resolution. A delay of between 1 μs and 10 ms with a resolution of less than 10 μs is particularly preferred.

A delay element is preferably implemented by an integrated circuit, e.g. B. a microprocessor. Other integrated circuits that can be used in digital electronics for fast data processing can also be used. For example, a delay element can be implemented by a DSP processor chip. An integrated The circuit can also include a number of delay elements. FIR filter and delay element(s) can be on the same integrated circuit, e.g. B. a DSP chip can be realized. A particularly simple, cost-effective and efficient system can thus be provided.

In the loudspeaker system, a delay element and a filter are configured for a relative adaptation of the output signals of the front loudspeaker and at least one non-front-radiating loudspeaker of a surround sound channel to an attenuation of an undesired direct sound of this non-front-radiating loudspeaker in a listening area. Thus, the attenuation of an undesired direct sound described above can preferably be achieved by adapting the filter and the delay element, in that the FIR filter has an adequate impulse response and the delay element causes a suitable delay in the electronic signal. A person skilled in the art knows how to achieve at least partially destructive interference between a direct sound and an attenuating signal. Now that it has surprisingly turned out that an attenuation is also possible with the loudspeaker system described, this knowledge can be transferred in order to achieve a desired attenuation with the components of the loudspeaker system. For example, in a simple exemplary embodiment, an FIR filter can be configured in such a way that an electronic signal of a surround sound channel is (phase) inverted and at the same time (preferably frequency-dependent) is adjusted in terms of level. This signal is then fed to the front speaker. In this way it can be made possible that the output signal of a front speaker connected downstream of the filter in the listening area is inverted and otherwise has the same strength as an undesired direct sound of a non-frontally radiating speaker of the surround sound channel. However, due to the different distances of the non-front radiating speaker and the front speaker to the listening area, and due to the electronic signal delay (latency) inherent in an FIR filter, these two sound signals may not arrive in the listening area at the same time. However, simultaneity of the overlapping output signals generated in this way is important for the destructive interference required for attenuation. The delay element is therefore used to ensure that the direct sound and the signal that is inverted and level-adjusted thereto arrive essentially at the same time in an audience area.

In this case, the delay element preferably essentially compensates for the signal delay of an FIR filter.

A preferred electronic structure is as follows: An electronic signal from a surround sound channel is divided at an electronic signal splitter and fed to an FIR filter in a signal arm, which is connected in front of a front speaker. The electronic signal of the surround sound channel is adjusted by the FIR filter in such a way that the front speaker generates an output signal which is used to attenuate the direct sound. At the same time, the electronic signal of the surround sound channel in the other signal arm is time-adjusted by a delay element before it is fed to a loudspeaker that does not radiate frontally.

It is preferred that the interference is essentially destructive and that the desired attenuation is achieved in the listener area in the desired spectral range. That means the Matching of the attenuating signals does not have to be perfect, it is sufficient that the preferred attenuation is achieved that leads to an improvement in the surround sound experience. The loudspeaker system is a particularly simple system for generating surround sound, in which the sweet spot can be relatively large. Due to the preferred use of non-directional, non-frontal speakers, the listening area is surprisingly large.

There is at least one delay element per surround sound channel. If several non-frontally radiating loudspeakers are used per surround sound channel, an output signal from a front loudspeaker is preferably sufficient for attenuation and the use of a single FIR filter. The runtime differences of the direct sound of the different non-frontally radiating loudspeakers can e.g. B. can be individually adjusted via respective delay songs connected upstream of the non-frontally radiating loudspeakers. In this way, a single FIR filter can be used to attenuate the direct sound per surround sound channel, even if several non-frontally radiating loudspeakers are used. It was surprising that a very wide audience area can be generated by effectively canceling out the direct sound without having to use multiple FIR filters.

However, it may also be preferable to use only one delay element per surround sound channel even with several non-radiating loudspeakers, particularly if these loudspeakers are spatially close together and a separate runtime adjustment to the attenuation signal is not required.

The front speaker can preferably play back its own channel as an output signal in addition to the signal from at least one FIR filter that has been explicitly processed to attenuate a surround sound signal, e.g. B. a classic stereo channel (left or right) or a center channel. These signals can be present as an output signal at the same time, since the energy of the attenuation signal is consumed in the generation of the at least partially destructive interference and is therefore no longer perceived by a listener, with the energy of the own channel being able to reach the ear of a listener and perceived unclouded can be.

It can be preferred that the configuration of the at least one FIR filter and the delay of a delay element are factory-set during manufacture and are based on the dimensions and geometries of average rooms z. B. average living room of consumers. It can also be preferred that the configuration for the attenuation of a direct sound can be adapted automatically or manually to individually different premises, situations and/or audience areas.

• Es gibt pro Raumklangkanal ein Verzögerungsglied mit einem nachgeschalteten, seitlich/zur Decke gerichteten Lautsprecher. Es gibt dabei einen Filter mit einem nachgeschalteten Frontlautsprecher zur Abschwächung des Direktschalls.
• Es gibt pro Raumklangkanal ein Verzögerungsglied mit einem nachgeschalteten, seitlich/zur Decke gerichteten Lautsprecher mit einem vorgeschalteten Verzögerungsglied. Es gibt dabei einen Filter mit mehreren nachgeschalteten Frontlautsprechern zur Abschwächung des Direktschalls.
• Es gibt pro Raumklangkanal ein Verzögerungsglied mit mehreren nachgeschalteten, seitlich/zur Decke gerichtete Lautsprechern. Es gibt dabei einen Filter mit einem oder mehreren nachgeschalteten Frontlautsprechern zur Abschwächung des Direktschalls. Diese Konstellation stellt einen besonders einfachen Aufbau dar, der in überraschender Weise für hervorragenden Raumklang sorgt, insbesondere wenn die nicht frontal strahlenden Lautsprecher räumlich nah beieinander liegen.
• Es gibt pro Raumklangkanal mehrere Verzögerungsglieder mit mehreren nachgeschalteten seitlich/zur Decke gerichtete Lautsprechern (bevorzugt einem pro Verzögerungsglied). Ansonsten wie oben, einer oder mehrere Frontlausprecher, aber nur ein Filter für jeden Raumklangkanal. Hierdurch kann eine besonders gute Anpassung der Ausgangssignale erreicht werden, der Raumklang hat eine hohe Qualität und einen breiten sweet spot, sogar in Konstellationen, bei denen die nicht frontal strahlenden Lautsprecher nicht nah beieinander liegen.
• Wie vorstehend, es kann dabei auch einen Frontlausprecher mit mehreren vorgeschalteten Filtern zur Abschwächung des Direktschalls mehrerer Raumklangkanäle geben, wobei ein Filter pro Raumklangkanal verwendet wird. Diese Konstellation bietet besondere Vorteile. Durch die Verwendung nur einen Frontlausprechers kann das System besonders kompakt, einfach und günstig gehalten werden. Es war überraschend, dass bei Verwendung nur eines Frontlausprechers mit jeweils einem pro Raumklangkanal vorgeschaltetem FIR-Filter zur Auslöschung von Direktschall ein hervorragendes Raumklangerlebnis mit breitem sweet spot erzielt werden konnte.
• Es werden jedoch nicht mehrere FIR-Filter für einen Raumklangkanal verwendet werden, z. B. zur Abschwächung verschiedener seitlich/zur Decke gerichteter Lautsprecher dieses Kanals. Eine Anpassung an mehrerer seitlich/zur Decke gerichteter Lautsprecher eines Raumklangkanals ist jedoch besonders einfach über mehrere Verzögerungsglieder möglich. So bleibt der Aufbau sehr einfach bei gleichzeitig verbesserter Leistung.

To clarify the invention, various constellations should now be listed:

• There is a delay element for each surround sound channel with a downstream loudspeaker directed to the side/to the ceiling. There is a filter with a downstream front speaker to attenuate the direct sound.
• There is a delay element per surround sound channel with a downstream loudspeaker directed to the side/ceiling with an upstream delay element. There is a filter with several downstream front loudspeakers to attenuate the direct sound.
• There is a delay element for each surround sound channel with several downstream loudspeakers directed to the side/to the ceiling. There is a filter with one or more downstream front speakers to attenuate the direct sound. This constellation is a particularly simple structure that surprisingly provides excellent surround sound, especially when the loudspeakers that do not radiate from the front are spatially close to one another.
• There are multiple delays per surround channel, followed by multiple side/ceiling-firing speakers (preferably one per delay). Otherwise as above, one or more front speakers, but only one filter for each surround sound channel. In this way, a particularly good adjustment of the output signals can be achieved, the surround sound has a high quality and a wide sweet spot, even in constellations in which the loudspeakers that are not radiating from the front are not close to each other.
• As above, there can also be a front speaker with a number of upstream filters for attenuating the direct sound of a number of surround sound channels, with one filter being used for each surround sound channel. This constellation offers special advantages. By using only one front speaker, the system can be kept particularly compact, simple and inexpensive. It was surprising that an excellent surround sound experience with a wide sweet spot could be achieved by using only one front speaker with an upstream FIR filter for each surround sound channel to eliminate direct sound.
• However, multiple FIR filters will not be used for one surround channel, e.g. B. to attenuate various side/ceiling-firing speakers of this channel. However, an adaptation to several loudspeakers of a surround sound channel directed laterally/towards the ceiling is possible in a particularly simple manner by means of several delay elements. This keeps the structure very simple while at the same time improving performance.

It was surprising that an FIR filter for attenuating a surround sound channel is sufficient to achieve the desired attenuation, even when using a plurality of non-frontally radiating loudspeakers per surround sound channel. In this way, costs can be saved and the loudspeaker system is special, simple and therefore robust, compact and inexpensive.

It was just as surprising that the invention made it possible to easily cover all constellations that are relevant for an untroubled spatial sound experience.

It was also surprising that such a loudspeaker system can produce a high-quality surround sound experience without loudspeakers surrounding (e.g. placed behind) and/or directional loudspeakers. A compact loudspeaker system for generating surround sound can thus be provided, which can be kept particularly inexpensive, compact and easy to manufacture by using fewer, simpler and more economical components.

In a preferred embodiment, the at least one non-frontal speaker and the at least one front speaker are positioned at a small spatial distance from one another. The distance between two loudspeakers is preferably smaller than the size of the loudspeakers used. The distance between the loudspeakers preferably means the spatial area between the outer boundaries of two adjacent loudspeakers. In this way, a particularly effective cancellation of the direct sound can be achieved in a wide audience area, because a very good overlap of the output signals to be adjusted can be achieved.

It is particularly preferred that small, non-frontal loudspeakers are used, which are particularly non-directional. In this way, a particularly wide radiation range of the reflected surround sound channel can be achieved, while the cancellation of the direct sound works very well at the same time.

As an example, non-front radiating loudspeakers can have a membrane diameter (preferably indicates the size of the loudspeaker) of 50 millimeters (mm) or less, preferably 40 mm or less, more preferably 30 mm or less and in particular 20 mm or less. In this case, the distance between the front speaker and adjacent speakers that do not radiate frontally could preferably also be smaller than the size of the speaker that does not radiate frontally.

It was particularly surprising that compact systems, preferably with the above properties, not only impress with their small size, but also with a particularly large sweet spot.

It can also be preferred that the front speaker is not particularly large and therefore not particularly directive and/or directed (preferably based on the divergence of the sound emission cone). As a result, the overlap between the direct sound and the attenuation signal can preferably be increased and an extended sweet spot can be achieved. The front speaker can have a membrane diameter of 70 mm or less, preferably 60 mm or less, particularly preferably 50 mm or less, more preferably 40 mm or less and in particular 30 mm or less. Preferably, however, a front speaker does not have to be as large as a speaker that does not radiate frontally.

In this case, it can also be preferable for the above-mentioned variable to be scaled in relation to the size of the audience area and/or the sound pressure to be generated accordingly.

In a preferred embodiment, at least one FIR filter and/or at least one delay element is implemented by a DSP chip. A single DSP chip can preferably be used for the loudspeaker system. This makes it particularly compact and inexpensive. Multiple DSP chips can also preferably be used. As a result, a particularly good adjustability and/or configurability of the loudspeaker system can be achieved.

Such a system is particularly simple, inexpensive and quick to implement. Standard components can be used. DSP chips are also particularly energy-efficient. DSP chips also offer the advantage that other standard sound effects and adjustments are possible at the same time.

In a preferred embodiment, the relative adjustment of the output signals of the front speaker and the non-frontally radiating speaker is carried out with regard to the amplitude, the phase response and the frequency response. In this way, an essentially destructive interference between the direct sound and the attenuation signal can preferably be achieved in the listener's area. In this case, the attenuation signal transmitted by the at least one front loudspeaker is preferably adapted accordingly, since this signal contains no information for a listener. A (fine) adjustment, in particular of the phase, can then also be achieved via the delay element by the at least one non-frontally radiating loudspeaker.

In a further preferred embodiment of the speaker system, the delay element is configured for a delay to compensate for a latency of the output signal of the front speaker caused by the FIR filter. An FIR filter has a certain electronic signal propagation time, which is preferably referred to as latency and must be compensated for so that the attenuation signal and the direct sound in the listening area essentially destructively interfere with one another. Of course, the propagation time differences between the attenuation signal and the direct sound are preferably also taken into account, which can exist due to different spatial distances between the loudspeakers involved and the listening area. As a result, the output signals of the front loudspeaker can be adjusted in a particularly simple manner, which leads to the weakening of the direct sound.

In a preferred embodiment of the speaker system, the relative matching of the front speaker and non-front-radiating speaker outputs to attenuate the unwanted direct sound causes partially destructive interference between the front speaker output and the unwanted direct sound of the non-front-radiating speaker in the listening area. The destructive interference is preferably only partial here, since preferably only the attenuation signal of the output signal interferes essentially destructively with the direct sound and any part of the output signal of the front speaker, which is used to reproduce its own channel information, essentially does not interact with the direct sound through interference. In this way, a particularly effective attenuation can be achieved, in which the front loudspeaker preferably reproduces its own channel information at the same time. In this way, resources can be saved.

In a preferred embodiment of the speaker system, the relative adjustment of the output signals of the front speaker and the non-frontally radiating speaker to attenuate the undesired direct sound in the listening area relates to those output signals whose frequencies include the mid-range and high-frequency range. An expert in the audio field knows what is meant by the middle and high-frequency range, in particular in contrast to the low-frequency range. It has been shown that lower frequencies are difficult for the human ear to localize anyway. Therefore, the Haas effect plays essentially little or no role at lower frequencies. This preferably affects frequencies between approximately 0 Hz and 800 Hz, more preferably up to 300 Hz, particularly preferably between 50 Hz and 200 Hz and in particular between 100 Hz and 150 Hz. This can also depend on a woofer used.

In the prior art, it was assumed that a surround sound experience through reflected signals would only be possible up to certain maximum frequencies. This assumption was based on the fact that smaller loudspeakers (smaller diaphragms) should preferably be used for higher frequencies for a certain signal quality. In turn, due to fundamental physical relationships, smaller loudspeakers are less directional and have a more divergent sound emission cone. Therefore, their direct sound is larger. In the prior art, this was regarded as a hindrance, since an attenuation, in particular a simple attenuation, of a direct sound according to the invention was not known. Due to the directional ones often used in the past, the sweet spot was also very small, since a reflected signal only covered a very small area. In the preferred embodiment, where mid and high frequencies are adjusted relative to each other for attenuation, the listening area can be increased significantly and the system can be kept compact while maintaining high sound quality even at high frequencies.

A maximum frequency results from the fact that above a certain pitch the membrane of the speaker has to be very small. Therefore, depending on the specific loudspeakers used, there can be a maximum frequency, preferably related to the loudspeakers that do not radiate frontally. This can e.g. B. at 12 kilohertz (kHz).

Frontal and non-frontal loudspeakers can preferably also be so-called multi-way loudspeakers, which include mid-range speakers and tweeters (in the sense of the frequency ranges that are preferably emitted). The use of additional tweeters can preferably provide improved sound quality, increase the maximum frequency and decrease the directivity, thereby achieving a wider sweet spot.

In a preferred embodiment, a channel is assigned to the front loudspeaker, with a signal from an FIR filter being added to a channel signal in order to generate the output signal from the front loudspeaker. Thus, the signal of an audio channel and the attenuation signal can be contained simultaneously as an output signal through the front speaker. Suitable circuits for adding an electrical audio signal are known to those skilled in the art. The circuit is preferably digital. The circuit can preferably be integrated in a DSP chip. In this case, the DSP chip can be the same chip on which there is also (at least) one FIR filter and/or a delay element. In this way, the signal processing can be kept particularly simple and compact.

In the loudspeaker system according to the invention, a high-pass filter precedes the FIR filter. In this way, low frequencies, which do not have to be attenuated because they are difficult for the listener to localize from the outset, are not fed to the filter. As a result, the computing power of the FIR filter can be reduced, latency can be reduced, power consumption is lower, and the filter can be designed more simply. The limitation of excluding low frequencies from the attenuation of the FIR filter further reduces the required computing power of the DSP chip, so even cheaper chips can be used. It is particularly advantageous that FIR filters generally require more computing power the lower they are to act in the frequency range. This results in a synergistic effect. In addition, if necessary, the at least one front speaker can also be made smaller, making the system more compact and improving the sound quality of the front speaker at high frequencies. The high-pass filter can preferably be controlled using a DSP chip, be realized in particular by the same chip on which there is (at least) one FIR filter and/or a delay element.

In a preferred embodiment of the loudspeaker system, the high-pass filter has a cut-off frequency of between 50 Hz and 200 Hz, preferably between 100 Hz and 150 Hz. These frequencies have proven particularly effective in achieving the above objectives. Filters for these frequencies can also be implemented particularly easily.

Depending on the speaker types used, other cutoff frequencies may also be preferred. In this way, the speaker system can be individually adjusted.

In a preferred embodiment of the speaker system, the non-radiating speakers include side speakers and/or ceiling speakers. This creates a comprehensive surround sound experience.

• Bereitstellen mindestens eines nicht frontal strahlenden Lautsprechers und einem dem nicht frontal strahlenden Lautsprecher zugeordneten Kanals, der ein Raumklangkanal ist;
• Bereitstellen mindestens eines Frontlautsprechers;
• Bereitstellen eines pro Raumklangkanal dem Frontlautsprecher vorgeschalteten Filters;
• Bereitstellen mindestens eines pro Raumklangkanal dem nicht frontal strahlenden Lautsprecher vorgeschalteten Verzögerungsglieds,

wobei der Filter ein FIR-Filter ist und das Verzögerungsglied und der FIR-Filter konfiguriert sind für eine relative Anpassung der Ausgangssignale des Frontlautsprechers und mindestens eines nicht frontal strahlenden Lautsprechers eines Raumklangkanals zu einer Abschwächung eines unerwünschten Direktschalls des nicht frontal strahlenden Lautsprechers in einem Zuhörerbereich, dadurch gekennzeichnet, dass ein Hochpassfilter dem FIR-Filter vorgeschaltet ist.In a further aspect, the invention relates to a method for attenuating undesired direct sound from at least one non-radiating loudspeaker in a listening area for a loudspeaker system for reproducing at least one channel, preferably as described above, comprising

• providing at least one non-front-radiating loudspeaker and a channel associated with the non-front-radiating loudspeaker, which channel is a surround sound channel;
• providing at least one front speaker;
• providing a filter upstream of the front speaker for each surround sound channel;
• Provision of at least one delay element per surround sound channel upstream of the loudspeaker that does not radiate from the front,

wherein the filter is an FIR filter and the delay element and the FIR filter are configured for a relative adaptation of the output signals of the front loudspeaker and at least one non-frontally radiating loudspeaker of a surround sound channel to an attenuation of an undesired direct sound of the non-frontally radiating loudspeaker in a listening area, characterized in that a high-pass filter precedes the FIR filter.

The average person skilled in the art recognizes that technical features, definitions and advantages of preferred embodiments of the loudspeaker system according to the invention also apply to the method according to the invention.

In a preferred embodiment of the method, the relative adjustment of the output signals of the front speaker and the non-frontally radiating speaker is carried out in relation to the amplitude, the phase response and the frequency response.

In a further preferred embodiment of the method, the relative adjustment of the output signals of the front speaker and the non-frontally radiating speaker causes the undesired direct sound to be attenuated by partially destructive interference between the output signal of the front speaker and the unwanted direct sound of the non-frontally radiating speaker in the listening area.

Detailed description

The invention is to be explained in more detail below using examples and figures, without being restricted to these.

Brief description of the illustrations

• figure 1 Figure 12 shows a schematic representation of a prior art speaker system.
• figure 2 FIG. 12 shows a further schematic representation of a loudspeaker system of the prior art.
• figure 3 shows schematically the basic principle of the attenuation of a direct sound.
• figure 4 shows the schematic structure of the speaker system.
• figure 5 shows a measurement of undesired direct sound and desired reflected sound without attenuation.
• figure 6 shows a measurement of unwanted direct sound and wanted reflected sound with attenuation.

Detailed description of the figure

figure 1 shows a schematic representation of a speaker system 1 of the prior art for generating surround sound. An output signal 5 is generated by a non-frontally radiating loudspeaker, which is reflected on a wall 8 6 and is intended to give a listener 9 in the listening area 11 the feeling that the sound source is at the point of reflection. In this case, however, an undesired direct sound 7 is also generated by the non-frontally radiating loudspeaker, which reaches a listener 9 in the listening area 11 because of the shorter path in front of the reflected sound 6 . Due to the Haas effect, the listener 9 will locate the sound source based on the direct sound. The spatial sound experience to be generated by the reflected sound 6 is thus marred.

figure 2 Figure 1 shows an identical prior art speaker system 1 . A loudspeaker 3 oriented in the direction of the wall 8 and not radiating frontally is also shown here.

figure 3 shows the basic principle of the attenuation of undesired direct sound 7. On the left, the constellation known from the prior art for generating surround sound is shown once again, in which undesired direct sound 7 also arises. The loudspeaker system 1 on the right-hand side also has a front loudspeaker 13 , the output signal 15 of which contains an attenuation signal which, through appropriate adjustment, attenuates the undesired direct sound 7 so that only a heavily attenuated sound signal 17 from this arrives at a listener 9 in the listener area 11 . Thus, the listener essentially only reaches the desired, reflected sound 6 from a surround sound channel of a loudspeaker 3 that does not radiate from the front.

figure 4 shows schematically the structure of the loudspeaker system, the high-pass filter connected upstream of the FIR filter according to the invention not being shown. An electronic signal 19 of a surround sound channel is divided at a signal splitter 21 and fed to an FIR filter 23 in a signal arm, which is connected upstream of a front speaker 13 . The electronic signal 19 of the surround sound channel is adjusted by the FIR filter following filtering by the high-pass filter (not shown) in such a way that the front loudspeaker 13 generates an output signal which is used to attenuate the direct sound. At the same time, the electronic signal 19 of the surround sound channel in the other signal arm is time-adjusted by a delay element 25 before it is fed to a loudspeaker 3 that does not radiate frontally. This allows the output signal of the non-frontally radiating loudspeaker 3 to be adjusted over time, which takes into account the latency of the FIR filter 23 and the different propagation times of the direct sound and the output signal of the non-frontally radiating loudspeaker 3 . In this way, the direct sound and the associated attenuation signal can be brought into a temporal correspondence required for the destructive interference.

figure 5 shows a measurement in a listening area of reflected sound and direct sound as a function of time with a pulse-like output signal from the non-frontally radiating loudspeaker. It can be seen that a considerable direct sound signal occurred before the reflected signal reaches the listening area. The resulting psychoacoustic Haas effect causes a listener to use the direction of the direct sound to locate the sound source. The spatial sound effect to be achieved by the reflected signal fizzles out.

figure 6 shows the same measurement with simultaneous attenuation of the direct sound according to the invention. You can see that essentially no more direct sound is measured. The spatial sound effect is created.

It is pointed out that various alternatives to the described embodiments of the invention can be used to carry out the invention and to arrive at the solution according to the invention. The loudspeaker system according to the invention and the method are therefore not limited in their explanations to the above preferred embodiments. Rather, a large number of design variants are conceivable, which can deviate from the solution shown.

Reference List

1

speaker system

3

Non-front radiating speaker

5

Output signal (of the non-front radiating speaker)

6

reflected sound

7

direct sound

8th

Wall

9

listeners

11

audience area

13

front speaker

15

Output signal (of the front speaker)

17

Attenuated direct sound

19

Electronic signal of the surround sound channel

21

signal switch

23

FIR filter

25

delay element

Claims (12)

1. A loudspeaker system (1) for playback of at least one channel, comprising

   at least one non-frontally emitting loudspeaker (3) and a channel associated with the non-frontally emitting loudspeaker that is a surround sound channel,

   at least one front loudspeaker (13),

   per surround sound channel, a filter upstream of the front loudspeaker (13), and

   per surround sound channel, at least one delay element (25) upstream of the non-frontally emitting loudspeaker (3), wherein the filter is an FIR filter (23) and the delay element (25) and the FIR filter (23) are configured for a relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and the non-frontally emitting loudspeaker (3) of the surround sound channel to attenuate an undesirable direct sound (7) of the non-frontally emitting loudspeaker (3) within an audience area (11),

   characterised in that

   a high-pass filter is upstream of the FIR filter (23).
2. The loudspeaker system (1) according to claim 1,
   wherein at least one FIR filter (23) and/or at least one delay element (25) are implemented by a DSP chip.
3. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein the relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and the non-frontally emitting loudspeaker (3) is performed in terms of amplitude, phase response, and frequency response.
4. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein the delay element (25) is configured for a delay to compensate for a latency of the output signals (15) of the front loudspeaker (13) caused by the FIR filter (23).
5. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein the relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and the non-frontally emitting loudspeaker (3) to attenuate the undesirable direct sound (7) causes a partially destructive interference between the output signal (15) of the front loudspeaker (13) and the undesirable direct sound (7) of the non-frontally emitting loudspeaker (3) within the audience area (11).
6. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein the relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and the non-frontally emitting loudspeaker (3) to attenuate the undesirable direct sound (7) within the audience area (11) relates to output signals (15, 5), the frequencies of which comprise the mid- and high-frequency ranges.
7. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein a channel is associated with the front loudspeaker (13), wherein a signal of an FIR filter (23) is added to a channel signal to generate the output signal (15) of the front loudspeaker.
8. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein the high-pass filter preferably has a cut-off frequency between 50Hz-200Hz, in particular between 100Hz and 150Hz.
9. The loudspeaker system (1) according to any one or more of the preceding claims,
   wherein the non-frontally emitting loudspeakers (3) comprise side loudspeakers and/or ceiling loudspeakers.
10. A method for attenuating an undesirable direct sound (7) of at least one non-frontally emitting loudspeaker (3) within an audience area (11) for a loudspeaker system (1) for playback of at least one channel, preferably according to any one or more of the claims 1-9,

    comprising

    providing at least one non-frontally emitting loudspeaker (3) and a channel associated with the non-frontally emitting loudspeaker (3) that is a surround sound channel;

    providing at least one front loudspeaker (13);

    providing, per surround sound channel, a filter upstream of the front loudspeaker (13);

    providing, per surround sound channel, at least one delay element (25) upstream of the non-frontally emitting loudspeaker (3),

    wherein the filter is an FIR filter (23) and the delay element (25) and the FIR filter (23) are configured for a relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and at least one non-frontally emitting loudspeaker (3) of a surround sound channel to attenuate an undesirable direct sound (7) of the non-frontally emitting loudspeaker (3) within an audience area (11),

    characterised in that

    a high-pass filter is upstream of the FIR filter (23).
11. The method for attenuating an undesirable output signal according to the preceding claim,
    wherein the relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and the non-frontally emitting loudspeaker (3) is performed in terms of amplitude, phase response, and frequency response.
12. The method for attenuating an undesirable output signal according to any one or more of the preceding claims,
    wherein the relative adjustment of the output signals (15, 5) of the front loudspeaker (13) and the non-frontally emitting loudspeaker (3) to attenuate the undesirable direct sound (7) causes a partially destructive interference between the output signal (15) of the front loudspeaker (13) and the undesirable direct sound (7) of the non-frontally emitting loudspeaker (3) within the audience area (11).

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