EP0642292B1 - Device for sonic stereo reproduction - Google Patents

Description

The invention relates to a device according to the Genus of the main claim.

The human ear receives its directional information the evaluation of level and transit time differences between the one received by the right and the left ear acoustic signals. With an ideal listening location in the middle a so-called stereo triangle from the left speaker, then corresponds to the right loudspeaker and listeners Direction information of the stereo recording.

On the other hand, the listener is in a place that asymmetrical to a two or more speaker system lies, the sound impression is spatially strong to that next speaker moved.

During level differences through conventional balance controls and faders can be adjusted manually usually the transit time differences of the sound signals individual speaker systems not balanced. These are however for directional hearing according to the psycho-acoustic Law of the first wavefront essential.

Car radios with runtime compensation are already known, however, these require manual measurement and then entering the distances between the listening location and the speakers.

EP 504 562 A1 describes a sound reproduction arrangement for a sound reproduction with a surround sound effect for motor vehicles demonstrated at the audio signal delay devices are provided to a certain in the speaker channels Effect delay time. The delay times of the Sound signal delay devices are set so that in addition a smoothing of the frequency response of the Sound level is reached at the listening location, with the Fluctuation range of the delay is used, which is on Listening location not noticeable.

The object of the present invention is in a Establishment according to the genus of the main claim Setting the delay times easier.

In the device according to the invention, this task solved in that for playback with the help of each Loudspeaker provided audio signals Pass through delay devices whose Delay time is adjustable that means for measuring the Sound transit times from the individual speakers to the listening location are provided and that the delay times are such are automatically adjustable that the sum of the Sound duration and the respectively set Delay time is the same for all speakers.

In addition to ease of use, the invention Establishment also has the advantage that the actual Sound duration is taken into account during manual Measurement for an assumed path of sound between the concerned speaker and the listening location is performed. In the latter, for example, a reflection or Redirection of the sound waves not taken into account.

Level differences at the listening location are according to a training the device according to the invention takes into account that further means for measuring the by reproducing a Measurement signal, preferably a noise signal, through the sound level caused by individual loudspeakers at the listening location are provided and that the volume of each Loudspeakers in the sense of level difference compensation can be preset automatically.

Another development of the device according to the invention is that the set delay times and if applicable, the saved presets of Volume can be stored in a non-volatile memory for several listening locations are. It is preferably provided that a Information about which of the saved Delay times and, if applicable, the saved ones Presets of the volume each time the Device are fed to the delay devices, is also non-volatile storable.

With this training, a car radio can, for example with the device according to the invention after measuring the Sound transit times for the individual seating positions like this be programmed to play by pressing a button can be optimized for the individual seating positions and that when switching on the device that of a predetermined Delay times assigned to the seat position are set become. This will generally be the seating position of the Driver.

Modern receiving devices, in particular car radios, include often digital signal processing. Here it is advantageous if according to an embodiment of the invention it is provided that the delay devices of digital memories are formed, from which the respective audio signals to be delayed compared to registered mail be read out with a time delay.

An advantageous embodiment of this embodiment consists in that the digital memories are part of a digital audio signal processing device, that after the measurement of the sound propagation times (T _x ) for all loudspeakers (1 ... x) the maximum sound propagation time (T _max ) is selected and that the individual delay _{times are} calculated in accordance with Ta _x = (T _max -T _x ) x, where Ta is the delay time to be set in sampling cycles of the digital audio signal processing device, x the respective loudspeaker and k the ratio between the processor cycle duration, in which the sound transit times T _x and T _{max were} measured, and the sampling cycle time.

An adaptation of the device according to the invention to the The respective arrangement of the speakers and the listening location is in advantageously possible in that for measuring the Sound transit time one speaker at a time Pulse signal is supplied, while a Timer is started, which measures the time until one Measuring microphone the sound level a predetermined threshold exceeds. To overload tweeters to avoid, it can be provided that the Pulse signal via a low-pass filter, preferably third Order with a cut-off frequency of 11 kHz, the loudspeaker is fed. The pulse signal itself is, for example realized by a rectangular pulse of approximately 3 ms duration.

In addition to the automatic adjustment to the sound transit times can also others in the inventive device Adjustments are made and saved. So is characterized, for example, by further training, that the audio signals further Frequency response equalizer circuits go through that means to measure the frequency response between the speakers and a measuring microphone are provided and that the Frequency response equalizer according to the results of the measurement are adjustable, the respectively set Frequency responses of the individual speakers for different ones Listening locations can be saved.

Fig. 1

ein Blockschaltbild einer erfindungsgemäßen Einrichtung,

Fig. 2

ein Ablauf-Diagramm zur Erläuterung der Messung der Schall-Laufzeiten und der Schallpegel sowie der anschließenden Einstellung der Verzögerungszeiten und Lautstärke und

Fig. 3

eine schematische Darstellung eines Autos mit vier Lautsprechern und einem Fahrer und mit den durch die Verzögerungszeiten für diese Hörposition entstehenden scheinbaren Lagen der Lautsprecher.

Exemplary embodiments of the invention are shown in the drawing using several figures and are explained in more detail in the following description. It shows:

Fig. 1

2 shows a block diagram of a device according to the invention,

Fig. 2

a flow chart to explain the measurement of the sound transit times and the sound level as well as the subsequent setting of the delay times and volume and

Fig. 3

is a schematic representation of a car with four speakers and a driver and with the apparent positions of the speakers resulting from the delay times for this listening position.

Identical parts are given the same reference symbols in the figures Mistake. In Fig. 1, signal lines are as solid Lines and control lines as dashed lines shown.

1 represents the NF part for example a car radio with inputs 1, 2, 3 for a receiver, a cassette player and one CD player. Another input 4, which is only for one of the stereo signals, for example the right signal R, is executed, signals from a microphone amplifier 5 fed. During an operating mode "Measure" the input switch 6 in the position 4, so that the Signals of the microphone amplifier 5 are forwarded. In In a "playback" mode, signals from one of the Inputs 1, 2 or 3 via the input switch 6 one Stereo-analog / digital converter 7 supplied. The Input switch 6 and others described later Changeover switches can be controlled by a control device 8.

The outputs of the analog / digital converter 7 are included Inputs of a two-way switch 9 connected to the is also controllable by the control device 8. In the the upper position of the double changeover switch 9 digitized audio signals L and R of two each controllable delay devices 10, 11; 12, 13. This can be used as read-write memory (RAM) on a digital Signal processor implemented or external to this be connected. The memory access takes place via the internal address and data management of the digital Signal processor. The sequence, switching and level control can by the digital signal processor itself or a external microcontroller.

The output signals of the controllable Delay devices are each for the left Front speaker, for the left rear speaker, for the right front speaker and for the right one Rear speakers provided and therefore with LF, LR, RF and RR designated. These signals become inputs of a Quadruple switch 14 fed and in the upper position the fourfold switch to two Stereo digital / analog converters 15, 16 forwarded.

The output signals LF ', LR', RF 'and RR' of the Digital / analog converters 15, 16 arrive via controllable Volume control 17, 18, 19, 20 and power amplifier 21, 22, 23, 24 as signals LF ", LR", RF "and RR" to the Speakers 25, 26, 27, 28. A measuring microphone 29 can the different listening locations, in a motor vehicle the different seating positions, and is brought with connected to the input of the microphone amplifier 5.

An operating and optionally connected display unit 30 with the in addition to the usual operating functions by a corresponding one Key input measuring the run times and the Sound level can be initiated. For this operating mode "Measure" the double switch 9 in the lower Position controlled. Furthermore, during the operating mode "Measure" the individual switches of the four-way switch 14 independently controllable such that one after the other one of the switches to the middle position (connection to Test signal impulse or noise) and the other switches take the lower position, in which the respective Speakers received no signals. That about the Signal chain 29, 5, 4, 6, 7, 9 incoming measurement signal MEAS is then a level meter 31 and then one Threshold discriminator 32 supplied. Whose exit is connected to a time meter 33 which is essentially consists of a counter from the control device started together with a pulse generator 34 and by the output signal of the threshold discriminator 32 is stopped.

The output of the pulse generator is through a low pass filter 35 connected to a first input of a changeover switch 36. At the second input of the switch 36 is a Noise generator 37 connected, also from the Control device 8 is controllable.

Fig. 2 shows the flow chart of a program for the Control device 8 (Fig. 1) during the operating mode "Measure" and in abbreviated form during the operating mode "Reproduction". In the operating mode "Playback" or in Normal operation are the usual functions, such as for example manual control of the volume controls 17 to 20 and the choice between inputs 1, 2 or 3, possible. Furthermore, in the "Playback" mode for several listening locations previously saved runtime and Volume settings from a non-volatile memory the control device 8 read out and the actuators 10 to 13 and 17 to 20 are supplied. The double switch 9 and the four-way switch 14 are in the upper Position o.

The program part 41, which effects these functions, is run through cyclically, with one before each repetition There is a query as to whether there is an acoustic measurement should. Is this using the operating device 30 has been entered, then after the branch 42 "Measure" operating mode activated. In a program part 43 the volume controls 17 to 20 (Fig. 1) on one defined standard value (medium volume). Furthermore, this part of the program waits for the Operator the measuring microphone 29 (Fig. 1) to the first measuring hearing place.

Then the input switch in the program part 44 the input 4 and the double switch 6 in the lower Position controlled. The four-way switch 14 is for the each channel to be measured to the middle position m and moved to the lower position u for the other channels, in which a mute of the connected Loudspeaker.

At 45, the switch 36 is in the left position 1 posed while the pulse generator 34 and the Runtime meter 33 are started. As soon as the sound level on the measuring microphone exceeds a certain threshold, the runtime meter 33 is stopped at 46 and the measured value stored in the control device 8 (FIG. 1).

Then the switch 36 in the program part 47 in the brought right position r and the noise generator for a Time of about 500 ms. With the help of Level meter 31 is determined at 48 average noise level at the microphone over a part of the time window, for example over 200 ms. This value is also saved.

At 49 the program branches depending on whether all four channels have been measured. If this is not yet the case, the program parts 44 to 49 are repeated for the next channel. However, if all four channels have been measured, the measured values T _LF , T _RF , T _LR , T _RR (T _x ) for the runtimes of the four channels and the measured values L _LF , L _RF , L _LR , L _RR (L _x ) before.

In the subsequent program part 50, the delay _{times to} be set for the delay devices 10 to 13 are calculated in accordance with Ta _x = (T _max -T _x ) * k, where Ta is the delay time to be set in sampling cycles of the digital audio signal processing device, x the respective loudspeaker (LF, RF, LR , RR) and k denotes the ratio between the processor cycle time in which the sound propagation times T _{x were} measured and the sampling cycle time. The maximum sound propagation time T _max (in processor cycles) was previously determined from the measured sound propagation times. Furthermore, in the program part 50, the delay devices 10 to 13 are set to the calculated values and the four values are stored together with an indication of the associated listening location in a non-volatile memory of the control device.

In program part 51, the corresponding steps for the measured volume level L _x follow. First L _{max is} formed. Then La _x = L _max -L _{x are} calculated for the different speakers. The four equalization levels La _x are added as a fixed offset to the respective volume level set by the user in the individual channels. After their calculation, the compensation levels are stored in the non-volatile memory for the associated listening location.

A branch 52 takes place depending on whether it is still additional listening locations should be measured. Isn't that the case, at 53 the volume controls are set to the front the activation of the operating mode "measure" existing values plus the offset determined in program part 51 set. At 53 that input 1 is also again 2 or 3 set which was active before the calibration. In addition, the other changeover switches are in accordance with the "Playback" mode switched. The program will then continued at 41. However, there should be additional listening locations be measured, what by an appropriate input after branching 52, the program becomes 43 repeated.

3 schematically shows a car 60 with a driver 61 and four speakers 25, 26, 27, 28. The distances a, b, c and d are from the driver's head to the individual speakers different sizes. As a result, the aforementioned adverse effects. In the case of the invention The facility is supported by the runtime adjustment with the help of controllable delay devices 10 to 13 (Fig. 1) of the effective distance for the psycho-acoustic listening impression made the same size for all speakers. The Speakers 28 farthest from driver 61 its distance d at. Get the other speakers also a distance of d and are apparently in positions 25 ', 26' and 27 ', which lie on a circle around driver 61.

Claims (10)

1. Device for stereophonic reproduction in an enclosed space, preferably in a motor vehicle, having a plurality of loudspeakers and at least one listening location which may be at various distances from the loudspeakers, audio signals which are provided for reproduction using the individual loudspeakers (25, 26, 27, 28) passing through delay devices (10, 11, 12, 13) whose delay time is settable, characterized in that means (5, 29, 31, 32, 33, 34, 35) are provided for measuring the sound propagation times from the individual loudspeakers (25, 26, 27, 28) to the listening location, and in that the delay times can be set automatically such that the sum of the sound propagation time and the delay time set in each case is the same for all loudspeakers (25, 26, 27, 28).
2. Device according to Claim 1, characterized in that means (5, 29, 31, 37) are additionally provided for measuring the sound levels produced at the listening location by the individual loudspeakers (25, 26, 27, 28) as a result of reproduction of a measured signal, preferably a noise signal, and in that the volume of the individual loudspeakers (25, 26, 27, 28) can be automatically preset for the purpose of compensating for level differences.
3. Device according to one of Claims 1 and 2, characterized in that the delay times set, and possibly presets for the volume, can be stored on a non-volatile basis for a plurality of listening locations.
4. Device according to Claim 3, characterized in that information about which of the stored delay times, and possibly of the stored presets for the volume, are supplied to the delay devices (10, 11, 12, 13) when the device is turned on can likewise be stored on a non-volatile basis.
5. Device according to one of the preceding claims, characterized in that the delay devices (10, 11, 12, 13) are formed by digital memories from which the respective audio signals to be delayed are read with a time delay with respect to writing.
6. Device according to Claim 5, characterized in that the digital memories are parts of a digital audio signal processing device, in that the device is suitable for selecting, once the sound propagation times (T_x) have been measured for all the loudspeakers, the maximum sound propagation time (T_max) from said sound propagation times (T_x) and calculating the individual delay times in accordance with Ta_x = (T_max - T_x)·k, where Ta denotes the delay time to be set in sampling cycles of the digital audio signal processing device, x denotes the respective loudspeaker and k denotes the ratio between the processor cycle duration in which the sound propagation times T_x and T_max were measured and the sampling cycle duration.
7. Device according to one of the preceding claims, characterized in that it is suitable, for the purpose of measuring the sound propagation time, for successively supplying a pulsed signal to a respective loudspeaker and at the same time starting a chronometer (33) which measures the time until the sound level exceeds a prescribed threshold value at a measurement microphone (29).
8. Device according to Claim 7, characterized in that the pulsed signal is produced by a square-wave pulse having a length of at least 3 ms.
9. Device according to one of Claims 7 and 8, characterized in that it is suitable for supplying the pulsed signal to the loudspeaker (25, 26, 27, 28) via a low-pass filter (35), preferably of third order with a cut-off frequency of 11 kHz.
10. Device according to one of the preceding claims, characterized in that the audio signals additionally pass through frequency response equalizer circuits, in that means are provided for measuring the frequency response between the loudspeakers and a measurement microphone, and in that the frequency response equalizers can be set on the basis of the results of the measurement, the respectively set frequency responses of the individual loudspeakers being capable of being stored for various listening locations.

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