Difference between revisions of "Time Correct Hearing In Space"
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=== Raum und Hördistanz ===
+
== Space and listening distance ==
 +
A sound document contains more or less distinct spatial information about the original acoustic environment. In the ideal case of perfect reproduction of a recorded sound event, there are no reflections through a listening room. In practice, this ideal case does not exist. A playback room adds its own, further room characteristics. The time window for the room-independent direct sound covers a very short time span of a few milliseconds (transients). So what is the sound-relevant information?<br />
 +
Ultimately, it is the form of vibration that we as listeners receive at the listening position, at our auditory organs. We should measure this mode of vibration and look at the influence of the room on it.
 +
*How does a reflection change the sound waves?
 +
*When do room resonances have an influence, and in what form?
 +
*How does a sheetrock wall affect the waveform when sound is reflected?
 +
*What happens to a sound wave when it passes through a curtain and reflects off the wall behind it?
 +
*What happens to the waveform when sound reflects off a cabinet wall?
 +
*What is the sum of direct sound and reflection in terms of what we hear, namely the waveform?
 +
Depending on the room conditions, the proportion of "room-independent" sound (direct sound) will be more or less. We can only compensate for room acoustics to a limited extent. The listener's head is located at a certain place in the room. Only if we always place it at exactly the same point in the room will there be a modest chance of success. Sliding into a chair or changing seats while listening in a relaxed manner, however, turns all corrective measures on their head. And if several people want to listen at the same time?
 +
You could still tinker with the speaker - but for which of the myriad room acoustics? There are almost as many different rooms as there are homes. So what are commonalities in the living spaces of the group of people buying a particular loudspeaker? One thing all living spaces have in common is a floor. This is very close to the acoustic centres for floorstanding speakers and for compact speakers on a stand. In the user's home, the floor is an ever-present boundary surface with a significant effect on bass response. It follows: Loudspeakers should have a clear vertical focus.<br />
 +
The second thing most living rooms have in common: There are several seating areas in the room. These are not arranged one above the other, but side by side. It follows: Loudspeakers should have a horizontal bundling that allows a practical, wide dispersion. In addition, the side walls, seen from the loudspeaker, should be rather averted and far enough away. And seating should also be a sufficient distance from reflective surfaces. A thick carpet in the area between the speakers and the seats is particularly beneficial. If there is a table in front of the seats, then its surface should be covered with a sound absorbing pad, table runners, etc., or numerous objects placed on it. This can also help.
 +
Since every listening room has its own reflection behaviour, there is no general validity for a somehow defined radiation behaviour of loudspeakers. The loudspeaker should emit a sound structure that is as exactly transformed as possible under the direct sound relevant radiation angles. The direct sound relevant radiation angles are in practice:<br />
 +
*horizontal approx. 0 to +/- 15°.<br />
 +
*vertical approx. 0 to +/- 5°.<br />
  
−
Je nach Raumgegebenheiten wird der Anteil des "raumunabhängigen" Schalls (Direktschall) mehr oder weniger groß sein.  
+
If you are building your own house, you can try to find an architect who designs rooms in such a way that they do not have parallel walls. Just a few degrees of slant to each other will do wonders. Not only when listening to loudspeakers, but any noise then builds up less.<br />
 +
[[File:2380350990 3 g-4.jpg]]<br />
 +
''[[Myro a priori 10.02]]''
 +
|}
  
−
*Bei geringem Hörabstand und großem Abstand der Lautsprecher von reflektierenden Flächen ist der Direktschall-Anteil groß.
+
{| class="wikitable" border="1"
−
*Bei großem Hörabstand und geringem Abstand der Lautsprecher zu reflektierenden Flächen ist der Direktschall-Anteil gering.
+
|-
−
*Bei Nahfeldmonitoren ist demzufolge die Übertragungsfunktion in der Regel besonders im Direktschall, also in direkter Abstrahlrichtung, wichtig.
+
|
−
*Bei Fernfeldmonitoren ist demzufolge die Übertragungsfunktion in der Regel auch außerhalb der direkten Albstrahlrichtung wichtig.
+
<gallery>
 +
Time1.step-response.jpg
 +
</gallery>
 +
|
 +
The sound structures arriving at the listening position consist of the direct sound components, which are unaffected by the room (exception: low frequencies), and the indirect sound components, which are changed by the reflection. The low frequency range is the area where the first reflections are already superimposed on the transient response. Here there is virtually no unaffected direct sound component left. As an example, consider a 3-way transducer, the [[Myro Time 2]]. With the size of this loudspeaker and the necessary larger measuring distance you can see (left) very nicely the first room reflection and its superposition of the step response.<br />
 +
We perceive the first milliseconds of direct sound, which reach our auditory organ unaffected by reflections, in the same way as those of a natural sound event. Impulses and transients, with the exception of the low-frequency range, reach the auditory organ directly. For the conversion and transmission of impulses and transients, it is logical to make a measurement at the location of the auditory organ.
  
 +
If the listening distance is small and the distance between the loudspeaker and reflecting surfaces is large, the direct sound component is large.
 +
*With a large listening distance and a small distance between the loudspeakers and reflecting surfaces, the direct sound component is small.
 +
*For near-field monitors, the transfer function is therefore usually particularly important in the direct sound, i.e. in the direct radiation direction.
 +
*For far-field monitors, the transfer function is therefore usually also important outside the direct albedo direction.
 +
|}
  
−
=== Direktschall ===
+
The deformations of the sound waves during the reflection process are extraneous influences, as is the deformation due to incoherent sound transducers. But errors in the reproduction also propagate in the room acoustics:
−
Der direkte Schallanteil erreicht den Hörer auf direktem Weg, ohne den Einfluss von Raumbegrenzungen oder Einrichtungsgegenständen, ohne Verdeckung, also praktisch bei direkter Sichtverbindung des Hörers zur Schallquelle. In diesem Schallanteil steckt ''die einzige unverfälschte Information'' über die Schallstruktur der Schallquelle und im Idealfall eines richtig wandelnden Lautsprechers bzw. über die Originalschallstruktur der Aufnahme. Nur im Direktschall ist die Einschwing- / Impulscharakteristik unverformt hörbar, und das ist die einzige Information, die uns eindeutig wahrnehmen lässt, von welcher Art und Charakteristik die Schallquelle ist und welche Dynamik und Zeitinformationen die Aufnahme beinhaltet. Nur hier hören wir wirklich, welcher Raumklang in der Aufnahme steckt. Der Direktschallanteil hat in Räumen, obwohl anteilmäßig geringer als der Indirektschall, darum eine größere Bedeutung. Das Erkennen und Orten der Schallereignisse innerhalb des Originals (Aufnahme), also auch das Erkennen des originalen Raumklanges, ist nur im Direktschall eindeutig möglich.
+
*Room reflections of faithfully transduced sound structures sound like reflections of the original.
−
<br />
+
*Room reflections of sound structures that have not been faithfully converted do not sound like reflections of the original.
−
Lautsprecher, die diese Charakteristik nicht richtig reproduzieren, verwehren uns den Zugang zum anderen Aufnahmeraum. Hier verzerrt sich das Bild und verschieben sich die verschiedenen Instrumente je nach Einsatz und Tonhöhe.
 
  
−
=== Indirektschall ===
+
For the decay of instruments or for continuous tones, the interaction of the listening room with the sound emitted by the loudspeaker plays the decisive role in addition to the direct sound component, because especially in the steady state, the interaction of loudspeaker and room determines what happens. To achieve this, a loudspeaker should of course have a sound structure that is as consistent as possible under different dispersion angles. The organ is the best example of an instrument with a high level in the steady state, and it is precisely here that the interaction of loudspeaker and room takes effect.  
−
Trift der Schall der Schallquelle auf ein Hindernis oder wird er von einer Fläche oder Wand reflektiert, so ändert sich dessen Druck-Zeitstruktur (die Signalstruktur). Bei jeder Reflexion wird Schallenergie selektiv absorbiert und in Materialschwingung und Wärme umgewandelt.
 
−
Zudem fügt die in Schwingung versetzte Reflexionsfläche durch verstärkte Eigenschwingung bei bestimmten Frequenzen Schallenergie hinzu bzw. absobiert Schallanteile durch Gegenphasigkeit der Eigenschwingung in Bezug zur auftreffenden Schallstruktur.
 
 
<br />
 
<br />
  
−
Fazit: Reflektierter Schall beinhaltet nicht mehr die gleiche Schallstruktur wie der Direktschall und ist somit viel schwerer zu verstehen.
 
−
<br />
 
−
Der indirekte Schallanteil gibt uns viele Eindrücke über die Charakteristik unseres Hörraumes. Auf Grund unserer Hörerfahrung erkennen wir sehr deutlich, ob wir in unserem Wohnzimmer, im Keller oder in der Dusche Musik hören.
 
−
Je höher also der indirekte Schallanteil, desto mehr passiert alles in unserem Raum und desto schlechter gelingt die Reproduktion des Originalklanges.<br />
 
−
 
−
Der indirekte Schallanteil und damit der Klang des Hörraumes wird wesentlich bestimmt durch die Reflexionen und die Resonanzen.
 
−
 
−
| [[Datei:Rebell3.jpg]]
 
−
|}
 
 
{| class="wikitable" border="1"
 
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|-
 
|-
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| [[Datei:GrandConcertEntwurf08 631x337.jpg]]
+
| [[File:GrandConcertEntwurf08 631x337.jpg]]<br />
 +
''[[Myro Grand Concert II]] Design Study''
 
|  
 
|  
−
==== Resonanzen ====
+
Ultimately, what counts is the sound structure that arrives / takes effect at the auditory organ. The direct sound component, although proportionally smaller than the indirect sound, has a greater importance in rooms, because only in it room-independent information about the original is contained. The recognition and localization of sound events within the original (recording), i.e. also the recognition of the original room sound, is only clearly possible in direct sound. The next most important are the early, briefly following, energetic, first reflections. Everything that reaches our hearing organ after multiple reflections and attenuation tends to get lost in the general chaos of reflections and is of secondary importance.<br />
 +
For the larger radiation angles relevant to indirect sound, the quality of the sound structure radiated by the loudspeaker is also decisive for the impression of "authenticity".<br />
  
−
Wird eine Schallwelle zwischen parallelen Wänden hin und her reflektiert, so schwingt sie sich zu einer Resonanz auf.
+
The listening experience with signal / time accurate loudspeakers is: Due to the excellent intelligibility and the detachment of the sound from the loudspeaker, the perception of the original information gains dominance over the perception of the listening room. The direct sound is of clearly superior importance for the perception of the original sound. Quantitatively, this experience cannot be justified, because the direct sound amounts to only about one fifth of the total sound.
−
Der Abstand der Wände zueinander bestimmt dabei das Frequenzspektrum der Resonanz.
 
−
Zwischen den Wänden entstehen je nach Frequenz Überhöhungen und Einbrüche im Frequenzbereich. An den Wänden haben die Grundresonanz und deren Vielfache ihr Druckmaximum. Das Klangbild wird hier ungleichmäßig überhöht, so ähnlich wie bei einer Transmissionlinebox.
 
  
−
'''''Experiment 1:'''''<br />
+
For locating and recognizing a sound structure stored in a recording, the following order of priority therefore applies:<br />
−
''Dazu brauch man entweder einen Frequenzgenerator oder eine Test-CD mit festen Testtönen im Bassbereich.''<br />
 
−
''Beispiel: ein 50 Hz Ton.''<br />
 
−
''Wir können nun den 50 Hz Ton über unsere Lautsprecher abspielen. Am besten den Player auf Repeat stellen.''<br />
 
  
−
''Nach wenigen Bruchteilen einer Sekunde erreichen wir den eingeschwungenen Zustand im Raum und erleben die Wirkung von Raumresonanzen unmittelbar. Wenn wir uns nun bewegen, vor und zurück, nach oben und nach unten, einfach durch den Raum gehen, dann wissen wir, warum wir bisher dachten, dass der eine Lautsprecher viel und der andere Lautsprecher weniger Bass machte. Und bei jeder anderen Frequenz ergibt sich eine andere Verteilung der Druckbäuche und -knoten. (So nennt man die Überhöhungen und Einbrüche im Schalldruckverlauf.)''
+
1. direct sound (transients)
  
−
==== Reflexionen ====
+
*30-fold (!) increased nerve firing rate from the auditory organ to the brain, thus maximum attention
−
Reflexionen finden in der Raumakustik besondere Bedeutung unter dem Aspekt der Nachhallzeiten. Auf Grund deren zeitlicher Verzögerung gegenüber dem Direktschall erhalten wir die Informationen, die wir benötigen, um die Geometrie des Hörraumes zu erkennen und die Schallquelle zu lokalisieren. In Bezug auf die Reproduktion einer Schallaufnahme durch Lautsprecher hat dies folgende Auswirkungen:
+
*maximum dynamics / amplitude values
 +
*the only sound component with the chance to transmit original structures
  
−
1. Wir hören zusätzlich zu den in der Aufnahme enthaltenen Rauminformationen den Raumeindruck eines zweiten Raumes, unseres Hörraumes, mit seiner typischen Charakteristik. Diese beiden Raumeindrücke überlagern sich und erzeugen eine mehr oder weniger ausgeprägte Unschärfe in der Wahrnehmung. Wir sind es nicht gewohnt, in zwei unterschiedlichen Räumen gleichzeitig zu sein.<br />
+
2. first early reflections
  
−
2. Die Lokalisation der Schallquelle, in diesem Fall des Lautsprechers, beschert uns neben den Musikern noch weitere Akteure.
+
*the shortest time sequence to direct sound
−
Erschwerend kommt hinzu, dass das bei fast allen Lautsprechern miserable Einschwingverhalten (100% Verzerrung der ersten Halbwellen) ebenfalls den Lautsprecher als Schallquelle ortbar macht.<br />
+
*high energy content
 +
*can superimpose and alienate direct sound
  
−
Ein weiterer sehr bedeutender Faktor ist die Signalverformung durch den Reflexionsvorgang. Hier stellt sich die Frage:
+
3. multiple reflected sound components (reverberation)
−
Wie klingen eigentlich die Reflexionen meines Hörraumes?
+
 
−
|}
+
*long time sequence on the direct sound
 +
*decreased energy content
 +
*strong structural deformations due to the reflection processes (non-linear absorption)
 +
 
 +
4. quasi steady states (space modes)
  
−
'''Zeitversatz'''<br />
+
*long time sequence to the direct sound
−
Folgt eine Reflexion kurzzeitig, extrem schnell dem direkten Schall, so ordnen wir diese Sekundärschallquelle in unserer Wahrnehmung eher der Ursprungs-Schallquelle zu. Jedoch verschwimmt dabei die Ortung etwas, so dass der Schall aus einem breiteren Bereich zu kommen scheint. In Bezug auf unsere Vorstellung der Positionierung von Musikern innerhalb eines Aufnahme-Raumes kommt es dabei zu einer Unschärfe der Lokalisation. Die Raumabbildung wirkt zudem breiter und verliert an Tiefenstaffelung.<br />
+
*high energy content
−
Später eintreffende Reflexionen werden vorrangig dem Raumempfinden des eigenen Hörraumes zugeordnet.<br />
+
*no longer contain original sound structures<br />
  
  
−
'''Die erste Überlagerung mit dem Direktschall'''<br />
+
And there are the aspects of the transformed sound components
−
Grundsätzlich überlagert sich der reflektierte Schall mit einem entsprechenden Zeitversatz dem Direktschall. Dabei ergeben sich durch Phasenverschiebungen Additionen und Subtraktionen. Der Frequenzgang wird stark wellig, so ähnlich wie bei kantigen wenig abgerundeten Lautsprechergehäusen. Dieses Phänomen wirkt sich im Hörraum zunehmend stärker aus, je tiefer die vom Lautsprecher abgestrahlte Frequenz ist. Tiefe Frequenzen werden eher breit abgestrahlt und beeinflussen demzufolge stärker das Reflexionsgeschehen.<br />
+
*excited self-resonances of the room-boundaries
−
Eine nahezu dramatische Auswirkung haben Reflexionen, die mit dem Einschwingvorgang interferieren (sich überlagern).
+
*excited self-resonances of all objects in space
−
Dies geschieht besonders häufig im Tiefton- und Grundtonbereich, da die ersten Halbwellen des Einschwingvorganges einen längeren Zeitraum zur Entstehung brauchen (Hz = Schwingungen pro Sekunde) als bei hohen Frequenzen. Dramatisch ist die Auswirkung deshalb, weil durch die Deformation der Einschwingvorgänge wesentliche Informationen über das Original-Klanggeschehen verzerrt werden.
+
which act as frequency-filters and transform certain sound-parts into mechanical vibrations and heat. The mechanical vibrations in turn act as sound sources and are not insignificantly involved in the sound of the room.
  
 +
In all considerations, the only thing that counts is the quality of the sound structure. First early reflections, which superimpose the transient processes, are next to the strong dynamic compression in some recordings at the top of the list of factors that can relativize the advantage of the signal / time accurate conversion. For playback with loudspeakers, the following therefore applies:
 +
* optimisation of room acoustic parameters, speaker placement, seating position, etc.
 +
* perfect reproduction of the direct sound component. Here, too, the transient response is of particular importance.
 +
* as little loudspeaker sound as possible in the direction of nearby room surfaces.
 +
* an as evenly as possible directed radiation behaviour of the loudspeaker.
 +
|}
  
−
'''''Experiment 2:'''''<br />
+
For the reproduction with loudspeakers applies:
−
''Wir brauchen eine CD mit Rauschen, am besten mit Rosa Rauschen, oder einen Rauschgenerator. Zur Not hilft auch ein Radio ohne Antenne!<br />
+
*optimization of room acoustic parameters, speaker placement, seating position, etc.
−
''Dann schließen wir nur einen Lautsprecher an und bitten einen Freund, eine Freundin oder die Nachbarin, uns zu helfen. Der helfenden Person drücken wir nun einen etwas größeren, flachen Gegenstand in die Hände, z.B. Regalboden, Weltatlas o.ä., und stellen sie neben den Lautsprecher.<br />
+
*a reproduction of the direct sound component as perfect as possible. Here, too, the transient response is of particular importance.
−
''Nachdem wir es uns im Sessel gemütlich gemacht haben, bitten wir nun unsere/n Helfer/in, den flachen Gegenstand als Schallreflektor einzusetzen, sich langsam dem Lautsprecher zu nähern, sich wieder zu entfernen und dabei den Reflektor in verschiedenen Winkeln zum Lautsprecher zu positionieren.<br />
+
*as little loudspeaker sound as possible in the direction of nearby room surfaces
 +
*as evenly directed radiation behaviour of the loudspeaker as possible
  
−
''Dieser Versuch macht unmittelbar und praktisch erlebbar, wie reflektierende Gegenstände oder Flächen in der Nähe von Schallquellen wirken.''
+
'''Can room correction help?'''<br />
 +
The sense of hearing is capable of differentiating the incoming pressure fluctuations of the air (sound waves). It does not simply form the sum of the amplitude values, like a measuring procedure, but perceives the individual information contained therein. Without this ability, all the many amazing hearing properties could not be explained.<br />
 +
An electronic room correction, which, if it is committed to the ideal of the original input signal, is an over-all correction, would have to be capable of a differentiated correction of the direct sound and the reflected sound components arriving at the listening position from different directions, with different transit times, with their individual structure. However, this is not possible due to the principle. In this respect the following recommendations result:
 +
# Use loudspeakers with a linear frequency band
 +
# The loudspeakers should have a regular directivity (over the whole frequency response an even decrease of the level off axis)
 +
# a favourable positioning of the loudspeakers and the listening place with regard to excitation and effect of the modes
 +
# even reverberation times of the room
 +
# only then, if there are still problems with modes, narrowband reduction of the frequencies of the disturbing modes
  
  
 
<''zurück [[Myroklopädie]]''><br />
 
<''zurück [[Myroklopädie]]''><br />
 
<''zurück [[Myro]]''>
 
<''zurück [[Myro]]''>

Latest revision as of 12:02, 31 October 2020

Template:Delete candidate

Space and listening distance[edit]

A sound document contains more or less distinct spatial information about the original acoustic environment. In the ideal case of perfect reproduction of a recorded sound event, there are no reflections through a listening room. In practice, this ideal case does not exist. A playback room adds its own, further room characteristics. The time window for the room-independent direct sound covers a very short time span of a few milliseconds (transients). So what is the sound-relevant information?
Ultimately, it is the form of vibration that we as listeners receive at the listening position, at our auditory organs. We should measure this mode of vibration and look at the influence of the room on it.

  • How does a reflection change the sound waves?
  • When do room resonances have an influence, and in what form?
  • How does a sheetrock wall affect the waveform when sound is reflected?
  • What happens to a sound wave when it passes through a curtain and reflects off the wall behind it?
  • What happens to the waveform when sound reflects off a cabinet wall?
  • What is the sum of direct sound and reflection in terms of what we hear, namely the waveform?

Depending on the room conditions, the proportion of "room-independent" sound (direct sound) will be more or less. We can only compensate for room acoustics to a limited extent. The listener's head is located at a certain place in the room. Only if we always place it at exactly the same point in the room will there be a modest chance of success. Sliding into a chair or changing seats while listening in a relaxed manner, however, turns all corrective measures on their head. And if several people want to listen at the same time? You could still tinker with the speaker - but for which of the myriad room acoustics? There are almost as many different rooms as there are homes. So what are commonalities in the living spaces of the group of people buying a particular loudspeaker? One thing all living spaces have in common is a floor. This is very close to the acoustic centres for floorstanding speakers and for compact speakers on a stand. In the user's home, the floor is an ever-present boundary surface with a significant effect on bass response. It follows: Loudspeakers should have a clear vertical focus.
The second thing most living rooms have in common: There are several seating areas in the room. These are not arranged one above the other, but side by side. It follows: Loudspeakers should have a horizontal bundling that allows a practical, wide dispersion. In addition, the side walls, seen from the loudspeaker, should be rather averted and far enough away. And seating should also be a sufficient distance from reflective surfaces. A thick carpet in the area between the speakers and the seats is particularly beneficial. If there is a table in front of the seats, then its surface should be covered with a sound absorbing pad, table runners, etc., or numerous objects placed on it. This can also help. Since every listening room has its own reflection behaviour, there is no general validity for a somehow defined radiation behaviour of loudspeakers. The loudspeaker should emit a sound structure that is as exactly transformed as possible under the direct sound relevant radiation angles. The direct sound relevant radiation angles are in practice:

  • horizontal approx. 0 to +/- 15°.
  • vertical approx. 0 to +/- 5°.

If you are building your own house, you can try to find an architect who designs rooms in such a way that they do not have parallel walls. Just a few degrees of slant to each other will do wonders. Not only when listening to loudspeakers, but any noise then builds up less.
2380350990 3 g-4.jpg
Myro a priori 10.02

  • Time1.step-response.jpg

The sound structures arriving at the listening position consist of the direct sound components, which are unaffected by the room (exception: low frequencies), and the indirect sound components, which are changed by the reflection. The low frequency range is the area where the first reflections are already superimposed on the transient response. Here there is virtually no unaffected direct sound component left. As an example, consider a 3-way transducer, the Myro Time 2. With the size of this loudspeaker and the necessary larger measuring distance you can see (left) very nicely the first room reflection and its superposition of the step response.
We perceive the first milliseconds of direct sound, which reach our auditory organ unaffected by reflections, in the same way as those of a natural sound event. Impulses and transients, with the exception of the low-frequency range, reach the auditory organ directly. For the conversion and transmission of impulses and transients, it is logical to make a measurement at the location of the auditory organ.

If the listening distance is small and the distance between the loudspeaker and reflecting surfaces is large, the direct sound component is large.

  • With a large listening distance and a small distance between the loudspeakers and reflecting surfaces, the direct sound component is small.
  • For near-field monitors, the transfer function is therefore usually particularly important in the direct sound, i.e. in the direct radiation direction.
  • For far-field monitors, the transfer function is therefore usually also important outside the direct albedo direction.

The deformations of the sound waves during the reflection process are extraneous influences, as is the deformation due to incoherent sound transducers. But errors in the reproduction also propagate in the room acoustics:

  • Room reflections of faithfully transduced sound structures sound like reflections of the original.
  • Room reflections of sound structures that have not been faithfully converted do not sound like reflections of the original.

For the decay of instruments or for continuous tones, the interaction of the listening room with the sound emitted by the loudspeaker plays the decisive role in addition to the direct sound component, because especially in the steady state, the interaction of loudspeaker and room determines what happens. To achieve this, a loudspeaker should of course have a sound structure that is as consistent as possible under different dispersion angles. The organ is the best example of an instrument with a high level in the steady state, and it is precisely here that the interaction of loudspeaker and room takes effect.

GrandConcertEntwurf08 631x337.jpg

Myro Grand Concert II Design Study

Ultimately, what counts is the sound structure that arrives / takes effect at the auditory organ. The direct sound component, although proportionally smaller than the indirect sound, has a greater importance in rooms, because only in it room-independent information about the original is contained. The recognition and localization of sound events within the original (recording), i.e. also the recognition of the original room sound, is only clearly possible in direct sound. The next most important are the early, briefly following, energetic, first reflections. Everything that reaches our hearing organ after multiple reflections and attenuation tends to get lost in the general chaos of reflections and is of secondary importance.
For the larger radiation angles relevant to indirect sound, the quality of the sound structure radiated by the loudspeaker is also decisive for the impression of "authenticity".

The listening experience with signal / time accurate loudspeakers is: Due to the excellent intelligibility and the detachment of the sound from the loudspeaker, the perception of the original information gains dominance over the perception of the listening room. The direct sound is of clearly superior importance for the perception of the original sound. Quantitatively, this experience cannot be justified, because the direct sound amounts to only about one fifth of the total sound.

For locating and recognizing a sound structure stored in a recording, the following order of priority therefore applies:

1. direct sound (transients)

  • 30-fold (!) increased nerve firing rate from the auditory organ to the brain, thus maximum attention
  • maximum dynamics / amplitude values
  • the only sound component with the chance to transmit original structures

2. first early reflections

  • the shortest time sequence to direct sound
  • high energy content
  • can superimpose and alienate direct sound

3. multiple reflected sound components (reverberation)

  • long time sequence on the direct sound
  • decreased energy content
  • strong structural deformations due to the reflection processes (non-linear absorption)

4. quasi steady states (space modes)

  • long time sequence to the direct sound
  • high energy content
  • no longer contain original sound structures


And there are the aspects of the transformed sound components

  • excited self-resonances of the room-boundaries
  • excited self-resonances of all objects in space

which act as frequency-filters and transform certain sound-parts into mechanical vibrations and heat. The mechanical vibrations in turn act as sound sources and are not insignificantly involved in the sound of the room.

In all considerations, the only thing that counts is the quality of the sound structure. First early reflections, which superimpose the transient processes, are next to the strong dynamic compression in some recordings at the top of the list of factors that can relativize the advantage of the signal / time accurate conversion. For playback with loudspeakers, the following therefore applies:

  • optimisation of room acoustic parameters, speaker placement, seating position, etc.
  • perfect reproduction of the direct sound component. Here, too, the transient response is of particular importance.
  • as little loudspeaker sound as possible in the direction of nearby room surfaces.
  • an as evenly as possible directed radiation behaviour of the loudspeaker.

For the reproduction with loudspeakers applies:

  • optimization of room acoustic parameters, speaker placement, seating position, etc.
  • a reproduction of the direct sound component as perfect as possible. Here, too, the transient response is of particular importance.
  • as little loudspeaker sound as possible in the direction of nearby room surfaces
  • as evenly directed radiation behaviour of the loudspeaker as possible

Can room correction help?
The sense of hearing is capable of differentiating the incoming pressure fluctuations of the air (sound waves). It does not simply form the sum of the amplitude values, like a measuring procedure, but perceives the individual information contained therein. Without this ability, all the many amazing hearing properties could not be explained.
An electronic room correction, which, if it is committed to the ideal of the original input signal, is an over-all correction, would have to be capable of a differentiated correction of the direct sound and the reflected sound components arriving at the listening position from different directions, with different transit times, with their individual structure. However, this is not possible due to the principle. In this respect the following recommendations result:

  1. Use loudspeakers with a linear frequency band
  2. The loudspeakers should have a regular directivity (over the whole frequency response an even decrease of the level off axis)
  3. a favourable positioning of the loudspeakers and the listening place with regard to excitation and effect of the modes
  4. even reverberation times of the room
  5. only then, if there are still problems with modes, narrowband reduction of the frequencies of the disturbing modes


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