The present invention relates to a system comprising an acoustically transparent display screen and a loudspeaker positioned immediately behind the display. The system can be configured to enable an optimal route for the acoustic signal to pass the display screen. The present invention also relates to a method of constructing or operating an acoustically transparent display screen and a loudspeaker positioned immediately behind the display.
The present invention pertains to the field of light emitting displays that are also acoustically transparent. Loudspeakers can be placed behind the light emitting display and the sound can be transmitted through the display. Acoustically transparent displays can be implemented by forseeing openings between the light sources where the sound can be transmitted. WO2010140811A1 discloses a sound penetrating display apparatus that has holes disposed between the pixels of the display panel. US20170164081A1 discloses an audio and display system having a housing wherein an audio speaker can be placed.
It is an objective of the present invention to provide a system comprising an acoustically transparent display screen and a loudspeaker positioned immediately behind the display. The system can be configured to enable an optimal route for the acoustic signal to pass the display screen. It is an objective of the present invention to provide a method of constructing or operating an acoustically transparent display screen and a loudspeaker positioned immediately behind the display.
Loudspeakers can be designed to provide a lambertian radiation distribution of the acoustic signal. This is an angle independent distribution which can avoid that the acoustic signal has high quality in only a very limited area (or volume) in front of the loudspeaker(s).
When using perforated projection screens (without intrinsic light source), the loudspeaker can be placed behind the projection screen. This has the advantage that the sound reaching the audience is independent of where the audience is located relative the loudspeaker (or how they turn their heads relative the loudspeaker). Since a perforated projection screen is non-rigid, it can vibrate with the acoustic signal.
A display screen built on an electronic board, such as a PCB, will involve a structure that is too rigid to admit such a resilient behavior.
One solution is to put the loudspeakers around the display. Using a control system it is possible to manipulate the acoustic signals from the multiple loudspeakers placed around the screen, and make them be heared as they where placed in their original position (behind the screen), but there may be phase differences that can be heard if a listener e.g. turns his/her head, and this kind of manipulation will be valid only for a reduced part of the audience area. Additionally, there is a need to allocate space next to the display to house the multiple loudspeakers.
Another alternative is to use a wave field solution, however this requires a large amount of loudspeakers (e.g. 80), which results in a monetary costly, bulky and complex system.
If the loudspeaker is placed too far behind the display screen, a remarkable amount of energy will be diffracted and/or reflected towards the room behind the screen, this energy don't reach the audience, or in the worse case it will reach the audience in an uncontrolled manner, which can cause degradation of the audio quality (e.g. attenuation, distortion).
The present invention enables a preservation of such angle independent distribution of the acoustic signal when the loudspeaker is placed behind the display screen.
Embodiments of the present invention provide a system for providing visual and acoustical signals, comprising
a light emitting display having light sources and a display surface, and perforations extending perpendicularly to the display surface and disposed between the light sources, and
at least one loudspeaker positioned behind the light emitting display, wherein the perforations comprise a non-cylindrical shape and the openings on the side of the light sources occupy at least 5% of the area of the light emitting display for sound passing through. The advantage of this system is that a better sound reproduction and distribution can be achieved.
The amount of open surface caused by the perforations, can be smaller on the side of the light sources than on the counter side. This has the advantage of reducing should reflection at the back of the display.
The perforations can have a truncated cone shape. This has the advantage of reducing should reflection at the back of the display and being economical to manufacture.
The perforations can have different shapes such as a concave shape or a convex shape or non-circular openings.
The perforations can have at least two sections with different shapes. For example the at least one perforation section can have a truncated cone shape or the at least one perforation section can have a concave shape or the at least one perforation section can have a convex shape or the at least one perforation section can have a non circular opening.
Embodiments of the present invention can provide a system for providing visual and acoustical signals, comprising
a light emitting display having light sources and a display surface, and perforations extending perpendicularly to the display surface, the perforations comprise a conical shape and are disposed between the light sources, at least one loudspeaker having a displacement amplitude and a frequency range of 5 to 30 kHz, wherein the at least one loudspeaker is placed immediately behind the display so that when it is positioned at its maximum displacement amplitude, it is in contact with the display.
The amount of open surface caused by the perforations, can be smaller on the side of the light sources than on the counter side. This creates a reduced optical impact on the side viewed by the viewers.
The perforations can have a truncated cone shape or have non circular openings.
The perforations shape can have at least two sections with different shapes.
Embodiments of the present invention can provide a system for providing visual and acoustical signals, comprising
a light emitting display having light sources, and perforations extending perpendicularly to the display surface, the perforations comprise a conical shape and are disposed between the light sources, at least one loudspeaker having a displacement amplitude and a frequency range of 0.1 kHz to less than 5 kHz, wherein the at least one loudspeaker is placed immediately behind the display so that when it is positioned at its maximum displacement amplitude, it separated from the display by 1 mm to 15 cm.
The amount of open surface caused by the perforations, is smaller on the side of the light sources than on the counter side.
The perforations perforations can have a truncated cone shape.
Embodiments of the present invention can provide a method for providing visual and acoustical signals, using a a light emitting display having light sources and a display surface, and perforations extending perpendicularly to the display surface and disposed between the light sources, wherein the perforations comprise a non-cylindrical shape and the openings on the side of the light sources occupy at least 5% of the area of the light emitting display for sound passing through, further comprising placing at least one loudspeaker behind the light emitting display.
Embodiments of the present invention can also provide a method for providing visual and acoustical signals, comprising a light emitting display having light sources and a display surface, and perforations extending perpendicularly to the display surface, the perforations comprise a conical shape and are disposed between the light sources, the method comprising
placing at least one loudspeaker immediately behind the display, the at least one loudspeaker having a displacement amplitude so that when it is positioned at its maximum displacement amplitude, this is in contact with the display, the at least one loudspeaker emitting sound at a frequency range of 5 to 30 kHz.
Embodiments of the present invention can provide a system for providing visual and acoustical signals, comprising
a light emitting display having light sources, a display surface and perforations extending perpendicularly to the display surface, the perforations comprising a conical shape and are disposed between the light sources, at least one loudspeaker having a displacement amplitude and a frequency range of 0.1 kHz to less than 5 kHz,
wherein the at least one loudspeaker is placed immediately behind the display so that when it is positioned at its maximum displacement amplitude, it separated from the display by 1 mm to 15 cm.
A “display screen” can be a light emitting image forming device comprising light sources and electronics.
A “light source” can in the present context be a solid state light source, e.g. LED, OLED, AMOLED, Chip on board (COB).
A “loudspeaker” or “speaker” can comprise one or more “drivers” housed in a speaker enclosure. A driver can transform an electrical signal into an acoustic signal, within a defined frequency range. A driver can comprise a lightweight diaphragm that when put into motion initiates a sound wave in the surrounding medium. The diaphragm is often cone shaped, but for e.g. electrostatic or magnetostatic loudspeakers, the diaphragm can be flat.
A “pitch” can be defined as the repetitive distance between the center points of two objects that are equally distanced. It can also refer to the overall geometrical distribution of the objects, e.g. if the objects are positioned at the corners of squares, it can be referred to as a square pitch.
The “acoustic transparency index” can be defined as
TI=nd2/ta2=0.04 P/πta2
where:
n=number of perforations per sq in;
d=perforation diameter (in);
t=sheet thickness (in);
a=shortest distance between holes (in); a=b−d, where
b=on-center hole spacing (in);
P=percent (not fractional) open area of sheet
(ACOUSTICAL USES FOR PERFORATED METALS: Principles and Applications, Theodore J. Schultz)
An advantage of the situation in
The conical shape of the perforations can be advantageous since it can reduce the reflected part of the incoming acoustic signal, as illustrated in
The conical shape of the perforation can be advantageous since it can reduce the reflected part 48 of the incoming acoustic signal 47, as illustrated in
In another embodiment of the present invention the perforations may be filled with an acoustically transparent material.
The size of the light sources may be 0.005 mm-3 mm.
The pitch of the light sources may be 0.4 mm-20 mm.
The diameter of the perforations can be 0.2-20 mm, and the pitch of the perforations can be 0.4-100 mm, depending on the diameter. The depth of a perforation can be 2 cm or smaller.
The shape of the perforations can be circular or noncircular. The latter having rounded or straight corners (depending on the manufacturing possibilities)
The perforations can also have a convex or concave shape. The shape of the perforations can be designed to reach an open surface ratio of 10% or more, this ratio is calculated on the LED side of the PCB (towards the audience). The open surface ratio is the total area of all perforations divided by the total area of the LED board.
One exemplary embodiment comprises the present invention being implemented as tiled modules which can be attached to a metal frame. Each module can comprise a PCB board, light sources, e.g. LED's, on side facing the audience and the electronics driving the light sources on the other side. The electronics can be placed so that it covers the smallest surface portion on the PCB.
Perforations can be distributed regularly over the PCB board surface between the light sources and in various layouts. For example in a square pitch and optionally closer to each other in the horizontal or vertical direction.
Alternatively, the holes can be distributed irregularly while preserving a locally uniform density distribution.
Such embodiment would further cancel out any phasing artefacts, mostly perceivable at the side positions in the front row.
A concrete example of such a uniform distribution is the Poisson disk distribution. Such distribution is known to de-correlate discrete frequency peaks and will thereby diffuse interference artefacts causing a “harsh” sound at certain positions.
The density of the holes must be substantially constant for any small fraction of the screen.
Depending on the dimensions of the screen, a good approximation for such an arrangement is the jittered displacement of a regular grid.
Similarly, direction specific constructive interferences can be reduced by varying the drilling depth with a conical(-like) drill, as this will introduce subtle frequency dependent sound pressure variations comparable to the effect of a jittered regular grid, which is known to approximate the ideal Poisson disk distribution very well.
All techniques described above reduce potential electromagnetic radiation, as the Poisson-distributed grid cancels out all potential constructive interferences which could be present with a regularly aligned micro-antenna-array.
The perforations can be drilled in a shape having wider diameter in the back side than on the front side of the PCB
Additionally, an extra layer of plastic material can be attached on the back side of the PCB acting as a sound wave guide. This sound wave guide should optimize and enlarge the shape of the perforations drilled in the PCB, so more sound energy is gently bend to the perforation opening in the front of the LED board.
The size of the openings on the front side of the PCB can be designed to reach at least 10% of the PCB surface to be open for sound to pass through.
The LED's can be mounted on the PCB to the front (i.e. towards the audience) also in a square regular pitch but shifted to the intersections between holes (for an optimal relationship between opening radius and LED distribution).
The PCB board and the LED's can be designed and mounted together to allow the thickness not to be larger than 2 mm.
The present invention can obtain an acoustic transparency index similar or higher than a common cinema projection screen. Such screen is reflecting or transmitting light instead of being intrinsically light emitting.
A cinema speaker can be placed behind it and the audience can hear the cinema sound with the same quality (or better) than by using a conventional projection screen.
The acoustical response from different screens were measured, using standard cinema screen speakers. The measuring microphones were placed in front of the speakers, and different types of perforated samples were placed between the speaker and the microphones, as illustrated in
The acoustical response from different screens can be measured, using one or more loudspeakers.
For each measurement a reference signal was first measured, and
The screens tested were: A conventional projection screen, a perforated LED board with perforation area of 12%, a perforated LED board with perforation area of 20%.
Between 0 degrees and −45 degrees the screen attenuation increases continuously with the frequency.
There are side lobes visible again, compared to
Filing Document | Filing Date | Country | Kind |
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PCT/EP2018/086816 | 12/21/2018 | WO | 00 |