GB2441368A

GB2441368A - Thinner bending wave device includes elements formed by printing

Info

Publication number: GB2441368A
Application number: GB0616973A
Authority: GB
Inventors: Geoffrey Boyd; Christopher James Cowdery
Original assignee: New Transducers Ltd
Current assignee: NVF Tech Ltd
Priority date: 2006-08-29
Filing date: 2006-08-29
Publication date: 2008-03-05
Also published as: GB0616973D0

Abstract

A device for applying bending wave energy to an acoustic member to cause the member to radiate an acoustic output, comprising a sheet-like substrate 7 adapted for application to the acoustic member, and an actuator 5, a battery power source 1 and a signal memory source 2 mounted on the substrate, wherein at least the signal memory source 2 is at least partly printed on the substrate. This is done to make the device thinner. The signal memory source may store sound material as compressed or uncompressed digital data. The device comprises means for synthesizing an analogue waveform from the stored digital data whereby the analogue waveform drives the device to produce bending wave vibration.

Description

TITLE: BENDING WAVE DEVICE

DESCRIPTION

The invention relates to a device for applying bending waves to a panel-form member to cause it to radiate sound, thus forming a sound generator or loudspeaker.

:. Flat panel bending wave loudspeakers are known, see for example International patent application WO 97/09842 S...

* to the present applicants. The invention described in this application has become known as distributed mode technology.

The trend towards ever smaller and thinner products S..,.. - * 25 incorporating loudspeakers has driven the reduction in size of the loudspeakers themselves. For example, sound enabled greetings cards currently use micro speakers of around 3mm thickness. These known micro speakers have limited performance and are approaching the minimum feasible thickness for a pistonic speaker.

There is however a number of known alternatives which are potentially thinner, including the distributed mode technology referred- to above, which may be used in conjunction with a piezoelectric beam actuator which can be made significantly less than 1mm thick to provide a speaker that is only marginally thicker than the substrate to which it is applied.

The problem facing the designer and manufacturer of ultra-thin products incorporating loudspeakers is in providing the supporting electronics, which may comprise a power source, e.g. a battery, a signal source, e.g. a digital memory and means, e.g. an amplifier, for driving the loudspeaker, to be equally thin.

According to the invention, there is provided a device for applying bending wave energy to a panel-form member to cause the member to radiate an acoustic output, comprising a sheet-like substrate adapted for application S...

* to the panel-form member, and an actuator, a power source and a signal memory source mounted on the substrate, wherein at least the signal memory source is at least partly printed on the substrate.

S.....

* 25 There is a significant move towards printed electronics, with effort being directed towards printed memory, printed batteries and printed display.

Developments in this field are clearly complementary to thin form factor sound generating components, e.g. piezoelectric actuators. It is logical to conclude that ultimately flat speaker technology may be driven by fully -printed electronics.

The mechanisms for storing sound material are many and varied. Chiefly there are two methods, compressed or uncompressed. Compressing sound material is a method whereby the data is reduced in size at some reduction in quality. This reduces the amount of memory required and hence the cost. Additional hardware is required to convert the compressed data into a reasonable representation of the original material. MP3 is an example.

Alternatively the data can be stored directly in memory in its raw form. This will require more memory, but there is no requirement for additional hardware to decompress the data.

There are also many mechanisms to drive the sound :. generating device. An analogue waveform may be synthesized from the stored digital data. Alternatively the digital * data may be used directly to drive the sound generating device directly. The ultimate simplification is to use the digital memory to directly drive the sound generating * S. * * S **.. device.

S

*5***S * 25 In this configuration, the contents of memory can be pre-processed to optimize sound quality.

The technical reason driving the need for printed memory is to support printed display. This requires random access and high speed, neither of which is available today. However, to support printed sound, a simpler memory which is sequential only and at a lower speed is suitable.

This simpler memory is technically feasible today.

A piezoelectric type transducer of the cheapest type generally requires a high' voltage to drive it. This can be in the region of 30 volts peak.

Early printed transistors are significantly different to silicon types in two ways, namely slow switching speed and high operating voltage. This high operating voltage is ideally suited to driving piezoelectric type transducers.

Their slow switching speed precludes them from complex computational tasks such as decompressing audio data but this does not prevent their use in sound reproduction.

The present invention may comprise one or more of the following features: - :. -Driving a sound transducer with a data stream :..::: 20 directly.

* -Pre-processing the data stored in memory to optimize sound quality.

-Using a printed memory that is configured as a shift register' S. * S 25 -Using printed transistors to drive piezoelectric beams.

-Printed sound will be possible as a side effect of other printed electronics roadmaps, and will be developed as a consequence of other technology drivers.

The invention is diagrammatically illustrated, by way of example, in the accompanying drawing which is a perspective view of a module comprising a substrate, e.g. of printable plastics film which carries a piezoelectric actuator or transducer, one or more batteries and a printed memory containing a signal store. The module is adapted to be mounted on a panel-form member, (not shown) e.g. the leaf of a greetings card, to apply bending wave vibration to the member to provide an acoustic output.

The means for mounting of the module on the member may be a pressure sensitive adhesive.

The present invention thus provides a means by which the form factor of loudspeakers may be reduced.

The driver (3) may be inherent in the technology used to implement the memory (2) and thus not separately manifested. * S * S.. U... * S * .* * . S * .. * S. * S S

S * S

Claims

CLA I MS

1. A device for applying bending wave energy to an acoustic member to cause the member to radiate an acoustic output, comprising a sheet-like substrate adapted for application to the acoustic member, and an actuator, a power source and a signal memory source mounted on the substrate, wherein at least the signal memory source is at least partly printed on the substrate.

2. A device according to claim 1, wherein the signal memory source stores sound material as compressed digital data.

3. A device according to claim 2, comprising means for converting the compressed data into a reasonable representation of the original uncompressed sound material.

4. A device according to claim 1, wherein the signal memory source stores sound material as uncompressed digital data.

5. A device according to any one of claims 2 to 4, comprising means for synthesising an analogue waveform from the stored digital data whereby the analogue waveform drives the device to produce bending wave vibration.

6. A device according to any one of claims 2 to 4, comprising means for driving the device direct from the stored digital data.

7. A device according to any one of claims 2 to 4, comprising means for pre-processing the stored data to optimize sound quality.

8. A device according to any one of the preceding claims, comprising printed transistors.

9. A device according to any one of the preceding claims, wherein the actuator is a piezoelectric actuator.

10. A loudspeaker comprising an acoustic member capable of supporting bending wave vibration and a device according to any one of claims 1 to 9 mounted to the acoustic member to excite bending wave vibration therein to cause the member to radiate sound.

11. A loudspeaker according to claim 10, wherein the sheet-like substrate of the device is mounted to the acoustic member using a pressure sensitive adhesive.