Audio transducers

Details Audio transducers Audio transducers

2000-11-30

2004-08-31

Le, Huyen (Department: 2643)

Electrical audio signal processing systems and devices

Electro-acoustic audio transducer

Having electrostatic element

C381S174000, C381S388000

Reexamination Certificate

active

06785393

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to audio transducers.
BACKGROUND OF THE INVENTION
Many different information, entertainment and communication devices having displays have been designed. It is desirable to use such devices to present multimedia, generally in the form of images and sound. Accordingly, such devices require interfaces capable of presenting information both in audio and visual forms.
Personal computers can be used to present real-time multimedia, for example to function as video telephones so that a user is provided with both voice and image of a person with whom he or she talks. A typical personal computer comprises a microprocessor based central unit and a keyboard. The monitor usually comprises a casing containing a CRT (Cathode Ray Tube) typically having a diagonal dimension of at least 35 cm (14 inches). If the personal computer is configured to produce sound, it is convenient to locate a speaker on each side of the CRT either integrated into the monitor casing or provided as discrete units. The personal computer may also comprise a microphone. Integration of the speakers into the monitor casing facilitates initial connecting of peripherals to the computer.
The speakers typically used in these devices are dynamic speakers. Other types of speakers have been suggested. EP 847 670 discloses a CRT monitor which has electrostatic speakers in the form of panels integrated into either side of the monitor casing. The electrostatic speakers integrate a vibrating diaphragm and an actuator to vibrate the diaphragm. Thus, an actuating diaphragm actuates itself to vibrate. This provides a speaker with reduced thickness, but also reduces the length of the maximum movement of the diaphragm resulting in a lower acoustic power per unit area of the diaphragm. Locating such speakers on the sides of the monitor casing allows them to extend from the front of the monitor casing to the back, thus allowing the areas of the sides of the monitor casing to be used while causing only a small increase to its width. However, since the speakers are arranged facing outwardly rather than towards a user, this arrangement directs sound sideways rather than towards the front of the monitor.
In the future it is intended that multimedia should also be presented by mobile stations such as those used in cellular telecommunications systems. Multimedia presentation has been suggested particularly for mobile stations of the so-called third generation. The Nokia® 9110 communicator is an example of a mobile station presently used to present audio and video signals. This is a multifunction mobile station having two hinged parts. The parts open to reveal a QWERTY keyboard in one part for entry of alphanumeric text and a large LCD-display (Liquid Crystal Display) in the other part for displaying information to a user. This mobile station can wirelessly communicate using fax, e-mail and telephony services. It also allows hands-free (HF) telephone calls to be made using a built-in speaker and a microphone. The speaker is mounted inside the mobile station and sound is conveyed via a specific conduit to the open space surrounding the mobile station. The speaker and the conduit occupy space within the mobile station. Accordingly, in using a speaker arrangement of a particular size a compromise is made between audio quality and space consumption. In addition to the HF-speaker, there is another speaker associated with the earpiece. This further increases the space occupied within the mobile station, and furthermore requires holes to be provided in the mobile station's casing, which provides entry points for dust and moisture.
As the size of handheld mobile stations such as mobile phones and smart telephones is a limiting factor, it is necessary to select speakers for such devices to be as small as possible. The need to maintain good audio quality and provide a small speaker volume will increase in the future. Additional functionality required to implement the third generation of mobile stations will inherently lead to bigger mobile stations and/or shorter periods of idle time and talk times due to increased power consumption. There is a conflict between very limited size and relatively high power consumption. If the size is limited to a comfortable maximum, it may be too small to hold a sufficiently high-capacity battery, or vice versa, a high-capacity battery that can operate the device for a long period would require too much space. Therefore there is a desire to miniaturise components of mobile stations. However, as speakers are miniaturised, the small size impairs the audio response making reproduced speech and other audio signals difficult to understand and/or less pleasant to listen to.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an audio transducer for changing a signal between an acoustic form and an electrical form, the audio transducer comprising an actuating diaphragm, a stator, and a support for supporting the actuating diaphragm adjacent to the stator, characterised in that both the actuating diaphragm and the stator comprise transparent material.
Advantageously, the audio transducer can be placed between a user and an object such as a screen without preventing the user from seeing the object, since the actuating diaphragm and the stator are transparent. This allows the transducer to be placed in front of objects that need to be seen.
According to a second aspect of the present invention, there is provided an audio-visual device comprising
an optical device, and
an audio transducer for changing a signal between an acoustic form and an electrical form, the audio transducer comprising an actuating diaphragm, a stator, and a support for supporting the actuating diaphragm adjacent to the stator, characterised in that
both the actuating diaphragm and the stator comprise transparent material and
the audio transducer is arranged adjacent to the optical device.
It is advantageous to combine a transparent audio transducer and an optical device. Thus, the very same area can be used to output or input image and to output or input sound or voice.
Preferably, the actuating diaphragm is arranged to vibrate in response to an electrical signal interacting with the actuating diaphragm to generate an acoustic response. Alternatively, the actuating diaphragm is arranged to vibrate in response to an acoustic signal interacting with the actuating diaphragm to generate an electrical response.
Preferably, the audio transducer is a speaker, a microphone, or a combination of both. In an embodiment of the invention in which the audio transducer is a transparent element disposed between a user and a display, this may provide a relatively large display surface area to be used as an acoustic element.
The optical device may be a mobile station, a mirror, a window, an electrical display, a solar cell, a touch screen or an illuminator. An electrical display is a display device comprising a screen, an input for receiving an electrical input signal and means for displaying on the screen texts or images corresponding to the electrical input signal.
Since the invention allows the surface area needed for a display to show information to be used for the audio transducer, a compact size of user interface device can be made with an audio transducer not smaller than the screen. This allows manufacture of smaller user interface devices and manufacture of user interface devices of ordinary size, but with an improved audio quality. Alternatively, if the optical device is a solar cell, then the surface of the solar cell can be used also to output sound, and efficiency of surface usage improves. If the audio response originates from the region of the optical device, the audio response appears, to a user, to come from the optical device. A display according to the invention used for video conferencing gives a realistic impression when the sound appears to come from the display. A rear-view mirror may be arranged to tell a user how far an object is behind a vehicle. A window o

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