Patent Application
20160219373
This application relates to speakers and, more specifically, to driving speakers.
Different types of acoustic devices have been used through the years. One type of acoustic device is a speaker or receiver. Generally speaking, a speaker or receiver converts an electrical signal into sound energy. These devices may be used in hearing instruments such as hearing aids or in other electronic devices such as cellular phones and computers.
One type of speaker typically includes a coil, a yoke, an armature (or reed), and magnets. An electrical signal applied to the coil and creates a magnetic field within the motor which causes the armature to move. Movement of the armature causes movement of a diaphragm, which creates sound. Together, the magnets, armature, and yoke form a magnetic circuit. The yoke may also serve to hold or support the magnets or other components.
Another type of speaker (dynamic) includes a coil and a diaphragm, which are coupled together. This type of speaker also has fixed magnets. Excitation of the coil creates a magnetic field which, with the presence of the magnets, causes the coil to move. The coil moves the diaphragm and coil in unison (mimicking the action of a moving piston), causing sound to be produced.
Unfortunately, previous approaches have performance limitations. More specifically, previous speakers had difficulty in providing adequate performance in ultrasonic frequency ranges. These problems have limited the usability of speakers and have resulted in some user dissatisfaction.
For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein:
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.
In the approaches presented herein, a piezoelectric driver is placed in close proximity to a speaker. In one example, the piezoelectric driver is disposed underneath the speaker and touches the speaker. The piezoelectric driver is actuated and used to drive the speaker in a frequency range where higher acoustic output is desired, complementing the speaker's intrinsic acoustic response. The frequency range may be in the audible band (approximately 20 Hz to 20 kHz) or in the ultrasonic frequency range (greater than 20 kHz). As the piezoelectric driver moves or bends, such movement or bending causes the speaker to move thereby creating sound energy in the target frequency range. The speaker is driven using separate leads for other normal audio frequencies.
The piezoelectric structure or driver, in one aspect, may include a first metal layer, a piezoelectric layer (e.g., a crystalline layer), and a second metal layer. As mentioned, the piezoelectric structure moves upon application of electric current (representing a desired signal) causing movement of the speaker, which in turn moves the speaker thereby causing the speaker to produce sounds in the audible or ultrasonic frequency range. In other words, these approaches enhance specific target frequencies of the speaker's acoustic response or extend the bandwidth of the speaker to frequencies that may be in the audible or ultrasonic frequency range when the piezoelectric structure is excited thereby producing an enhanced signal. The piezoelectric driver may include a crystalline structure, lead zirconate titanate (PZT), or barium titanate to mention a few examples. Other examples of materials are possible. In some aspects, the piezoelectric material exhibits motion when an electric field is applied.
The present approaches improve current receivers (speakers) that are used for proximity detection because these receivers can be designed to have a resonant peak in the ultrasonic band. Additionally, the entire surface area of the speaker is used to generate the ultrasonic signal, thereby increasing the range of possible applications that can be enabled. Further and advantageously, the present approaches can be used with any speaker or receiver. The present approaches also improve the acoustic response of current receivers (speakers) by enhancing targeted frequencies in the audible range.
Referring now to
It will be understood that the approaches described herein operate with audible signals in the approximately 20 Hz-20 kHz range (referred to herein is the normal audio operating range). It will also be understood that the approaches described herein operate with inaudible ultrasonic signals beyond the human audible range of approximately 20 kHz range. Such signals may be any signal that is inaudible to human beings which, while most are above 20 kHz, can be below 20 kHz (these are referred to as the ultrasonic operating range).
Referring now to
The top speaker casing or cover 202 attaches to the bottom speaker casing or basket 204. The top speaker casing 202 and the bottom speaker casing 204 may be constructed of any suitable material such as plastic. Together, casings 202 and 204 enclose, hold, and secure the interior elements of the speaker 200.
The membrane 208 may be constructed of any flexible material. The annulus 212 is a flexible material in the opening between in proximity to the speaker casing 204. The purpose of the annulus 212 is to provide compliance for the movement of the membrane and stiffening plate structure and ensure all motion during transduction is in the vertical axis 238. It will be understood that some speakers may not have membranes.
Electrical contacts 214 provide electrical connections to another device (e.g., an electronic component in a consumer device, or an amplifier to mention two examples). In one aspect, the other device provides an electric signal representative of sound energy. These electrical signals applied to the speaker 202 create sound energy in the normal audio operating range.
As mentioned, the acoustic motor 216 includes the coil 218, center magnet 220, and pot 222. Current supplied by the contacts 214 flows through the coil 218. The coil extends around a periphery of the center magnet 220. The pot 222 creates a path for the static magnetic field. As the current flows, a changing magnetic field is created within the motor and this moves the diaphragm assembly.
As mentioned, the diaphragm assembly may also include the stiffening plate 206 that acts as a stiffener to the diaphragm. Examples of materials that can be used include ceramic, metallic, or piezoelectric. Other examples are possible.
A piezoelectric structure 250 is disposed below (or otherwise in close proximity to the speaker 200) so that movement (or bending) of the piezoelectric structure can be communicated or transferred to the speaker 202. The piezoelectric structure 250 includes a first metal layer 232, second metal layer 234, and piezoelectric layer 236. The metal layers 232 and 234 can be constructed of any suitable metal such as copper. The piezoelectric layer 236 exhibits stress when an electric field is applied. The material used to construct the piezoelectric layer 236 may have a crystalline structure, and may be PZT, or barium titanate to mention a few examples. Other examples of materials are possible.
Electric leads 252 are coupled to the piezoelectric structure 250. The leads 252 supply a signal that represents ultrasonic sound energy. The piezoelectric structure may be shaped in a convenient manner (e.g., as a solid square or rectangle, or as a ring-shaped element).
It will be understood that the speaker 202 may be disposed in some other structure such as in a consumer electronic device (e.g., cellular phone, personal computer, laptop computer, or tablet). Features, elements, or components of this other structure together with the speaker may create a front volume and a back volume, in which the diaphragm assembly moves and creates sound. The sound so-created may exit the front volume by a sound tube or channel so that the sound can be presented to a user for listening.
In one example of the operation of the system of
Electrical signals representing the targeted frequency range, which may be in the audible or ultrasonic frequency range are applied to the piezoelectric structure 250. The piezoelectric structure 250 moves or bends, which moves the speaker 102. Responsively, the speaker assembly 102 moves up and down also in the direction indicated by the arrow labeled 238. This action creates sound in the front volume that exits the sound tube or some other suitable element, but this sound is in the targeted frequency range, which may be in the audible or ultrasonic frequency range since the movement that created the sound originates with the piezoelectric structure 250.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. It should be understood that the illustrated embodiments are exemplary only, and should not be taken as limiting the scope of the invention.
This patent claims benefit under 35 U.S.C. §119(e) to U.S. Provisional Application No. 62/107,059 entitled “Piezoelectric Speaker Driver” filed Jan. 23, 2015, the content of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62107059 | Jan 2015 | US |
