Patent Publication Number: US-8116508-B2

Title: Dual-mode loudspeaker

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a loudspeaker and, more particularly, to a loudspeaker that can be acoustically excited at different frequency ranges to produce audible sounds. 
     BACKGROUND OF THE INVENTION 
     A device, such as a gaming console, usually produces sound when the user plays a game with the console. When the user plays a game on such device in a public place, for example, sometimes it is desirable to let people around the user hear the sound. In other times, it is desirable to keep the sounds to the user so as not to disturb other people in the vicinity. Likewise, a mobile phone can be used for music playback and audio/video playback. There are times when the playback sound is to be shared with a group of people. There are times when the playback sound is to be heard mainly by the user so that others around the user are not disturbed. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and an apparatus that can be used to produce both audible acoustic waves in a wide beam and in a narrow beam. On the one hand, the apparatus is an acoustic component that can be acoustically excited to produce audible acoustic waves in a conventional way, for example. It can include a vibrating structural component (also called transducer) such as a membrane, a clamped-clamped beam, or a cantilever, or an array of such structures, which can be excited by a specific exciting signal so that it produces audible sound waves in the 20 Hz to 20 kHz range, for example. On the other hand, the apparatus can also be excited in a higher frequency range, such as an ultrasonic frequency range (about 30 kHz-120 kHz). When the vibration is in the ultrasonic frequency range, the ultrasonic signal is modulated by audio signal for creating better directivity. At this frequency range, the transducer or transducer array can produce a directional beam of ultrasonic waves. Due to the non-linear interaction of ultrasonic waves in the air, the directional beam of ultrasonic waves becomes audible after traversing a distance. 
     Thus, the first aspect of the present invention is a method for producing audible signals in a wide-beam audio mode or a narrow-beam audio mode. The method comprises providing an acoustic component configured to produce acoustic waves in a lower frequency range and a higher frequency range, the lower frequency range comprising at least part of the audible frequency range and the higher frequency range comprising a frequency range higher than the audible frequency range; and exciting the acoustic component for producing acoustic waves in the lower frequency range or in the higher frequency range. 
     According to various embodiments of the present invention, the higher frequency range comprises at least part of an ultrasonic frequency range, and the acoustic component comprises a transducer or transducer array configured to receive electrical signals for producing vibration in the ultrasonic frequency range based on the electrical signals. The transducer is also configured to produce vibration in the lower frequency range based on the electrical signals. 
     According to embodiments of the present invention, when the vibration is in the higher frequency range, the electrical signals are obtained by modulating an audible signal by a carrier signal in the ultrasonic frequency range. 
     In one embodiment of the present invention, a deflectable component is coupled to the transducer for producing the acoustic waves in response to the vibration. 
     The second aspect of the present invention is an apparatus for producing audible signals. The apparatus, comprises: 
     an acoustic component configured to produce acoustic waves in a lower frequency range or in a higher frequency range, the lower frequency range comprising at least part of the an audible frequency range and the higher frequency range comprising a frequency range higher than the audible frequency range. The higher frequency range comprises at least part of an ultrasonic frequency range, and the acoustic component comprises a transducer or transducer array configured to receive electrical signals for producing vibration in the ultrasonic frequency range based on the electrical signals. The transducer is also configured to produce vibration in the lower frequency range based on the electrical signals. When the vibration is in the higher frequency range, the electrical signals are obtained by modulating an audible signal modulated by a carrier signal in the ultrasonic frequency range. 
     According to one embodiment of the present invention, a deflectable component is coupled to the transducer for producing the acoustic waves in response to the vibration. 
     According to one embodiment of the present invention, the acoustic component comprises: 
     a substrate having a first side and an opposing second side, wherein a second side comprises a cavity defining a deflectable area on the substrate; 
     a piezoelectric layer; and 
     a pair of electrodes coupled to the piezoelectric layer, the electrodes arranged to receive electrical signals so as to cause the piezoelectric layer to vibrate and wherein part of the deflectable area is acoustically coupled to the piezoelectric layer for producing the acoustic waves in response to vibration of the piezoelectric layer. 
     According to one embodiment of the present invention, the acoustic component comprises: 
     a substrate having a first side and an opposing second side, wherein a second side comprises an array of cavities, each cavity defining a deflectable area on the substrate; 
     a plurality of piezoelectric layer segments; and 
     a pair of electrodes coupled to the piezoelectric layers, the electrodes arranged to receive electrical signals so as to cause the piezoelectric layers to vibrate and wherein each of the deflectable area is acoustically coupled to one of the piezoelectric layers for producing the acoustic waves in response to vibration of the piezoelectric layers. 
     According to one embodiment of the present invention, the acoustic component is operable in a first audio mode to produce acoustic waves in the lower frequency range and in a second audio mode to produce acoustic waves in the higher frequency range. The apparatus further comprises a processor, coupled to the acoustic component, for selecting between the first audio mode and the second audio mode; and a user interface, coupled to processor, for selecting between the first audio mode and the second audio mode. 
     The apparatus can be a mobile terminal, a portable device that provides music playback, video playback, camcording, games, radio or the like. 
     The present invention will become transparent upon reading the description taken in conjunction with  FIGS. 1-10 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of an acoustic device, according to one embodiment of the present invention. 
         FIG. 2  is a cross sectional view of the acoustic device of  FIG. 1 . 
         FIG. 3  shows an array of acoustic devices, according to various embodiments of the present invention. 
         FIG. 4  shows a cross sectional view of an acoustic device, according to another embodiment of the present invention. 
         FIG. 5  is a block diagram showing an exemplary module for use in producing sound in conjunction with the acoustic device, according to the present invention. 
         FIG. 6  shows a directional sound pattern of the acoustic waves, according to the present invention. 
         FIG. 7  is a flowchart of algorithms for generating parametric sound beams. 
         FIG. 8  shows an electronic device having an acoustic device, according to various embodiments of the present invention. 
         FIG. 9  shows various components in the electronic device of  FIG. 8 . 
         FIG. 10  shows a different sound producing module wherein two or more acoustic devices are used to produce sounds. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Mobile phones and portable devices can include audio features. The audio features include music playback, video playback, camcording, games, radio and so forth. It has become common that these audio features are carried out in public places. It is desirable that those devices are capable of producing sounds in at least two ways: one using a conventional speaker that produces sound in a large range of solid angles (wide beam), and one producing sound in a directional pattern (narrow beam) so as not to disturb other people when the user listens to the sound in public. 
     The present invention provides a method and an apparatus that can be used to produce both audible acoustic waves in a wide beam and in a narrow beam. On the one hand, the apparatus is an acoustic component that can be acoustically excited to produce audible acoustic waves in a conventional way, for example. It can include a vibrating structural component (also called transducer) such as a membrane, a clamped-clamped beam, or a cantilever, or an array of such structures, which can be excited by a specific exciting signal so that it produces audible sound waves in the 20 Hz to 20 kHz range, for example. On the other hand, the apparatus can also be excited in a higher frequency range, such as an ultrasonic frequency range (about 30 kHz-120 kHz). At this frequency range, the transducer or transducer array can produce a directional beam of ultrasonic waves. Due to the non-linear interaction of ultrasonic waves in the air, the directional beam of ultrasonic waves becomes audible after traversing a distance. According to the present invention, the acoustic component that produces the audible sound in a conventional way is the same acoustic component that, when excited by ultrasound waves, produces substantially directional sound after the ultrasonic waves traverse a specific distance. 
       FIG. 1  is a top view of an acoustic device, according to one embodiment of the present invention. As shown in this embodiment, the acoustic device is produced with a micro-electro-mechanical systems (MEMS) technology. For example, the acoustic device is produced on a silicon substrate  10 . As shown in  FIG. 1 , the acoustic device  5  comprises a cantilever diaphragm  20  with free edges. Part of the cantilever diaphragm is acoustically coupled to a transducer  30 , wherein the transducer  30  is connected to a pair of electrodes  14  and  16 . 
       FIG. 2  is a cross sectional view of the acoustic device of  FIG. 1 , showing the transducer  30  coupled to the cantilever diaphragm  20  on the substrate  10 . As shown, the cantilever diaphragm  20  comprises a plurality of low temperature oxide (LTO) layers  42 ,  44 ,  46  on top of a silicon nitride layer  60 . Below the silicon nitride layer  60 , there is a thermal oxide layer  70 , followed by a number of other layers, such as layer  80 . The transducer  30  comprises a piezoelectric (PZT) layer  50  sandwiched between two LTO layers  42  and  44 . On top of the transducer  30  is an electrode layer  40 , while the bottom electrode layer  48  is below the PZT layer  50 . It should be noted that the acoustic device, according to various embodiments of the present invention, can be produced as part of an array, as shown in  FIG. 3 . As shown in  FIG. 3 , an array  1  comprises a plurality of acoustic devices  5  produced on the same silicon substrate  10 . 
     Another example of the acoustic device, according to a different embodiment of the present invention, is shown in  FIG. 4 . As shown in  FIG. 4 , the acoustic device  5  has a thin section on the silicon substrate  180  to be used as a diaphragm of the low frequency acoustic component  120 . On top of the low frequency acoustic component  120 , a transducer  130  having a piezoelectric (PZT) layer  150 , and a polynitride layer  143  is provided. A top electrode layer  140  and a bottom electrode layer  148  are used to provide an excitation electrical signal in order to induce the movement of the PZT layer  150 . The transducer  130  is coupled to the low frequency acoustic component  120  via a plurality of layers, including an LTO layer  146 , a silicon nitride layer  160  and silicon dioxide layer  170 . 
       FIG. 5  also shows a system architecture of the acoustic device. As shown in  FIG. 5 , the sound producing module  200  is used in an apparatus, such as a mobile terminal (see  FIGS. 8 and 9 ). The module  200  comprises a mobile device processing IC  220  configured to receive information or commands from a user interface  210 . The processing IC  220  comprises an application specific integrated circuit (ASIC) multimedia chip  222  and an ASIC system chip  230 . The ASIC multimedia chip  222  can be configured to receive audio data from another mobile station or a multimedia streaming source, or from its own audio data storage or generating module, for example. The audio data from the ASIC multimedia chip  222  can be turned into electrical signal indicative of the audio data. According to the present invention, the audible sound indicative of the audio data can be produced in different ways depending upon a signal  232  from the ASIC multimedia chip. If the signal  232  indicates that the sound will be produced similar to that by a regular speaker, then the electrical signal indicative of the audio data is directed to a regular amplifier  242 . The low frequency electrical output (in the range of 20 Hz to 20 kHz, for example) from the regular amplifier  242  is provided to the transducer or transducer array  250  so that an audible sound can be produced in the low frequency acoustic component (component  20  in  FIG. 2 , or component  120  in  FIG. 4 , for example). If the signal  232  indicates that the sound the sound will be produced as directional acoustic waves, then the electrical signal will be conveyed to a beam-forming data signal processor (DSP)  234  so that a high frequency carrier signal modulated by the audio data (or signal) is provided to an ultrasonic amplifier  244 . The output from the ultrasonic amplifier  244  is also provided to the transducer or transducer array  250  so that ultrasonic waves are produced directly by the transducer or transducer array (component  30  in  FIG. 2  or component  130  of  FIG. 4 , for example). Ultrasonic waves produced by a transducer or a transducer arrays as depicted in  FIGS. 2 and 4  can be directional in that the wave pattern is confined to a narrow solid angle as illustrated in  FIG. 6 . 
     As shown in  FIG. 6 , the waves (carrier waves modulated by audio signal) in the near field are in the ultrasonic frequency and, therefore, not audible. As the waves travel through air, the carrier frequencies are lost due to the non-linear interaction of ultrasonic waves in the air. The envelope of the modulated waves produces audible sound while retaining at least part of the directivity of the wave pattern. As such, the audible sound produced by a device is largely confined to a small number of people. 
       FIG. 7  is a flowchart of algorithms for generating parametric sound beams, regarding the directional beam. As show in the flow-chart  300 , an audio input signal  310  is conveyed to an excitation signal synthesis module  320  where the input signal  310  is modulated by a carrier signal. The carrier signal has a frequency within the ultrasonic frequency range of 30 kHz to 120 kHz, for example. The modulate signal is processed in a distortion compensation module  330  in order to remove distortion caused by excitation signal synthesis process (block  320 ) as well as by amplifier and transducer, for example. The signal is again processed in a performance data adjustment module  340  to become a processed parametric signal  350  so that the specific performance parameters (such as the directional audio beam angle and traversing distance, for example) can be implemented. The processed parametric signal  350  is conveyed to an amplification stage  360 . The amplification stage comprises the transducer or transducers (block  250  of  FIG. 5 , for example) via an optional amplifier (block  244  of  FIG. 5 , for example). 
     The acoustic device, according to various embodiments of the present invention, can be implemented in an electronic device or telecommunications apparatus that is configured to produce sounds. As shown in  FIG. 8 , an electronic device  500  has a display device  502  and a keypad  504 . The electronic device has a speaker or sound producing device  510  and a microphone  530 . The sound producing device  510  comprises an acoustic device  5 . It is possible to provide a user interface  520  on the electronic device  500  to allow the user to select between the wide-beam audio mode or the narrow-beam audio mode. 
       FIG. 9  shows an exemplary arrangement of various components in the electronic device of  FIG. 8 . As shown in  FIG. 9 , the electronic device  500  includes a user interface  520  for selecting to audio modes. The user interface  520  is connected to a processing IC  220  in the module  200  (see  FIG. 5 ). The electronic device  500  also includes a display device, such as a liquid crystal display panel  502 . The electronic device  500  can be used as a communications apparatus, such as a mobile terminal, having a transceiver  540  for transmitting and receiving signals via an antenna  544 , for example. 
     In sum, the present invention provides a method and an apparatus for producing audible sounds. The apparatus combines the transducer for both a conventional loudspeaker and a directional loudspeaker in the same structural component. In the present invention, the transducer of the loudspeaker works in such a way that its low frequency characteristic satisfies the requirements of the conventional loudspeaker, while one of natural frequencies of the transducer is located in the ultrasonic range. As such, when the input exciting signal of the transducer (or transducer array) is a conventional audio signal, the transducer can produce conventional audio waves by working on its low frequency range. On the other hand, when the input signal of the transducer (or transducer array) is the ultrasonic signal modulated by audio signal for creating better directivity, it can produce the ultrasonic signals by working near of the specific natural frequency of the transducer in the ultrasonic range as mentioned; then the nonlinear interaction of ultrasonic waves in air can reproduce directional audible sound. Therefore, a loudspeaker with both the conventional loudspeaker and the directional loudspeaker function can be realized by the same transducer (or transducer array). 
     According to various embodiments of the present invention, the selection of the audio mode can be carried out automatically or manually. For example, the processing IC  220  ( FIG. 5 ) can be configured to set the acoustic mode to the narrow-beam audio mode as a default when acoustic device is caused to start producing sounds. The user then decides whether to keep the narrow-beam audio mode unchanged or to switch it to the wide-beam audio mode. Alternatively, the processing IC is programmed to select the audio modes based on the nature of the sound producing event or the use case of the device. For example, when the electronic device  500 , such as a mobile terminal, receives a telephone phone call, the processing IC will automatically select the narrow-beam audio mode. But if the user turns on an MP3 program to listen to music or podcast, the wide-beam audio mode is automatically selected. The user then decides whether to change the current audio mode. The user can change or select the audio modes through the user interface  210 . 
     It should be noted that, according various embodiments of the present invention, the electronic device  500  allows a user to set playback to simultaneous in that the transducer or transducer array  250 , as shown in  FIG. 5 , simultaneously receives electrical signals from the regular amplifier  242  and the ultrasonic amplifier  244 . Alternatively, the electronic device  500  can have two or more transducers or transducer arrays to produce sounds in three or more modes. As shown in  FIG. 10 , the sound producing module  200 ′ can be used in an apparatus, such as a mobile terminal (see  FIGS. 8 and 9 ). The module  200 ′ comprises a mobile device processing IC  220  configured to receive information or commands from a user interface  210 . The processing IC  220  comprises an application specific integrated circuit (ASIC) multimedia chip  222  and an ASIC system chip  230 . The ASIC multimedia chip  222  can be configured to receive audio data from another mobile station or a multimedia streaming source, or from its own audio data storage or generating module, for example. The ASIC system chip  230  can be configured to control a plurality of regular amplifiers  242 , a plurality of beam-forming data signal processors  234 , a plurality of ultrasonic amplifiers  244  and a plurality of transducers or transducer arrays  250 . As such, the sound producing module  200 ′ can be used to play back in at least three different modes: 
     1) two transducers  250  are caused to produce wide-beam audio sounds simultaneously; 
     2) two transducers  250  are caused to produce narrow-beam audio sounds simultaneously; and 
     3) one transducer  250  produces narrow-beam audio sounds, while the other transducer  250  produces wide-beam audio sounds simultaneously. 
     The sounds from different transducers can be the same or different. The sounds can be stereo sounds, for example. 
     Mode selection can be achieved by a signal  223  from the ASIC multimedia chip  222 , for example. The user is allowed to decide which mode to be selected. 
     Thus, although the present invention has been described with respect to one or more embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the scope of this invention.