Patent Publication Number: US-2006016324-A1

Title: Sound outputting apparatus having compensation characteristics

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to sound outputting apparatuses, and particularly to a sound outputting apparatus having compensation characteristics.  
      2. Description of the Related Art  
      A speaker is used to convert audio signals within a certain frequency range into sounds having adequate sound pressure levels. For true listening pleasure, users require a speaker that turns audio signals into high fidelity sound.  
      The voices of humans and various sounds of music are various signals having very complicated waveforms. The frequency of sound audible to the human ear is generally in the range from 20 Hz to 20 KHz. The frequency range of speech is mainly from 150 Hz to 4 KHz, and the frequency range of music is mainly from 40 Hz to 18 KHz. The energy of the human voice is mostly distributed in the frequency range of 200 Hz-3.5 KHz. Therefore, in order to correctly play such a wide variety of signals and attain high quality timbre, a speaker is required to have a wide frequency response characteristic, adequate sound pressure levels, and a large dynamic range. Further, a speaker is also desired to attain a perfect frequency-efficiency characteristic and a perfect frequency-phase delay characteristic. If this is achieved, the output of the speaker maintains high power efficiency and low phase leads or delays as compared to the input of the speaker. In the following description, phase leading and phase delaying are collectively referred to simply as phase delaying.  
      A conventional speaker system typically has a frequency-efficiency characteristic and a frequency-phase delay characteristic. These characteristics typically cause much deviation of the output of the speaker from the input of the speaker. That is, the output is far from an ideal output, and frequently results in poor timbre. To solve such problem, some special systems correct characteristics which affect the frequency-efficiency characteristic and the frequency-phase delay characteristic of a speaker. For example, one kind of correcting system corrects for adverse characteristics such as reactance, inertia and response of a power amplifier driven load such as a speaker system. The correcting system works by utilizing a program voltage and a reference load, which responds to the program voltage to develop a correction voltage signal for the driven load. However, the correcting system employs numerous resistances and capacitances to achieve its function, and is unduly complicated. Further, the system cannot compensate according to individual characteristics of the drive load.  
      Thus, an improved sound outputting apparatus and system which have compensation characteristics and can overcome the above-mentioned problems are desired.  
     SUMMARY  
      To solve the above-mentioned and other problems, a sound output apparatus having compensation characteristics (hereinafter “the apparatus”) in accordance with the preferred embodiments of the present invention is provided herein. The apparatus includes one or more sound outputting unit and a memory unit. Each type of the sound outputting units has been assigned an ID (identification) code and is used transform audio signals in a preset frequency range into sounds having corresponding sound pressure levels. The sound outputting units have real characteristics per se which cause outputs of the sound outputting units to deviate from ideal outputs. The memory unit stores ID codes and compensation parameters for each types of the sound outputting units. Each of the compensation parameters being built according to the corresponding real characteristics of the type of the sound outputting units, and is adapted to minimize or even eliminate deviations of the outputs of the sound outputting units due to the corresponding real characteristics of the sound outputting units.  
      In addition, to build the compensation parameters for each type of the sound outputting units, a compensation system in accordance with the preferred embodiments of the present invention is also provided herein. The compensation system includes a controllable signal source, a sensing apparatus, a reference source and a control unit. The controllable signal source is adapted to send audio signals to the sound outputting units. The sensing apparatus is adapted to sense outputs of the sound outputting units. The reference source is employed to have outputs indicating ideal outputs the sound outputting units to be attained. The control unit is employed to determine whether deviations between the outputs of the sound outputting units and the idea outputs fall within predetermined ranges, and storing compensation parameters in a memory if the deviations fall in the predetermined ranges, or regulating outputs of the controllable signal source if the deviations between the outputs of the sound outputting units and the idea outputs fall outside of the predetermined ranges.  
      Further, a sound outputting system having compensation characteristics (hereinafter “the system”), which adapts the sound outputting apparatus to output sounds, in accordance with a preferred embodiment of the present invention is also provided herein. The system includes the sound outputting apparatus and a device interconnected therewith. A sound outputting unit of the sound outputting apparatus receives audio signals from the device. The device generally includes a micro-controller, a signal processor and a signal source. The micro-controller reads an ID (identification) code of the sound outputting unit and determines whether the ID code exists in a memory unit of the sound outputting apparatus. If the ID code exists in the memory unit, the micro-controller reads the compensation parameters corresponding to the ID code and sends them to the signal processor  64  to regulate the outputs of the sound outputting unit. After regulation based on the compensation parameters, the sound outputting unit approaches or even reaches its ideal output.  
      Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a block diagram of a sound outputting apparatus having compensation characteristics in accordance with a preferred embodiment of the present invention;  
       FIG. 2  is a block diagram of a first compensation system for building compensation characteristics of the sound outputting apparatus of  FIG. 1 ;  
       FIG. 3  is a block diagram of a second compensation system for building compensation characteristics of the sound outputting apparatus of  FIG. 1 ;  
       FIG. 4  is a graph of frequency versus phase delay for one type of speaker according to a preferred embodiment of the present invention;  
       FIG. 5  is a graph of frequency versus efficiency for the speaker referred to in the above paragraph; and  
       FIG. 6  is a block diagram of a system for sound output having compensation parameters, in accordance with a preferred embodiment of the present invention; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       FIG. 1  is a block diagram of a sound outputting apparatus having compensation characteristics (hereinafter “the apparatus ”) in accordance with the preferred embodiment of the present invention. The apparatus  10  includes one or more speakers  12  (only one shown) and a memory unit  14 . According to the preferred embodiment, the speaker  12  can be substituted by any other sound outputting unit which can transform audio signals into sounds, such as earphones or the like. The speaker  12 , having been assigned an ID (identification) code, is used to transform audio signals in a preset frequency range into sounds having corresponding sound pressure levels. The speaker  12  has real characteristics per se, including but not being limited to a real frequency-efficiency characteristic and a real frequency-phase delay characteristic. The real characteristics cause outputs of the speaker  12  to deviate from ideal outputs of the speaker  12 , and therefore corresponding compensation parameters are needed to make up for the deviations. The compensation parameters include a compensation frequency-efficiency parameter and a compensation frequency-phase delay parameter. Each of the compensation parameters is built according to the corresponding real characteristics of the speaker  12 , and is adapted to minimize or even eliminate deviations between uncompensated outputs and ideal outputs of the speaker  12 . The memory unit  14  is readable/writable, and used to store the ID (identification) code and the compensation parameters of the speaker  12 . According to the preferred embodiment, the apparatus  10  is adapted to regulate the outputs of all those speakers  12  whose ID codes have been stored in the memory  14  in advance. An external device with which the apparatus  10  is connected, such as an MP3 player, a CD player or a host computer, validates the ID code of each speaker  12  according to the ID codes already in the memory  14 . If the ID code of a speaker  12  is in the memory  14 , a processor of the external device implements the compensation function for the speaker  12 . Otherwise, the processor of the external device omits to regulate the output of the speaker  12 , and the speaker  12  maintains its original timbres.  
      Referring also to  FIG. 2 , this is a block diagram showing relationships between a compensation system  20  and the apparatus  10 , wherein the compensation system  20  is employed to build compensation parameters for the speaker  12 . The compensation system  20  mainly includes a controllable signal source  22 , a sensor  24 , a reference source  26 , and a control unit  28 . The controllable signal source  22  respectively connects with the speaker  12  and the control unit  28 , and is controlled by the control unit  28 . The sensor  24  respectively connects with the speaker  12  and the reference source  26  at its input port, and connects with the control unit  28  at its output port. The reference source  26  is preferably an analog signal source, and has a plurality of outputs. In the preferred embodiment, the outputs of the reference source  26  are designated as ideal outputs of the speaker  12 , and reflect an ideal frequency-phase delay characteristic and an ideal frequency-efficiency characteristic which the speaker  12  is expected to attain after compensation. The control unit  28  is connected to the memory unit  14  of the apparatus  10 .  
      Referring also to  FIG. 3 , this is a block diagram showing relationships between an alternative compensation system  20 ′ and the apparatus  10 . The compensation system  20 ′ is the same as the compensation system  20  of  FIG. 2 , except that the reference source  26  is preferably a digital signal source, and is connected with the control unit  28 .  
      Referring also to  FIGS. 4 and 5 , these are a frequency-phase delay graph and a frequency-efficiency graph for the speaker  12 . The controllable signal source  22  sends audio signals in a certain frequency range to the speaker  12 . The speaker  12  receives the audio signals, and transforms the audio signals into sounds in a corresponding frequency range. Generally, sound frequencies audible to the human ear are in the range from approximately 20 Hz to 20 KHz. Therefore the audio signals with different frequencies in the range from 20 Hz to 20 KHz are selected to be transformed by the speaker  12  into sounds with corresponding frequencies. When not compensated, the sounds have phase delays and low efficiencies when compared to the corresponding audio signals, because of the real characteristics of the speaker  12 . In  FIGS. 4 and 5 , curves  100  and  90  respectively represent the real frequency-phase delay characteristic and the real frequency-efficiency characteristic of the speaker  12 , and lines  102  and  92  respectively depict an ideal frequency-phase delay characteristic and an ideal frequency-efficiency characteristic of the speaker  12 . As seen in  FIGS. 4 and 5 , the curves  100  and  90  respectively deviate from the corresponding lines  102  and  92 , which indicate that uncompensated outputs of the speaker  12  deviate from the ideal outputs. Thus, to adjust the respective deviations so that they fall within a predetermined acceptable range, a plurality of compensation parameters including frequency-phase delay parameters and frequency-efficiency parameters need to be built. The frequency-phase delay parameters and frequency-efficiency parameters are denoted respectively by curves  104  and  94  in  FIGS. 4 and 5 .  
      During the building of the compensation parameters, in one preferred embodiment according to  FIG. 2 , the sensor  24  first senses the output of the speaker  12 , compares the output with the ideal output of the speaker  12  defined by the reference source  26 , and sends the comparison results to the control unit  28 . The control unit  28  determines whether deviations between the output of the speaker  12  and the ideal output fall within predetermined ranges according to the comparison results. In an alternative preferred embodiment according to  FIG. 3 , the sensor  24  only senses the output of the speaker  12 , and outputs what it senses to the control unit  28 . The control unit  28  compares the output of the speaker  12  with the ideal output, and produces comparison results. Similarly, based on the comparison results, the control unit  28  determines whether deviations between the output of the speaker  12  and the ideal output fall within predetermined ranges. In the preferred embodiments, the deviations between the output of the speaker  12  and the ideal output include a frequency-phase delay deviation and a frequency-efficiency deviation, and accordingly the predetermined ranges are preset to include a frequency-phase delay range and a frequency-efficiency range. If the deviations fall within the predetermined ranges, the control unit  28  sets the compensation parameters for the speaker  12  under this particular frequency at zero, and stores the compensation parameters in the memory unit  14 . If the deviations fall outside of the predetermined ranges, the control unit  28  regulates the output of the controllable signal source  22  so as to change the output of the speaker  12  under this particular frequency, compares the output with the ideal output, and re-determines whether deviations fall within the predetermined ranges, based on the comparison results from the sensor. The above-described operations of changing the output, comparing the output with the ideal output, and re-determining based on the comparison results are repeated until the comparison results fall within the predetermined range. Finally, discrepancies between the latest output of the speaker  12  after regulation thereof and the original output of the speaker  12  are stored in the memory unit  14  as the compensation parameters for the speaker  12  under this frequency.  
      The above description relates to the building of compensation parameters for a particular speaker  12  under a particular frequency. However, the compensation system  20 ,  20 ′ also builds compensation parameters for the speaker  12  under any particular frequency. For such situations, the frequency of the output of the controllable signal source  22  needs to be changed to meet with the particular frequency. The compensation system  20 ,  20 ′ is also adapted to build compensation parameters for a plurality of speakers  12 , and for any other type of sound outputting unit(s) which can transform audio signals into sounds.  
      Referring also to  FIG. 6 , this is a block diagram of an exemplary application of the apparatus  10 , which is connected with an audio signal generating device  60  (hereinafter, “the device  60 ”). In this application, the apparatus  10  and the device  60  together constitute a sound outputting system having compensation characteristics. The speaker  12  of the apparatus  10  receives audio signals from the device  60 . The device  60  may be an MP3 player, a CD player, or a host computer, and generally includes a micro-controller  62 , a signal processor  64 , and a signal source  66 . The memory unit  14  of the apparatus  10  is connected to the micro-controller  62 . The micro-controller  62  and the signal source  66  are connected to the signal processor  64 . The signal processor  64  is connected to the speaker  12 . The micro-controller  62  reads the ID (identification) code of the speaker  12  and determines whether the ID code is valid; that is, the micro-controller  62  determines whether the ID code exists in the memory unit  14 . If the ID code is valid, the micro-controller  62  reads the compensation parameters corresponding to the ID code from the memory unit  14 , and sends the compensation parameters to the signal processor  64  to regulate the output of the speaker  12 . After regulation based on the compensation parameters, the speaker  12  approaches or even attains its ideal output.  
      It is to be understood, however, that even though numerous characteristics and advantages of the preferred embodiments have been set forth in the foregoing description, together with details of the structures and functions of the preferred embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of type and arrangement of components within the principles of the invention to the full extent indicated by general meaning of the terms in which the appended claims are expressed.