Abstract:
Embodiments of methods and apparatus of compensating for speaker distortion in an audio apparatus can compensate for frequency components of an input audio signal that will be distorted by a nonflat frequency response of a speaker. The compensation can occur before the input audio signal is applied to the speaker. Thus, the frequency response of the cascaded system including a compensator and the speaker can be flatter than that of the speaker. Embodiments of the present invention can reduce or prevent distortion of an input audio signal distorted by the speaker.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a method and apparatus of compensating for speaker distortion in an audio apparatus.  
         [0003]     2. Background of the Related Art  
         [0004]     Various audio apparatuses that play recorded audio data with high-quality/high-power amplification are commercially available on the market.  FIG. 1  illustrates a block diagram of an audio signal processing system of a conventional audio apparatus. As shown in  FIG. 1  the system has a pre-amp  10 , a power amp  11 , and a speaker  20 .  
         [0005]     The pre-amp  10  takes a low-level audio signal from an input and alters its amplitude. The pre-amp  10  prepares the signal for the power amp  11 . Receiving the pre-amplified audio signal, the power amp  11  generates high-power audio signal needed to drive the speaker  20 .  
         [0006]     It is desirable that a speaker should have a flat frequency response (equal amplification of all audio frequencies) over the entire audible frequency range from 20 Hz to 20 kHz. However, it is extremely difficult to obtain such a flat frequency response, and the frequency response changes depending on the manufacturer or the model of the speaker  20 .  
         [0007]     In the case of  FIG. 1 , even though the pre-amp and power amp have a very desirable frequency response, the sound reproduced by the speaker will be distorted to some extent because of the imperfect frequency response of the speaker. For example, if the speaker  20  has a frequency response as shown in  FIG. 2  in which the frequency response is not flat especially in the mid-frequency range of 200 Hz-2 KHz and the high-frequency ranges of 6-8 KHz and 12-15 KHz, the speaker  20  cannot provide high-fidelity sound.  
         [0008]     The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.  
       SUMMARY OF THE INVENTION  
       [0009]     An object of the invention is to solve at least the above problems and/or disadvantages or to provide at least the advantages described hereinafter.  
         [0010]     Another object of the present invention is to provide a method and an apparatus capable of a frequency response that can compensate for speaker distortion.  
         [0011]     Another object of the present invention is to provide a method and apparatus capable of compensating for speaker distortion by pre-modifying input audio signals in consideration of the nonflat frequency response of the speaker.  
         [0012]     In order to achieve at least the above objects or advantages in a whole or in part, in accordance with one aspect of the present invention there is provided an apparatus including a speaker that includes a compensator device having a frequency band dependent gain configured to compensate for a frequency response of the speaker, wherein the frequency band dependent gain amplifies or attenuates frequency components of an input audio signal depending on the frequency band to which the frequency component belongs and a power amplifier configured to amplify a power of an audio signal provided by the compensator device to drive the speaker.  
         [0013]     To further achieve at least the above objects or advantages in a whole or in part, in accordance with one aspect of the present invention there is provided an apparatus that includes a speaker having a corresponding frequency response, a power amplifier configured to amplify the power of an audio signal provided to drive the speaker and a compensator having a frequency band dependent response configured to make an effect on an audio signal output by the speaker closer to a prescribed frequency response than the frequency response of the speaker alone.  
         [0014]     To further achieve at least the above objects or advantages in a whole or in part, in accordance with one aspect of the present invention there is provided an audio signal processing method that includes amplifying or attenuating a plurality of frequency components of an input audio signal according to a frequency band dependent gain set for compensating a frequency response of an audio output device and outputting the modified input audio signal obtained by said amplifying or attenuating the frequency components of the input audio signal.  
         [0015]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:  
         [0017]      FIG. 1  illustrates a block diagram of an audio signal processing system of a conventional audio apparatus;  
         [0018]      FIG. 2  illustrates a frequency response graph of a conventional speaker;  
         [0019]      FIG. 3  illustrates a block diagram showing an audio signal processing system in accordance with a preferred embodiment of the present invention;  
         [0020]      FIG. 4  illustrates a block diagram showing an exemplary system for adjusting frequency response thereof to compensate for speaker distortion;  
         [0021]      FIG. 5  illustrates a frequency response graph including a speaker distortion compensator and a speaker in accordance with a preferred embodiment of the present invention;  
         [0022]      FIG. 6  illustrates a block diagram of an audio signal processing system in accordance with another preferred embodiment of the present invention; and  
         [0023]      FIG. 7  illustrates an exemplary data structure of compensation data for a plurality of speakers. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0024]     Embodiments of an apparatus and methods of compensating for speaker distortion in accordance with the present invention can be applied to various audio apparatuses having speakers.  FIG. 3  illustrates a block diagram of an embodiment of an audio signal processing system of an audio apparatus embodying the present invention. As shown in  FIG. 3 , an audio signal processing system  300  can include a pre-amp  30 , a power amp  31 , a speaker  20 , and a speaker distortion compensator  32 .  
         [0025]     The frequency response of the speaker distortion compensator  32  can be adjusted depending on the frequency response of the speaker  20 . For example, the gain of the speaker distortion compensator  32  at each frequency band divided from an audible frequency range can be determined. Experiments using a measurement apparatus (e.g., apparatus  400 ) that measures the frequency response, can determine the gain of the speaker distortion compensator at each frequency band.  
         [0026]     As shown in  FIG. 4 , an exemplary measurement apparatus  400  can include a microphone  50 , an audio level detector  51 , and a controller  52 . The gain of the speaker distortion compensator  32  at each frequency band can be set by the controller  52 , which will be described below.  
         [0027]     Initially, the gain of the speaker distortion compensator  32  at every frequency band can be set to 0 dB. A test sound signal having frequency components belonging to a each of a plurality of frequency bands can be applied to the pre-amp  30 . The test sound signal may be generated by a conventional signal generator. Sound corresponding to the test sound signal can be reproduced by the speaker  20  through the pre-amp  30 , the speaker distortion compensator  32 , and the power amp  31 .  
         [0028]     The sound reproduced by the speaker  20  is converted into an electrical signal by the microphone  50  of the measurement apparatus  400 , and then the level of the electrical signal can be detected by the audio level detector  51 . The controller  52  can compare the detected audio level with a preset reference level (e.g., corresponding to the test sound signal) and adjust the gain of the speaker distortion compensator  32  at the frequency band so that the detected sound level is closer to or preferably equals the reference level. The same operation can be performed at a subset of or all the other frequency bands.  
         [0029]     After the gain of the speaker distortion compensator  32  is adjusted (e.g., at every frequency band), the overall frequency response of the speaker distortion compensator  32  and the speaker  20  becomes flatter (e.g., frequency zones marked ‘FA’, 200 Hz˜2 kHz, 6 kHz˜8 kHz, 12 kHz˜15 kHz) as shown in  FIG. 5  compared to the frequency response shown in  FIG. 2 . This is because frequency components that are relatively attenuated by the speaker  20  can be amplified and frequency components that are relatively amplified by the speaker  20  can be attenuated by the speaker distortion compensator  32 . Different frequency bands or components can be independently amplified attenuated by the speaker distortion compensator  32 .  
         [0030]     The speaker distortion compensator  32  can be implemented in various apparatus such as a portable computer or a home theater system. However, the present invention is not intended to be so limited.  
         [0031]      FIG. 6  illustrates another embodiment of an audio apparatus according to the present invention. Unlike the embodiment of  FIG. 3  wherein the gain of the speaker distortion compensator  32  at each frequency band can be directly set, for example, by the exemplary external measurement apparatus  400 , in the embodiment of  FIG. 6  the gain of the speaker distortion compensator  32  at each frequency band can be pre-stored, which is, the gain of the speaker distortion compensator  32  can be stored as compensation data (e.g., SC_C_Data) in a non-volatile memory  34  such as an EEPROM included in the audio apparatus. For example, the data or the gain of the speaker distortion compensator  32  for a plurality of frequency bands can be provided by a manufacturer according to model of a speaker or system or can be determined by the controller  52  of the measurement apparatus  400 .  
         [0032]     The compensation data (e.g., SC_C_Data) can be registered as the gain of the speaker distortion compensator  32  at each frequency band by a microcomputer  33  at an initial operation of the audio apparatus such as power-up reset. However, the present invention is not intended to be so limited.  
         [0033]     The experiment shown in  FIG. 4  may be repeated for various speakers, (e.g., by type, model, manufacturer, etc.) and the obtained set of compensation data may be stored in the memory  34 . For example, compensation data can be stored as a data structure as shown in  FIG. 7 , wherein the entire audible frequency range from 20 Hz to 20 kHz is divided into 20 frequency bands.  
         [0034]     Compensation data for each speaker is preferably referenced by the maker code and model number thereof. If a user enters a maker code and model number into the audio apparatus shown in  FIG. 6 , the microcomputer  33  can retrieve the compensation data corresponding to the maker code and model number from the memory  34  and set the gain of the speaker distortion compensator  32  accordingly. If the requested compensation data does not exist in the memory  34 , the microcomputer  33  can set the gain of the speaker distortion compensator  32  to 0 dB, which can prevent the speaker distortion compensator  32  from distorting input audio signal. However, the present invention is not intended to be so limited.  
         [0035]     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. Furthermore, for ease of understanding, certain method procedures may have been delineated as separate procedures; however, these separately delineated procedures should not be construed as necessarily order dependent in their performance. That is, some procedures may be able to be performed in an alternative ordering, simultaneously, etc.  
         [0036]     As described above, embodiments of the method and apparatus for compensating speaker distortion according to the present inventions have various advantages. For example, embodiments of a method and apparatus of compensating speaker distortion in accordance with the present invention can compensate for speaker distortion caused by a nonflat frequency response of a speaker (e.g., in advance) by adjusting the frequency response of a distortion compensator. In one embodiment, the speaker distortion is measured then a compensator is correspondingly adjusted. In one embodiment, the frequency band dependent gain of the speaker distortion compensator can be stored in a memory and retrieved from the memory at an initial operation of the audio apparatus by a controller. Accordingly, embodiments can provide high-fidelity sound despite speaker distortion.  
         [0037]     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.