Abstract:
An audio test apparatus, and an exemplary audio test method that includes: processing an audio file through two independent channels; outputting no signals from a left channel and from a right channel in a first time period; receiving noise signals from the left and right channels; outputting single-frequency signals from the left channel only in a second time period; receiving the single-frequency signals from the left channel and crosstalk signals from the right channel; outputting multi-frequency signals from the left and right channels in a third time period; receiving the multi-frequency signals from the left and right channels; outputting single-frequency signals from the right channel only in a fourth time period; receiving the crosstalk signals from the left channel and the single-frequency signals from the right channel; and testing parameters according to the signals received during the four time periods.

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to an audio test apparatus capable of decreasing test time in audio devices and a test method thereof. 
     2. General Background 
     Nowadays, handheld devices (e.g., mobile phones) are becoming more popular and multifunctional. Although mobile phones are primarily used as a means of communication, people typically use the mobile phone to listen to music. As a result, the sound quality outputted by handheld devices is an important factor in determining user satisfaction. The quality of the audio port of the mobile phone, such as an earphone port, directly correlates to the overall sound quality. Therefore, it is necessary to test and verify the quality of the mobile phone&#39;s audio port. 
     In general, testing the quality of the audio port is accomplished by receiving the audio signal outputted by the audio port and analyzing parameters of the audio signal. These parameters include signal to noise ratio (SNR), total harmonic distortion (THD), and frequency response (FR). The general method is to test different parameters by outputting different audio signals for the different tests. The general method is time consuming. 
     Therefore, an audio test apparatus that reduces test time and a test method are desired to overcome the above-identified deficiencies. 
     SUMMARY 
     An audio test method includes processing a media test file through two independent channels. In a first time period, no signals are outputted from the first and second channels. Noise signals from the first and second channels are collected, converted into digital noise signals, and stored in a storage unit. In a second time period, single-frequency signals are outputted from the first channel and no signal is outputted from the second channel. Single-frequency signals from the first channel and crosstalk signals from the second channel are received, converted into digital single-frequency signals and digital crosstalk signals, and stored in the storage unit. In a third time period, multi-frequency signals are outputted from the first channel and the second channel. Multi-frequency signals from the first and second channel are received, converted into digital multi-frequency signals, and stored in the storage unit. In a fourth time period, no signals are outputted from the first channel and single-frequency signals are outputted from the second channel. The crosstalk signals from the first channel and the single-frequency signals from the second channel are received, converted into digital crosstalk signals and digital single-frequency signals, and stored in the storage unit. Tests are performed during the four time periods. 
     An audio test apparatus is also provided. 
     Other advantages and novel features will become more apparent from the following detailed description of embodiments when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the test apparatus and test method. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the various views. 
         FIG. 1  is a block diagram of an audio test apparatus in accordance with an embodiment of the present invention; 
         FIG. 2  is a sketch diagram of an audio signal outputted by the audio device in accordance with an embodiment of the present invention; 
         FIG. 3  is a flowchart illustrating an audio test method of an embodiment of the present invention; 
         FIG. 4  is a flowchart illustrating a signal to noise ratio test method of an embodiment of the present invention; 
         FIG. 5  is a flowchart illustrating a crosstalk test method of an embodiment of the present invention; 
         FIG. 6  is a flowchart illustrating a total harmonic distortion test method of an embodiment of the present invention; 
         FIG. 7  is a flowchart illustrating a full scale distortion test method of an embodiment of the present invention; and 
         FIG. 8  is a flowchart illustrating a frequency response test method of an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Referring now to the drawings in detail,  FIG. 1  is a block diagram of an audio test apparatus  2  in accordance with an exemplary embodiment of the present invention. The audio test apparatus  2  includes an audio collection device  10 , a central processing unit (CPU)  20 , a display  30 , and a storage unit  40 . The storage unit  40  stores a media test file. The audio collection device  10  is a sound card  10  in the exemplary embodiment of the present invention. An audio device  1  is an electronic device equipped with an audio port  101  and a data interface (not shown). The data interface can be a USB interface or an IEEE 1394 interface. The audio port  101  is used to output audio signals to a transducer (not shown). In the exemplary embodiment of the present invention, the audio device  1  is a mobile phone or a media player, and the audio port  101  is a dual channel headphone interface equipped with a first channel (a path over which audio signals can pass) and a second channel. 
     The audio device  1  is connected to the audio test apparatus  2  via a data cable  14 . The data cable  14  facilitates data transfer of a media test file (not shown) from the audio test apparatus  1  to the audio device  2 . The audio port  101  is connected to an audio port  102  of the audio test apparatus  2  via an audio cable  12 . The audio device  1  processes the media test file and produces analog audio signals. The audio port  101  outputs the analog audio signals and transmits the analog audio signals to the sound card  10  through the audio cable  12 . The sound card  10  converts the analog audio signals into digital audio signals and transmits the digital audio signals to the CPU  20 . The CPU  20  stores the digital audio signals in the storage unit  40 . The CPU  20  tests the parameters of the first channel and the second channel according to the digital audio signals. These parameters include signal to noise ratio (SNR), crosstalk, total harmonic distortion (THD), full-scale distortion, and frequency response (FR). After testing the parameters, the CPU  20  outputs the test results to the display  30  and stores the test results in the storage unit  40 . 
     The media test file includes a plurality of data sections. For example, the preset data sections include a first data section, a second data section, a third data section, and a fourth data section. The first data section of the media test file is configured for the first channel and the second channel of the audio device  1  has no signals when processed. The second data section of the media test file is configured for the first channel outputs single-frequency signals and the second channel does not output signals when processed. The third data section of the media test file is configured for the first and second channels output multi-frequency signals when processed. The fourth data section of the media test file is configured for the first channel does not output signals and the second channel outputs single-frequency signals when processed. 
     In one embodiment of the present invention, the first channel corresponds to a left channel and the second channel corresponds to a right channel. In another embodiment of the present invention, the first channel and the second channel may correspond to the right channel and the left channel, respectively. 
       FIG. 2  is a sketch diagram of waveforms of audio signals outputted by the audio device  1  of an embodiment of the invention. In a first time period T 1 , the first channel and the second channel do not output signals. In a second time period T 2 , the first channel outputs single-frequency signals and the second channel does not output signals. In a third time period T 3 , the first channel and the second channel output multi-frequency signals. In a fourth time period T 4 , the first channel does not output signals and the second channel outputs single-frequency signals. 
       FIG. 3  is a flowchart illustrating an audio test method of an embodiment of the present invention. In step S 310 , the audio test apparatus  2  transfers the media test file to the audio device  1 , and the audio device  1  processes the media test file to produce the analog audio signals and outputs the analog audio signals through the left channel and the right channel of the audio port  101 . 
     Step S 311  reflects the first time period T 1 , when the left channel and the right channel do not output signals. 
     In step S 312 , the sound card  10  receives noise signals from the left and right channels during the first time period and converts the noise signals of the left channel into left channel digital noise signals and the noise signals of the right channel into right channel digital noise signals. The left channel digital noise signals and right channel digital noise signals are stored in the storage unit  40  by the CPU  20 . 
     Step S 313  reflects the second time period T 2 , when the left channel outputs a single-frequency signal and the right channel does not output signals. 
     In step S 314 , the sound card  10  receives single-frequency signals from the left channel and crosstalk signals from the right channel during the second time period and converts the single-frequency signals into left channel digital single-frequency signals and the crosstalk signals into right channel digital crosstalk signals. The left channel digital single-frequency signals and right channel digital crosstalk signals are stored in the storage unit  40  by the CPU  20 . 
     Step S 315  reflects the third time period T 3 , when the left channel and the right channel output multi-frequency signals. 
     In step S 316 , the sound card  10  receives the multi-frequency signals from the left and right channels of the audio port  101  during the third time period and converts the multi-frequency signals into left channel digital multi-frequency signals and right channel digital multi-frequency signals. The left channel digital multi-frequency signal and the right channel digital multi-frequency signals are then stored in the storage unit  40  by the CPU  20 . 
     Step S 317  reflects the fourth time period T 4 , when the left channel does not output signals and the right channel outputs single-frequency signals. 
     In step S 318 , the sound card  10  receives crosstalk signals from the left channel and the single-frequency signals from the right channel during the fourth time period and converts the left channel crosstalk signals into left channel digital crosstalk signals and the right channel single-frequency signals into right channel digital single-frequency signals. The left channel digital crosstalk signals and the right channel digital single-frequency signals are then stored in the storage unit  40  by the CPU  20 . 
     In step S 319 , the CPU  20  tests the parameters of the left channel and the right channel according to the digitalized data generated during the time periods correspondingly. 
     After testing the parameters, the display  30  displays the results of the parameters. 
       FIG. 4  is a flowchart illustrating an SNR test method of an embodiment of the present invention. In step S 401 , the CPU  20  computes a left channel noise level N L  according to the left channel digital noise signals, and computes a right channel noise level N R  according to the right channel digital noise signals generated during the first time period T 1 . 
     In step S 402 , the CPU  20  computes a left channel signal level S L  according to the left channel digital single-frequency signals generated during the second time period T 2 . 
     In step S 403 , the CPU  20  computes a right channel signal level S R  according to the right channel digital single-frequency signals generated during the fourth time period T 4 . 
     In step S 404 , the CPU  20  calculates an SNR of the left channel using the formula: SNR L =20 lg(S L /N L ), and calculates an SNR of the right channel using the formula: SNR R =20 lg(S R /N R ). 
       FIG. 5  is a flowchart illustrating a crosstalk test method of an embodiment of the present invention. In step S 501 , the CPU  20  computes the left channel signal level S L  according to the left channel digital single-frequency signals generated during the second time period T 2 , and computes a right channel crosstalk signal level C R  according to the right channel digital crosstalk signals generated during the second time period T 2 . 
     In step S 502 , the CPU  20  computes a left channel crosstalk signal level C L  according to the left channel digital crosstalk signals generated during the fourth time period T 4 , and computes the right channel signal level S R  according to the right channel digital single-frequency signals generated during the fourth time period T 4 . 
     In step S 503 , the CPU  20  calculates crosstalk CT L  of the left channel using the formula: CT L =20 lg(C L /S R ), and calculates crosstalk CT R  of the right channel using the formula: CT R =20 lg(C R /S L )). 
       FIG. 6  is a flowchart illustrating a total harmonic distortion test method of an embodiment of the present invention. In step S 601 , the CPU  20  converts the left channel digital single-frequency signals into left channel frequency domain signals and the right channel digital single-frequency signals into right channel frequency domain signals using a Fast Fourier Transform (FFT). 
     In step S 602 , the CPU  20  obtains amplitudes (H Li (i=1, 2 . . . , N)) of harmonic compositions of the left channel frequency domain signals and amplitudes (H Ri (i=1, 2 . . . , N)) of harmonic compositions of the right channel frequency domain signals. 
     In step S 603 , the CPU  20  calculates THD of the left channel using the formula: 
               THD   L     =         (       H     L   ⁢           ⁢   2     2     +     H     L   ⁢           ⁢   3     2     +   …   +     H     L   ⁢           ⁢   N     2       )     /     (       H     L   ⁢           ⁢   1     2     +     H     L   ⁢           ⁢   2     2     +     H     L   ⁢           ⁢   3     2     +   …   +     H     L   ⁢           ⁢   N     2       )               
and calculates THD of the right channel using the formula:
 
     
       
         
           
             
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       FIG. 7  is a flowchart illustrating a Full Scale distortion test method of an embodiment of the present invention. In step S 701 , the CPU  20  computes the left channel signal level S L  according to the left channel digital single-frequency signals generated during the second time period T 2  and computes the right channel signal level S R  according to the right channel digital single-frequency signals generated during the fourth time period T 4 . 
     In step S 702 , the CPU  20  compares the left channel signal level S L , and the right channel signal level S R , with a predetermined signal level. 
     In step S 703 , the CPU  20  determines that there is a Full Scale distortion in the left channel or the right channel if the difference between the left channel signal level S L  and the predetermined signal level or the difference between the right channel signal level S R  and the predetermined signal level exceeds a predetermined range. 
       FIG. 8  is a flowchart illustrating a frequency response test method of an embodiment of the present invention. In step S 801 , the CPU  20  samples a plurality of segments according to the left channel digital multi-frequency signals and a plurality of segments from the right channel digital multi-frequency signals generated during the third time period T 3 . 
     In step S 802 , the CPU  20  windows the segments of the left channel digital multi-frequency signals and the right channel digital multi-frequency signals, and converts the windowed segments into a plurality of left channel frequency domain signals and right channel frequency domain signals through the FFT. 
     In step S 803 , the CPU  20  calculates an average left channel frequency domain signal and an average right channel frequency domain signal. 
     In step S 804 , the CPU  20  calculates a left channel Frequency Response FR L  according to the average left channel frequency domain signal o, and calculates a right channel Frequency Response FR R  according to the average right channel frequency domain signal. 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being embodiments of the invention.