Abstract:
An audio signal measurement method for a speaker and an electronic apparatus having the speaker are provided. The electronic apparatus further has a processing circuit and a power amplifier. The processing circuit is coupled to the speaker and configured to execute a time domain to frequency domain transform according to a voltage value of an audio signal and a current value of current feedback from the speaker so as to obtain a frequency response curve. The power amplifier is coupled to the speaker and configured to drive the speaker according the voltage value of the audio signal. The processing circuit is capable of determining whether the frequency response curve is located within a predetermined area such that the processing circuit generates a signal when the frequency response curve is located out of the predetermined area. Thereby, the electronic apparatus may measure its transducer distortion and acoustic box leakage.

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure is directed to an audio signal measurement method for a speaker, and an electronic apparatus having the speaker, and more particularly to an electronic apparatus capable of self-testing a speaker thereof and an audio signal measurement method for the speaker. 
     2. Description of Related Art 
     In current modern society with increasingly developed multi-media, the quality of speakers is often one of the keys leading to virtue or vice of sounds heard by users. A speaker having bad quality usually results in a certain level of transducer distortion and acoustic box leakage. Conventionally, a microphone is usually used to test transducer distortion and acoustic box leakage for the speaker. However, such measurement method typically requires enough spaces and cost for installing an anechoic room and an acoustic analyzer. Thus, for the users, the conventional audio signal measurement method for the speaker in the related art will be difficult to put into use due to an obstacle to budgets and spaces that is difficult to overcome. 
     SUMMARY 
     The disclosure is directed to an electronic apparatus capable of self-testing whether a speaker thereof is operated normally. 
     The disclosure is directed to an audio signal measurement method for a speaker, which is adopted to determining whether the speaker is operated normally. 
     The disclosure is directed to an audio signal measurement method for a speaker. The audio signal measurement method includes measuring a voltage value of an audio signal and measuring a current value of a current feedback from the speaker. The audio signal measurement method further includes executing a time domain to frequency domain transform according to the voltage value and the current value so as to obtain a frequency response curve. The audio signal measurement method yet further includes determining whether the frequency response curve falls within a predetermined area and sending out a signal if the frequency response curve falls out of the predetermined area. 
     The disclosure is directed to an electronic apparatus. The electronic apparatus includes a speaker, a processing circuit and a power amplifier. The speaker is configured to send out sounds. The processing circuit is coupled to the speaker and configured to execute a time domain to frequency domain transform according to a voltage value of an audio signal and a current value of a current feedback from the speaker so as to obtain a frequency response curve. The power amplifier is coupled to the speaker and configured to drive the speaker according the voltage value of the audio signal. Herein, the processing circuit is capable of determining whether the frequency response curve falls within a predetermined area and sending out a signal when the frequency response curve falls out of the predetermined area. 
     In one embodiment of the disclosure, the time domain to frequency domain transform is a Fourier transform. 
     In one embodiment of the disclosure, the Fourier transform is a fast Fourier transform (FFT). 
     In one embodiment of the disclosure, the time domain to frequency domain transform is a Laplace transform. 
     In one embodiment of the disclosure, the voltage value is represented by a time function v(t), the current value is presented by a time function i(t), and the frequency response curve is obtained by executing the time domain to frequency domain transform on [v(t)/i(t)], where t represents time. 
     In one embodiment of the disclosure, the voltage value is represented by the time function v(t), the current value is presented by the time function i(t), and the frequency response curve is obtained by executing the time domain to frequency domain transform on 
               (       ∫   0   t     ⁢           v   ⁡     (   t   )       -       i   ⁡     (   t   )       ×     R   dc           B   ⁢           ⁢   1       ⁢           ⁢     ⅆ   t         )     ,         
where t represents time, R dc  is a resistor value of the driving device of the speaker under a normal room temperature, and B 1  is a constant value of the speaker.
 
     In one embodiment of the disclosure, the electronic apparatus further includes an augmenter, which is coupled to the processing circuit and configured to augment a source signal to generate the audio signal. When the frequency response curve falls out of the predetermined area, the processing circuit adjusts a gain for the audio signal. 
     In one embodiment of the disclosure, the frequency response curve is configured to present a relationship between an impedance of the speaker and a frequency of the sound sent from the speaker. 
     In one embodiment of the disclosure, the frequency response curve is configured to represent a relationship between a stroke of a diaphragm of the speaker and the frequency of the sound sent from the speaker. 
     To sum up, the electronic apparatus as described according to the embodiments of the disclosure may self-measure whether the speaker thereof meets desired requirements. Since neither an anechoic room nor an acoustic analyzer requires to be additionally installed, the usage convenience may be significantly enhanced, and the testing cost for the speaker may be lower down. 
     In order to make the aforementioned and other features and advantages of the disclosure more comprehensible, embodiments accompanying figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings constituting a part of this specification are incorporated herein to provide a further understanding of the disclosure. Here, the drawings illustrate embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1  is a functional block diagram of an electronic apparatus of one embodiment of the disclosure. 
         FIG. 2  is a diagram showing a frequency response curve of an electronic apparatus of one embodiment of the disclosure. 
         FIG. 3  is a functional block diagram of an electronic apparatus of another embodiment of the disclosure. 
         FIG. 4  is a diagram showing a frequency response curve of an electronic apparatus of another embodiment of the disclosure. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Referring to  FIG. 1 ,  FIG. 1  is a functional block diagram of an electronic apparatus of one embodiment of the disclosure. An electronic apparatus  100  may be a mobile phone, a tablet computer, a multi-media screen, a television and so on, but the disclosure is not limited thereto. The electronic apparatus  100  has a processing circuit  110 , a power amplifier  120  and a speaker  130 . The speaker  130  is configured to send out sounds based on an audio signal S IN . The processing circuit  110  is coupled to the speaker  130  and measures a voltage value v(t) of the received audio signal S IN . The processing circuit  110  transmits the received audio signal S IN  to the power amplifier  120  such that the power amplifier  120  drives the speaker  130  to send out one sound according to the voltage value v(t) of the audio signal S IN . Typically, the power amplifier  120  is connected with a system voltage of the electronic apparatus  100  to supply power to the speaker  130 . The speaker  130  feeds back a current I to the processing circuit  110 , and the processing circuit  110  measures the current value i(t) of the current I. In addition, The processing circuit  110  executes a time domain to frequency domain transform according to the voltage value v(t) of the audio signal S IN  and the current value i(t) of the current I feedback from the speaker  130  so as to obtain a frequency response curve. 
     Referring to  FIG. 2  with  FIG. 1 ,  FIG. 2  is a diagram showing a frequency response curve of an electronic apparatus of one embodiment of the disclosure. A frequency response curve C 1  is one frequency response curve obtained by the processing circuit  110  executing the time domain to frequency domain transform according to the voltage value v(t) and the current value i(t). The horizontal axis in  FIG. 2  represents each frequency of each sound sent out from the speaker  130 , and the vertical axis represents each feature value corresponding to the speaker  130  based on each frequency. Herein, after voltage value v(t) and the current value i(t) are transformed to the frequency domain, the frequency of the processing circuit  110  corresponds to the frequency of the sound sent from the speaker  130 , and thus, the horizontal axis in  FIG. 2  may also represent the frequency corresponding to the voltage value v(t) or the current value i(t) transformed to the frequency domain. In one embodiment of the disclosure, the feature value as described above is an impedance of the speaker  130  measured by the processing circuit  110  and namely, the frequency response curve C 1  is configured to present a relationship between the impedance of the speaker  130  and the frequency of the sound sent from the speaker  130 . In another embodiment of the disclosure, the feature value as described above is a stroke of an diaphragm  134  of the speaker  130  measured by the processing circuit  110  and namely, the frequency response curve C 1  is configured to present a relationship between the stroke of the diaphragm  134  of the speaker  130  and the frequency of the sound sent from the speaker  130 . The processing circuit  110  determines whether the frequency response curve C 1  falls within a predetermined area II. When the processing circuit  110  has determined that the frequency response curve falls within an area I or an area III rather than within the predetermined area II, the processing circuit  110  sends a signal S A  to remind a user of the electronic apparatus  100 . For example, a portion of a frequency response curve C 2  falls out of the predetermined area II, and accordingly, if the frequency response curve obtained by the processing circuit  110  is the frequency response curve C 2 , the processing circuit  110  sends out the signal S A . The aforementioned areas I, II and III are defined by an upper-limit curve L U  and a lower-limit curve L D , and each feature value corresponding to the upper-limit curve L U  and the lower-limit curve L D  based on each frequency may be configured according to different user demands. 
     In another embodiment of the disclosure, the electronic apparatus  100  may also includes a display unit  140 , which is configured to display a message in connection with the signal S A  to remind the user. The display unit  140  may be a touch screen or a non-touch screen. 
     In one embodiment of the present disclosure, the speaker  130  has a driving device  132  and the diaphragm  134 . The driving device  132  is configured to drive the diaphragm  134  to vibrate according to a signal outputted by the power amplifier  120  so as to generate an acoustical wave. In one embodiment of the disclosure, the driving device  132  is a coil, which is configured to drive the diaphragm  134  to vibrate in an electromagnetic induction manner. In addition, in one embodiment of the disclosure, the driving device  132  and the diaphragm  134  are respectively disposed on two substrates, and the driving device  132  is a thin film electrode formed by metal, and the diaphragm  134  may carry statistic electricity. The aforementioned two substrates may be made of fiber. In other words, the two substrates may be two pieces of paper. 
     In one embodiment of the disclosure, the time domain to frequency domain transform executed by the processing circuit  110  is a Fourier transform, and the Fourier transform includes a fast Fourier transform (FFT). In one embodiment of the disclosure, the time domain to frequency domain transform executed by the processing circuit  110  is a Laplace transform. 
     In addition, in one embodiment of the disclosure, the voltage value of the audio signal S IN  is represented by a time function v(t), the current value of the current I is presented by a time function i(t), where t represents time, and the processing circuit  110  executes the time domain to frequency domain transform on [v(t)/i(t)] to obtain one frequency response curve. The processing circuit  110  executes the time domain to frequency domain transform on [v(t)/i(t)] to obtain the frequency response curve, and the feature value corresponding thereto is the impedance of the speaker  130 . In one embodiment of the disclosure, the processing circuit  110  executes the time domain to frequency domain transform on 
             (       ∫   0   t     ⁢           v   ⁡     (   t   )       -       i   ⁡     (   t   )       ×     R   dc           B   ⁢           ⁢   1       ⁢           ⁢     ⅆ   t         )         
to obtain one frequency response curve, where R dc  is a resistor value of the driving device  132  of the speaker  130  under a room temperature (about 25° C.), and a constant value B 1  varies with of different speakers  130 . The processing circuit  110  executes the time domain to frequency domain transform on
 
             (       ∫   0   t     ⁢           v   ⁡     (   t   )       -       i   ⁡     (   t   )       ×     R   dc           B   ⁢           ⁢   1       ⁢           ⁢     ⅆ   t         )         
to obtain the frequency response curve, and the feature value corresponding thereto is the stroke of the diaphragm  134 .
 
     In one embodiment of the disclosure, the electronic apparatus may further include an augmenter, which is configured to augment a source signal to generate the audio signal S IN . Referring to  FIG. 3 ,  FIG. 3  is a functional block diagram of an electronic apparatus  300  of another embodiment of the disclosure. The major difference between the electronic apparatus  300  and the electronic apparatus  100  relies on the electronic apparatus  300  having an augmenter  150 . As for other devices of the electronic apparatus  300 , they are the same as those in the electronic apparatus  100 , and will not be described repeatedly hereinafter. The augmenter  150  is coupled to the processing circuit  150  and configured to gain a source signal S 0  to generate the audio signal S IN . When the frequency response curve obtained by the processing circuit  110  according to the voltage value v(t) and the current value i(t) falls out of the predetermined area, the processing circuit  110  adjusts the gain of the augmenter  150  so that the adjusted frequency response curve may fall within the predetermined area. Usually, the processing circuit  110  lowers down the gain of the augmenter  150  so that the adjusted frequency response curve may fall within the predetermined area. 
     Referring to  FIG. 4  with  FIG. 3 ,  FIG. 4  is a diagram showing a frequency response curve of an electronic apparatus of another embodiment of the disclosure. Therein, a frequency response curve C 3  is one frequency response curve obtained by the processing circuit  110  executing the time domain to frequency domain transform according to the voltage value v(t) and the current value i(t). The horizontal axis in  FIG. 4  represents each frequency of each sound sent out from the speaker  130 , and the vertical axis represents each feature value corresponding to the speaker  130  based on each frequency. In one embodiment of the disclosure, the feature value as described above is the stroke of the diaphragm  134  of the speaker  130  measured by the processing circuit  110  and namely, the frequency response curve C 3  is configured to present a relationship between the stroke of the diaphragm  134  of the speaker  130  and the frequency of the sound sent from the speaker  130 . 
     The processing circuit  110  determines whether the frequency response curve C 3  falls within a predetermined area A. When the processing circuit  110  has determined that the frequency response curve falls within an area B rather than within the predetermined area A, the processing circuit  110  sends the signal S A  to remind the user of the electronic apparatus  100 . The aforementioned areas A and B are defined by an upper-limit curve B U , and a feature value corresponding to the upper-limit curve B U  based on each frequency may be configured according to different user demands. 
     In light of the foregoing, the disclosure is directed to an electronic apparatus capable of self-testing whether a speaker thereof is operated normally. Since neither an anechoic room nor an acoustic analyzer requires to be additionally installed, the usage convenience may be significantly enhanced, and the testing cost for the speaker may be lower down. 
     Although the disclosure has been described with reference to the above embodiments, it will be apparent to one of the ordinary skill in the art that modifications to the described embodiment may be made without departing from the spirit of the disclosure. Accordingly, the scope of the disclosure will be defined by the attached claims not by the above detailed descriptions.