Abstract:
An audio processing apparatus ( 20 ) connected between an audio source ( 10 ) and an audio output ( 30 ) is provided. The audio processing apparatus is suitable for singing practice of users and includes a vocal removing unit ( 210 ) and a pitch change unit ( 220 ). The vocal removing unit is for removing vocal signals from audio signals of the audio source, and the pitch change unit is for changing pitch of the audio signals and outputting the audio signals to the audio output.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to audio processing apparatuses, and particularly to an audio processing apparatus suitable for singing practice. 
         [0003]    2. Related Art 
         [0004]    Most acoustic devices are generally equipped with features or functions that control the volume, bass, or treble, but not the pitch. If users sing karaoke with such an acoustic device and when a pitch of music goes beyond what the users&#39; singing voices can reach, harmony between the music and the users&#39; singing is destroyed and affects singing practices of the users. The term “Karaoke” refers to a form of entertainment that people sing popular songs into a microphone over pre-recorded backing tracks. 
         [0005]    Further, if the vocals are not removed from the music, the users will also be affected. 
         [0006]    Therefore, there is a need for providing an audio processing apparatus which can solve the problems listed above and are suitable for singing practice. 
       SUMMARY 
       [0007]    An audio processing apparatus that is connected between an audio source and an audio output is provided in accordance with a preferred embodiment. The audio processing apparatus is suitable for sing practice and includes a pitch change unit for changing the pitch of audio signals from the audio source and outputting the audio signals to the audio output. 
         [0008]    The audio processing apparatus further includes a vocal removing unit connected between the audio source and the pitch change unit. The vocal removing unit is provided for removing vocal signals from the audio signals. 
         [0009]    Other advantages and novel features will be drawn from the following detailed description with reference to the attached drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a block diagram of an audio processing apparatus in accordance with a preferred embodiment of the present invention; 
           [0011]      FIG. 2  shows a first embodiment of details of function units of the audio processing apparatus of  FIG. 1 ; and 
           [0012]      FIG. 3  shows a second embodiment of details of function units of the audio processing apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0013]    Referring to  FIG. 1 , the audio processing apparatus  20  in the preferred embodiment is an acoustic equipment  20  connected between an audio source  10  and audio output  30  such as a speaker. The acoustic equipment  20  is configured with a mode select switch  250 . The mode select switch  250  is operable to change the acoustic equipment  20  between a normal mode and a karaoke mode. In the normal mode audio signals from the audio source  10  is amplified by an amplifier  240  in the acoustic equipment  20  and then transmitted to the audio output  30 . 
         [0014]    In the karaoke mode the audio signals is filtered to remove vocal signals by a vocal removing unit  210 , changed a pitch by a pitch change unit  220 , amplified by the amplifier  240  and then transmitted to the audio output  30 . A mode selector  230  is employed to change the mode of the acoustic equipment  20  according to the mode select switch  250 . In the preferred embodiment the mode selector  230  is a changeover switch  230  that either connects the audio source  10  to the amplifier  240  or the pitch change unit  220  to the amplifier  240 . 
         [0015]    In alternative embodiments, the changeover switch  230  connects the audio source  10  either to the vocal removing unit  210  or to the amplifier  240 . The amplifier  240  is controlled by a volume adjust switch  260  configured on the acoustic equipment  20 . The volume adjust switch  260  is operable to obtain a suitable output volume from the audio output  30 . 
         [0016]    Referring to  FIG. 2 , the vocal removing unit  210  mainly includes a high pass filter  211 , a low pass filter  212 , and a mixer  213 . The high pass filter  211  and the low pass filter  212  are connected in parallel between the audio source  10  and the mixer  213 . The high pass filter  211  and the low pass filter  211  cooperatively filter out middle frequency components that are considered to include vocal signals from the audio signals. In depth, the high pass filter  211  passes high frequency components and the low pass filter  211  passes low frequency components from the audio signals to the mixer  213 . The mixer  213  mixes the high frequency components with the low frequency components to produce mixed audio signals and output the mixed audio signals to the pitch change unit  220 . Generally, the high pass filter  211  and the low pass filter  212  have suitable cutoff frequencies to efficiently remove the vocals from the audio signals. In alternative embodiments, a bandstop filter may be employed to constitute the vocal removing unit  210 . The bandstop filter also has suitable cutoff frequencies to efficiently remove the vocals from the original audio signals. 
         [0017]    The pitch change unit  220  includes an A/D (analog to digital) converter  221 , and a D/A (digital to analog) converter  223  connected in series with the A/D converter  221 . A clock circuit  222  is employed to provide clock signals both to the A/D converter  221  and the D/A converter  223 . The A/D converter  221  has a sampling rate different from that of the D/A converter  223  in order to change the pitch of the mixed audio signals when the mixed audio signals are put through the pitch change unit  220 . For example, if the D/A converter  223  has a sampling rate (hereinafter refers to as “D/A sampling rate”) higher than that of the A/D converter (hereinafter refers to as “A/D sampling rate”), the pitch of the mixed audio signals is raised by the pitch change unit  220 . Otherwise, if the D/A sampling rate is lower than the A/D sampling rate, the pitch of the mixed audio signals is lowered by the pitch change unit  230 . The pitch of the mixed audio signals is either lowered by a factor of N (N is a natural number ranging from 1 to 7) degrees if the D/A sampling rate is (1−N/16) times than the A/D sampling rate, or raised by a factor of N degrees if the D/A sampling rate is (1+N/8) times than the A/D sampling rate. 
         [0018]    In alternative embodiments the pitch change unit  220  may include more than one D/A converters.  FIG. 3  depicts an alternative embodiment of the pitch change unit  220  that includes two D/A converters. The two D/A converters refer to as a first D/A converter  224  and a second D/A converter  225  that both receive the clock signals from the clock circuit  222 . The first D/A converter  224  has a sampling rate different from that of the second D/A converter  22 . The first D/A converter  224  and the second D/A converter  225  are both connected to the A/D converter  221  via a pitch select circuit  226 . The pitch select circuit  226  in this embodiment is also a changeover switch  226  that connects either the first D/A converter  224  or the second D/A converter  225  to the A/D converter  221  by a pitch select switch  270  configured on the acoustic equipment  20 . The pitch select switch  270  is operable to select a suitable output pitch from the audio output  30 . 
         [0019]    In the embodiment relative to  FIG. 3 , there are two pitch selections. However in embodiments when more than two D/A converters are employed, there may be more than two pitch selections. In those embodiments, the D/A converters are connected to the A/D converter  221  via the pitch select circuit  226  which may be a multiplex switch. 
         [0020]    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 preferred or exemplary embodiments of the invention.