MATLAB Simulink Model of Music Equalizer using DSK 6713
What is Music Equalizer ?
Music equalizers are devices or software used for amplifying and attenuating predetermined frequency bands. Every music system, including some portable systems as well as professional stereo systems typically has an equalizer to equalize the audio data. Older system has analog equalizer which was tuned manually, but now a day’s digital music equalizer is very common. The advantage of digital equalizer is that we can store the preset gains of frequencies as desired and can be used in future by just pressing button. An audio equalizer typically will adjust the energy levels of the audio data in one or more different frequency bands in order to change the characteristics of the audio data. The equalizer may generate equalized audio data that may then be converted into analog data so that sound may be generated by a sound generating device, such as a speaker or headphone. The center frequencies for the various filters are distributed across an overall bandwidth having an upper and lower boundary. In general, the analog equalizer includes a combination of a simulated inductor and a bridging amplifier which are constructed of operational amplifiers whereas digital equalizer are made with software and processed by digital signal processor. The same has been accomplished on DSK 6713
Block Diagram of Music Equalizer
Audio Input: The Audio input can be taken from any music player. Mobile phone music player is used as the music input which is feed to DSK 6713 kit through line in connector. Mono channel is used for simplicity.
Analog to Digital Conversion: DSK 6713 has the built in A/D converter which converts the analog input signal into digital signal so that digital processing can be done on the input. The sampling frequency is set to 48kHz. Word length is 16-bit, scaling is normalized and samples per frame are 64. Refer to the diagram below :-
Low and Band Pass Filters for Music Equalizer: Filters are used for separating the signal of different frequencies. One low pass and six band pass filters are designed in MATLAB’s tool, FDATOOL, for filtering seven different bands of frequencies. IIR filters are faster than the FIR filter and give smoother amplitude response as compare to FIR filters. So, IIR filters are used. The key to filters the music correctly is that filter’s cut off frequencies must overlap. The cut off frequencies of all filters are given in table below.
Preset Band Gains for Equalizer: Music effects are produced simply by changing the gains of separated signals of different frequencies. For example, the bass effect is achieved by increasing the gain of lower frequency signals. Preset Band Gain block consists of the 4 set of preset gain which produces Flat, Rock, Bass and Opera Effects. Gain setting for Bass effect is shown below.
Preset Selector: Dip switches on the DSK-6713 are used for preset selection. Zero indexing is used so that normal (flat) preset is selected when no button is pressed. Led on the Kit indicates the preset selection. Parameters of DIP switches are set as shown in figure.
Signal Adder: Signal adder combines all separated signals of different frequencies after completing the processing. Simple adder is used for this purpose.
Digital to Analog Conversion: After the combining, the signal is converted in analog. This is done by DSK 6713 built in D/A converter. The sampling frequency of the A/D and D/A should be same for better output.
SIMULINK MODEL FOR MUSIC EQUALIZER ON DSK 6713
You can download the simulink model for the above equalizer from the link given below, however the snapshot of our working simulink model is given below :
Important Note: This term project of Digital Signal Processing is supervised by Assistant Professor S K Hasnain and is the property of the following students of Pakistan Navy Engineering College (NUST).
- Ahmed Fawad
- Waseem Ahmed
- Aziz Ahmed
- Arslan Amin Dhoraji Wala
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