Spectrogram semester presentation project

Hi guys, this semester i took digital signal processing lecture and at the end of semester, teacher said us everyone select a topic and give me your presentation. on presentation, i failed. next week i gonna represent my topic(makeup). My topic is Spectrogram.

my teacher asking these(below) things if i want to pass this course.

• FFT and Spectrogram of 100Hz Sinusoidal Signal (matlab code)
• FFT and Spectrogram of 500Hz Sinusoidal Signal (matlab code)
• FFT and Spectrogram (1st half time 100Hz and 2nd half time 500hz) (matlab code)
• Frequency starting 100hz to 1000hz FFT and Spectrogram(matlab code)
• How can i obtain a spectrogram and what is the advantage? ( why we are using more spectrogram than FFT)
• How window length(in spectrogram) effect to obtained spectrogram?

i hope you gonna help me want to pass this course, thank you if you help me.

Answer 1

[Walter Roberson]

"How can I obtain a spectrogram"

http://www.mathworks.com/help/signal/ref/spectrogram.html

"why we are using more spectrogram than FFT"

That is a research question for you, not a MATLAB question. You can get some ideas by examining http://www.mathworks.com/help/signal/examples/practical-introduction-to-time-frequency-analysis.html

"How window length(in spectrogram) effect to obtained spectrogram?"

That is a matter for you to experiment with.

 FFT and Spectrogram of 100Hz Sinusoidal Signal (matlab code)
 FFT and Spectrogram of 500Hz Sinusoidal Signal (matlab code)
 FFT and Spectrogram (1st half time 100Hz and 2nd half time 500hz) (matlab code)
 Frequency starting 100hz to 1000hz FFT and Spectrogram(matlab code)

All of those are homework questions for you.

Answer 2

[Deniz S]

is there any solution of these matlab questions? maybe someone solved recently, i haven't any idea of this topic.

[Walter Roberson]

Of course there are solutions to those MATLAB questions. They start with you generating a signal and then passing it to spectrogram() . You can find an example in the spectrogram documentation that I linked to, or see http://www.mathworks.com/help/signal/examples/signal-generation-and-visualization.html