Sound into Light shows

Step 4 When life isn't ideal....

Unfortunately, i was unable to get my band pass filter circuits to work out ideally so i had to test them to see what they were actually doing and thats what i’ll cover next. For this part i used a frequency generation program with sweep capability as my input that whyameye wrote for me using his favorite toy, the PD environment. I wanted to use a spectrum analyzer to check the output but since i didn’t have one i subbed in an oscilloscope. Since there are whole manuals about how to use an oscilloscope, i won’t cover how to use one here.

To test an audio circuit using the above tools, you need to have a working microphone circuit. i hooked my oscilloscope to the output of the mic circuit then just talked into it to  make sure that the microphone was actually “hearing” it. You should see the level increase as you talk into the mic and go down as silence takes over. Once i was sure my mic circuit worked, i fed the output of the mic into the input of the filter i was testing and moved my oscilloscope test point to the filter output. this time instead of talking into it i used the sweep function of the frequency generation program. make sure and set your sweep time high (relatively for an oscilloscope) i chose 2 seconds. since your sweeping threw the selected frequency range while maintaining the same volume level, any differences you see in amplitude are differences in amplification at those frequency's. you should see some sort of "high point". this is when i discovered that my circuits were not filtering for the frequency’s i had thought, however they were performing as band pass filters. i was basically using an arrow head shape.