1. RockSat-C 2012 ISTR Individual Subsystem Testing Report Minnesota Sound Wreckers University of Minnesota 2/13/12 1 Alexander Richman Jacob Schultz Justine Topel Will Thorson

2. RockSat-C 2012 ISTR Mission Overview Our mission is to design and build an Active Noise Cancellation (ANC) system capable of attenuating the noise on board a rocket. –We require at least some reduction in intensity of noise in the test chamber compared to the control chamber as well as the safe operation of the entire payload. 2

3. RockSat-C 2012 ISTR Mission Overview cont. We expect to show that this technique is a viable solution to noise sensitive testing onboard rockets. This would benefit any sound sensitive experiment onboard a rocket including any testing in which live subjects are used and it is desired to lower their stress levels. 3

4. RockSat-C 2012 ISTR Functional Block Diagrams 4 ANC speaker microphone Data Logger microphone Power Supply Wallops activation signal

5. RockSat-C 2012 ISTR ANC system 5 Dummy Chamber Control Systems Power Supply Mic Preamps Power amplifier Mic Speaker Data Logger ANC In Out

6. RockSat-C 2012 ISTR Changes from CDR Instead of trying to design a complicated ANC system from scratch using a DSP and programming our own control models into it we will be adapting an already built ANC system. –The ANC system found in high quality headphones work well in the spectrum we hope attenuate sound. –Some work will be required to integrate the system and optimize its output for our application. 6

7. RockSat-C 2012 ISTR Program Management and Team Updates We are continuing with the same overall team organization as last semester. 7

8. RockSat-C 2012 ISTR Schedule Update We are mostly on schedule at this time There has been a slight delay in the fabrication of the structure. –The shop is backed up with several projects at the moment but should be able to finish ours in time for testing. The ANC system requires adjustments in order to operate correctly and some further testing 8

9. RockSat-C 2012 ISTR Subsystem Overview Subsystems involved in our experiment –Active Noise Cancellation system (Presented by Alex Richman) –Power supply (Presented by Will Thorson) –Data Logger (Presented by Will Thorson) 9

10. RockSat-C 2012 ISTR Power Supply Subsystem Overview We will be using the power supply that was flown last year. We have not conducted extensive testing of this system as of yet. 10

11. RockSat-C 2012 ISTR Data Logger Subsystem Overview We will be using the data logger that was flown last year. We have not conducted extensive testing of this system as of yet either. 11

12. RockSat-C 2012 ISTR ANC Subsystem Overview We have completed basic audio cancellation testing in our test chamber with our ANC system we recovered from a pair of noise cancelling headphones. As of now, our system is not performing as we hoped, but we are optimistic that we can solve our problems. 12

13. RockSat-C 2012 ISTR ANC Subsystem Update - Pictures 13 Test chamber with microphone Egg carton with foam added to top of chamber Dismantled ANC system from headphones

14. RockSat-C 2012 ISTR ANC Subsystem Update - Pictures 14 Above – Recording audio data in Ableton Live Below – Analyzing data in Matlab

15. RockSat-C 2012 ISTR ANC Subsystem Update 15 Above – Audio Amplifier to give more power to our speaker Above – Boundary Microphone to be used with launch

16. RockSat-C 2012 ISTR ANC Subsystem Update Testing Procedure To perform basic audio cancellation tests, we agitated our test chamber with a 300Hz signal, as our ANC system from the headphones has two settings to cancel noise – 300Hz and 120Hz. We recorded audio data from our test microphone in the chamber with the noise cancellation system OFF, ON(300Hz), and ON(120Hz). 16

17. RockSat-C 2012 ISTR ANC Subsystem Update TestRMS of Signal Control Signal0.0102 300Hz Targeted ANC0.0439 120Hz Targeted ANC0.0268 17 Current data shows that our noise cancelling system is not attenuating our noise, but amplifying it. We believe this is may be caused by constructive interference due to the increased distance from the driving speaker to the microphone, as compared to the human ear and the headphone speaker. It is encouraging that we get more interference at the 300Hz ANC setting, as it may suggest that we will get attenuation if we can eliminate the phase difference.

18. RockSat-C 2012 ISTR ANC Subsystem Update – FFT Plot 18

19. RockSat-C 2012 ISTR ANC Subsystem Update – FFT (Wider Range) 19

20. RockSat-C 2012 ISTR ANC subsystem II We are no longer exploring the method of building our own ANC system using a DSP at this time –The required components put a severe strain on space allotted for electronics onboard –Coding and testing would have taken many hours of work which can better be spent integrating the ANC headphone system into our designs. 20

21. RockSat-C 2012 ISTR Plan for Subsystem Integration We have removed the power supply system from the old canister and are preparing to integrate it with our current ANC setup Our next challenge is to integrate our subsystems and fit them within the physical constraints of the NASA cylinder. 21

22. RockSat-C 2012 ISTR Lessons Learned Noise cancellation is a delicate process and careful control of gains and phases is required to tread the thin line between noise cancellation and noise amplification. The direction of this project hasn’t always been clear. Now that we have a clear path, the concern is alleviated. 22

23. RockSat-C 2012 ISTR Lessons Learned Our testing methods are working and giving us clear results. The noise cancelling headphone system seems to work. We are still working on filtering audio measurements to the specified bandwidth, which will be a helpful step forward to measuring signal power for the frequency range of concern. 23

24. RockSat-C 2012 ISTR Conclusions We are no longer exploring multiple ANC systems at the same time. We have to try to eliminate the phase difference in order to get attenuation. 24