Digital Guitar Tuner
Eric Tai | Daniel Tsui
ECE 476: Spring 2005
In the beginning, the hope was that a digital tuner could be constructed that could outperform all of the guitar tuners made by the leading brands in the market. As we soon realized, the level of accuracy needed in order to do that could be achieved, but at the same time, the inability for any musical device to hold a completely still waveform made this dream impossible. While ultimately the guitar tuner still worked with precision, it was not the amount of precision as hoped.
In our testing we discovered how hard it is to design a tuner that would be effective for a wide range of guitars. Since each guitar has its own overtone characteristics, it is difficult to setup the digital filter and period measuring thresholds to a constant value. The settings that work for one guitar may not work for another guitar since each guitar will produce its individual signal characteristic. The overtone characteristics also vary over time after a string is initially plucked and allowed to propagate. The most accurate measurements are taken after the string is nearing the end of its vibration and the majority of the higher harmonics have already been attenuated. Unfortunately this attenuated signal also has a lot smaller magnitude which makes it more difficult to measure accurately.
Time became an issue in this project as the digital lab was constantly full, especially as the deadline approached. As vast amounts of sleep were given up so that we could secure a bench, the drawback was that our minds could not perform as well so early in the morning or late at night.
If this entire project could be redone, the added functionality of also outputting a certain notes’ sound would be added. While it seems like a small thing, we found out through extensive lab testing that there is no substitute tuner for the human ear. The goal of the tuner is to tune the guitar so that it sounds acceptable when played, and if a human ear cannot detect the difference between 440 and 441 Hz, then there is no need to differentiate as much. Allowing the user to listen to a certain string, and then play that same note on the guitar would probably be a less painful way of tuning.
We were fully aware that guitar tuners have been made in previous semesters of ECE476, yet decided to make one anyway. While we did not reuse anyone’s project in its entirety, we gained some inspiration and ideas from seeing how others approached similar projects. For example, we figured out that the best way to do note matching was not by comparing them in the frequency domain, but in the time domain. In terms of signal filtering, we figured that we could make low pass filters that were better than the ones made by other groups. The ADC was code reused from previous labs, as well as code from lecture. This was code in the public domain.
1. to accept responsibility in making engineering decisions consistent with the safety, health and welfare of the public, and to disclose promptly factors that might endanger the public or the environment; There were no known elements of the project that could possibly endanger the user or environment.
2. to avoid real or perceived conflicts of interest whenever
possible, and to disclose them to affected parties when they do exist; In the
designing of this project, there were no conflicts of interest. As this project was done by two individual
students who did not have alterior agendas, there were no other affected
3. to be honest and realistic in stating claims or estimates based on available data; We did not make any false claims in the analysis of our project.
4. to reject bribery in all its forms; Fortunately, we were not bribed into doing this project, or for fulfilling any other motives.
5. to improve the understanding of technology, its appropriate application, and potential consequences; Our understanding of the components involved in the guitar tuner was enhanced through continual usage and evaluation.
6. to maintain and improve our technical competence and to undertake technological tasks for others only if qualified by training or experience, or after full disclosure of pertinent limitations; We did not attempt to do a project that was beyond our scope.
7. to seek, accept, and offer honest criticism of technical work, to acknowledge and correct errors, and to credit properly the contributions of others; We received criticism as well as accolades for our project from the instructor as well as the teaching assistants on a continual basis. We also noted that people have done this project in the past, and gave proper citations otherwise.
8. to treat fairly all persons regardless of such factors as race, religion, gender, disability, age, or national origin; There was no discrimination involved in this project.
9. to avoid injuring others, their property, reputation, or employment by false or malicious action; We made no attempt to hurt anyone with our tuner, nor did we try to sabotage anyone else’s project.
10. to assist colleagues and co-workers in their professional development and to support them in following this code of ethics. We helped other groups in the lab when they asked for it.
There were no legal considerations.