Study projects

Projects are an essential part of the curriculum of Mobile Computing. Students get the chance to directly apply the theoretical knowledge which is acquired during their studies. This is not only an innovative and exciting approach to teaching but has also been a starting point to successful startups like runtastic and Butleroy.

Detecting Fundamental Frequency of Drums

Zeitraum
Mar 2018 - Jul 2018
FH Studierende
Dennis Sivak
FH BetreuerIn
FH-Prof. DI Dr. Gerald Ostermayer

Ziel

This project deals with the basics of drum tuning and methods to do it. Problems of conventional tuning methods are described and practical solutions for those are presented. The goal is to implement a suitable and modern application for Android smartphones which assists the user in tuning the drums by detecting and displaying the fundamental frequency of the drum. However, this part of the project is limited to finding a suitable algorithm for detecting the frequency from pre-recorded audio samples and implementing it in MATLAB.

Umsetzung

The used algorithms utilize pre-processing in terms of down-mixing and normalization. Windowing and filtering of the signal is also considered in the implementation.

Pre-recorded audio samples of drums are used for proof of concept. The detection of the fundamental frequency is done in frequency domain by computing the fast Fourier transform of the pre-processed signal. From this, the magnitude spectrum and the normalized autocorrelation function are calculated and plotted.

The simplest way of estimating the fundamental frequency of a sound is by extracting the frequency with the highest magnitude relative to the others. Generally, this approach is considered to be very unreliable and inaccurate although it can still produce decent results in some cases.

Utilizing the normalized autocorrelation function, the distance between the fundamental frequency and its harmonics can be estimated. This distance or lag corresponds to the fundamental frequency because the harmonics are positioned at integer multiples of the fundamental frequency.