Temperature and Pitch By Thomas Henson
COOL INFO • To change the pitch of a drum you tighten or loosen the lugs on the side of the shell • Tightening the screws pulls the head tighter and makes the pitch higher or sharper • Loosening the screws loosens the head and makes the pitch lower or flatter • The drum has a range of tones its head can reach.
OTHER STUFF YOU WANT TO KNOW • Drumheads are made of many different materials like plastics, animal hides, and Kevlar • As drumheads get older they become more elastic and can stretch easier. • Tuning works on an exponential scale where the more you tighten it the less it changes
?? Possible Questions ?? • How does age and use affect elastic properties of the head over time • Rate of change; how fast does the head lose its tone. • How does the number of turns correlate to the pitch changes • How does temperature affect sound wave frequency
Hypothesis • If the temperature changes, then the Frequency of the sound waves will change.
Materials • Lab pro software program • Lab pro pressure microphone • Vernier lab quest mini • Digital temperature gauge • 14 by 14 inch sold maple floor tom • 5a hickory drumstick with round tip
Testing Procedure • First I set up the Lab Pro microphone system and load fast Fourier transform program under the Music file, (5 feet from the drum) • Record the temperature with digital thermometer on surface of head. • Hit the record button. • Strike the drum between 3-4 inches from the rim with 5a drumstick (round tip) • record the sound wave and use FFT to determine characteristic frequency. • Record characteristic frequency on data sheet • Repeat these steps ten times for each temp.
Fast Fourier Transform • In my project I need a way to pick out a characteristic frequency • FFT helps us characteristic Frequency What is important is this repeating pattern of movements that distinguishes sounds from noises. A sound has a pitch, which is determined by the frequency with which the pattern repeats itself. But a movement of a plucked string usually consists of a superposition of several more regular movements--modes of vibration. Such a regular movement is described by a sine wave which has a particular frequency. the computer program I use uses FFT to separates complex waves into the components.. • The computer program converts data points into graphs like.
More Data Don’t know where the % sign came from can’t get rid of it either
Middle C Note range achieved during testing The Frequencies varied 34.18 hertz and the wavelengths varied 33 cm.
So what happened? • Like most instruments, Drums lose their tune over time. • Unlike most they don’t simply loosen and go flat. • The way they keep their tone is fundamentally different.
For Example • String instruments tune by turning one knob • Wind instruments tune by pushing the slide in and out • Percussion tune by turning 12 different lugs
How is temperature involved • Temperature fluctuations act as a catalyst speeding up change and increasing entropy • these fluctuations affect the wood shell and push and pull on the head and lugs. • The lugs don’t loosen the same and they compensate for each other.
Further Analysis • Since the drum no longer only produces one frequency. Multiple sounds are produced (12 sounds one for each lug) • This collection of sounds created can morph into different wave shapes. • Some shapes include, Sine, square, triangle, and saw tooth • However the combination of different sound waves would create Complex Waves which are repeating synthesis waves composed of 2 or more different sound waves.
How does this work • When 2 or more sound waves overlap their peaks and troughs blend to form a new wave.
Final Conclusion • In conclusion we can say that the data confirmed that temperature does affect frequency. • In analyzing the data, there did not seem to be any correlation. • There does not appear to be a linear function that describes this relationship. That is we can not predict how the drum frequency will change with a given change in temperature only that it will change. • However improvements in the method might give better results.
Procedure Improvements • Control Pressure. • Control Humidity. • Retune between measurement. • Improve consistency of drum strikes. • These factors went basically uncontrolled during my experiment.
Bibliography • "Documentation Center." Fast Fourier Transform. N.p., n.d. Web. 29 May 2013. • "Frequencies of Musical Notes." Frequencies of Musical Notes. N.p., n.d. Web. 29 May 2013. • "Interesting Facts about Sound - Waves, Vibration, Properties, Speed, Acoustics, Music." Interesting Facts about Sound - Waves, Vibration, Properties, Speed, Acoustics, Music. N.p., n.d. Web. 29 May 2013. • The Science of Sound." The Science of Sound. N.p., n.d. Web. 29 May 2013.