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Physics Behind the Music

Physics Behind the Music. Down to the River to Pray. Take out the Papers and the Trash. 8 mile . Knock Three Times. Enter Sand Man. Barefoot Blue Jean Baby. How do you define the difference between Noise and Music?.

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Physics Behind the Music

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  1. Physics Behind the Music Down to the River to Pray Take out the Papers and the Trash 8 mile Knock Three Times Enter Sand Man Barefoot Blue Jean Baby How do you define the difference between Noise and Music? ~ Noise is often associated with very loud and grating noise – chaotic sound and “unpleasant” to the ear ~ If Music Consist of sounds with rhythmic tones of certain frequency then the sound of Jackhammer might be considered a musical instrument – it does pound the street with a very regular frequency ~ Intent vs. “Pleasing” Intent to organize sound – create Rhythm

  2. Music vs. Noice • Music vs Noise? • Music is periodic, consist of Harmonic (fundamental, overtones) , notes (frequency) with a rhythm - intent to create sound with a rhythm. • Noise: irregular wave form, sudden change in amplitude or wavelength.

  3. Key Terms • Timbre: quality of sound • Trumpet and violin play exactly the same note, pitch, and loudness but each has a different timbre. Sound Quality – the characteristic that gives the identity to the sound being produced. • Loudness of Sound – amplitude of sound • One can increase the amplitude of sound through forced vibration • Measure loudness with a dB reader • Pitch of sound– frequency of sound • Everyone note is related to a frequency • Every sound has a frequency even noise

  4. Key Terms • Octave – doubling the frequency • 40hz is one octave higher than 20hz • All sound can be characterized by their speed, frequency, amplitude and timbre

  5. Deeper look at Resonance Resonance is a condition in which a vibrating system responds with maximum amplitude to a periodic driving force. (resonance - when one object vibrating at the same natural frequency of a second object forces that second object into vibrational motion.)~ Mechanical systems (beams, pendula, springs, wine glasses, guitar strings etc) will have a number of possible frequencies at which this occurs. These are the system's natural frequencies of vibration. When resonance occurs, when the driving force has the same value as one of the natural frequencies What does this have to do with Music?

  6. Resonance and Music • Musical instruments are set into vibrational motion at their natural frequency when a person hits, strikes, strums, plucks or somehow disturbs the object. • Each natural frequency of the object is associated with one of the many standing wave patterns by which that object could vibrate. • The natural frequencies of a musical instrument are sometimes referred to as the harmonics of the instrument. • An instrument can be forced into vibrating at one of its harmonics (with one of its standing wave patterns) if another interconnected object pushes it with one of those frequencies. This is known as resonance . • So what is the interconnect object? Design of the instrument and YOU!

  7. Standing Waves The modes of vibration associated with resonance in extended objects like strings and air columns have characteristic patterns called standing waves. These standing wave modes arise from the combination of reflection and interference such that the reflected waves interfere constructively with the incident waves

  8. Harmonics • Each natural frequency that an instrument produces has its own characteristic vibrational mode or standing wave pattern. • These patterns are only created within the object or instrument at specific frequencies of vibration; these frequencies are known as harmonic frequencies, or merely harmonics • At any frequency other than a harmonic frequency, the resulting disturbance of the medium is irregular and non-repeating (noise) The lowest frequency produced by any particular instrument is known as the fundamental frequency. fundamental frequency is also called the first harmonic of the instrument.

  9. Stringed Instrument. How to determine the frequency: = f*ƛ n (

  10. 1. A guitar string with a length of 80.0 cm is plucked. The speed of a wave in the string is 400 m/sec. Calculate the frequency of the first, second, and third harmonics. 2. A frequency of the first harmonic is 587 Hz (pitch of D5) is sounded out by a vibrating guitar string. The speed of the wave is 600 m/sec. Find the length of the string.

  11. Closed-End Air Columns • vibrational antinodes will be present at any open end • vibrational nodes will be present at any closed end. * Side Note: Diameter of instrument will effect the sound

  12. Open-End Air Columns The positions of the nodes and antinodes are reversed compared to those of a vibrating string, but both systems can produce all harmonics

  13. 1. Titan Tommy and the Test Tubes at a night club this weekend. The lead instrumentalist uses a test tube (closed-end air column) with a 17.2 cm air column. The speed of sound in the test tube is 340 m/sec. Find the frequency of the first harmonic played by this instrument 2. Stan Dinghwaives is playing his open-end pipe. The frequency of the second harmonic is 880 Hz (a pitch of A5). The speed of sound through the pipe is 350 m/sec. Find the frequency of the first harmonic and the length of the pipe.

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