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Announcements 10/22/12

Announcements 10/22/12. Prayer Term project proposals: I responded to all I received, and everyone should have a score. You can change your project idea, but if so you’ll need to send me a new proposal Careful: Lab 6 due Wed night Exam 2 starts Thurs morning, goes until next Tues evening

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Announcements 10/22/12

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  1. Announcements 10/22/12 • Prayer • Term project proposals: I responded to all I received, and everyone should have a score. • You can change your project idea, but if so you’ll need to send me a new proposal • Careful: Lab 6 due Wed night • Exam 2 starts Thurs morning, goes until next Tues evening • Review session: this Tues, 5:30 – 7 pm, C255 Frank & Ernest

  2. Demos f(x,t) tests with Slinky (results from last lecture)

  3. From warmup Extra time on? (nothing in particular) Other comments? Liked it! If i did the lab on time but forgot to turn it in...is it still late?

  4. From warmup Why does a trumpet playing a 440 Hz note sound qualitatively different than when a violin plays the same note? Both are producing 440 Hz waves, aren't they? Yes they are, but they have different timbres- meaning that they are both playing the fundamental and then certain levels of the harmonics above the fundamental. Due to the different levels of harmonics played there is a different feel to the final tone. wave shape

  5. Tone “quality” • Why does a trumpet playing 440 Hz sounddifferent than when I whistle or sing the same frequency? • The wave: Spectrum Lab as oscilloscope • The sounds have different ____________ … but both sounds have the same ____________ • What does that imply about their Fourier frequency components?

  6. Tone quality, cont. • Frequency analysis From unknown website

  7. Tone quality, cont. • Odd-sounding instruments (“tonal percussion”: bells, xylophone, tympani, etc.) From http://web.telia.com/~u57011259/Bellspectra.htm

  8. From warmup What is a chapter on musical scales doing in a physics textbook? What's the connection to physics? It is acoustics and AWESOME. Relation between notes of frequencies. Types of scales used were mathematical relations between frequencies. Everything's connected to physics. Physics defines how things happen. Music created by sound waves of certain frequencies, and as we've been learning in class, waves, frequencies, and harmonics have a lot of physics applications. Just cause we are physicists doesnt mean we are incapable of doing anything else...like art or music. This statement is not reflexive however, If you are a musician....you probably cant do physics.

  9. Piano keyboard layout Image: http://www.music-for-music-teachers.com/piano-keyboard.html • Half step: C to C-sharp (or, e.g. E to F) • Whole step (C to D): ___ half steps • Octave (C to C): ___ half steps • Fifth (C to G): ___ half steps • Fourth (C to F): ___ half steps • Major Third (C to E): ___ half steps • Minor Third (C to E-flat): ___ half steps C E G B C-sharp/D-flat D F A C 2 12 7 5 4 3

  10. Chords Image: http://www.music-for-music-teachers.com/piano-keyboard.html • Why does this sound “good”? • Because they are all harmonics of the same note! What is the note? • It’s actually a C, two octaves below the C that’s being played! • The frequencies of the three notes are 4:5:6 C E G (plus higher harmonics of each term)

  11. C, E, G

  12. G combined with G#

  13. Chords, cont. • “nice” chords: simple frequency ratios (small integers), many harmonics of each note overlap • “ugly” chords: not many harmonics match

  14. Trumpets (Lets suppose a “C trumpet” instead of a regular “B-flat” trumpet, so we don’t have to worry about the usual whole-step shift between piano and trumpet scales.) • The notes you can play with no valves pushed in: B-flat on piano = 932.3 Hz

  15. Back to Pianos • Why is a high B-flat on a piano 932.3 Hz? • How many half steps is it? • How many half steps in an octave? • How much frequency change in an octave? • Each half step = increase freq by a factor of ______ high B-flat A = 440 Hz (defined as reference) (middle C)

  16. So, why are there 12 half-steps in an octave? • Smallest number of tones that can give you close to the right ratios needed for harmonics and chords  Fewer equally-spaced tones in a scale wouldn’t get close enough  More equally-spaced tones in a scale adds unnecessary complexity

  17. Which is better? The debate Disclaimer: In actuality, piano tuners don’t use a strict equal-tempered scale

  18. The Exam • “What’s on the exam?” (you ask)

  19. The wave nature of light • What is “waving”? http://stokes.byu.edu/emwave_flash.html • Medium? • Polarization: quick definition

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