|Acoustics - PH 105
Vibrations and waves, perception and measurement of sound, musical instruments, the human ear and voice, electrical production of sound, acoustics of rooms, electronic music and environmental noise.
Textbook: The Science of Sound, 2nd
Edition, Thomas Rossing, Addison Wesley (1990).
Instructor: David R. Renneke, Science 205, 309-794-3403, firstname.lastname@example.org.
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|Mar. 5||1||Introduction, survey, pictures, what is "sound", definitions of physical quantities (handout)|
|Mar. 7||2||Vibrations. Examples, amplitude, frequency, period, spring/mass system, radio frequencies (AM, FM, shortwave - WWV), NIST, pendulum, computer demos, time graph of periodic motion, oscilloscope|
|Later we will return to the other examples in chapter 2: Helmholtz resonator, drumheads, vibrating bars and plates (xylophone, cymbals). Also, we will cover the vibration spectrum later (Section 2.7).|
|Mar. 9||3||Waves. definitions of transverse and longitudinal wave, examples, velocity = frequency x wavelength, standing waves, sound waves in air, sound creation with a tuning fork, two short videos|
|Mar. 12||3, 4||velocity of sound in different media, change of velocity with temperature, reflection of waves (i = r), refraction of waves, resonance of various systems|
|Mar. 14||3, 8.4||interference of sound, beats, diffraction, interference (water waves, electronic sound, tuning fork)|
|Mar. 16||3,4||Doppler effect, video: "Doppler Effect - Rotating Whistle" (II, #8), vibrating strings, demo: vibrator and elastic string, video: "Vibrations of a Guitar String" (III, #6), demos: guitar sound (keyboard), acoustic guitar (David Spaude), video: "Washtub bass" (5:00).|
|End of material that will be on Test 1.|
Vibrating air columns. open
tube, computer demo, flue pipes, whistle, 4
foot organ pipe, videos: "Cork Dust ..." (III, #1, 4:35),
"Gas Flame" (III, #2, 4:43)
2, 4, 13
|Do we need end corrections?
Experiment with a plastic tube 36.4 cm long with an inside diameter of
3.5 cm (measure,
calculate), Robert Greenler video: 1. whistle and rubber hose, 2.
build-a-sound, 3. recorders - long and short, 4. clarinet (10
Helmholtz resonantor - having fun with bottles. Mufflers.
|Mar. 23||Test 1 - topics covered from Mar. 5-16. See the review sheet handed out earlier.|
|Mar. 26||2, 13||Vibrating bars. video: vibrating rods, xylophone, Nailolian. Vibrating plates. 2 dimensional standing waves (lab), video: "Chladni Plate", IIi, #4 (3:22). Vibrating membranes. equation, demo. Percussion Instruments.|
|Mar. 28||13, 5||Steel Drums. "Acoustics of Carribean Steel Drums", lecture by Dr. Rossing on April 6, 2000. Science News article. Demo pan - Java applet - start with D4 and go up the scale. Listen to a drum band at NIU. Bells and carillons, handbells. video: "Resonant Modes of a Vibrating Bell using Holography", III, #5 (3:32). Hearing - the human ear|
|Mar. 30||13, 6||Cymbals, glass bell, wine glass, video:
"Glass Harmonica", Sound pressure, power and loudness. decibel
|Apr. 2||6||Demo: sound level meter - measure SPL
(sound pressure level) in dB.
CD: The Decibel Scale (1:57), adding sounds of the same frequency and different frequency, musician's scale (SSL in sones vs. LL in phons).
|Apr. 4||6, 7||Equation relating SSL and LL. Masking. Hearing Loss. Harmonics. Partials. Timbre. Sound synthesis. Fourier analysis.|
|Apr. 6||7, 9||Video: "Sound of a Trombone",
III, #7 (4:14). Sounds recorded in lab: 1
- 2 - 3.
Formants. CD: "Effect of Tone Envelope
on Timbre". Vibrato and tremolo.
Musical intervals and scales. Consonant and dissonant intervals. Pythagorean scale.
|Apr. 9||Test 2 - topics covered from Mar.19 - Apr. 6|
|Apr. 11||9||Just diatonic scale. TrueBASIC program. Equal tempered scale. Interval for adjacent notes = twelfth root of 2 = 1.05946... Intervals expressed in cents. One octave = 1200 cents - corresponding to 12 notes on the scale. CD (handout): 18. Linear and Logarithmic Frequency Scales, 16. Stretched and Compressed Scales, 27. Circularity in Pitch Judgment.|
|Apr. 18||23||Auditorium acoustics. Sound absorbers, anechoic rooms, reverberation.|
|Apr. 23||23, 24||Measurement of reverberation time, calculation for a classroom, sound amplification, precedence effect, ringing, video: "Tuning of Meyerhoff Hall" (15 min.), outdoor music pavilion - Central Park in New York (handout).|
|Apr. 25||20||Microphones and Loudspeakers. Transducers (devices that convert energy from one form to another), four microphone types: crystal (piezoelectric), dynamic (moving coil), condenser (capacitor), electret condenser (metalized plastic), dynamic loudspeaker, horn speakers, baffles and enclosures.|
|Apr. 27||26, 27, 29||Electronic music (handout) - musique concrete, music by animation, computer-composed music (demo - "ILLIAC Suite for String Quartet", composer Lejaren Hiller, mathematician Leonard Isaacson - 1957), computer-played music (demo - Numerology), synthesized music, Arp Axxe keyboard, comparison of a violin and a synthesizer (handout), ADSR envelope (attack, decay, sustain, release).|
|Apr. 30||19||Sound synthesis (p. 128) - time graphs, sound spectrum. Filters: low-pass, high-pass, band-pass, band-reject. Octave band analyzer, envelope generator (ADSR - attack, decay, sustain, release). Elements of a clarinet, patch for synthesizing a clarinet sound. Noise - white, pink.|
|May 2||29, 10||Digital sound file formats.
String instruments - Chpt. 10. Sound analysis of a tuning fork and a violin, the four strings: G3 (196 Hz), D4 (294 Hz), A4 (440 Hz) and E5 (660 Hz). Special thanks to Amanda Young for playing her violin in lab (Spring 2000) so these sounds could be recorded and analyzed. Parts of a violin, vibrations of a plucked string (snapshot), conclusions, motion of a bowed string.
|May 4||10, 28||Playing the violin, vibrational modes of
the bridge, plate resonance - holographic
interferometry (Augustana graduates: Josh Murphy and Craig Schmaus
- summer research), vibrations of the
violin body (MWR - main wood resonance about 440 Hz), vibration of the
air cavity (MAR - main air resonance from 260 to 290 Hz), acoustical
characteristics of violins (handout).
Digital audio compact discs (p. 568). 12 cm in diameter, 782 megabytes of data (74 min of audio), focused laser beam (1.7 micrometer diam.), red light - semiconductor laser (790 nm), read and record speed = 1.25 m/s, variable rotation rate - 500 rpm inside track, 200 rpm outside track, sampling time = 44,100 per second, freq. range 20-2000 Hz, dynamic range - 90 dB. Demo - laser beam reflecting off an audio CD, laser beam through a diffraction grating.
|May 7||15, 16||Speech production. Human
vocal organs, glottal puffs (waveshapes, sound spectrum), resonator,
resulting sound (waveshapes, sound spectrum), formants - peaks in the
sound spectrum, shape of the vocal tract for various vowel sounds (i, ae,
Analysis of speech. Sound spectrograph, speech spectrogram, demo using Real Player Plus - "sound analyzer": spectrum, spectrogram, waveform, graph - 16 band frequency display. Science New article - see below.
without Borders" - Science News, April 15, 2000, p.
252. This is an interesting article about singing birds and
musical compositions, e.g. some by Mozart. Four sonograms are
shown at the right: (a) warbler, (b) whale, (c) flute, (d) person.
Sonograms show frequency rising vertically as time progresses horizontally. Note that sonograms (the term used in this article) are equivalent to "sound spectrograms" as used by your textbook (and many others). Also notice that the time graph (waveshape) is shown along the top of each of these sonograms.
Last update: May 7, 2001