Sound Design and Music Technology - Class 1

Sound Design and Music Technology - Class 1

• Lectures are scheduled Thursday and Friday, 12:30-14:00, concluding likely on December 20th.
• Exam format: Multiple choice quiz (18 points), podcast (6 points), and short movie sonoriation (9 points), plus an individual project.
• Exam dates: February 4th and 18th, 2025, at 10:00 AM.

Introduction to Musical Acoustics - Class 2

• Sound Definition:
  • Mechanically, a disturbance from equilibrium that propagates through an elastic medium.
  • Subjectively, what is perceived by the ear, involving internal bodily and brain processes.

Sound Properties - Class 3

• Elasticity: The ability of a material to return to its original shape after deformation.
• Sound Propagation: Occurs through the compression and rarefaction of molecules in an elastic medium.
• Impulse Sounds: Brief, impact-driven sounds, often arising from interactions between objects.
• Frequency (f): The number of events per second, measured in Hertz (Hz).
• Period (T): The time interval between two consecutive events, measured in seconds (T = 1/f).
• Pitch: A perceptual property of sound related to frequency; higher frequency usually corresponds to a higher perceived pitch. The relation is not direct, also depending on repetition rates; fast repetition/ frequency = higher perceived pitch; slow repetition/frequency = lower perceived pitch.
• Frequency and Pitch Relationship: Pitch is a perceptual property of the sound depending on the repetition rate, faster repetition means higher pitch. The sound of an elastic body propagates through another elastic material, the ear.
• Sound Wave Shapes: Different types of waves, including sinusoidal and triangular waves can be produced.
• Frequency and Pitch: A high frequency = a high pitch, and vice versa.

Well-Tempered Tuning- Class 4

• Concept of Octaves: A system of 12 tones, organized into octaves; the frequency between two octaves is a factor of 2.
• Frequency & MIDI Key Numbers: A relation between the MIDI key number and the note (C = Do, A = La etc). The Middle C on a keyboard has a MIDI key number 60.
• Well-Tempered Tuning: A tuning system now commonly used in Western music that has a fairly consistent relationship across octave intervals, and is related to frequencies of each note.

Time Analysis - Class 5

• Amplitude Envelope: A graphical representation of how sound amplitude changes over time; it has distinct phases (Attack, Decay, Sustain, and Release). This curve outlines the extremes of the sound's amplitude changes. Different sounds display different amplitude envelopes.
• ADSR Model: Used to analyze sound amplitude changes over time by dividing them into 4 phases.
  • Attack (the beginning)
  • Decay (decay in amplitude)
  • Sustain (constant amplitude)
  • Release (end of the sound).

Pressure Amplitude & Loudness - Class 6

• Pressure Amplitude: A measure of the variation in air pressure caused by a sound fluctuation.
• Decibel (dB): A unit used to express the ratio between two sound pressure levels; it's not a quantity but a ratio.
• Sound Pressure Level (SPL): A measurement of sound pressure relative to a standardized reference pressure (0.00002 Pascal).
• Loudness: A perceptual attribute of sound, relating to its perceived intensity or volume; is related, but not entirely explained, by pressure amplitude.
  • factors like frequency, shape of the oscillation, context,etc influence.

Root Mean Square (RMS) Amplitude - Class 7

• RMS Amplitude: A measure of sound amplitude, useful for relating it to subjective loudness. Is calculated by squaring the instantaneous amplitude, finding the mean value of these squared values, and then square-rooting the mean. Provides a more relevant measure of sound loudness in relation to peak amplitude (peak amplitude times 0.707 = RMS).
• RMS amplitude relating to loudness: RMS is more related to the perception of loudness, compared to peak amplitude. For example, a sinusoidal sound has RMS amplitude = 0.707 x peak amplitude.

Equal Loudness Curves - Class 10

• Phon: A unit of loudness, relating the perceived loudness of sinusoidal sounds to a measurement in decibels (dB) that are perceived as equally loud.
• Equal-Loudness Curves: Curves illustrating how loudness and frequency depend on the sound's pressure level.

Fine Time Analysis & Frequency Analysis - Classes 11-13

• Spectrogram: A visual representation showing how the frequency content of a sound changes over time. Each partial (the simplest parts making up a complex sound) has a frequency, amplitude (color and thickness), and duration corresponding to a color in the spectrogram.
• Frequency Analysis (Spectrum): A representation of the fundamental frequencies and their amplitudes. Analyzes a sound to break it down into its constituent frequencies and their strengths (amplitudes); useful for complex tones.
• Spectrum of Complex Periodic Waves: Complex waves are not formed by just one main peak, but by many peaks and troughs, which are called spectral formants; partials are different than spectral formants.

Waves Propagation - Class 19

• Wavelength: The distance between consecutive peaks or troughs of a wave. This depends on the wave's propagation speed and its frequency.
• Propagation Rate/Velocity (v): The speed at which a wave travels; depends on the medium (and its properties such as density, elasticity, and temperature).
• Reflection, Transmission and Absorption: Some of the parts of the sound wave is reflected, another transmitted outside the wall, and yet another converted into heat. It has a related Absorption Coefficient.

Normal Modes and Wave Superposition - Class 20

• Normal Modes: Patterns of vibration where all parts of an oscillating system move sinusoidally at a constant frequency
• Wave Superposition: When two or more vibrations combine; the result depends on the relative phases of the waves (in-phase or out-of-phase).

Standing Waves - Class 20

• Standing Waves: A phenomenon that happens when two similar waves are traveling in opposite directions; they result in the formation of nodes and antinodes.
• Sympathetic Vibration: Occurs when a body starts to vibrate in response to vibrations from another body; important concept in musical instrument design and acoustic phenomena.
• Frequency Response: Graph representing the output of an oscillating system in relation to the frequencies of external stimuli.