Revision as of 19:55, 15 January 2007

Review Properties 1

There is a good reading an a bunch of supplemental reading in the High School Physics Tutorial

Hold mouse over for answer

1. Which wave (Wave1 or Wave2) has a Lower Frequency?
2. Which wave (Wave1 or Wave2) has a Higher Amplitude?
3. Which wave (Wave1 or Wave2) has a Longer Wavelength?
4. Which wave (Wave1 or Wave2) has a Faster Speed?
5. Which wave (Wave1 or Wave2) has a Higher Pitch?
6. Which wave (Wave1 or Wave2) is Louder?

The Ear and Hearing Loss

The Ear

Outer Ear

• Pinna
• Auditory Canal
• Ear Drum

Inner Ear

• Mallus, Incus, Stapes
• Semi-Circular Canals
• Cochlea
• Estachian Tube
• Auditory Canal

Hearing Loss

Perception of Amplitude and Frequency

Humans do not hear all frequencies equally. We perceive different frequencies with equal energy to have different amplitudes. The Fletcher Munson Curves show the phons scale, how amplitude is perceived by frequency

Fletcher Munson Curves 1 http://arts.ucsc.edu/EMS/Music/tech_background/TE-02/AcNumbers/AcNumbers.html

Fletcher Munson Curves 2 http://www.allchurchsound.com/ACS/edart/fmelc.html

Behaviour of sound waves

• Interference and Beats
• The Doppler Effect and Shock Waves
• Boundary Behavior
• Reflection, Refraction, and Diffraction

Phase

Phase in measured in degrees.

The phase of a sound has to do with the time domain.

Adding two Simple Harmonic waves -Applet

Adding two Simple Harmonic waves2 - Applet

http://library.thinkquest.org/19537/java/Wave.html

In class demo of how waves add show beats

Timbre/Harmonic structure

Timbre is a descriptive word used to help describe the 'color' and envelope of a sound.

All sound is made up of simultaneous sounding tones. In the 1700 Joseph Fourier a French mathematical physicist proved that all sound can be synthesized be adding sine waves. The way these sine waves are added together make things sound different.

http://www.gac.edu/~huber/fourier/

Different sound don't sound the same due to different fundamental frequencies, harmonics, complexity, and envelope.

Timbre is made up of Harmonics and Envelope. The Harmonics define the different frequencies present in a a sound and the envelope defines the amplitude through time.

Harmonic Structure

http://www.rane.com/par-t.htm Harmonics defined @ rane

Understanding Harmonics Fundamental Frequency and Harmonics Instruments

   * Guitar string
   * Open-End Air Columns
   * Closed-End Air Columns

Natural harmonics are multiple of the fundamental/

Understanding Harmonics @ Harmony Central

http://ptolemy.eecs.berkeley.edu/~eal/eecs20/berkeley/scale/demo/timbre.html

Envelope

Envelope is the Time/Amplitude shape of the wave. It is essentially a means of amplitude thought time.

Robert L Mott's Nine Components of Sound

Attack -- Decay-- Sustain -- Release

Different Domains of sound

Time Domain

Time along X axis and Amplitude Y axis -Fixed 2/29/00

Sine wave looks like a sine wave

Frequency Domain

Freq. along X axis and Amplitude Along Y axis-Fixed 2/29/00

Sine wave looks like a line

RMS

root mean square Abbr. rms, RMS Mathematics. The square root of the average of the squares of a group of numbers. A useful and more meaningful way of averaging a group of numbers.

from http://www.rane.com/par-r.html

The RMS averaging method is a better method for determining the amplitude of sound. Dynamic Range Definition @http://www.rane.com/par-d.html

The dynamic range of an audio system or and audio performance is the difference between the peak noise level and the noise floor.

Dynamic Range

Dynamic range = (Peak Level - Noise Floor)

Head Room

Definition @http://www.rane.com/par-h.html

The head room of an audio system is is the difference between the nominal level and the Peak level (or clipping point) Frequency Response Definition @http://www.rane.com/par-f.html

The range in frequency that an audio system or program contains or can pass between certain deviation.

Home Work

• Study for Quiz on weeks 1,2, and 3 and Chapter 1 in Sound Design for Interactive Multimedia
• Sound Sculpture or Audio Enviroment
• Review for Quiz1 Next Week

Quiz 1 review

  Properties of sound High school physics tutorial

   * Sound Is a Longitudinal wave
   * Speed of sound (measured in m/s)
   * Frequency (measured in Hz)
   * Period (seconds per cycle)
   * Wavelength (measured in meters)
   * Amplitude/Pressure (for this class we will only look at dBs)
   * Phase (measured in degrees)

  Understand the difference between transverse and longitudinal waves.

  Be able to calculate frequency from wavelength or period and visa-versa.

  Understand

   * dB's
   * Different ways of representing and audio wave (the Domains of Sound)
   * Timbre/Harmonic structure
   * Dynamic Range and Headroom