# SCI206 Study Guide - Final Guide: Acoustic Suspension, Joseph Fourier, Riaa Equalization

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Published on 16 Oct 2011
School
University of Waterloo
Department
Science
Course
SCI206
SCI 205 EXAM NOTES:
Chapter 2 The Anatomy of High-Fidelity Systems:
Building Blocks of a Sound System:
Sound Source
Preamplifier
Power Amplifier
Speakers
Summary of Terms:
RIAA Equalization Amplifier: A collection of electronic circuits which boosts and “equalizes” the
signal coming from the magnetic Phono cartridges. (Recording Industry Association of America)
is found in the preamp/control centre.
Chapter 3 Waves and Sound:
Frequency = 1/Period
Speed = Distance Travelled/Elapsed Time
Wavelength x Frequency = Wave Speed
Sound Intensity = 

Summary of Terms:
Condensations: regions along a sound wave where the pressure is largest. Also called crests.
Rarefactions: Regions along a sound wave where the pressure is the smallest. Also called
troughs.
Law of Refraction: When sound travels from a low-velocity medium into a higher velocity
medium the refracted sound will bend away from the normal. If the sound travels from a higher-
velocity medium into a lower-velocity medium, the refracted sound will bend toward the
normal.
Reverberation: Numerous reflections of sound which arrive close together and cannot be
perceived as individual echoes.
Reverberation Time: The time required for the reverberated sound to decay to one-millionth of
its original level after the speakers have been turned off. Typical reverberation times are
between 0.5 and 2.2 seconds.
Reverberation Unit: A component that will add reverberation to the sound when connected to
an audio system.
Ultrasonic: Sound whose frequency lies above the audible range of 20kHz.
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Chapter 4 Complex Waves and Interference:
Fundamental (1st Harmonic)
1st Overtone (2nd Harmonic)
2nd Overtone (3rd Harmonic)
3rd Overtone ( 4th Harmonic)
4th Overtone (5th Harmonic)
5th Overtone (6th Harmonic)
Summary of Terms:
Diffraction: The bending of waves around objects or corners.
Fourier Analysis: A method, discovered by Joseph Fourier, that will resolve any complex
wave into a sum of simple sine waves which are harmonically related to each other.
Timbre: A term which describes the characteristic tonal quality of the sounds emitted by
a musical instrument. The timbre of a musical note is governed by the number and
relative amplitudes of the harmonics or overtones which are present.
Chapter 5: Decibels and You:
Summary of Terms:
dBW: a unit for measuring the power of an amplifier, in terms of decibels, relative t a reference
level of 1 watt.
Fletcher-Munson Curves: A series of graphs which characterize the ears sensitivity to various
frequencies at different loudness levels.
Threshold of Hearing is 0dB Lowest sound produced which can be heard.
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Chapter 6- Loudspeakers:
Parts of A Speaker:
The Diaphragm (or cone)
The Flexible Edge
The Voice Coil
The Permanent Magnet
% Efficiency = 
 x 100%
Summary of Terms:
Acoustic Suspension: A loudspeaker design which permits good bass reproduction from a
relatively small-sized enclosure. The acoustic suspension systems utilize a floppy, highly
compliant cone suspension and the trapped air to provide the proper suspension characteristics.
They are generally of low-efficiency design, requiring relatively high amplifier powers compared
to the vented and horn enclosures.
Bass Reflex (Vented Enclosure, Phase Inverter, or Tuned Port) A loudspeaker design in which the
cone’s “back-surface wave” is sent out through a port in the face of the enclosure to reinforce
the bass output.
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