THA 342 - Sound
Design and Engineering - Spring - 2006
Sound Waves: molecular movement
(air) at 1,130 ft. per second in all directions.
Phasing: Diagram of sound pressure movement
Frequency: number of peaks (cycles) in a given distance (time).
100 cycles (waves per second + 1 Hertz
Rate of peaks per second changes pitch of sound
More Hertz (Hz) = higher pitch
Amplitude: intensity of frequency, volume
Change in height of peaks (number of cycles per second remains the same)
Volume measured in decibels (dB).
More dB = more volume.
0 dB is arbitrarily set at the threshold of hearing
Inverse Square Law: volume drops at the square of the distance from source
Harmonics: equal division of cycles
Middle C = 256 Hz
1 octave above middle C = 512 Hz
In and out of Phase: Multiple sound sources in combination
Doppler Effect: sound approaching increases in pitch
Sound waves are compressed creating the illusion of more cycles per second.
The Human Ear
Discernment: ears are located
on the sides of human heads.
Horizontal discernment: 15 degrees
Vertical discernment: 45 degrees
Envelope: Shape of sound as
defined by how it begins, changes interally over time, and how it ends.
Reverberation: Time of decay 60 dB
(1 millionth of original sound)
Directionality of various pitches (higher frequencies are more directional)