Sound for the Theatre
Molecular movement (air) at 1,130 ft. per second in all directions
(at sea level)
Sound Waves - Air Compression
Diagram of sound
Frequency - measured in Hertz
of peaks (cycles) in a given distance (time)
- 100 cycles per second = 1 Hertz
- As number of peaks per second changes, pitch of sound changes
- More Hertz (Hz) = higher pitch
Intensity of frequency, height of sine wave = 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
Contrasting Sound Wave Graphics
- Inverse Square Law
As distance from the source increases, volume drops at the square of the distance from source.
For a sound to have the same apparent volume at twice the distance, it must be amplified four times as much. At a distance three times as far away, the sound must be amplified nine times as much.
Equal division of Cycles
- Middle C = 256 Hz
- 1 octave above middle C = 1st Harmonic: 512 Hz (256 x 2)
2 octave above middle C = 2nd Harmonic: 1024 Hz (512 x 2)
- In and out of Phase
Multiple sound sources in combination
Sound approaching appears to increase in
Sound waves are compressed creating the illusion of more cycles per second.
Cross section of Cochlea
Ears are located on the sides of human heads
Horizontal discernment: 15 degrees
Vertical discernment: 45 degrees
- Dynamic Range
- 20 - 20,000 Hertz
Shape of sound as defined by how it begins, changes internally
over time, and how it ends.
To hear these sounds, go to the Handbook for Acoustic Ecology at http://www.sfu.ca/sonic-studio/handbook/Envelope.html
- Release (acoustic environment)
RT60: Time of decay 60 dB (1 millionth of original sound)
Directionality of various pitches (higher frequencies are
Acoustic Shell at the Duluth Entertainment and Convention Center