3 CHARACTERISTICS OF SOUND (how we perceive them)
1) What is FREQUENCY?
2) FREQUENCY and its relationship to PITCH:
1) The number of complete cycles of vibration occurring in a second.
2) Not linear; At higher frequencies, it takes more frequency change to get an equivalent pitch change.
--From middle C to C sharp; less frequency change than from High C to C sharp.
FREQUENCY / PITCH expanded:
Rougher sounds are perceived as lower pitch than clearer sounds: its frequency
Lowest to highest frequency the human ear can detect: 20 to 20K Hz.
Usable range (what we use day to day): 100 Hz - 5K Hz.
Speech: 80 Hz - 500 Hz;
Noises for consonants: 80 - 500 Hz
We measure Frequency with Hz, and we measure Pitch with:
PERIOD; a 100 hz tone is 1/100th sec (low pitch)
--Most pitch perception: periodic complexes, or pure tones
--You can have perception of pitch for nonperiodic complex tones;
1) What is INTENSITY?
2)INTENSITY (loudness) is directly related to:
1) Magnitude of sound expressed in power or pressure;
--The underlying physical (acoustic) characteristic of a sound that leads to our perception of a sounds' loudness.
2) amplitude (distance away from point of rest)
How do we measure Intensity?
In POWER: Watt/cm squared (a watt is a flow of electricity)
In PRESSURE (force over surface area)--how we measure Intensity in speech: dynes/ cm squared.
The dB scale:
--A logarithmic ratio scale comparing one sound to another; the scale converts a large range of sounds the ear is sensitive to into manageable numbers;
smaller value scale, in which each dB is equivalent into a just noticeable difference.
The dB scale formula, and what it means:
dB SPL = 20 log 10 P1/P2
--Logarithm is how many times a number must be multiplied by itself to give you another number; in this case, log to the base 10.
For ex: 20 log 10 100/1 = 20 * 2 = 40
Answer = 40 dB SLP
--So when you've got a sound whose pressure is 100 time greater than another sound, the solution = 2, b/c 10 squared = 100. So 20 * 2 = 40 db SPL.
Another ex: : 20 log 10 1000/1 = 20 * 3 = 60.
Answer = 60 db SPL.
1) SPECTRUM (quality)
a) what is the lowest spectrum of sound?
1) what frequencies comprise any sound; how we distinguish between sounds (for ex, flute & piano have different spectrum.)
a) a single frequency
b) PERIODICITY (paired with Spectrum)
2) whether or not the pattern or oscillation of the sound-wave repeats, or how it is repeating
--pure tones are only tones whose periodicity is same cycle to cycle