Chapter 11 Sound, Auditory system, and Pitch perception Flashcards
Sound (physical)
Pressure in the air or other medium
Sound (perceptual)
Experience we have when we hear
- Condensation
- Refraction
- When surrounding air molecules are pushed together, increasing the air pressure
- When air molecules spread out, filling in the increased space = decreased air presure.
Sound wave
Pattern of pressure change in a medium.
Air: 340m/s
Water: 1,500m/s
How do sound waves travel?
The air molecules move back and forth, but stay in the same place. Analogous to ripples in water when a pebble is dropped.
Pure tone
A sound wave that is characterized by a sine wave pattern of pressure change.
Amplitude
Size of the pressure change
Frequency
Number of times per second that the pressure changes repeat.
Decibel (dB)
Unit of sound indicating the presence of a tone relative a reference pressure.
dB = 20 log (p/po)
(p): pressure of the tone (stimulus)
(po): reference pressure (usually set at 20 micropascal)
SPL (sound pressure level)
ex. 20 dB SPL
Indicates we have a standard pressure (po) of 20 micropascals
Level/Sound level
Refers to decibels or sound pressure of a sound stimulus
What perception of sound is frequency associated with?
Pitch. Higher frequency = higher pitch
Frequency is indicated in what units?
Hertz. 1 Hz = 1 cycle per second
Fundamental frequency
First harmonic (lowest frequency) of a complex tone
Periodic tone
The properity of sound waves to repeat (pure tones, complex tones)
Additive synthesis
Technique for building a complex tone in which a number of sine waves (pure tones) are added together. Fundamental frequency (ex. 200 Hz) is added with another pure tone that is a multiple of the fundamental (ex. 200Hz +200Hz = 400Hz).
Harmonics
Additional tones added too the fundamental frequency during additive synthesis.
Loudness
Quality of sound related to amplitude or sound pressure. Also referred to as the level of an auditory stimulus. dB is often associated with loudness.
Decibel vs. Loudness
Decibel is a physical measure.
Loudness is psychological
Pitch
The attribute of auditory sensation in terms of which sounds may be ordered on a musical scale. Perceptual quality we describe as “high” or “low”. Closely related to frequency.
Tone height
The increase in pitch due to the frequency being increased.
Tone chroma
Perceptual similarity of notes seperated by octaves.
Octave
Tones that have frequencies that are binary multiples of each other. ex. 800Hz is one octave above 400Hz.
How is pitch determined?
By information that indicates the fundamental frequency (ie. spacing of harmonics, repetition rate of waveform), NOT b/c of its presence.
Effect of the missing fundamental
When the fundamental or other harmonics are removed but does not change the tones pitch. Produces a periodicity pitch.
Periodicity pitch
A pitch that maintains its tone when some harmonics are removed.
Range of hearing
Specific range of frequencies in which sound can be heard.
Audibility curve
Indicates the threshold for hearing by comparing free-field presentation (listening to loud speaker) vs. frequency.
What is our range of hearing?
What frequencies are we most sensitive too?
20Hz - 20,000Hz
-Most sensitive between 2,000Hz - 4,000Hz.
Auditory repsonse area
Light green area above the audibility curve. We can hear sounds within this area.
How do we determine the loudness of a tone?
By knowing its dB level and its frequency
Equal loudness curves
Tones that create the same perception of loudness at different frequencies.
Timbre
Another perceptual quality of tones; Distinguishes between two tones that have the same loudness, pitch, and duration, but still sound different.
Attack
The buildup of sound at the beginning of the tone.
