Week 5 Flashcards
(10 cards)
How can sounds be described?
Pitch (related to frequency), loudness (related to intensity) and quality (related to vocal tract shape).
How do we perceive sound?
Sound is a series of small variations in air pressure (compressions and rarefactions) which travel in air. Sound waves are the means of transmitting acoustic energy between a sound source and a receiver.
Describe air compression and rarefaction.
When particles are close together the air is compressed. A region of rarefaction occurs when air particles are farther apart than normal. Sound waves propagate.
What are sine waves?
Sine waves are a pure tone represented by smooth and regular curves. Sinusoidal movement is graphically represented on a waveform.
What is a waveform?
A graphical representation of air pressure variation over time. (X-axis = time, Y-axis = amplitude).
What are the simple wave properties?
Frequency — number of cycles per second (Hz), associated with pitch. Period — time between similar points (s). Amplitude — distance between equilibrium and peak, associated with loudness. Phase — horizontal alignment of peaks.
Describe pitch.
The varying rate of the vibration of a body of air affects the rate at which pressure peaks are produced which affects the pitch of a sound. For a sound to have pitch, the variations in air pressure must be regular. A complete variation of air pressure from normal to peak to trough to normal is a cycle (T).
Describe the frequency of a sound.
Related to pitch, frequency refers to the rate at which cycles occur per one second. To calculate frequency, you divide one second by the length of the cycle to get cycles per second.
Describe amplitude.
Amplitude is the distance from equilibrium to peak/trough. It is associated with “loudness” and measured in pascals (Pa) or decibels (dB). The loudness of a sound depends on the size of variations in air pressure being produced.
Describe phase.
Phase is the horizontal alignment of peaks, measured as an angle. Rarely important for phonetics.
