Speech Science: Physiological Phonetics, Acoustic Phonetics, and Speech Perception

Speech Science: Physiological Phonetics, Acoustic Phonetics, and Speech Perception

1. Definitions

   • Acoustics
     • A branch of physics. It's the study of the physical properties of sound and how sound is generated and propagated.
     • Psychoacoustics
       • A study of how humans respond to sound as a physical phenomenon; it's a branch of both psychology and acoustics.
     • Sound
       • May be defined both physically and psychologically (perceptually). Physically defined, sound is the result of a vibration or disturbance in the molecules of a medium (air, gas, or liquid). Psychologically defined, sound is a vibration or disturbance in the air that is potentially audible, although instruments can measure inaudible sound.
       • Sound Waves
         • Movements of particles in a medium containing expansions and contractions of molecules.
         • Compression/Condensation
           • A phase of sound in which the vibratory movements of an object (e.g., the tines of a tuning fork) increase the density of air molecules because the molecules are compressed or condensed; it's the opposite of retraction.
           • Rarefaction
             • The thinning of air molecules when the vibrating object returns to equilibrium; it's the opposite of condensation.
             • Reflection
               • The phenomenon of sound waves traveling back after hitting an obstacle, with no change in the speed of propagation. 
               • Refraction
                 • The bending of the sound wave due to change in its speed of propagation; this happens, for example, when sound waves move from one medium (e.g., air) to another (e.g., water).
                 • Resonance
                   • The modification of sound by other sources. In speech acoustics, resonance refers to modification of the laryngeal tone predominantly by the nasal and oral cavities.
         • Simple Harmonic Motion
           • Refers to the back-and-forth movement of particles when the movement is symmetrical and aperiodic; also known as a sine wave.
         • Sinusoidal Motion
           • A wave with horizontal and vertical symmetry because it contains one peak or crest and one valley or trough. A sinusoidal wave contains a single frequency and is a result of simple harmonic motion.
         • Aperiodic Waves
           • Those that don't repeat themselves at regular intervals; their vibratory patterns are random and difficult to predict from one time interval to the next.
         • Periodic waves
           • Sound waves that repeat themselves at regular intervals and are predictable.
       • Displacement
         • Change in position; air molecules are said to be displaced because of the vibratory action of an object. 
         • Oscillation
           • Oscillation refers to the back-and-forth movement of the air molecules because of a vibrating object.
           • Transmitting Medium
             • Any matter that carries or transmits sound. Air, liquids, and solids can all transmit sound. The mass and elasticity of a transmitting media affect sound.
     • Amplitude
       • One of two characteristics of vibratory motion and is the magnitude and direction of displacement. In acoustics, it's the strength or magnitude of a sound signal; the greater the amplitude, the louder the sound signal.
       • Intensity
       • Bel
         • A logarithmic unit of measure of sound intensity. It's a basic and relative reference measure that helps express the wide range of sound intensities to which the human ear is sensitive by means of a compressed, logarithmic scale.
         • Decibel
           • (DB) is a measure of sound intensity that equals one tenth of a bel.
       • Frequency
         • One of the two characteristics of vibratory motion. It's the rate of vibratory motion that's measured in  terms of the number of cycles completed per second or, more recently, in terms of hertz (Hz). Hertz is the unit of measure for frequency and is the same as the cycle per second; 1 cycle per second is 1 Hz.
         • Natural Frecuency
           • The frequency with which a source of sound normally vibrates It's determined by the source's mass  and stiffness. Mass is the quantity of matter, and is not to be confused with weight, which is gravitational force exerted on mass. The mass of a medium of sound affects its transmission. Increased mass results in decreased frequency, and increased stiffness results in increased frequency.
         • Formant Frequency
           • A frequency region with concentrated acoustic energy. It's the enter frequency of a formant, which is a resonance.
           • Fundamental Frequency
             • The lowest frequency of a periodic wave; it's the first harmonic.
         • Octave
           • An indication of the interval between two frequencies. The intervals always maintain a ration of 1:2; thus, each octave doubles a particular frequency (e.g., 200 HZ is one octave above 100 HZ, and 2,000 HZ is one octave above 1,000 HZ).
           • Impedance
             • Acoustic, mechanical, or electrical resistance to motion or sound transmission. 
   • csg System
     • A metric system of measuring length in centimeters (cm), time in seconds (sec), and mass in grams (g); it can be contrasted with the MKS system. The MKS system is a metric system of measuring length in meters (m), mass in kilograms (k), and time in seconds.
     • Dyne
       • A measure of force in the cog metric system; 1 dyne is the force required to accelerate a mass of 1 gram from a velocity of 0 cm per second to a velocity of 1 cm per second in 1 second.
       • Density
         • The amount of mass per unit volume. Density of matter serves as a medium for sound and affects sound transmission.
         • Force
           • A vector quantity that tends to produce an acceleration of a body in the direction of its application; it's also defined as the product of mass and acceleration. Force is measured in terms of Nt (newton); 1 newton equals the force required to accelerate a mass of 1 kg from a velocity of 0 m (meter) per second to a velocity of 1 m per second in 1 second.
           • Elasticity
             • A property that makes it possible for matter (which helps transmit sound) to recover its form and volume when subjected to distortion. when force is applied to it. 
             • Velocity
               • A change in position of, for example, air molecules when an object is set to vibration. Velocity is measured in terms of the distance an object moves per the time and the direction it takes as it moves.
           • Pressure
             • The amount of force per unit area. Force is measured either as dynes or as newtons and is important to understanding the amount of force sound waves exert on the eardrum.
     • Newton's Law of Motion
       • Explain's motion and its characteristics. Basically, sound involves motion. The law of inertia states that all bodies remain at rest or in a state of uniform motion unless another force acts in opposition. In other words, a body in  motion tends to remain in motion unless another force acts in opposition. The law of reaction forces says that every force is associated with a reaction force of opposite direction.