Speech Science: Basic Physics Concepts

Pressure

A force that acts perpendicularly on a surface area P=F/A ***The force of any pressure, including air pressure can move objects.

Acoustics

Acoustics is the study of the production, control, transmission, reception and effects of sound.

What is the definition of power? How do we measure it?

Amount of energy expended in a given time Measured in watts (W) Watt=10million ergs/sec or 1 joule/sec

Force

Any influence that causes an object to undergo a change in speed, direction or shape Measured in: Newtons (N) in the MKS system 1 N= a force that accelerates 1 kilogram at a rate of 1 meter per second squared Dynes in the CGS system 1 dyne=a force that accelerates 1 gram at a rate of 1 centimeter per second squared

Energy

Capacity to do work Many forms of energy exist Can be categorized as potential or kinetic Kinetic is mass in motion Potential: stand still (pendulum)

What are changes in pressure due to?

Changes in pressure are due a disturbance in elastic medium and associated with some type of movement.

Speed

Distance traveled by an object (or structure in speech production) in a given unit of time Measured in meters per second Velocity specifies speed and the direction of the movement

Elasticity

Elasticity is determined by the amount of force required to displace the object by a given distance Elasticity is Measured in Stiffness (K) Stiffness= the resistance of an elastic body to deformation by an applied force K (stiffness)=Force (in newtons)/meters Greater the stiffness the greater the force required to displace the object

Work

Force extended over a distance (newtons times distance in meters) Work is measured in Joules (J) in MKS or ergs in cgs One Joule is a force of 1 newton acting through a distance of 1 meter One erg is the amount of work done when a force of 1 dyne displaces an object by 1 cm

Weight

Force of gravity on an object Measured by newton (1 kilogram of mass weighs 9.8 newtons) Greater the mass, greater the gravitational force, greater the weight

How is Sound Generated?

Generated by changes in pressure in some type of medium gas, liquid, or solid

What is a U tube manometer, and what is it's purpose?

If you blow into a tube that is partially filled with water Force of your breath—exerts pressure on the surface of the water Water will be displaced by a certain distance. So if you displace the water by 5 cm you have generated enough pressure to shift the level 5 cm it means the pressure is 5cm H20 5-10cm of water pressure is what we need to sustain connected speech.

Momentum

Mass times the velocity of an object during motion Measured by kilograms times meters per second Directly proportional to the velocity Greater the mass, the greater the momentum Changing mass or velocity, changes momentum

Pressure

Measuring pressure in the MKS system (unit=pascal, PA) In the equation for Pressure, P=F/Area Unit of force is the newton Unit of area is the square meter (m2) Therefore, Pressure=newtons per square meter (N/m2) 1 (N/m2)=1 pascal (Pa) Unit used for measuring large amounts of pressure ***** µPa (micropascal)-one millionth of 1 Pa used for measuring small pressure in speech and hearing research

Two Metric Systems

Metric system- (International System of Units) (SI) Two systems: MKS system, cgs system Based on distance, mass, time MKS=Meters, Kilogram, Seconds (large units) cgs=centimeters, grams, seconds (small units)

How do we study sound?

Must be able to detect the movement of a source as it moves through a medium For speech-medium is: air Acoustics: Deals with the generation, transmission and modification of sound waves

Measuring Pressure in the CGS System

P=F/A Unit of force-- dyne (d) Measures small amount of force Unit of area-square centimeter (cm2) Pressure=dyne/cm2 1 dyne/cm2= 1 microbar (0.1 Pa), 10 microbar= 1 Pa Example: To measure pressure acting on eardrum

What is the definition of intensity ? How do we measure it?

Power measured per unit area Measured in W/m2 (MKS) or W/cm2 (CGS) Loudness is a perception, intensity is how we objectively measure that feeling.

Elasticity

Property where a material has the ability to return to original shape (after deformation by external force) Stress=external force that is applied Deformation-change in shape Strain=amount of deformation that has occurred

Volume

Quantity of three dimensional space for a liquid, volume or gas (what is occupied) Measured in Liters 1 liter = 1000 milliliters (mL) or 1000 cubic centimeters (cc)

How is pressure in the air produced?

Random movement produces collision of air molecules Collision known as PRESSURE Composition of air is made up of many gases Air molecules that make up the gases: Constant random movement (Brownian motion)

Inertia (Newton's First Law of Motion)

Resistance of a physical object to a change in its state of motion or rest. Velocity of an object will remain constant unless an external force acts upon it Source of the resistance is the object's mass, measured in grams or kilograms

Where does sound occur?

Sound occurs when some type of disturbance causes a pressure change in some type of elastic medium---gas, liquid, or solid Usually the disturbance occurs due to some type of movement (Tuning fork, vocal folds, book hitting the floor) Sound in air creates increases and decrease in air pressure These increases and decreases are transmitted through the air, In the medium air, pressure changes are perceived as sound

Mass

The amount of matter in an object Kilograms or grams (not the same as weight!!)

Bioacoustics

The study of human speech requires understanding of: Bioacoustics Combination of the study of acoustics and biology Focuses on the study of sound production and perception in animals

Measuring Pressure

We can measure air pressure in a number of different ways Measurement of pressure includes the applied force over a surface area One example would be the measurement of air pressure acting on the eardrum to produce the perception of sound Unit is the dyne Used to measure small amounts of force over a surface area For the eardrum the unit of measure would be the sq cm Larger amounts of force/larger surface areas psi Car tires example 30 psi Both of these measures are used in speech path and audiology

Acceleration

When velocity of an object changes as a function of time Directly proportional to the force applied Inversely proportional to the mass If force is held constant, the greater the mass the smaller the acceleration or the smaller the mass the greater the acceleration a=F/m or F=ma (Newton's Second Law of Motion)

What do you need for efficient sound production in humans?

You need: A source (Vocal Folds) capable of movement A medium (Air) which can be disturbed by the source and undergo pressure changes A receiver (Ear) that detects the vibrations of the sound source