Essentials of Audiology (4th Edition) - Comprehensive Flashcards

Acoustics

The scientific study of sound, which is a specialized branch of physics.

Mass ($M$)

A fundamental physical quantity related to an object's density, quantified in kilograms ($\text{kg}$) in the MKS system or grams ($\text{g}$) in the cgs system.

Length ($L$)

A fundamental scalar physical quantity describing distance, quantified in meters ($\text{m}$) in the MKS system or centimeters ($\text{cm}$) in the cgs system.

Time ($t$)

A fundamental scalar physical quantity that is quantified in units of seconds ($\text{s}$).

Scalar

A physical quantity that can be completely specified by its magnitude or size alone, such as mass, time, or length.

Vector

A physical quantity that requires both a magnitude and a direction to be completely described, such as displacement, velocity, or force.

Displacement ($d$)

A vector quantity representing the distance and spatial direction between two points ($x_1$ to $x_2$).

Velocity ($v$)

A vector quantity representing the amount of displacement occurring per unit of time ($v = \frac{d}{t}$), measured in meters per second ($\text{m/s}$).

Average Velocity

The total displacement between two points divided by the total time taken to travel that distance: $v = \frac{x_2 - x_1}{t_2 - t_1}$.

Instantaneous Velocity

The velocity of a body at a specific point in time, mathematically defined as the first derivative of displacement with respect to time: $v = \frac{dx}{dt}$.

Acceleration ($a$)

The time rate of change in velocity ($a = \frac{v}{t}$), expressed in units of $\text{m/s}^2$ in the MKS system or $\text{cm/s}^2$ in the cgs system.

Instantaneous Acceleration

The acceleration of a body at a specific instant, defined as the first derivative of velocity ($\frac{dv}{dt}$) or the second derivative of displacement ($\frac{d^2x}{dt^2}$) with respect to time.

Force ($F$)

The outside influence (a push or a pull) that causes a mass to accelerate, defined as the product of mass and acceleration: $F = Ma$.

Newton ($\text{N}$)

The MKS unit of force, defined as the amount of force needed to accelerate a $1\,\text{kg}$ mass by $1\,\text{m/s}^2$ ($1\,\text{N} = 1\,\text{kg}\cdot\text{m/s}^2$).

Dyne

The cgs unit of force, defined as the force required to accelerate a $1\,\text{g}$ mass by $1\,\text{cm/s}^2$ ($1\,\text{N} = 10^5\,\text{dynes}$).

Momentum

The product of an object's mass and its velocity ($Mv$); force can also be specified as momentum divided by time ($F = \frac{Mv}{t}$).

Equilibrium

The state of a physical system in which the net resultant force acting upon an object is equal to zero.

Friction (Resistance, $R$)

The opposing force generated when one body slides across another, which converts mechanical energy into thermal energy (heat).

Elasticity

The physical property of a deformed material that enables it to recover and return to its original form or shape after an applied force is removed.

Restoring Force ($F_R$)

The internal force that opposes the deformation of an elastic object, which increases proportionally with stiffness ($S$) and displacement ($d$): $F_R = Sd$.

Pressure ($p$)

The amount of force applied perpendicular to a surface divided by the area over which it is distributed ($p = \frac{F}{A}$).

Pascal ($\text{Pa}$)

The MKS unit of pressure, equivalent to one newton per square meter ($1\,\text{Pa} = 1\,\text{N/m}^2$).

Reference Sound Pressure

The internationally standardized reference pressure value for sound measurement, equal to $2 \times 10^{-5}\,\text{N/m}^2$ ($20\,\mu\text{Pa}$) in MKS units, or $2 \times 10^{-4}\,\text{dyne/cm}^2$ in cgs units.

Work ($W$)

The physical energy expended when an applied force causes displacement of an object: $W = Fd$.

Joule ($\text{J}$)

The MKS unit of work, equal to one newton-meter ($1\,\text{J} = 1\,\text{N}\cdot\text{m} = 10^7\,\text{ergs}$).

Erg

The cgs unit of work, equivalent to one dyne-centimeter ($1\,\text{erg} = 1\,\text{dyne}\cdot\text{cm}$).

Power ($P$)

The rate at which work is accomplished over time ($P = \frac{W}{t} = Fv$), measured in watts ($\text{w}$).

Watt ($\text{w}$)

The standard unit of power, defined as one joule of work per second ($1\,\text{w} = 1\,\text{J/s} = 10^7\,\text{ergs/s}$).

Sound Intensity ($I$)

The sound power distributed per unit of surface area ($I = \frac{P}{A}$), expressed in $\text{w/m}^2$ in MKS units or $\text{w/cm}^2$ in cgs units.

Reference Sound Intensity

The standard physical reference level for acoustic intensity, defined as $10^{-12}\,\text{w/m}^2$ in MKS units or $10^{-16}\,\text{w/cm}^2$ in cgs units.

Inverse Square Law

The principle stating that sound intensity drops by one over the square of the change in distance ($\frac{1}{d^2}$) from a source in an unobstructed spherical field.

Intensity-Pressure Relationship

The physical rule stating that acoustic power/intensity is directly proportional to the square of sound pressure ($I \propto p^2$ and $p \propto \sqrt{I}$).

Vibration

The mechanical back-and-forth oscillation of an object around its resting point.

Simple Harmonic Motion (SHM)

A fundamental form of periodic vibratory oscillation that repeats smoothly over time due to the interaction of linear restoring forces and inertia.

Cycle

One complete round-trip or replication of an oscillating motion from its starting point back to the identical state.

Frequency ($f$)

The number of completed cycles of an oscillating waveform per second, quantified in hertz ($\text{Hz}$).

Period ($t$)

The duration of time required to complete one entire cycle of a wave ($t = \frac{1}{f}$).

Damping

The gradual dissipation or dying out of mechanical vibratory oscillations over time caused by friction converting mechanical energy into heat.

Waveform

A graphical representation that plots instantaneous displacement (or other magnitude measures) along the vertical axis as a function of time along the horizontal axis.

Compression (Condensation)

A state of increased air pressure relative to ambient atmospheric pressure, occurring when vibrating air molecules are forced close together.

Rarefaction

A state of reduced air pressure below ambient atmospheric pressure, occurring when vibrating air molecules are spread farther apart than their resting positions.

Transverse Wave

A wave in which the particles of the medium oscillate at right angles (perpendicularly) to the direction of wave propagation.

Longitudinal Wave

A wave in which individual medium particles oscillate back and forth parallel to the direction in which the wave is traveling, as occurs in airborne sound.

Sine Wave

A smooth periodic wave whose instantaneous amplitude is strictly determined by the sine of its phase angle ($d = r\sin(\theta)$).

Phase Angle ($\theta$)

The angle formed by a rotating radius vector relative to the horizontal baseline, expressing position within a cycle from $0^\circ$ to $360^\circ$.

Peak-to-Peak Amplitude

The total linear vertical distance measured between the positive peak and the negative peak of a waveform.

Peak Amplitude

The maximum absolute displacement measured from the baseline (zero) to the maximum positive or negative displacement peak.

Root-Mean-Square (RMS) Amplitude

An effective measure of overall ongoing waveform magnitude equal to $0.707$ times peak amplitude ($0.354$ times peak-to-peak amplitude) for a sinusoid.

Wavelength ($\lambda$)

The physical distance in space occupied by one full cycle of a propagating wave: $\lambda = \frac{c}{f}$, where $c$ is the speed of sound ($\sim 344\,\text{m/s}$ in air).

Complex Wave

Any acoustic waveform generated by the combination of two or more pure tone sine waves.

Fourier Analysis

The mathematical operation (based on Fourier's theorem) of decomposing a complex waveform into its constituent sine wave components.

Acoustic Spectrum

A graph plotting the amplitude (or phase) of constituent frequency components on the vertical axis as a function of frequency on the horizontal axis.

Fundamental Frequency ($f_0$)

The lowest frequency component of a complex periodic wave, which corresponds to the largest common whole-number denominator of its harmonics.

Harmonics

Integral whole-number multiples of the fundamental frequency ($1f_0, 2f_0, 3f_0,\dots$).

Square Wave

A complex periodic waveform generated by combining odd harmonics of a fundamental frequency whose amplitudes diminish inversely with frequency.

Aperiodic Wave

An acoustic signal whose waveform does not repeat regularly over time, lacking harmonically related components.

Transient

An abrupt, nonrepeating sound event of extremely brief duration, yielding a continuous, flat acoustic spectrum.

White Noise (Random Noise)

An aperiodic acoustic signal containing all audible frequencies at equal average amplitude over time, exhibiting a flat continuous spectrum.

Standing Wave

A stationary wave pattern formed by the superposition of two identical waves traveling in opposite directions, creating fixed nodes and antinodes.

Node

A position along a standing wave pattern where particle displacement remains constantly at zero.

Antinode

A position along a standing wave pattern where particle displacement reaches its maximum amplitude.

Half-Wavelength Resonator

A tube open at both ends whose fundamental resonant frequency has a wavelength equal to twice the tube's length ($\lambda = 2L$; $f = \frac{c}{2L}$), generating all whole-number harmonics.

Quarter-Wavelength Resonator

A tube open at one end and closed at the other, having a fundamental resonant wavelength four times the tube length ($\lambda = 4L$; $f = \frac{c}{4L}$), producing only odd harmonics.

Acoustic Immittance

A general term encompassing both acoustic impedance (opposition to energy flow) and acoustic admittance (ease of energy flow).

Acoustic Impedance ($Z_a$)

The total opposition to the flow of acoustic energy through a system, defined as the ratio of sound pressure ($P$) to volume velocity ($U$): $Z_a = \frac{P}{U}$, measured in ohms.

Acoustic Admittance ($Y_a$)

The ease with which acoustic energy flows through a system, defined as the reciprocal of acoustic impedance: $Y_a = \frac{1}{Z_a} = \frac{U}{P}$, measured in acoustic millimhos (mmhos).

Mass Reactance ($X_m$)

The component of reactance associated with inertia that opposes the flow of energy, increasing proportionally with frequency ($X_m = 2\pi fM$).

Stiffness Reactance ($X_s$)

The component of reactance associated with compliance and restoring force that opposes energy flow, decreasing inversely with frequency ($X_s = \frac{S}{2\pi f}$).

Resonant Frequency

The specific frequency at which mass reactance ($X_m$) and stiffness reactance ($X_s$) are equal and cancel each other out, leaving only resistance to oppose energy flow.

Conductance ($G$)

The in-phase component of acoustic admittance, defined as the mathematical reciprocal of resistance: $G = \frac{1}{R}$.

Susceptance ($B$)

The out-of-phase reactive component of admittance, consisting of compliant susceptance ($B_s$) and mass susceptance ($B_m$).

Decibel ($\text{dB}$)

A logarithmic unit expressing the ratio of a measured physical quantity to a specified reference level, calculated as $10\log_{10}\left(\frac{P}{P_0}\right)$ for power or $20\log_{10}\left(\frac{p}{p_0}\right)$ for pressure.

Intensity Level ($\text{dB IL}$)

Acoustic intensity expressed in decibels relative to the reference intensity of $10^{-12}\,\text{w/m}^2$: $\text{IL} = 10\log_{10}\left(\frac{I}{10^{-12}}\right)$.

Sound Pressure Level ($\text{dB SPL}$)

Acoustic sound pressure expressed in decibels relative to the reference pressure of $20\,\mu\text{Pa}$: $\text{SPL} = 20\log_{10}\left(\frac{p}{20\,\mu\text{Pa}}\right)$.

Sound Level Meter (SLM)

An electronic measurement instrument consisting of a high-quality microphone, amplifier, weighting networks, and display calibrated to read sound levels in $\text{dB SPL}$.

A-Weighting Network

A sound level meter filtering circuit that substantially de-emphasizes low frequencies, mimicking human auditory sensitivity at low sound levels.

Pistonphone

A high-precision acoustical calibrator that produces a known sound pressure level (typically $114\,\text{dB SPL}$) to calibrate sound level meters, requiring barometric adjustment.

Temporal Bone

The paired cranial bone forming the inferior lateral aspect of the skull, housing the structures of the middle ear and inner ear.

Squamous Part of Temporal Bone

The thin, fan-shaped lateral superior plate of the temporal bone that features the anteriorly directed zygomatic process and mandibular fossa.

Mastoid Part of Temporal Bone

The posterior segment of the temporal bone containing the mastoid process, tympanic antrum, and interconnecting air cells.

Petrous Part of Temporal Bone

The extremely dense, pyramid-shaped portion of the temporal bone forming part of the cranial floor and housing the sensory labyrinths of the inner ear and internal auditory meatus.

Tympanic Part of Temporal Bone

The curved plate of the temporal bone forming the floor, anterior wall, and lower posterior wall of the external auditory meatus.

Styloid Process

A slender, anteroinferior pillar-like bony projection extending from the inferior aspect of the temporal bone that serves as an anchor for speech muscles.

Tegmen Tympani

The thin bony ceiling of the tympanic cavity and mastoid antrum that separates the middle ear from the middle cranial fossa of the brain.

Pinna (Auricle)

The visible external cartilaginous appendage of the outer ear, designed to collect sound and provide directional localization cues.

Concha

The deep, cup-shaped depression of the auricle leading directly into the entrance of the external auditory meatus.

Tragus

The cartilaginous projection pointing posteriorly over the entrance to the external auditory canal.

Helix

The prominent outer curved rim forming the superior and posterior margin of the pinna.

Antihelix

The curved inner ridge of pinna cartilage lying anterior to the scaphoid fossa and bifurcating superiorly into two crura.

External Auditory Meatus (Ear Canal)

An S-shaped canal approximately $2.5\,\text{to}\,3.5\,\text{cm}$ long, composed of an outer cartilaginous third with ceruminous glands and an inner bony two-thirds.

Tympanic Membrane (Eardrum)

The thin, translucent, cone-shaped membrane tilted at roughly $55^\circ$ to the canal that separates the external ear canal from the middle ear cavity.

Umbo

The deepest, central concave point of the tympanic membrane where the inferior tip of the manubrium of the malleus attaches.