chapter 1 Flashcards
Audiology
the healthcare profession devoted to
The prevention, identification, and evaluation of hearing disorders (including balance disorders)
Educational preparation
Doctoral entry-level degrees
Clinical PhD/ScD
Professional doctorate AuD
PhD
Professional certification
American Speech–Language Hearing Association (ASHA): the national organization that certifies audiologists and speech–language pathologists in the United States
Certificate of Clinical Competence (CCC)
American Academy of Audiology (AAA)
Professional licensure
State licensing board
Most states model their regulatory rules in audiology after the ASHA standards for the certificate of clinical competence
Continuing Education Units, around 30 per 3 years
Required by most states to maintain licensure
Often, separate licenses for audiology and hearing aids
Less schooling required to become a hearing aid dispenser (i.e., associate’s degree)
Evolution of the profession
Relatively new profession
Began in 1940s
Roots took hold in the United States following WWII
Clinics set up to rehabilitate veterans with hearing loss
Non-VA diagnostic clinics (both independent and within physician offices) set up later
Hearing aids dispensed by dispensers (not audiologists)
Scope of practice
Comprehensive audiometric evaluation (CAE)
Includes evaluation of middle ear function using immittance measures (tympanometry, acoustic reflex)
Auditory brainstem response (ABR) evaluation
Intraoperative monitoring of CN VII and CN VIII
Otoacoustic emission (OAE) evaluation of outer hair cell function
Electronystagmography (ENG) evaluation and vestibular rehabilitation
Cochlear implant programming/mapping of speech processor
Prescriptive fittings of hearing aid and assistive listening devices
ACOUSTICS
1) the properties or qualities of a room or building that determine how sound is transmitted in it.
2) the branch of physics concerned with the properties of sound.
PSYCHOACOUSTICS
Interdisciplinary science of the perception of sound.
2) Audiology
Prevalence
Prevalence refers to proportion of persons who have a condition at or during a particular time period,
Incidence
Incidence refers to the proportion or rate of persons who develop a condition during a particular time period.
Sound
Sound: the movement of a disturbance (vibration) through an elastic medium (liquid/solid/gas) without permanent displacement of the particles
◦We are generally concerned with AIR
Hearing
Hearing: the perception of sound
Mass
Mass: quantity of matter present
•Not identical to weight (because weight is affected by gravitational force)
•For our purposes, mass ~ weight
Force
Force: a push or a pull on an object; a vector
Inertia
Inertia: tendency to resist any change in motion (Newton’s First Law)
•Outside force must be applied to change this tendency
•The greater an object’s mass, the greater its inertia
Elasticity
–Elasticity: tendency to resist deformity of an object and to return to its rest position
Nature of sound
Initial impact starts movement (displacement) away from rest
2)Elasticity in the fork allows displacement, but also generates a restoring force that stops the movement
3)Restoring forces push the fork back to rest position
4)Inertia carries the tines past rest position (overshoot)
5)Restoring force builds up in the other direction
6)Fork returns to rest position again (one full cycle)
7)Overshoots . . . builds up restoring force . . . the pattern repeats
In an elastic medium such as air, the molecules next to the sound source move first. Then, they pass the movement to adjacent molecules. This motion is propagated, or transferred, through the air to the ear.
Compression
Compression: occurs when air particles are pushed together, resulting in an increase of air pressure; aka condensation
Rarefaction
Rarefaction: occurs when air particles are separated, resulting in a decrease of air pressure
Sound in air: longitudinal
Sound in air: longitudinal (pressure) wave
◦Particles vibrate alternately in the same direction of propagation (away from/toward the source) so that propagation is parallel to energy source
◦Particles approach and recede from each other to create pressure variations
Simple harmonic sound
Simple harmonic motion: the symmetrical to-and-fro motion of a body over a rest position
◦When the amplitudes of the vibrating body are plotted as a function of time, the resulting pattern is a sine wave
◦Pure tones, sounds with definite tonal quality, are produced by simple harmonic motion
Frequency
Frequency: a measurable characteristic of acoustic signals that is described by the number of complete cycles that a periodically vibrating source passes through in a 1-second time period
◦Measured in units called Hertz (Hz)
In a pure tone, only one frequency is described (e.g., 1000 Hz)
◦A sinusoid—forms a sine wave when graphed
◦Periodic in nature—repeats at regular intervals over time
Octave
Octave: twice the frequency of a given frequency
◦Octaves assessed via audiometer:
◦250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz, 8000 Hz
Pitch
◦Pitch: related to the listener’s perceptual response mainly to frequency (and, to a degree, intensity)
◦Frequency and pitch are related
◦Higher perceived pitch results (mostly) from higher frequency
◦However, this relationship is non-linear, especially at frequencies > 1000 Hz
Amplitude
Amplitude: a derived unit of measurement that describes the distance that the sound-producing body moves during vibration
◦The greater the distance from the point of rest, the greater the amplitude
◦In general, the greater the amplitude, the louder the sound
◦Decreases over time as energy is lost to damping (friction and other outside forces)
Intensity
Intensity: a derived unit of measurement that describes the amount of acoustic energy that passes through a unit of area in a given time span
◦Measured in units of power or pressure directly
Intensity versus loudness
◦Intensity: amplitude (magnitude) of the sound
Pascal
Pascal: unit of pressure describing the force per unit area; measured in N/m2 or dyne/cm2
◦Bel: unit of power
◦Decibel: one-tenth of a Bel (dB)
◦Logarithmic
◦Ratio of the measured pressure to a reference pressure (I/Ir)
Loudness
◦Loudness: the perception of intensity
Periodic vibration
Periodic vibration: vibration that repeats itself regularly over time
◦Recurs in the same way
◦Takes the same amount of time to complete each successive to-and-fro movement of one cycle of vibration
Aperiodic Vibration
Aperiodic vibration: vibration that is not repeatable over time
◦Generally classified as noise
Velocity
◦Velocity: magnitude of distance traveled per unit of time
◦Denoted by c (celeritas; Latin for speed or swiftness)
◦As sounds are physical phenomena, they obey physical laws (such as those governing velocity of objects traveling through a medium….like air)
◦How fast the sound wave moves depends on the density and elastic properties of the medium though which it is moving
◦In dry air at 20 °C (68 °F), the speed of sound is 344 m/s (1235 km/h, or 758 mph, or 1130 ft/s)
Inverse square law
Inverse Square Law: intensity varies inversely as the square of the distance from the sound source
Another look at the inverse square law; this is why classroom acoustics must be managed for optimal learning.
Free vibration
◦Free vibration: vibration of a mass independent of the application of any external force
Natural (resonant) vibration
Natural (resonant) vibration: frequency at which a mass vibrates with the least amount of external force
◦Vibration of an object greatest when vibratory frequency coincides with its resonant frequency
Force vibration
Forced vibration: application of additional force to sustain the vibration; vibration of a mass controlled and maintained by the application of an external impetus
Friction opposes vibration
◦Gradual decay in vibratory amplitude over time
the speed of sound
In dry air at 20°C (68°F), the speed of sound is 344 m/s (1235 km/h, or 758 mph, or 1130 ft/s)
Ranges
20 Hz - 20,000 Hz ( range of human hearing)
250 Hz - 8000 Hz (ranges of testing hearing)
0 Db - 140 dB (how we measure intensity) we can hear beyond this but it will damage our hearing
