Sound Waves and Hearing Tests

Audiology

• Audiology studies hearing, balance, and related disorders.
• Audiologists provide services to people with auditory or vestibular impairments.

Audiologist Activities

• Identification
• Assessment
• Diagnosis of hearing disorders
• Treatment
• Prevention of hearing loss

Evolution of Audiology

• Before WWII, primary physicians and instrument specialists handled hearing issues
• After WWII, technology advancements led to louder weaponry and severe hearing impairments
• Audiologists were needed for otology to diagnose ear disease

Raymond Carhart

• Created aural rehabilitation centers
• Known as the "Father of Audiology"
• Started the first audiology academic program at Northwestern University

Doctor of Audiology (AuD)

• The AuD is an entry-level professional doctorate
• It is a 4-year graduate degree requiring a comprehensive curriculum.
• It requires over 2500 hours of clinical experience
• The fourth year involves an externship.

AuD vs. PhD

• AuD is a clinical doctorate for practitioners.
• PhD is an academic doctorate for researchers.

History of the AuD

• The move from a clinical master's degree to a professional doctorate began in the late 1980s.
• In 1978, ASHA discussed the need for a professional doctorate to allow Ph.D. programs to focus on research
• In 1995, ASHA endorsed a plan to transition from master's to doctorate.
• Full implementation occurred by 2007.
• There are over 70 professional doctorate programs to date.

Licensure and Certification

• Current in Louisiana
• Licensure is needed to practice
• Achieved by completing a doctoral degree and clinical assignments
• Requires passing a national exam (Praxis)
• Requires applying for licensure through the state board (LBESPA)
• Requires mandatory Continuing Education Units (CEUs), such as 10 hours per year or 30 hours every 3 years with ASHA
• Certification, such as membership in ASHA for the Certificate of Clinical Competence (CCC), is optional
• The American Board of Audiology (ABA) offers specialization certification
• Certification is acquired to showcase knowledge and skills, especially when supervising students(ASHA CCC).

Medical Audiology

• It is the largest audiology specialty
• Settings include hospitals
• Activities include hearing tests, newborn hearing screenings, ototoxic monitoring, pre-screenings, hearing aids, cochlear implants, and bone-anchored devices.

Educational Audiology

• Settings include schools
• It involves identifying hearing impairments/infections
• Activities include screening, acoustic environment accommodations, faculty and parent education, and preventing hearing loss.

Pediatric Audiology

• Settings include children's hospitals and speech and hearing centers.
• Activities include guiding parents and typical audiology treatments.

Additional Audiology Specialties

• Hearing Aid Dispensing Audiologist: provide aids
• Industrial Audiology: OSHA- ensure companies meet standards to prevent noise-induced hearing loss, employee screening/testing/education/monitoring
• Tele-Audiology: remote aids, counseling
• Academic Audiologist: university-level training and teaching
• Research Audiologist: PhD required
• Forensic Audiologist: expert witness for occupational and environmental noise cases
• Intraoperative Monitoring Specialist: auditory response when kids/adults are sedated (ABR- auditory brainstem testing)

Audiologists and Other professionals - Employment settings

• Otoscopic examination: looking in the ear
• Comprehensive audiological evaluations: hearing tests

High risk identification factors

• Noise exposure
• Age
• Ear infections
• Medicines
• Illnesses (esp. with babies)
• Family history

Audiology Activities

• Conduct tests of vestibular function: hearing and balance
• Treatment of vestibular disorders: benign proximal vertigo disorder
• Cochlear implant mapping: programming devices for deafness
• Noise measurements: industrial monitoring of levels of loudness
• Cerumen management: removing ear wax
• Perform & interpret tests of evoked potentials: hearing tests while asleep
• Tinnitus evaluation and treatment: sensitivity to loud sounds/ringing
• Hearing Conservation: education
• Audiology research

Professional Organizations

• Professional organizations provide advocacy, publish scholarly journals, provide educational opportunities and participate in political action committees
• ASHA (American Speech, Language, Hearing Association)
• AAA (American Academy of Audiology)
• LSHA (state association)
• Louisiana Academy of Audiology
• ADA (Academy of Doctors of Audiology)
• Educational Audiology Association
• Academy of Rehabilitation Audiology
• American Auditory Society
• Association for Research in Otolaryngology
• American Tinnitus Association

Salary Expectations

• Median income: $80,000
• Median salary for Au.D. with 1-3 years of experience: $72,000
• Median salary for Ph.D.: $112,705

Acoustics

• Branch of physics that deals with sound and sound waves
• Sound: An auditory experience, “act of hearing something”
• Sound travels through any elastic medium
• Solids are more elastic than liquids, liquids are more elastic than gases
• Psychoacoustics explains how people perceive the acoustic properties of sound
• Loudness is a perceptual correlate of intensity (dB)
• Pitch is a perceptual correlate of frequency (Hz)

Measurement Techniques

• Method of constant stimuli: use a fixed set of tones, that differ in intensity
  • Subject responds "yes" or "no"
• Method of limits: an audible tone is presented, descending until subject cannot hear
  • Tone is then increased until audibility

Acoustics - aspects of sound

• Production: vibrations
  • Given the proper amount of energy, a mass can be set into vibration
  • Impedance: forces that oppose vibration
  • Free vibrations: no outside force
  • Forced vibration: outside force
  • A simple vibration: described by frequency, amplitude, and starting phase
    • Pure tones: sine wave characterized by frequency, wavelength, or amplitude
    • Graphic way to represent sound waves
    • Each cycle of compression and rarefaction, as a function of time
    • Described in terms of: wavelength, frequency, amplitude, phase
  • Complex vibration: combinations of simple vibrations

Sound Transmission

• The source will send vibrations that travel, or propagation
• Propagation occurs through some medium (air, water, etc.)
• Propagation is a result of the back and forth movement of air molecules
• Longitudinal wave process of localized back and forth propagation
• Condensation happens due to pressure increase, and when more molecules per volume
• Rarefaction happens due to pressure decrease, and the when less molecules per volume Waves are successive compressions and rarefactions
• Sound travels faster in water and most solids than air
• Rapid and random movement of air particles is called Brownian motion
• Elasticity determines if an object returns to original shape when distorted

Wave Motion

• Diffraction: a wave is partially obstructed and changes shape around obstruction
• Constructive interference: reflected wave and next incident wave add together
• Destructive interference: reflected wave and next incident wave cancel each other

Wave Analysis

• Wavelength: distance from any point on a sinusoid to the same point on the next cycle of the wave
  • The maximum pressure to the minimum, and back to maximum, this is also called a cycle
• Frequency: How often or how frequently an event occurs
  • In acoustics, "second(s)" is used as the unit of time
  • *number of cycles per second (cps)
  • Hertz (Hz) is the unite of one cycle per second
    • E.g., 1000Hz: a pressure wave repeating 1000 times in one second, a pure tone
  • The frequency range of audibility for humans is between 20-20,000Hz
• Period: amount of time required for the completion of one cycle
  • Period = seconds per cycle (seconds/cycle)
  • Frequency = cycles per second (cycles/second)
• Amplitude: the magnitude of sound
  • The range of displacement from its point of equilibrium
  • Peak amplitude is the point at which displacement is greatest
  • Force per unit area, is called the Pascal
• Decibel - The dB is a relative measure of intensities or pressures, based on a ratio
• Complex sounds are characterized through analysis of their simple wave components, called Fourier Analysis
  • Fundamental frequency means lowest frequency component
  • Higher wave components are harmonics
• White noise: sound containing all frequencies simultaneously

Sound Measurement - Hearing

• Threshold of audibility
  • Stimuli: single-frequency pure tone
  • Intensity dimension of sound: measured using dB
  • Measurement scale: sound-pressure level (SPL)
• References for the dB
  • Sound-Pressure Level (dBSPL)
  • Sound Level Meter
  • Minimum Audibility Curve (reference equivalent threshold SPL)
• Hearing level scale
  • Ears not equally sensitive
  • HL: scale that references the average normal hearing thresholds
  • Audiometric zero
  • 0dB is equal to the minimal audibility curve
  • Hearing Level (HL)
  • American National Standards Institute (ANSI)
  • Sensation Level (dBSL)
• Pure-tone audiometer
  • AC transducers
  • BC transducers
  • 125Hz to 8000Hz AC
  • 250Hz to 4000Hz BC

Conductive Mechanism vs. Sensory-neural mechanisms of travel through the ear

• Travel through entire system
• Tested via air conduction
• Sensory/neural mechanism: bypassing the outer and middle ear and testing beyond, at the inner ear and auditory nerve
• Tested via bone conduction, where the vibrated skull directly stimulates fluids in the cochlea
  • Bone conduction can never be poorer than air conduction
  • Travels through the whole passage

Types of Hearing Loss

• Conductive hearing loss:
  • attenuation and loss of volume, with a barrier in the outer or middle ear, resulting in impaired air conduction and normal bone conduction
  • Ear wax in outer and middle ear infections are main factors
• Sensorineural hearing loss:
  • impacts the sensory cochlea, or the neural auditory nerve, resulting in impaired air and bone conduction, with equal AC and BC amounts
• Mixed hearing loss:
  • both conductive and sensorineural loss impact the outer and middle ear, + inner/auditory nerve, resulting in impaired air and bone conduction, and AC loss greater than BC loss
• Non-organic hearing loss: hearing loss on audiogram but normal hearing
• Tuning fork tests
  • Pure-tone test

Patient Case History

• Needed to build rapport, establish a relationship, and gain trust
• Preliminary hypothesis:
  • Determine presenting problem
  • Observe the patient's gender/age, hearing aids, and craniofacial anomalies to determine their ability to attend to speec
• Information needed from the client should identify demographics such as name and DOB, presenting complaint, accompanying symptoms, communication, family, & noise-exposure history; general medical/birth & social history; previous assessments; and where to send a formal report

"Do's" of Client interaction

• Keep info at a simple reading level and as concise as possible
• Translate it into commonly used local languages
• Fill out the form in front of the patient
• Mail and post the form on the website

"Don'ts" of Client interaction

• Hand out forms and fail to review it
• Conduct otoscopic examination at the initial evaluation

Otoscopic Examination

• Always examine the good ear first to avoid cross contamination
• Examine the pinna, or outer part of the ear, for embryotic-development abnormalities
• Straighten the External Auditory Canal (EAC) and insert the speculum
• Examine the ear canal
• Look for the light reflex that makes the eardrum cone-shaped
• The long process of malleus (manubrium) is a long bone of malleus
• The Umbo is the point of greatest retraction of the TM where the malleus and manubrium attach
• The lateral process of malleus forms a triangular shape
• The pars flaccida is the superior portion of TM which is flaccid, less layers of tissues and moves more
• The pars tensa is "tense"
• the long process of incus is a "crew and loses the TM

Characteristics of Tympanic Membrane (TM)

• Cone-shaped
• Pearl grey
• Semitransparent
• Rich in blood supply
• TM Quadrants:
  • anterior superior (in front of above), anterior inferior, posterior superior, and posterior inferior

Pure Tone Audiometry (PTA)

• Why use?
  • Easy to produce and calibrate
  • Look for patterns of hearing loss as a function of frequency
• Allows medical staff to:
  • Describe the amount of hearing loss, determine which parts of auditory system are involved, determine if a medical referral is needed, and predict how loss may relate to the ability to communicate
• Components
  • Diagnostic or clinical audiometer
  • Screening audiometer
• Transducers (calibrated yearly)
  • Supra-aural earphones (AC) are headphones
  • Insert earphones (AC)
  • Bone oscillator (BC): placed on mastoid bone and vibrates entire skull, stimulating both cochlea
  • Speakers (AC)
• Air conduction vs. Bone conduction: measuring how much hearing loss is sensorineural or conductive

Audiological Testing Rooms

• Should be sound-proofed, sound-treated, isolated from external noise, ideally in double-walled suites

• Pure Tone testing is the most basic diagnostic measure and reveals concept of threshold/softest the sound you can hear

• Patient orientation: ideal to be sitting sideways

• Patient responses include false positives (saying there is a sound when there is not) and false negatives (hearing a sound but not responding)

The procedures of Pure Tone Testing

• Clear Instructions
• Red = right; blue = left
• 1-2 seconds for presentation
• Continuous or pulsed with pulse ideal

Air Conduction Testing

• AC: 250Hz-8000Hz → how to test pure tones
  • Dotted-line = tested as needed "interoctave;" Solid line = octave
• Test the ½ octave if there is a difference of 20 dB or more
• Test in Frequency order and re-rest 1000Hz to account for learning the test and improvement
• After testing all the frequencies for the good ear, move on to testing all the frequencies of the other ear before increasing dB
• Conduct in 5 dB increments to determine dB HL- intensity

Audiogram Details:

• A graphic representation of hearing results, indicating a frequency on the x-axis
• Frequency begins with 125Hz and extends to 8000Hz
• Intensity on the y-axis goes from -10 to 120dB
• Procedure: Hughson-Westlake and Up 5, down 10;
  • For suspected hearing loss begin at 70dB, otherwise begin testing at 30dB and 1000Hz
  • If there is no response, increase by 20dB steps and present a tone for 1-2 seconds
  • After a positive response drop 10dB, until there is no response
  • Then increase by 5 dB increments until they respond again, ascending in 5dB steps
  • Ascend in 5dB steps. Two out of three ascending responses at the same level indicates inaudibilty
  • Decrease in 10dB steps until NR
• Threshold: lowest intensity level that patient responds to at least 50% of ascending presentations
• Documentation of thresholds
  • Red = right = O for AC; Blue = left = X for AC
  • Symmetric: X and O overlap
• Asymmetry: big difference between X and O

Pure Tone Averages (PTA)

• Averages at three frequencies with the most speech energy: 500, 1000, 2000Hz
• Add averages and divide by 3

Bone Conduction Testing

• Only the ways to determine what type of hearing loss a patent has
• Degree of hearing loss:
  • Normal = 0-25dB (slight HL 16-25 dB); Mild = 26-40dB; Moderate = 41-55dB; - Moderately-Severe = 56-70dB; Severe = 71-90dB; Profound = 90+ dB Measurements of Common Sounds
  • 20dB = a whisper; 45dB - Soft Conversation Speech; 80dB - loud music from a radio; 120dB – chain saw; - 140dB – jet engine at takeoff

Distortional Bone Conduction:

• Skull vibration (distortion) vibrates bone around cochlea
• Stimulates hair cells in cochlea and stimulates bone around both cochlea
• Inertial Bone Conduction
• Cochlea vibration causes ossicular chain to lag and causes stapes tube to vibrate (inertia)
• Causes vibration into column of air in ear; air escaping out of outer ear and then tympanic membrane vibrates

Bone Conduction Testing Details

• Testing Bone conduction
  • Conduct a Bone Conduction test at 250Hz – 4000Hz
  • Unspecified how hearing reaches the "better ear"
• Do not know which ear hears the sound
• Assume "better ear" represented by a stapple symbol
• Procedure: 1000Hz at 30dB
• Air and bone the same, its a normal or sensorineural loss
• Tactile responses
• Symbols consist of: stapple + *VT-vibrato tactile response ( louder meaning they are feeling vibration, not hearing ); <> unspecified Bone Conduction, []=masked Bone Conduction.

Bone Conduction and Hearing Loss

• Determining bone conduction reveals the type of hearing loss
  • Air Conduction determines degress and where hearing loss is Conductive results from loss as a result of Air Conduction while bone conduction remains normal
• Sensorineural= equal loss of Air+Bone Conduction
• Mixed= loss by Bone, with greater loss by Air Conduction
• Characteristics of hearing impairment: degree, type, and configuration (clue us in on disorder causing the hearing loss (diagnosis))

Characterizing Hearing Impairment

• Configuration clue in on disorder causing hearing loss [diagnosis]
  • Flat line; Sloping = diagonal line downward; Precipitous= steep slope; Rising= diagonal line uptrend;
  • Notched= flat than drop down then back; Corner= arrows at bottom of audiogram marks NR, No Response.
• Location: Bilateral (both ears), Unilateral (one ear)
• Difference btwn Ears: Asymmetric-hearing varies vs. Symmetrical - hearing same in both ears
• No response exists when those tested are unable to hear, marked by circle/arrow on X at bottom of audiogram chart
• Tactile responses: pt reports vibration , yet unable to hear
• Cookie bite: half-moon shape

Normal dynamic range notes

• Dynamic range indicates range a person can hear, including all degrees of loudness/softness -Hearing loss can occur due to a reduced dynamic area. - Uncomfortable Loudmess does Not Change: Stays steady at 120dB
• dBSL: sensation level; vs. dbHL: Pure tone avg
• Ex. 50dB threshold; OdBSL

Explore the intricacies of sound waves: period, frequency, and harmonics. Investigate decibel scales, hearing levels, and audiometry. Learn about air and bone conduction tests, conductive hearing loss, and ear canal examination.